EXPERIMENTAL STUDY ON A VENTURI VALVE APPLICATION
FOR STEAM TRUBINES

By

DAEJUNG KIM

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Mechanical Engineering

2010

ABSTRACT
EXPERIMENTAL STUDY ON A VENTURI VALVE APPLICATION
FOR STEAM TRUBINES

By

DAEJUNG KIM

In 2003, Elliott-Ebara Company and the MSU Turbomachinery laboratory
carried out a series of experimental and numerical studies on a venturi valve
application for stream turbines. It was proved by the studies that a nonaxisymmetric flow pattern caused non-axisymmetric pressure distribution along
the plug and generated an unbalanced force and moment at the valve. This
excited the plug, and the plug could be broken in a very short time if the
amplitudes of these excitations were to become large over the short time.
A new governor valve was designed to reduce flow non-axisymmetry and
instability. To investigate the relationship between plug and seat, the newly
designed governor valve was tested under the same conditions as the previous
valve test. In the new experiment, four microphones and five accelerometers
were set up to study the new valve‟s interaction with fluid in addition to the static
pressure taps from the previous experiments.
The results of model experiments on a newly designed governor valve are
reported here. Mass flow rates for new LRCO valves are measured at different
valve openings and pressure ratios. To clarify the interaction of the new LRCO
valves with the working fluid, flow axisymmetry and instability are discussed.

ACKNOWLEDGEMENTS

I would like to express my gratitude to my advisor Dr. Abraham Engeda for
giving me the opportunity to work on the venturi valve application experiment and
for his invaluable supervision and support throughout the course as a Master‟s
student at Michigan State University. I would also like to thank Dr. Craig
Somerton and Dr. Nobert Muller for being on my thesis committee. Particular
thanks go to James Hardin for providing valuable suggestions on this project and
the Elliott-Ebara Turbomachinery Group for supporting this work.
I am delighted to have such a valuable opportunity to work with a group of
very knowledgeable colleagues, Christopher Bolin, Marco Vagani, Kang Soo Im
in the Turbomachinery laboratory. I would like to give special thanks to
Christopher Bolin for helping me set up experiments and giving me useful
information whenever I encountered difficulties.
Finally, I would like to thank my family, my uncle and aunt (Mr. and Mrs.
Barbeau), and friends for their countless support and encouragement. They have
helped me through difficult times and they are always with me through the ups
and downs. Without them, I would not have been able to finish this task. Thank
you very much!

iii

TABLE OF CONTENTS

LIST OF TABLES……………………………………………………………...............vi
LIST OF FIGURES...............................................................................................vii
LIST OF SYMBOLS .............................................................................................xi
CHAPTER 1: INTRODUCTION.............................................................................1
1.1 Steam Turbine..............................................................................................1
1.2 Venturi Valve................................................................................................2
1.3 Objective of New venturi valve study............................................................5
CHAPTER 2: FUNDAMENTALS AND THEORY ANALYSIS...............................8
2.1 Mass Flow Rate........................................................................................8
2.2 Valve Passage Area..................................................................................10
2.3 Speed of sound and Mach number..........................................................11
2.4 Converging-Diverging Nozzle...................................................................14
2.5 Flow Axisymmetry......................................................................................15
2.6 Decibel A-weighting (dBA).........................................................................17
2.7 Sound Level Meter....................................................................................18
CHAPTER 3: RESULTS FROM THE PREVIOUS WORK...................................21
3.1 Mass Flow Rate................................................................................21
3.2 Flow Regions and Patterns...............................................................22
3.3 Flow Axisymmetry...................................................................................25
3.4 Flow Instability........................................................................................26
CHAPTER 4: EXPERIMENTAL SET UP............................................................33
4.1 Win Tunnel................................................................................................33
4.2 Short Seat and Long Seat..........................................................................35
4.3 Microphones..........................................................................................37
4.4 Accelerometers......................................................................................38
4.5 DSA 3017...............................................................................................39
4.6 LX-120 and Omega Amplifier..................................................................40
CHAPTER 5: RESULTS OF LONG SEAT.......................................................41
5.1 Mass Flow Rate..............................................................................41
5.2 Flow Regions and Patterns..............................................................47
5.3 Flow Axisymmetry............................................................................52
5.4 Flow Instability.................................................................................57
5.5 Noise........................................................................................64
5.6 Vibration.................................................... ..............................65

iv

CHAPTER 6: RESULTS OF SHORT SEAT..............................................69
6.1 Mass Flow Rate..............................................................................69
6.2 Flow Regions and Patterns.............................................................75
6.3 Flow Axisymmetry.........................................................................79
6.4 Flow Instability.................................................................................84
6.5 Noise................................................................ .............................88
6.6 Vibration........................................................................................89
CHAPTER 7: COMPARISON OF THE OLD VALVE AND NEW VALVES..........93
7.1 Mass Flow Rate..........................................................................................93
7.2 Flow Axisymmetry.......................................................................................95
7.3 Flow Instability............................................................................................98
7.4 Non-axisymmetric Unstable Flow.............................................................114
7.5 Noise and Vibration...................................................................................115
CHAPTER 8: CONCLUSION AND FUTURE WORK........................................116
BIBLOGRAPHY.................................................................................................119

v

LIST OF TABLES

Table 5.1 Valve passage area results from Section 2.2
Table 5.2 Long seat background noise
Table 5.3 Long seat noise at each channel at h/D=5.4%
Table 6.1 Valve passage area results from Section 2.2
Table 6.2 Short seat background noise
Table 6.3 Short seat noise at each channel at h/D=5.4%
Table 7.1 Old valve background noise
Table 7.2 Old valve noise at each channel at h/D=5.4%

vi

LIST OF FIGURES
Images in this thesis are presented in color.

Figure 1.1 Cross section of multiple venturi valves (after J.Hardin).......................3
Figure 1.2 Crack initiation location in the venturi valve (left) and fracture surface
(right) ................................................................................ ........................5
Figure 1.3 A ½ -scale venturi valve for a steam turbine..........................................6
Figure 1.4 Large Radius Cutout (LRCO) plug.......................................................6
Figure 1.5 Long seat (a) and Short seat (b)..........................................................7
Figure 2.1 Flow through an orifice meter..............................................................9
Figure 2.2 Quasi-normal height (h) and radius (R) on LRCO long seat...............11
Figure 2.3 Venturi valve (a) and converging-diverging nozzle (b).......................15
Figure 2.4 Taps on the plug and seat..................................................................16
Figure 3.1 Mass flow ratio versus pressure ratio at various openings.................22
Figure 3.2 Flow regions......................................................................................23
Figure 3.3 Flow patterns.....................................................................................24
Figure 3.4 Pressure oscillations on the plug at different pressure ratios at
h/D=0.085............................................................................................................27
Figure 3.5 Peak-to-Peak values of pressure oscillation on the plug.................31
Figure 4.1 Schematic figure of experiment set up...............................................34
Figure 4.2 Previous (a) and current (b) experiment set up..................................35
Figure 4.3 Short seat mounted on the metal plate...............................................36
Figure 4.4 Long seat mounted through the metal plate.......................................36
Figure 4.5 Fully closed LRCO long seat viewed through the inlet pipe...............37

vii

Figure 4.6 Microphones and their fixture.............................................................37
Figure 4.7 Accelerometers mounted on the inlet and outlet chest...................38
Figure 4.8 Digital Sensor Arrays (DSA) CH66 (a) and CH65 (b).........................39
Figure 4.9 TEAC LX-120 data recorder and Omega Amplifier............................40
Figure 5.1 Mass flow rates versus pressure ratio (PR) from h/D=5.4% to
h/D=103.3%.....................................................................................................41
Figure 5.2 Mass flow rates at low pressure ratios (PR=0.4~0.8) from h/D=43.5%
to h/D=103.3%.....................................................................................................42
Figure 5.3 Mass flow rates at middle pressure ratios (PR=0.8~0.9) from
h/D=43.5% to h/D=103.3%..................................................................................43
Figure 5.4 Mass flow rates at high pressure ratios (PR=0.9~0.99) from
h/D=43.5% to h/D=103.3%..................................................................................44
Figure 5.5 Mass flow ratio versus pressure ratio (PR) from small opening
(h/D=5.4%) to fully opening (h/D=70.7%)............................................................46
Figure 5.6 Long seat flow regions.......................................................................48
Figure 5.7 Cross section S4-S2 and S3-S1on the long seat...............................48
Figure 5.8 Flow pattern A....................................................................................49
Figure 5.9 Flow pattern B....................................................................................49
Figure 5.10 Flow pattern D..................................................................................50
Figure 5.11 Flow pattern E...................................................................................50
Figure 5.12 A plot of α versus pressure ratio (PR) on the inner ring of the LRCO
plug.....................................................................................................................52
Figure 5.13 A plot of α versus pressure ratio (PR) on the outer ring of the LRCO
plug......................................................................................................................52
Figure 5.14 A plot of α versus pressure ratio (PR) on the long seat....................53
Figure 5.15 A plot of α versus pressure ratio (PR) at h/D=5.4%..........................54
Figure 5.16 A plot of α versus pressure ratio (PR) at h/D=32.6%........................54

viii

Figure 5.17 A plot of α versus pressure ratio (PR) at h/D=54.4%........................55
Figure 5.18 Pressure oscillations versus Time at different pressure ratios at
h/D=5.44%...........................................................................................................57
Figure 5.19 Pressure oscillations versus Time at different pressure ratios at
h/D=16.3%...........................................................................................................61
Figure 5.20 Vibration at different pressure ratios at h/D=16.32%.......................66
Figure 6.1 Mass flow rates versus pressure ratio (PR) from h/D=5.4% to
h/D=81.6%...........................................................................................................69
Figure 6.2 Mass flow rates versus low pressure ratios (PR=0.4~0.8) from
h/D=43.5% to h/D=81.6%....................................................................................70
Figure 6.3 Mass flow rates versus middle pressure ratios (PR=0.8~0.9) from
h/D=43.5% to h/D=81.6%...................................................................................71
Figure 6.4 Mass flow rates versus high pressure ratios (PR=0.9~0.99) from
h/D=43.5% to h/D=81.6%...................................................................................72
Figure 6.5 Mass flow ratio versus pressure ratio (PR) from small opening
(h/D=5.4%) to fully opening (h/D=65.3%)............................................................74
Figure 6.6 Short seat flow regions.......................................................................76
Figure 6.7 Cross section S4-S2 and S3-S1 on the short seat.............................76
Figure 6.8 Flow pattern F.....................................................................................77
Figure 6.9 Flow pattern G....................................................................................77
Figure 6.10 Flow pattern I....................................................................................78
Figure 6.11 A plot of α versus pressure ratio (PR) on the inner ring of the LRCO
plug......................................................................................................................79
Figure 6.12 A plot of α versus pressure ratio (PR) on the outer ring of the LRCO
plug......................................................................................................................79
Figure 6.13 A plot of α versus pressure ratio (PR) on the short seat...................80
Figure 6.14 A plot of α versus pressure ratio (PR) at h/D=5.4%..........................81
Figure 6.15 A plot of α versus pressure ratio (PR) at h/D=32.6%........................82

ix

Figure 6.16 A plot of α versus pressure ratio (PR) at h/D=54.4%........................82
Figure 6.17 Pressure oscillations versus Time at different pressure ratio at
h/D=32.6%...........................................................................................................84
Figure 6.18 Vibration at different pressure ratios at h/D=16.32%........................89
Figure 7.1 Mass flow rate versus Area Ratio (AV/AM) at PR=0.9........................94
Figure 7.2 Mass flow rate versus Area Ratio (AV/AM) at PR=0.7.........................94
Figure 7.3 Mass flow rate versus Area Ratio (AV/AM) at PR=0.5.........................95
Figure 7.4 A plot of α versus PR on the inner ring at h/D=5.4%........................97
Figure 7.5 A plot of α versus PR on the outer ring at h/D=5.4%........................97
Figure 7.6 A plot of α versus PR on the outer ring at h/D=5.4%........................98
Figure 7.7 Gage pressure oscillations on the inner ring of the hemispherical plug
with the old seat at different pressure ratios at h/D=10.8%.................................99
Figure 7.8 Gage pressure oscillations on the inner ring of the LRCO plug with the
long seat at different pressure ratios at h/D=10.8%...........................................101
Figure 7.9 Gage pressure oscillations on the inner ring of the LRCO plug with the
short seat at different pressure ratios at h/D=10.8%....................................102
Figure 7.10 Gage pressure oscillations on the outer ring of the hemispherical
plug with the old seat at different pressure ratios at h/D=10.8%........................104
Figure 7.11 Gage pressure oscillations on the outer ring of the LRCO plug with
the long seat at different pressure ratios at h/D=10.8%.....................................106
Figure 7.12 Gage pressure oscillations on the outer ring of the LRCO plug with
the short seat at different pressure ratios at h/D=10.8%....................................107
Figure 7.13 Gage pressure oscillations on the old seat at different pressure ratios
at h/D=10.8%...................................................................................................109
Figure 7.14 Gage pressure oscillations on the LRCO long seat at different
pressure ratios at h/D=10.8%...........................................................................111
Figure 7.15 Gage pressure oscillations on the short seat at different pressure
ratios at h/D=10.8%..........................................................................................112

x

LIST OF SYMBOLS

α

Averaged pressure difference across the plug and seat

A, B, C, D, E

Long seat flow regions

AV

Valve passage area

AM

Minimum area in the long seat and the short seat

F, G, H, I

Short seat flow regions

LS

Long seat

OS

Old seat

P

Pressure

PL1~PL4

Taps numbers on the inner ring of the LRCO plug

PL5~PL8

Taps numbers on the outer ring of the LRCO plug

SS

Short seat

S1~S4

Taps number on both the long seat and the short seat

PR

Pressure ratio (Outlet plenum pressure/Inlet plenum pressure)

t

Time

xi

CHAPTER 1
INTRODUCTION
1.1 Steam Turbine
Steam turbines are devices that convert the mechanical energy of high
pressure steam or water vapor, into electrical energy by the use of a generator.
An early electric generator called the dynamo was created by British physicist
Michael Faraday in the 1830s. Other inventors invented new method in which a
steam engine could create the necessary rotary motion to produce electricity.
They soon encounter a limit of the number of revolutions per minute a steamdriven piston could provide. This problem was solved by Hero in A.D. 75.
Whereas Hero's steam turbine called for steam to be jetted from the perimeter of
the object to be rotated, the early 19th century engineers proposed directing
steam straight onto blades attached to the perimeter of a wheel. However, steel
was not yet strong enough to hold up to the stress of such rapid rotation. In 1884,
British engineer Charles Algernon Parsons put new steel technology to use. He
created a turbine which was capable of using compounded steam that turned a
dynamo at 18,000 revolutions a minute. In 1890, his steam turbine and
accompanying electric generator were installed in the Forth Banks power station.
The technology soon spread through Europe. Parsons also applied his steam
turbine technology to naval purposes, introducing his vessel, Turbinia, at Queen
Victoria's Diamond Jubilee in 1897. Parsons was subsequently commissioned to
fit a Royal Navy destroyer with a turbine engine.

1

In modern, the steam turbine continues to be a major factor in electric
power generation throughout the world. Even nuclear power plants use the heat
from a controlled nuclear chain reaction to produce needed steam. In the United
States, more than 88 percent of all electricity is produced by steam turbines.
Many of today's power plants use supercritical steam (when enough
pressure is applied to steam, the molecules are forced together to the point that
the water becomes more like a liquid again, while retaining the properties of a
gas), with pressure and temperature at the critical point. The resulting highpressure fluid of supercritical steam provides excellent energy efficiency. With
the aid of high pressure, supercritical steam turbines can be driven to much
higher speeds for the same amount of heat energy as traditional steam power.
They also release less CO2 exhaust into the atmosphere.
Because steam power plants are operated at higher temperatures and
pressures, the control of a turbine with a governor is essential. Uncontrolled
acceleration of the turbine rotor can lead to an overspeed trip, closing the steam
inlet valves and shutting off the fuel supply. If this fails then the turbine may
continue accelerating until it breaks apart. Therefore, the inlet control valve plays
an important role in the steam turbine.

1.2 Venturi Valve
As a turbine inlet control valve, venturi valves are widely used. The ventiru
valve consists of a plug and seat shown in Fig.1.1. The plug is either lifted or
lowed in a response to turbine‟s output and the seat is mounted on the bottom of

2

the valve chest. In modern turbines, multiple smaller valves are used instead of
one large valve to reduce a lifting force and improve turbine efficiency. Fig.1.1
shows the multiple venturi valves used in real steam turbines.

Figure1.1 Cross section of multiple venturi valves (after J.Hardin)

These valves are operated in sequence. When the turbine is not running, all
valves are in the closed position. The valve opening is controlled by the liftbar.
When the liftbar is lifted by the liftrod, the No. 1 valve is opened first, No.2
second, No. 3 third, and No. 4 last. Each valve starts to open as the previous
valve is almost fully open so there is overlap.

3

As a turbine became larger, the inlet valves are operated under very
severe conditions. For example, the steam inlet temperature, pressure, and
pressure drop through a fully open valve can reach as high as 1000F, 4,000Psi
and 200Psi respectively. In this situation, the high speed flow can be very
asymmetric and unstable. Thus, hydraulic forces due to the strong asymmetric
and unstable pressure distribution along the plug surface cause severe problems,
such as vibration and noise. If that occurs, the valve plug can be broken in a very
short time due to the large amplitude of forces, or in long-term operation due to
material fatigue. It is very costly to stop the turbine to replace a valve.
Since the 1960‟s, many valve failure incidents were reported due to
increasing turbine size and upstream steam pressure. Because of the
complicated nature of the flow through a valve, this research field was in a slow
progress until the early 70‟s. There were several papers investigating the valve
noise and failure problems. Among them, Araki‟s research is useful to
understand the flow phenomenon in the valve because he conducted
experiments with the venturi valve. His study proved that the valve plug vibration
was not caused by flow vibration resulted from of turbine feedback so adding a
damping is not a solution for the valve vibration. The main reason for the valve
failure was the flow-induced vibration.
A recent valve failure was reported in 1998. The valve started operation in a
multistage steam turbine in 1998. After 3 months of running, the No. 2 valve
failed after the crack developed in the location shown in Fig. 1.2.

4

Stem

Crack
Initiation
Location

Plug

Seat

Figure 1.2 Crack initiation location in venturi valve (left) and
fracture surface (right)

It happened as the No.1 valve was almost fully open and No. 2 valve was at an
opening of 0.147(h/D). The falling plug drove the seat into the steam chest wall
approximately 0.7in. Before the failure, there was higher noise coming out of the
machine, which means that fluid‟s chattering may have existed.

1.3 Objective of New venturi valve study
In 2003, Donghui Zang carried out experiments for a ½ -scale venturi valve
for a steam turbine shown in Fig.1.3. Flow asymmetry and instability were
determined from tests at different valve openings and pressure ratios. From his
study, it was confirmed that asymmetric and unstable flow occurs in the valve,
which can result in plug vibration causing valve failure.

5

Fig.1.3 A ½ -scale venturi valve for a steam turbine
For interpretation of the reference to color in this and all other figures, the reader
is referred to the electronic version of this thesis.

To

reduce

flow

non-axisymmetry

and

instability,

Elliotta-Ebara

Turbomachinery Company has designed a large radius cutout (LRCO) plug
shown in Fig.1.4 and a long seat (a) and a short seat (b) in Fig. 1.5.

Figure 1.4 Large Radius Cutout (LRCO) plug

6

(a) Long seat

(b) Short seat
Fig. 1.5 Long seat (a) and short seat (b)

The objective of new venturi valve study is to characterize a LRCO long
seat and short seat in terms of mass flow rate, flow axisymmery, and instability.
This research work has been achieved by the experimental investigation.

7

CHAPTER 2
FUNDAMENTALS AND THEORY ANALYSIS

As the plug is lifted from the fully-closed position, a space between the plug and
seat is created, and it is called a valve passage. Depending on the amount of lift,
the valve passage is the throat because it is the smallest area in the valve
system. However, when the valve reaches fully open, the surface area of the
valve passage is larger than the minimum area of the seat. This minimum seat
area then becomes the throat of the valve system. A fully-closed position is
defined when the plug is pushed all the way down on the seat and no flow can
pass by the valve. Mass flow will increase as the plug is lifted from the fullyclosed position to a position after the mass flow rate no longer changes. This
position is defined as the fully-open position.

2.1 Mass Flow Rate
Mass flow rate (

) is calculated by the relation

(1)
where ρ is the fluid density, V is the speed, and A is the area. The working fluid in
these experiments is air, which is modeled as a compressible, ideal gas. Air
density is obtained from the ideal gas law
(2)

8

where P is the static pressure, R is the ideal gas constant of air (287 J/kg-K), and
T is the static temperature.

Downstream
Pressure

P2

P1

Upstream
Pressure
Flow direction

Do

D

Figure 2.1 Flow through an orifice meter

Since fluid speed at the inlet of the pipe is not given, the discharge Q, equal to
the area multiplied by velocity at the orifice, is used to calculate mass flow rate.
The discharge Q is given by the relation

(3)

where K is a flow coefficient, Ao is the cross sectional area of the orifice, and h1
and h2 are the piezometric head

,

(4)

where the specific weight is γ = ρg and the height of piezometer location is z. If z1
and z2 are at the same height, the difference h1-h2 in Eq. (1) can be simplified in
terms of upstream and downstream pressures:

9

(5)

The unknown variables h1 and h2 can be calculated with known values shown in
Fig.1. To find K, the diameter ratio β (Do/D) is calculated from the known values
of Do and D and then K is interpolated from a graph [reference]. Now Eq. (1)
becomes

(6)

which is the final version used here to determine the mass flow rate from
pressure measurements upstream and downstream of the orifice plate.

2.2 Valve Passage Area
As the plug is lifted from the fully-closed position, a space between the
plug and seat is created and it is called a valve passage area. Depending on the
amount of lift, the valve passage area is the throat because it is the smallest area
in the valve system. However, when the valve reaches fully open, the valve
passage area is larger than the minimum area of the seat. This minimum seat
area then becomes the throat of the valve system. Therefore, the throat area (AT)
increases until the valve is fully open. From there AT remains constant.
The valve passage area is calculated by finding quasi-normal lines
between the seat and plug. Each quasi-normal line defines a cone in 3D. The
surface area of that cone is the area at the quasi-normal. The area is 2Rh,

10

where R is the radius at the midpoint of the quasi-normal and h is the height (or
length) of the quasi-normal. Based on the throat area calculation, several lines
are drawn to find the combination of R and h, which makes the smallest area
(throat area) at each opening. It is proved that the smallest area at each opening
is found when a quasi-normal line is the normal line between the plug and seat.

h
R

Figure 2.2 Quasi-normal height (h) and radius (R) on LRCO long seat

2.3 Speed sound and Mach number
Two important parameters in the study of compressible flow are the speed
of sound (or sonic speed) and the Mach number. To obtain a relation for the
speed of sound in a medium, consider a pipe that is filled with a fluid at rest. A
sonic wave is created when a piston fitted in the pipe is moved to the right with a
constant incremental velocity dV. As the wave front moves to the right through
the fluid at the speed of sound c, the region where the wave passes through

11

experiences an incremental change in thermodynamic properties while the fluid
in front of the wave still at rest. If a control volume is considered enclosing the
wave front, the mass balance right and left at the wave front for a steady-flow
process can be expressed as
(7)

(8)

By canceling the cross-sectional area A and neglecting the higher order terms,
this equation reduces to

(9)

No hear or work crosses the boundaries of the control volume during this steadyflow process, and the potential energy change can be neglected because of no
changes of height. Then, the steady-flow energy balance ein=eout becomes

(10)

It gives a simplified form as

(11)

where the second-order term dV2 is neglected. The amplitude of the ordinary
sonic wave is very small and does not cause any appreciable change in the
pressure and temperature of the fluid. Therefore, the propagation of a sonic wave
12

is not only adiabatic but also very nearly isentropic. Since it is isentropic, the
second Tds equation reduces to

(12)

By combining Eq.(9), (11), and (12) the speed of sound is expressed as

(13)

Eq. (13) can also be written as

(14)

where γ is the specific heat ratio of the fluid. When the fluid is an ideal gas
(P=ρRT), the differentiation form in Eq. (14) can be replaced with the form
differentiated in an ideal gas in term of density (ρ). Then, Eq. (14) becomes

(15)

Once the speed of sound is calculated, the Mach number (Ma) is easily obtained.
Ma is the ratio of an actual velocity of the fluid to the speed of sound.

(16)

13

The flow is called sonic when Ma =1, subsonic when Ma<1, supersonic when
Ma>1, hypersonic when Ma>>1, and transonic when Ma

.

2.4 Converging-Diverging Nozzle
An important relation for isentropic flow in ducts is

(17)

In supersonic flow (Ma>1), the term 1-Ma2 is negative, and thus dA and dP must
have opposite signs. That is, the pressure of the fluid must increase as the flow
area of the duct decreases and must decrease as the flow area of the duct
increases. Thus, at supersonic velocities, the pressure decreases in diverging
ducts (supersonic nozzles) and increases in converging duct (supersonic
diffusers).
To accelerate a fluid, a converging nozzle should be used at subsonic
velocities and a diverging nozzle at supersonic velocities. The highest velocity
achieved in a converging nozzle is the sonic velocity, which occurs at the exit of
the nozzle. Extending the converging nozzle by further decreasing the flow area
does not accelerate the fluid to supersonic. It just moves the exit further down
that the sonic velocity will occur instead of the original exit, and the mass flow
rate through the nozzle will decrease because of the reduced exit area.
Therefore, a diverging section should be added to a converging nozzle at the
throat to accelerate a fluid to supersonic velocities. The combined flow section is
14

called a converging-diverging nozzle. The venturi valve in Fig.2.3 (a) can be
idealized as a converging-diverging nozzle shown in Fig.2.3 (b).

Venturi Valve (a)

Converging-diverging nozzle (b)

Figure 2.3 Venturi valve (a) and converging-diverging nozzle (b)

2.4 Flow Axisymmetry
Fig.2.4 shows the locations of the static pressure taps on the plug and
seat of new LRCO valve system. Tap 1, 2, 3, and 4 on the seat are named as S1,
S2, S3, and S4 respectively. PS1, PS2, PS3, and PS4 are static pressures
measured from S1, S2, S3, and S4 on the seat. The time averaged of static
pressure differences across the seat is

which is defined as

(18)

Tap1, 2, 3, 4, 5, 6, 7,and 8 on the LRCO plug are names as PL1, PL2, PL3, PL4,
PL5, PL6, PL7, and PL8 respectively. PPL1, PPL2, PPL3, PPL4, PPL5, PPL6, PPL7, and
PPL8 are static pressures measured from tap PL1, PL2, PL3, PL4, PL5, PL6, PL7,
15

and PL8 respectively on the plug. Taps 1, 2, 3, and 4 are placed in an inner ring
of the plug and the rest are in an outer ring. The time averaged of static pressure
differences across the inner ring and outer ring are

and

respectively.

They are defined as

(19)

(20)

Flow direction

Flow direction

Inner ring
PL6
PL2

Outer ring

S2

PL3

PL5

PL7

PL1

S3

S1

PL4
S4

PL8
(a) Plug viewed from the bottom

(b) Seat viewed from the top

Figure 2.4 Taps on the plug and seat

16

2.5 Decibel A-weighting (dBA)
When sound travels through air, the atmospheric pressure changes
periodically. The frequency of sound is defined as the number of pressure
variations per second and it is measured in Hertz (Hz) that is defined as cycles
per second.
A loud noise usually has a larger pressure variation and a weak noise has
smaller pressure variation. Pressure variations are expressed in Pascal (N/m 2).
The softest sound a normal human ear can hear has a pressure variation of 20
µPa, which is called the threshold of hearing. On the other hand, the sound
pressure such as launching of the space shuttle can produce 2000 N/m 2. Instead
of expressing sound or noise in terms of Pascal, a logarithmic scale with 10 as
the base is used. Sound pressure level (SPL) is defined as

SPL(in dB)= 20 log10(Measured sound pressure/Reference pressure)

(21)

where the reference pressure is the hearing threshold of 20µPa or 20 x 10 -6. The
decibel scale gives a much better approximation to the human perception of
relative loudness because human ear responds to the logarithmic change in level.
A normal human ear is able to hear sounds with frequencies from 20 Hz to
20,000 Hz. The range of 20 Hz to 20,000 Hz is called the audible frequency
range. The entire audible frequency range can be divided into 8 or 24 frequency
bands know as octave bands or 1/3 octave bands respectively. The human ear
has peak response around 2,500 to 3,000 Hz and has a relatively low response
at low frequencies. Hence, the single sound pressure level obtained by simply

17

adding the contribution from all octave bands or 1/3 octave bands together will
not correlate well with the non-linear frequency responds of the human ear. This
has led to the concept of A-weighting scale. In the A-weighting scale, the sound
pressure levels for the lower frequency bands and high frequency bands are
reduced by certain amounts before they are being combined together to give one
single sound pressure level value. This valve is designated as dBA. The dBA is
often used because it reflects more accurately the frequency response of the
human ear.

2.6 Sound Level Meter
A-weighing is typically used in many commercial sound level meters. In
order to design a sound level meter in Matlab, mathematical concepts applied to
the sound level meter are reviewed.
The A-weighting filter is obtained from American National Standards
Institute (ANSI). The filter response

is defined as

(22)
A=

, B=
D=

, C=

,

, E=

The corresponding frequency of each DFT sample X[k] is obtained from

(23)

18

where fs is the smapling frequency, N is the length of the input sequence, and ∆f
is the frequency resolution. To achieve a real-time implementation of the sound
level meter, the FFT algorithm is used to evaluate DFT.
The A-weighted FFT samples are given by

(24)

where fk is k∆f. Since A-weighting has been applied in the frequency domain,
Parseval‟s relation is used to estimate the signal energy in the frequency domain.
Parseval‟s relation is given by

(25)

For real-valued input signals, the DFT samples have complex-conjugate
symmetry that is

(26)

Since the input time-domain samples must be real-valued, the frequency
spectrum must be symmetric about the N/2 sample. As a result, the signal
energy using only the first N/2+1 samples of the A-weighted spectrum is followed
as
(27)

19

As a result, Eq. (27) can be sued to estimate the total energy of the signal within
the observation interval. Since the sound level meter supports several sampling
rates and observations intervals, the average signal power should be used in the
follow analysis. The average instantaneous signal energy in an observation
interval of ∆t seconds is

(28)

Applying these equations, a numerical output in dBA (A-weighted decibels) is
defined as
Signal Level in dBA=10log10

where

is a measured sound pressure and

pressure of 0.0000204 Pa.

20

(29)

is the referenced sound

CHAPTER 3
RESULTS FROM THE PREVIOUS WORK
3.1 Mass Flow Rate
Mass flow rates increase dramatically before h/D=30% where h is the
height of the lifted plug from the seat and D is the diameter of the plug. Mass flow
rate continues to increase very slowly until about h/D=50%. After that, mass flow
rate no longer changes and remain constant. Therefore, the valve is fully opened
at h/D=50%. In order to compare mass flows at various valve openings, mass
flow rates are non-dimensionalized by the maximum (choked) mass flow rate at
the same valve opening. At small openings, for instance h/D=0.022, the flow is
choked at about PR=0.6. At larger openings, the choke pressure ratio is larger.
At h/D=0.734, flow is choked at PR=0.8. From Fig.3.1, the transonic region can
be roughly judged. For example, the flow is transonic and likely unstable at
between PR=0.65 and 0.8 at h/D=0.147.

21

Mass flow ratio

Pressure Ratio (P2/P1)
Fig.3.1 Mass flow ratio versus pressure ratio at various openings

3.2 Flow Regions and Patterns
Four major flow regions, A, C, D, and E are identified in terms of opening
ratio (h/D) and pressure ratio (PR) by considering pressure distributions,
pressure oscillation frequency, and amplitude.
One kind of pressure distribution can occur in regions A, D, and E. In
those regions, pressure oscillates with high frequency and small amplitude
because of strong turbulence. The most unstable flow can be found in region C.
In this region, several types of pressure distribution happen because of large
amplitude of pressure oscillation. All transition regions between C and other
regions are included in region C. Because the flow in the valve is three
dimensional, it is difficult to visualize. Thus, the flow pattern is determined from

22

measurement results of static pressure on the plug and seat. The static pressure
on the surface to which the flow is attached is lower than that on the surface with
which the flow is not in contact. Also, the pressure on the surface over which the
flow is steadily in contact varies randomly, with larger amounts of variation than
in the regions where flow is separated. These flow trends were proved
experimentally by Araki. The flow patterns and corresponding pressure
distribution are roughly drawn in Fig. 3.2. Although the flow patterns are not very
accurately visualized due to the complicated flow behavior and difficulty of
judgment from limited numbers of sensors, they can still help understand the flow

Pressure ratio (P2/P1)

phenomena.

Opening ratio (h/D)
Figure 3.2 Flow regions

23

Pattern A

Pattern D

/

Pattern C

Pattern C

Pattern C0

Pattern C1

Pattern E
Figure 3.3 Flow Patterns

Pattern A occurs in region A at a large pressure ratio at small openings.
Pattern A is not axisymmetric because flow attaches to the seat in one cross
section, while it expands to the center in the other cross section. Pattern D can
be found in region D. It is almost axisymmetric free jet due to supersonic result
from small opening and pressure ratio. After valve throat, flow expands and joins
24

together. Flow in region E is axisymmetric. Due to large mass flow rate at large
opening, flow is full of or almost (with some separation at downstream seat side)
full of the valve. Separation occurs in the center of plug. Flow in region C is most
unstable. A lot of reported failures occur in this region. For pattern C, flow
attaches to one side of the seat and separates from the other and joins together
near the plug center in one cross section. In the other cross section, flow
attaches to the seat sides and the two streams join farther from the plug center.
Part of the flow also attaches to the plug center. The „hollow‟ region actually is full
of flow shown in the other cross section and a vortex. This is a very unstable flow
pattern. It can change to three other patterns: C0, C1, and C/. At a small opening
(h/D<0.064), the flow pattern keeps changing between C0, C1, and sometimes C.
At somewhat larger opening, it keeps changing between C and C1. At opening
ratios larger than about 0.106 h/D, the flow pattern oscillates between patterns C
and C/. As the transient regions between different regions are also included in
region C, at the boundary of the region, some intermediate flow patterns happen.
It was found that flow in upper part of region C is transonic.

3.3 Flow Axisymmetry
At small openings, the plug side pressure difference has similar trends
and similar amplitudes to the seat side. The peak value occurs at some place
near the pressure ratio of 0.5 located in region C at most cases (at very small
opening, such as h/D=0.022, the peak pressure happens in region D). At a
middle opening (h/D=0.168), the seat side pressure difference is higher than that

25

on the plug side. At large openings, which are located in region E, the plug side
pressure difference is very small at large pressure ratio, similar to all other
openings. Then, as pressure ratio is decreased, the plug side pressure difference
increases and reaches a constant value at a pressure ratio of about 0.7. At this
opening, flow diffuses in the seat passage after the throat. At pressure ratios
between 0.65 and 0.85, asymmetric flow happens in the passage after the throat,
making the seat side pressure difference much larger. As the valve plug travels
to the fully open position, the maximum pressure difference in the plug side
decreases. The seat side pressure difference increases and reaches its peak
value at about 0.23 h/D opening, then drops down. Because the pressure
difference in the plug side causes hydraulic forces on the plug, for venturi valve,
smaller openings mean more possibility of valve failure when upstream pressure
is constant. The pressure curve shows that the maximum pressure difference
happens in the lower part of region C in most cases except the very small
opening situation such as h/D=0.02. Under very small opening situation, the
maximum pressure difference happens in region D.

3.4 Flow Instability
Pressure oscillation on the plug surface at 0.085 h/D opening is shown in
Fig. 3.4.For example, the curve 0 shows the absolute gauge pressure (psi)
oscillation at the plug center. The x-axis is time. At large pressure ratio, Pr=0.95,
pressure oscillation is random around some average mean value with small
amplitude. This is in region A. Flow is typically turbulent. At pressure ratio of 0.9,

26

it is clearly shown that the flow pattern jumps from A to C0 then quickly to C1. At
pressure ratio of 0.8, flow pattern A disappears, while patterns C0, C1, and C
keep changing to each other with large amplitude and low frequency. Decreasing
pressure ratio further, the pattern changing frequency becomes higher until the
pressure ratio reaches 0.4, below which the flow becomes pattern D, supersonic
free jet flow. The trend is the same for any other valve opening except the very
large opening (h/D>0.168). At very large openings, only pattern E occurs, as
shown in Fig. 6.21. Pressure oscillation is due to turbulence with small amplitude.

Gage pressure (psi)

Plug
Sensor#

Time (second)
(a) PR=0.95

Figure 3.4 Pressure oscillations on the plug at different pressure ratios
at h/D=0.085

27

Gage pressure (psi)

Plug
Sensor#

Time (second)
(b) PR=0.9
Figure 3.4 cont‟d

Gage pressure (psi)

Plug
Sensor#

Time (second)
(c) PR=0.8
Figure 3.4 cont‟d

28

Gage pressure (psi)

Plug
Sensor#

Time (second)
(d) PR=0.7
Figure 3.4 cont‟d

Gage pressure (psi)

Plug
Sensor#

Time (second)
(e) PR=0.6
Figure 3.4 cont‟d

29

Gage pressure (psi)

Plug
Sensor#

Time (second)
(f) PR=0.5
Figure 3.4 cont‟d

Gage pressure (psi)

Plug
Sensor#

Time (second)
(g) PR=0.4
Figure 3.4 cont‟d

30

To compare the pressure oscillation amplitude, the maximum peak-topeak value of oscillation ΔP is calculated. It is also nondimensionalized by the
inlet chest pressure P1. Pressure oscillation maximum peak-to-peak values at
different positions on the plug surfaces at three openings are shown in Fig. 3.5.
At small or large openings, a large amplitude pressure oscillation happens in the
region near the plug center, while at middle openings, it occurs on the whole
surface. The center pressure oscillation mainly causes vertical force oscillation,
and the pressure oscillation of the upstream side surface of the plug mainly
causes lateral force oscillation. So, for a real valve, large amplitude of vertical
vibration will happen at small openings, whereas large amplitude of both lateral
and vertical vibration will happen at middle openings. This may be a reason that
the recent reported valve failure happened at the opening ratio of 0.147 h/D.

ΔP/P1

Plug
Sensor#

Pressure Ratio (P2/P1)
(a) h/D=0.022
Figure 3.5 Peak-to-Peak values of pressure oscillation on the plug

31

ΔP/P1

Plug
Sensor#

Pressure Ratio (P2/P1)
(b) h/D=0.106
Figure 3.5 cont‟d

ΔP/P1

Plug
Sensor#

Pressure Ratio (P2/P1)
(c) h/D=0.189
Figure 3.5 cont‟d

32

CHAPTER 4
EXPERIMENTAL SET UP
4.1 Wind Tunnel
The apparatus used in these experiments is shown schematically in
Fig.4.1. A wind tunnel was used to investigate patterns of static pressure
distribution on both the old and the new governor valves. In addition to the static
pressure measurements made on the old valve in previous experiments using
pressure taps and dynamic sensor arrays (DSA Validyne model 3017),
microphones, dynamic pressure probes and accelerometers were used to make
measurements of noise, test rig vibration and inlet and outlet chest dynamic
pressure respectively. A ROOTS RAMTM Whispair 616 DVJ dry vacuum pump
was used to generate low pressure in the outlet chest to draw air through the
valve. The pressure ratio across the valve was controlled by means of a butterfly
valve which regulated the flow of air through a bypass system. To maintain a
constant pressure ratio for a given bypass valve position, the inlet and outlet
chests were designed with diameters which are much larger than the inside
diameter of the valve seat so that they act as plenums. In the wind tunnel,
pressure ratio (PR) is calculated by dividing the outlet chest pressure (P2) by the
inlet chest pressure (P1). At the smallest valve opening, the lowest pressure ratio
across the valve reached is about 0.194. When the valve is close to fully open,
the lowest pressure ratio obtained is about 0.4.

33

Air Inlet

Discharge

Air Inlet

1. Inlet silencer 2.Support structure 3.Orifice
4. Inlet chest 5. Test valve 6. Outlet chest
7. Bypass valve 8.Throttle valve 9.Vacuum pump
Figure 4.1 Schematic figure of experiment set up

The arrangement of the experimental setup was the same as the previous
experiments with the following exceptions: the inlet pipe was rotated 60 degrees
from its original location and the silencer was parallel to the primary pump
discharge. Fig.4.2 shows the previous and current experiment‟s setup.

(a) Previous experiment set up

34

(b) Current experiment set up
Figure 4.2 Previous (a) and current (b) experiment set up

4.2 Short Seat and Long seat
The short seat and the long seat are shown in Fig.4.3 and Fig.4.4
respectively. The short seat was mounted on the upper surface of the rectangular
metal plate which separates the inlet and outlet chests. Mounting through the
plate, as used for the LRCO long seat and the old valve seat, would cause the
lower pressure taps to be blocked by the plate. Mounting of the long seat
generated three main concerns: maximum lift height, inlet flow and ease of
experimental setup. If the seat sits on the upper surface of the separating plate,
its upper surface encroaches on the plane of the inlet pipe, the maximum valve
lift is reduced, and the plumbing of the static pressure taps is easier. Mounting
the seat through the separating plate, as the old valve seat was designed to be
mounted, increased the maximum lift height, lowered the upper surface of the
seat by 0.25 inches and made the plumbing more difficult (i.e., the tubing must
be cut out to remove the seat and re-sealed each time the seat is mounted).
35

Because the maximum required lift was unknown, it was decided to mount the
seat through the separating plate.

Figure 4.3 Short seat mounted on the metal plate

Figure 4.4 Long seat mounted through the metal plate

Fig.4.5 is a picture of the LRCO long seat in the fully closed position as seen
from the inlet pipe. When the LRCO valves are at the fully closed position, Tap 6
on the plug lines up with Tap 2 on the seat, see Fig.2.4 for numbering. Although
the long and short seats were mounted in different vertical locations, all taps
were aligned similarly.

36

Figure 4.5 Fully closed LRCO long seat viewed
through the inlet pipe

4.3 Microphones
Four G.R.A.S high-sensitivity array microphones having a nominal
sensitivity of 50mV/Pa at 250Hz are used to measure noise coming out of the
valve. Three microphones were arranged around the inlet chest in the plane of
the inlet pipe located at 90, 180, 270 degrees from the centerline of the inlet pipe
and one foot away from the outer surface of the inlet/outlet chest. The last
microphone was placed one foot above the top of the inlet chest and
approximately in line with the mean diameter of the inlet chest. Fig.4.6 shows the
fixture holding microphones.

Figure 4.6 Microphones and their fixture

37

4.4 Accelerometers
Five PCB accelerometers having a sensitivity of 1.043 mV/m/s2are used to
measure the vibration of the inlet and outlet chests. The five accelerometers
were mounted on the outer surface of the inlet and outlet chests with Loctite 454
instant adhesive. Two were located 5.5 inches above the steel plate separating
the inlet and outlet chests. These were placed on the inlet chest 90 and 180
degrees from the inlet pipe so that they were aligned with the microphones in the
horizontal plane of the inlet. The other accelerometers were attached to the outlet
chest 5.5 inches below the steel plate dividing inlet from outlet and in the same
vertical planes as the two accelerometers attached above this plate. The last
accelerometer was mounted on the top of the test assembly under the upper
microphone.

Figure 4.7 Accelerometers mounted on the inlet and outlet chest

38

4.5 DSA 3017
DSA 3017 is a digital sensor array measuring static pressures. Two
different pressure ranges of DSA 3017s with system accuracy

full scale

are used. The DSA 3017‟s model 66, left in Fig.4.8, has a small pressure
range

. Since there are small pressure changes in the inlet chest and at

the orifice in the inlet pipe, tubings from the inlet chest and the upstream and
downstream at the orifice are connected to the model 66. The DSA 3017‟s model
65, on the other hand, can measure large pressure ranges

. Thus, the old

valve and new LRCO vales in which large pressure changes are anticipated are
connected to the model 66, right in Fig. 4.8. Both DSA 3017s are connected to a
L-Com Ethernet converter which is connected to a laptop for data recording. DSA
Link 3, computer software for communicating with DSA3017s, is setup to make
static pressure measurements at rate of 25Hz.

(a) DSA CH66

(B) DSA CH65

Figure 4.8 Digital Sensor Arrays (DSA) CH66 (a) and CH65 (b)

39

4.6 LX-120 and Omega Amplifier
The signals from the microphones, accelerometers, and dynamic pressure
probes were amplified using an Omega external amplifier if input signals were
weak. The amplified data were sent to LX-120. LX-Navi, computer software for
communicating with LX-120, was used to record data on a laptop computer. The
LX-120 and Omega amplifier are shown in Fig.4.9.

LX-120

Omega amplifier

Figure 4.9 TEAC LX-120 data recorder and Omega Amplifier

40

CHAPTER 5
RESULTS OF LONG SEAT
5.1 Mass Flow Rate
0.35

h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38.0%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%
h/D=87.0%
h/D=92.5%
h/D=97.9%
h/D=103.3%

Mass flow rate(kg/s)

0.3

0.25

0.2

0.15

0.1

0.05

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.1 Mass flow rates versus pressure ratio (PR) from h/D=5.4% to
h/D=103.3%

In this experiment, the plug is lifted by h/D= 5.4% from the fully closed
position, and the mass flow rate is calculated at each opening. Fig.5.1 shows the
results of mass flow rates at each opening ratio. From h/D=5.4% to h/D=27.2%,
mass flow rate increases about 5% at each opening. After h/D=27.2%, the
increase of mass flow rate reduces about 2% and then the increase decreases
less than 1% at high opening ratios. Mass flow rates still increases very slightly
41

as seen in Fig.5.1. In order to investigate the increase of the mass flow rate for
opening ratios of h/D=32.6% and higher, Fig.5.1 is divided into three sections:
lower pressure ratios from PR=0.4 to 0.8, Fig.5.2, middle pressure ratios from
PR=0.8 to 0.9, Fig.5.3, and high pressure ratios from PR=0.9 to 0.99%, Fig.5.4.

0.255
0.254
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%
h/D=87.0%
h/D=92.5%
h/D=97.9%
h/D=103.3%

Mass flow rate(kg/s)

0.253
0.252
0.251
0.25
0.249
0.248
0.247
0.4

0.5

0.6

0.7

0.8

PR
Figure 5.2 Mass flow rates versus low pressure ratios (PR=0.4~0.8) from
h/D=43.5% to h/D=103.3%

At the low pressure ratios shown in Fig.5.2, mass flow rates from h/D=43.5%
to h/D=76.1% increase and decrease irregularly; the mass flow rate at h/D=54.4%
is less than h/D=48.9%. On the other hand, the mass flow rate from h/D=81.6%
to 103% behaves similarly; not much mass flow rate changes from PR=0.4 to 0.5
and decrease, increase, and decrease from PR=0.5 to 0.8 identically. Maximum

42

mass flow rate is observed at h/D=70.7%. The h/D=76.1% shows the similar
mass flow rate as h/D=70.7% from PR=0.4 to PR=0.6 and both mass flow rates
decrease after PR=0.6. The rate of decrease at h/D=76.1% is greater than
h/D=70.7% so the mass flow rate at h/D=70.7% shows the maximum at the rest
of pressure ratios. Therefore, the valve is considered at the fully open at
h/D=70.7% in the low pressure ratios and it is investigated at the middle and high
pressure ratios.

0.255
0.25
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%
h/D=87.0%
h/D=92.5%
h/D=97.9%
h/D=103.3%

Mass flow rate(kg/s)

0.245
0.24
0.235
0.23
0.225
0.22
0.215
0.21
0.8

0.82

0.84

0.86

0.88

0.9

PR
Figure 5.3 Mass flow rates versus middle pressure ratios (PR=0.8~0.9) from
h/D=43.5% to h/D=103%

At the middle pressure ratios shown in Fig.5.3, all mass flow rates tend to
decrease as the pressure ratio increases. Mass flow rates at high opening ratios

43

from h/D=81.6% to 103.3% are less than those opening ratios from h/D=43.5% to
h/D=76.1%. Several opening ratios are within a narrow band of high mass flow
rates through the middle pressure ratios. In this band, h/D=59.8% has a
maximum mass flow rate, and h/D=70.7% is also observed. However, the mass
flow rate‟s difference between h/D=59.8% and 70.7% is very small. Therefore, it
can be considered that the mass flow rate at h/D=70.7% is still eligible for the
maximum mass flow rate at the middle pressure ratios.

0.24
0.22
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%
h/D=87.0%
h/D=92.5%
h/D=97.9%
h/D=103.3%

Mass flow rate(kg/s)

0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.9

0.92

0.94

0.96

0.98

PR
Figure 5.4 Mass flow rates versus high pressure ratios (PR=0.9~0.99) from
h/D=43.5% to h/D=103.3%

At the high pressure ratios shown in Fig.5.4, all mass flow rates decrease
almost linearly without large fluctuations. A narrow band of mass flow rates is

44

observed as the middle pressure ratios and the mass flow rate at h/D=70.7% is
within this band. The mass flow rate difference at each opening over the
pressure ratios is much smaller than the middle opening ratios. It is difficult to
determine the maximum mass flow rate because all mass flow rates are also
identical. However, the mass flow rate at h/D=59.8% has a slightly high mass
flow rates among other opening ratios. The mass flow rate difference between
h/D=59.8% and h/D=70.7% in high pressure range is much smaller than the
previous pressure ratios. Based on these observations and those in the other
pressure ratios, a full-open lift height for New LRCO long seat can be determined
to be h/D=70.7%. Valve passage area (AV) and area ratio (AV/AM), which
corresponds to opening ratios, are tabulated in Table 5.1.

Table 5.1 Valve passage area results from Section 2.2
h/D (%)
5.4
10.8
16.3
21.7
27.2
32.6
38.0
43.5
48.9
54.4
59.8
65.3
70.7

h(in)
0.055
0.100
0.145
0.195
0.245
0.300
0.370
0.413
0.480
0.546
0.615
0.681
0.750

R(in)
1.019
1.037
1.055
1.074
1.094
1.115
1.142
1.110
1.129
1.147
1.129
1.142
1.147

AV
0.352
0.651
0.961
1.315
1.683
2.101
2.655
2.880
3.405
3.933
4.362
4.889
5.406

AV/AM
0.191
0.354
0.522
0.714
0.914
1.141
1.442
1.564
1.849
2.136
2.368
2.655
2.935

AV=Valve passage area (in2), AM=Minimum area in the seat (in2)

To more directly compare mass flow rates at different opening ratios, the
mass flow rates are non-dimensionalized by the maximum measured mass flow
45

rate at the same opening and it is called mass flow ratio. The maximum
measured mass flow rate is defined at the pressure ratio where mass flow rate
does not increase anymore even if pressure ratio further reduces. Since this
maximum mass flow rate represents a choked mass flow rate at which the Mach
number is 1, mass flow ratios are representative of the Mach number. Since the
Mach number of transonic flow is approximately between 0.8 and 1.2, transonic
flow regimes can now be defined by mass flow ratios between about 0.8 and 1.
Fig.5.5 shows the mass flow ratios versus pressure ratio (PR) at different valve
openings.

1.1
1
0.9

Mass flow ratio

0.8

h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38.0%
h/D=70.7%

0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.5 Mass flow ratio versus pressure ratio (PR) from small opening
(h/D=5.4%) to fully opening (h/D=70.7%)

46

At small openings, from h/D=5.4% to 10.8%, the flow is choked at PR=0.6.
As the valve opens more, the flow becomes choked at higher pressure ratio.
From h/D=16.3% to 21.7%, the flow is choked at PR=0.7, and after h/D=21.7%
the flow is choked at PR=0.8. From Fig.5.6, the transonic regimes at h/D=5.44%
and h/D=10.88% are determined to be between PR of 0.4 and about 0.8. For the
rest of the valve openings, the transonic regime is found between PR of 0.4 and
about 0.9. In the transonic regime non-axisymmetry and instability can occur.

5.2 Flow Regions and Patterns
The flow is attached to the lower pressure side because high pressure
sides push flow to low pressure sides. Thus, the lower pressure side is in contact
with the flow while the high pressure side is not. The pressure on the surface
where the flow is steadily in contact varies randomly with larger amounts of
variation than in the regions where flow is separated. These trends were proved
by the experimental results of Araki. By applying these trends to the long seat
with consideration of pressure distribution and pressure oscillation, five flow
regions (A, B, C, D, and E) are roughly drawn in terms of valve opening and
pressure ratio shown in Fig.5.6.

47

1

0.9

C

A

PR

0.8

D

0.7

0.6

E

B

0.5

0.4

10

20

30

40

50

60

70

80

90

Opening ratio (h/D)
Figure 5.6 Long seat flow regions

S2

S3

S1

S4

Figure 5.7Cross section S4-S2 and S3-S1 on the long seat

48

100

(a) Cross section S4-S2

(b) Cross section S3-S1

Figure 5.8 Flow pattern A

(a) Cross section S4-S2

(b) Cross section S3-S1

Figure 5.9 Flow pattern B

49

(a) Cross section S4-S2

(b) Cross section S3-S1

Figure 5.10 Flow pattern D

(a) Cross section S4-S2

(b) Cross section S3-S1

Figure 5.11 Flow pattern E

50

Pattern A happens in region A. In region A, pressure oscillates with small
amplitude and pressure differences across the seat are almost identical. By
looking at the cross section S4-S2 and S3-S1 in Fig.5.7, the flow attaches to the
seat shown in Fig.5.8. In region B, Pattern B can occur in Fig.5.9. PS2 and PS1
are slightly larger than PS4 and PS3 so the flow is attached to the side of S4 and
S3. Since the pressure differences are very small, the flow is almost
axisymmetric. In region D, PS4 and PS3 are larger than PS2 and PS1. PS4 and PS3
have almost the same pressure variations as well as PS2 and PS1. Thus, pattern
D in Fig.5.10 can be observed. In region C, pressure oscillates with large
amplitude and pressure differences across the seat are very large so the flow is
unstable. The flow pattern changes from pattern B to D or D to B irregularly
(Figure of pattern C is not shown because it is the combination of pattern B and
D shown). In region E, PS3 is relatively larger than Ps1 while PS4 and PS2 are
almost identical. Thus, flow pattern E in Fig.5.11 can be observed.

51

5.3 Flow Axisymmetry

0.025
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%

0.02



0.015

0.01

0.005

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.12 A plot of α versus pressure ratio (PR) on the inner ring of LRCO plug

0.08
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%

0.07
0.06



0.05
0.04
0.03
0.02
0.01
0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.13 A plot of α versus pressure ratio (PR) on the outer ring of LRCO plug

52

0.09
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%

0.08
0.07
0.06



0.05
0.04
0.03
0.02
0.01
0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.14: α at different pressure ratio (PR) on the long seat

A brief examination of Fig. 5.12, 5.13, and 5.14 shows that a few general
trends are present in the value of α. In both the inner ring, Fig. 5.12, and outer
ring, Fig. 5.13, the value of α tends to decrease as the pressure ratio increases at
a given opening. The inner ring is axisymmeric over the entire range of
experiments, but there is no clear trend in terms of opening. The outer ring is not
axisymmetric for the full range of tests; however, αout reduces as the valve opens
and becomes axisymmetric. General trends in the seat, Fig. 5.14, are harder to
identify, but there does seem to be a range of openings where α behaves as it
did in the outer ring (h/D=32.6% to h/D=48.9%). Also based on these figures,
three different ranges of openings can be identified where similar trends, specific
to each figure, occur. These ranges are small openings (h/D=5.4% to 27.2%,
indicated by solid lines), intermediate openings (h/D=32.6% to 48.9%, indicated

53

by dashed-dot lines), and large openings (h/D=54.4% to h/D=70.7%, indicated by
solid lines with asterisk).

0.08
0.07
0.06



0.05
Inner ring
Outer ring
Seat

0.04
0.03
0.02
0.01
0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.15 A plot of α versus pressure ratio (PR) at h/D=5.4%

0.03

0.025



0.02
Inner ring
Outer ring
Seat

0.015

0.01

0.005

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.16 A plot of α versus pressure ratio (PR) at h/D=32.6%

54

0.045
0.04
0.035
0.03
Inner ring
Outer ring
Seat



0.025
0.02
0.015
0.01
0.005
0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 5.17 A plot of α versus pressure ratio (PR) at h/D=54.4%

The combinations of the inner ring, outer ring and seat at each beginning
opening ratio in the three different ranges of openings are shown in Fig. 5.15,
5.16, and 5.17. At the smallest opening, h/D=5.4%, a difference in axisymmetry
conditions is observed in the inner ring, outer ring, and seat in Fig.5.15. In the
inner ring αIn is less than 0.02 over the entire range of pressure ratios so
axisymmetric flow pattern is observed. However, αOut is much greater than the
inner ring. The outer ring has a value of α about 0.07 from PR=0.4 to 0.6. After
PR=0.6, αOut begins to decrease and becomes less than 0.02 at about PR=0.93.
The high values of α at the outer ring are caused by relatively higher pressure at
PL6 and PL7 than PL5 and PL8. This similar phenomenon is observed in the
seat. Relatively high pressures at S2 and S3 cause non-axisymmery on the seat.
Similar trends are observed in the inner ring, outer ring, and seat until h/D=27.2%.
55

At intermediate openings, h/D=32.6%, some changes of α are observed in the
outer ring and seat, while the inner ring is still axisymmetric shown in Fig.5.16.
The pressure difference across the outer ring is reduced so the outer ring
becomes axisymmetric. For the seat, unlike at the small opening, the variation of
αSeat shows a trend like αOut; αSeat looks like αOut is shifted up about 0.01 in the
value of α. As the plug continues to be lifted, the pressure difference on the outer
ring is getting smaller as well as on the seat side. After h/D=32.6%, the inner ring,
outer ring, and seat become axisymmetric. At large openings, h/D=54.4%,
relatively high pressures at S3 and S4 appear and these cause non-axisymmetry
on the seat while the pressure differences across the inner and outer ring are
small enough to stay as axisymmetry in Fig. 5.17. A peak of αSeat is observed at
PR=0.6 with almost the same magnitude of α at PR=0.5 at h/D=5.44%. As the
plug is lifted toward the fully open, the peak is found at PR=0.8 and 0.9 at
h/D=59.8% and 65.3% respectively. At fully opening, the peak comes back to
PR=0.6 and stays there even though the plug is lifted higher.

56

5.3 Flow Instability
Pressure oscillation on the seat at different pressure ratios at h/D=5.44% is
shown in Fig.5.18. The x axis is time (second) and the y axis is gauge pressure
(lb/in2). All figures in Fig.5.18 shows pressure oscillation during 10 seconds. S1,
S2, S3, and S4 are tap numbers for the seat shown in Fig. 2.4(b).

Pressure [psi]

-1

-1.5
S1
S2
S3
S4

-2

-2.5
0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 5.18 Pressure oscillations versus Time at different pressure ratios
at h/D=5.44%

57

-3

Pressure [psi]

-3.2
-3.4

S1
S2
S3
S4

-3.6
-3.8
-4
-4.2
-4.4
0

2

4

6

8

10

Time [s]
(b) PR=0.8
Figure 5.18 Cont‟d

-4.6
-4.8

Pressure [psi]

-5
-5.2

S1
S2
S3
S4

-5.4
-5.6
-5.8
-6
0

2

4

6

Time [s]
(c) PR=0.7
Figure 5.18 Cont‟d

58

8

10

-6.4
-6.6

Pressure [psi]

-6.8
-7

S1
S2
S3
S4

-7.2
-7.4
-7.6
-7.8
0

2

4

6

8

10

Time [s]
(d) PR=0.6
Figure 5.18 Cont‟d

-8.2
-8.4

Pressure [psi]

-8.6
-8.8

S1
S2
S3
S4

-9
-9.2
-9.4
-9.6
0

2

4

6

Time [s]
(e) PR=0.5
Figure 5.18 Cont‟d

59

8

10

Pressure [psi]

-9

-9.5
S1
S2
S3
S4

-10

-10.5
0

2

4

6

8

10

Time [s]
(f) PR=0.4
Figure 5.18 Cont‟d

Pressures on S1, S2, S3, and S4 oscillate with large amplitude at PR=0.9
in Fig.5.18 (a). Since all pressures on the seat have almost similar large pressure
variations, it is turbulent and is at high pressure range in region C. As pressure
ratio decreases, from (b) ~ (f) in Fig.5.18, pressure oscillation is random around
some average mean value with small amplitude. S3 has the largest pressure
among others. S4 is the second largest pressure, and S1 and S2 have almost
the same pressure variation trend. Thus, it is in region D. As time changes, any
sudden increase or decrease in pressure are not observed. Pressures oscillate at
the average mean value within recorded time. These trends are the same for
other opening ratios. However, this trend is not observed at h/D=16.3%. At this
opening ratio, all pressures are turbulent over the entire pressure ratios.

60

Pressure fluctuates with a clear background oscillation super-posed on the trace.
It is shown in Fig.5.19.

-2

Pressure [psi]

-2.2
-2.4
S1
S2
S3
S4

-2.6
-2.8
-3
-3.2
-3.4
0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 5.19 Pressure oscillations versus Time at different pressure ratios
at h/D=16.3%

61

-4.6

Pressure [psi]

-4.8
-5
S1
S2
S3
S4

-5.2
-5.4
-5.6
-5.8
-6
0

2

4

6

8

10

Time [s]
(b) PR=0.8
Figure 5.19 Cont‟d

-6.2

Pressure [psi]

-6.4
-6.6
S1
S2
S3
S4

-6.8
-7
-7.2
-7.4
-7.6
0

2

4

6

Time [s]
(c) PR=0.7
Figure 5.19 Cont‟d

62

8

10

-7.4

Pressure [psi]

-7.6
-7.8
S1
S2
S3
S4

-8
-8.2
-8.4
-8.6
-8.8
0

2

4

6

8

10

Time [s]
(d) PR=0.6
Figure 5.19 Cont‟d

Pressure [psi]

-8.5

-9
S1
S2
S3
S4

-9.5

-10
0

2

4

6

Time [s]
(e) PR=0.5
Figure 5.19 Cont‟d

63

8

10

-10.4
-10.6

Pressure [psi]

-10.8
-11

S1
S2
S3
S4

-11.2
-11.4
-11.6
-11.8
0

2

4

6

8

10

Time [s]
(f) PR=0.4
Figure 5.19 Cont‟d

5.4 Noise
In order to compare the sound pressure levels as measured at each
microphone location over the range of pressure ratios tested, an example set of
measurements made at h/D = 5.44% is tabulated in Table.3 with background
noise in Table2. Major differences are not observed at each channel and overall
dBA variations are between 120 and 150 for each opening. At PR=70%, the
maximum value of dBA is found for each valve. For all openings the maximum
sound pressure level was found between PR=0.7 and 0.8. In this pressure ratio
range, a loud whistling sound was produced by the bypass valve.

64

Table 5.2 Long seat background noise
dBALS

CH1
CH2
CH3
CH4
121.03 120.44 121.96 121.98
LS: Long Seat

Table 5.3 Long seat noise at each channel at h/D=5.4%
PR
0.99
0.9
0.8
0.7
0.6
0.5
0.4

CH1
128.48
126.81
136.28
145.75
139.18
138.43
131.19

CH2
120.71
127.23
135.92
143.99
138.18
139.18
131.46

CH3
121.64
128.52
137.23
145.20
140.15
139.57
130.87

CH4
121.17
127.43
137.32
145.64
141.73
141.00
130.92

5.5 Vibration
In Fig.5.20, A1 means an accelerometer connected to channel 1 on the
LX-120;

the

same

naming

convention

is

followed

for

the

remaining

accelerometers. Accelerometer results of the LRCO long seat at h/D=16.32% is
shown in Fig.5.20 as an example. The maximum amplitudes are found at around
4000 Hz. As pressure ratio decreases, peaks are observed at high frequency
range. This phenomenon is observed at other opening ratios. Most of peaks
observed are from A4.

65

18
A1
A2
A3
A4
A5

16

Amplitude (m/s2)

14
12
10
8
6
4
2
0

0

1000

2000

3000

4000

5000

6000

Frequency (Hz)
(a) PR=0.9
Figure 5.20 Vibration at different pressure ratios at h/D=16.32%

80
A1
A2
A3
A4
A5

70

Amplitude (m/s2)

60
50
40
30
20
10
0

0

1000

2000

3000

4000

Frequency (Hz)
(b) PR=0.8
Figure 5.20 Cont‟d

66

5000

6000

35
A1
A2
A3
A4
A5

Amplitude (m/s2)

30
25
20
15
10
5
0

0

1000

2000

3000

4000

5000

6000

Frequency (Hz)
(c) PR=0.7
Figure 5.20 Cont‟d

45
A1
A2
A3
A4
A5

40

Amplitude (m/s2)

35
30
25
20
15
10
5
0

0

1000

2000

3000

Frequency (Hz)
(d) PR=0.6
Figure 5.20 Cont‟d

67

4000

5000

6000

35
A1
A2
A3
A4
A5

Amplitude (m/s2)

30
25
20
15
10
5
0

0

1000

2000

3000

4000

5000

6000

Frequency (Hz)
(e) PR=0.5
Figure 5.20 Cont‟d

25
A1
A2
A3
A4
A5

Amplitude (m/s2)

20

15

10

5

0

0

1000

2000

3000

Frequency (Hz)
(f) PR=0.4
Figure 5.20 Cont‟d

68

4000

5000

6000

CHAPTER 6
RESULTS OF SHORT SEAT
6.1 Mass Flow Rate
0.35
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38.0%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%

Mass flow rate(kg/s)

0.3

0.25

0.2

0.15

0.1

0.05

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 6.1 Mass flow rates versus pressure ratio (PR) from h/D=5.4% to
h/D=81.6%

Mass flow rates for the LRCO short seat at different pressure ratios at
various opening are shown in Fig. 6.1. The plug is lifted by h/D= 5.4 % from the
fully-closed position and the mass flow rate is calculated at each opening. From
h/D=5.4% to h/D=27.2%, the mass flow rate increases about double at each
opening. After h/D=27.2%, the increase of mass flow rate reduces about 2% and
then the increase decreases less than 1% at high opening ratios. Mass flow rates

69

still increase very slightly as seen in Fig.6.1. In order to investigate the increase
of the mass flow rates for opening ratios of h/D=32.6% and higher, Fig.6.1 is
divided into three sections; lower pressure ratios from PR=0.4 to 0.8, Fig.6.2,
middle pressure ratios from PR= 0.8 to 0.9, Fig.6.3, and high pressure ratios from
PR=0.9 to 0.99, Fig.6.4.

0.255

Mass flow rate(kg/s)

0.25

h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%

0.245

0.24

0.235

0.23

0.225
0.4

0.5

0.6

0.7

0.8

PR
Figure 6.2 Mass flow rates versus low pressure ratios (PR=0.4~0.8) from
h/D=43.5% to h/D=81.6%

At the low pressure ratios shown in Fig.6.2, mass flow rates from h/D=43.5%
to h/D=59.8% increase as the plug is lifted. The mass flow rate at h/D=65.3% is
slightly less than at h/D=59.8%, but it has a very similar trend as the mass flow
rate at h/D=59.8%. At each opening ratio, the mass flow rate does not change
much from PR=0.4 to 0.7 and then mass flow rates tend to decrease. After

70

h/D=65.3%, mass flow rates decrease and they are less than the previous
opening ratios. Therefore, the LRCO short seat is considered fully opened at
either h/D=59.8% or 65.3%.

Mass flow rate(kg/s)

0.25

0.24
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%

0.23

0.22

0.21

0.2
0.8

0.82

0.84

0.86

0.88

0.9

PR
Fig.6.3 Mass flow rates versus middle pressure ratios (PR=0.8~0.9) from
h/D=43.5% to h/D=81.6%

At the middle pressure ratios shown in Fig.6.3, all mass flow rates tend to
decrease as pressure ratio increases. Larger mass flow rates are found as the
plug is lifted from h/D=43.5% to 65.3%. This order is broken after h/D=65.3%.
Mass flow starts to decrease and all mass flow rates from h/D=70.7% to 81.6%
are less than h/D=65.3%. Mass flow rates at h/D=59.8% and 70.7% increase a
little after PR=84% but their mass flow rates are not much different from

71

h/D=65.3%. Thus, the LRCO short seat is considered to be fully opened at
h/D=65.3%.

0.25

Mass flow rate(kg/s)

0.2
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%
h/D=70.7%
h/D=76.1%
h/D=81.6%

0.15

0.1

0.05

0.9

0.92

0.94

0.96

0.98

PR
Figure 6.4 Mass flow rates versus high pressure ratios (PR=0.9~0.99) from
h/D=43.5% to h/D=81.6%

At the high pressure ratios shown in Fig.6.4, all mass flow rates decrease
almost linearly without large fluctuations. A narrow band of mass flow rates is
observed as the middle pressure ratios and the mass flow rate at h/D=65.3% is
within this band. The mass flow rate difference at each opening over the
pressure ratios is much smaller than the middle opening ratios. It is difficult to
determine the maximum mass flow rate because all mass flow rates are almost
identical. However, it can be determined from Fig.6.4 that the mass flow rate at
h/D=81.6% has a slightly high mass flow rates among other opening ratios. The

72

mass flow rate difference between h/D=65.3% and h/D=81.6% at high pressure
ratios is much smaller than the previous pressure ratios. Therefore, the LRCO
short seat is considered to be fully opened at h/D=65.3%.Based on observations
from the small pressure ratios to the high pressure ratios and those in the other
pressure ratios, a full-open lift height for the LRCO short seat can be determined
to be h/D=65.3%.
To more directly compare mass flow rates at different opening ratios, the
mass flow rates are non-dimensionalized by the maximum measured mass flow
rate at the same opening and it is called mass flow ratio. The maximum
measured mass flow rate is defined at the pressure ratio where mass flow rate
does not increase anymore even if pressure ratio further reduces. Since this
maximum mass flow rate represents the choked mass flow rate at which the
Mach number is 1, mass flow ratios are representative of the Mach number.
Since Mach number of transonic flow is approximately between 0.8 and 1.2,
transonic flow regimes can now be defined by mass flow ratios between about
0.8 and 1. Fig.6.5 shows mass flow ratios at different pressure ratios (PR) at
different valve openings.

73

Table 6.1 Valve passage area results from Section 2.2
h/D(%)
5.4
10.8
16.3
21.7
27.2
32.6
38.0
43.5
48.9
54.4
59.8
66.3

h(in)
0.055
0.100
0.145
0.195
0.245
0.300
0.370
0.413
0.480
0.546
0.615
0.681

R(in)
1.019
1.037
1.055
1.074
1.094
1.115
1.142
1.110
1.129
1.147
1.129
1.142

AV
0.352
0.651
0.961
1.315
1.683
2.101
2.655
2.880
3.405
3.933
4.362
4.889

AV/AM
0.191
0.354
0.522
0.714
0.914
1.141
1.442
1.564
1.849
2.136
2.368
2.655

AV=Valve passage area (in2), AM=Minimum area in the seat (in2)

1
0.9

Mass flow ratio

0.8
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38.0%
h/D=65.3%

0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 6.5 Mass flow ratio versus pressure ratio (PR) from small opening
(h/D=5.4%) to fully opening (h/D=65.3%)

74

At small openings, from h/D=5.4% to 10.8%, the flow is choked at PR=0.6.
As the valve opens more, the flow becomes choked at higher pressure ratio.
From h/D=16.3% to 21.7%, the flow is choked at PR=0.7, and after h/D=21.7%
the flow is choked at PR=0.8. From Fig.6.5, the transonic regimes at h/D=5.4%
and h/D=10.8% are determined to be between PR of 0.4 and about 0.8. For the
rest of the valve openings, the transonic regime is found between PR of 0.4 and
about 0.9. In the transonic regime non-axisymmetry and instability can occur.

6.2 Flow Regions and Patterns
High pressure sides push flow to low pressure sides so the flow is
attached to the lower pressure side. Thus, the lower pressure side is in contact
with the flow while the high pressure side is not. The pressure on the surface
where the flow is steadily in contact with varies randomly with larger amounts of
variation than in the regions where flow is separated. These trends were proved
by Araki‟s experiments. By applying these trends to the short seat with
consideration of pressure distribution and pressure oscillation, four flow patterns
(F, G, H, and I) are roughly drawn in terms of valve opening and pressure ratio
shown in Fig.6.6.

75

1

0.9

H

PR

0.8

0.7

F

0.6

I

G
0.5

0.4

10

20

30

40

50

60

70

80

90

100

Opening ratio (h/D)
Figure 6.6 Short seat flow regions

S3

S4

S2

S1

Figure 6.7 Cross section S4-S2 and S3-S1 on the short seat

76

(a) Cross section S4-S2

(b) Cross section S3-S1

Figure 6.8 Flow pattern F

(a) Cross section S4-S2

(b) Cross section S3-S1

Figure 6.9 Flow pattern G

77

(a) Cross section S4-S2

(b) Cross section S3-S1

Figure 6.10 Flow pattern I

Pattern F happens in region F. In region F, both PS2 and PS3 are slightly
larger than PS4 and PS1 respectively with small pressure oscillation. By looking at
the cross section 4-2 and 3-1 in Fig.2.4 (b), the flow attaches to the seat shown
in Fig.6.8. In region G, flow pattern G can occur in Fig.6.9. PS4 and PS1 are larger
than PS2 and PS3 respectively so the flow is more attached to the side of S2 and
S3. In region I, PS3 is larger than PS1, and PS4 and PS2 are almost the same. Thus,
the flow is attached to Ps1 in the cross section 3-1 and the flow is push from S4
and S2 toward the center of the plug. Thus, flow pattern I in Fig.6.10 can be
observed. In region H, the flow is unstable. Pressure oscillates with large
amplitude. In this region, the combination of flow pattern F, G, and I can be
observed (Figure of pattern H is not shown here because it is the combinations of
other flow patterns shown in Fig. 6.8, 6.9, and 6.10).

78

6.3 Flow Axisymmetry
0.025
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%

0.02



0.015

0.01

0.005

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 6.11 A plot of α versus pressure ratio (PR) on the inner ring of LRCO plug

0.07
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%

0.06
0.05



0.04
0.03
0.02
0.01
0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 6.12 A plot of α versus pressure ratio (PR) on the outer ring of LRCO plug

79

0.07
h/D=5.4%
h/D=10.8%
h/D=16.3%
h/D=21.7%
h/D=27.2%
h/D=32.6%
h/D=38%
h/D=43.5%
h/D=48.9%
h/D=54.4%
h/D=59.8%
h/D=65.3%

0.06
0.05



0.04
0.03
0.02
0.01
0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 6.13 A plot of α versus pressure ratio (PR) on the short seat

A few general trends are present in the value of α in Fig.6.11, 6.12, and
6.13. In both the inner ring, Fig. 6.11, and outer ring, Fig.6.12, the value of α
tends to decrease as the pressure ratio increases at a given opening. The inner
ring is non-axisymmetric at PR=0.4 at h/D=10.8% and at PR=0.6 h/D=16.3%.
Overall, the inner ring is axisymmeric over the entire range of experiments, but
there is no clear trend in terms of opening. The outer ring is not axisymmetric
from h/D=5.4% to 21.7%. After h/D=21.7%, the outer ring becomes axisymmetric.
The general trend of αout is to reduce as the valve opens and become almost
identical at large valve openings. General trends in the seat, Fig.6.13, are harder
to identify, but there does seem to be a range of openings where α behaves as it
did in the outer ring (h/D=32.6% to h/D=48.9%). Also based on these figures,
three different ranges of openings can be identified where similar trends, specific

80

to each figure, occur. These ranges are small openings (h/D=5.4% to 27.2%,
indicated by solid lines), intermediate openings (h/D=32.6% to 48.9%, indicated
by dashed-dot lines) and large openings (h/D=54.4% to h/D=65.3%, indicated by
solid lines with asterisk).

0.07
0.06
0.05
0.04



Inner ring
Outer ring
Seat

0.03
0.02
0.01
0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR

Figure 6.14 A plot of α versus pressure ratio (PR) at h/D=5.4%

81

0.012

0.01



0.008
Inner ring
Outer ring
Seat

0.006

0.004

0.002

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR

Figure 6.15 A plot of α versus pressure ratio (PR) at h/D=32.6%

0.02



0.015

Inner ring
Outer ring
Seat

0.01

0.005

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR

Figure 6.16 A plot of α versus pressure ratio (PR) at h/D=54.4%

82

The combination of the inner ring, outer ring, and seat at each beginning
opening ratio in the three different ranges of openings is shown in Fig. 6.14, 6.15,
and 6.16.

At the smallest opening, h/D=5.4%, a difference in axisymmetry

conditions are observed in the inner ring, outer ring, and seat in Fig.6.14. In the
inner ring αIn is less than 0.02 over the entire range of pressure ratios so
axisymmetric flow pattern is observed. However, αOut is much greater than the
inner ring. The outer ring has a value of α about 0.067 from PR=0.4 to 0.6. After
PR=0.6, αOut begins to decrease and becomes less than 0.02 at about PR=0.93.
The high values of α at the outer ring are caused by relatively higher pressure at
PL6 and PL7 than PL5 and PL8. This similar phenomenon is observed in the
seat. Relatively high pressures at S2 and S3 cause non-axisymmery on the seat.
Similar trends are observed in the inner ring, outer ring, and seat until h/D=27.2%.
At intermediate openings, h/D=32.6%, some changes of α are observed in the
outer ring and seat while the inner ring is still axisymmetric shown in Fig.6.15.
The pressure difference across the outer ring is reduced so the outer ring
becomes axisymmery. For the seat, unlike at the small opening, the variation of
αSeat shows a trend like αOut; αSeat looks like αOut is shifted up about 0.01 in the
value of α. As the plug continues to be lifted, the pressure difference on the outer
ring is getting smaller as well as on the seat side. After h/D=32.6%, the inner ring,
outer ring, and seat become axisymmetric and they stay axisymmetry until large
opening. At a large opening, the seat is axisymmetric, but the trend of αseat is
quite different from the inner and outer ring shown in Fig. 6.16. There are still
pressure differences across the seat, which is caused by relatively high

83

pressures at S3 and S4. A peak of αSeat is observed only at PR=0.8 from the
intermediate opening to the fully opening.
6.4 Flow instability
Pressure oscillation on the seat at PR=0.6 at h/D=32.6% is shown in Fig.6.17
The x-axis is time (second) and the y-axis is gauge pressure (lb/in2). All figures in
Fig.6.17 shows pressure oscillation during 10 seconds. S1, S2, S3, and S4 are
tap numbers for the seat shown in Fig. 2.4(b).

Pressure [psi]

-2.5

-3

S1
S2
S3
S4

-3.5

-4
0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 6.17 Pressure oscillations versus Time at different pressure ratios
at h/D=32.6%

84

-5.2

Pressure [psi]

-5.4
-5.6
S1
S2
S3
S4

-5.8
-6
-6.2
-6.4
-6.6
0

2

4

6

8

10

Time [s]
(b) PR=0.8
Figure 6.17 Cont‟d

-7.2
-7.4

Pressure [psi]

-7.6
-7.8

S1
S2
S3
S4

-8
-8.2
-8.4
-8.6
0

2

4

6

Time [s]
(c) PR=0.7
85

8

10

Figure 6.17 Cont‟d

-7.4
-7.6

Pressure [psi]

-7.8
S1
S2
S3
S4

-8
-8.2
-8.4
-8.6
-8.8
0

2

4

6

8

10

Time [s]
(d) PR=0.6
Figure 6.17 Cont‟d

-7.4
-7.6

Pressure [psi]

-7.8
S1
S2
S3
S4

-8
-8.2
-8.4
-8.6
-8.8
0

2

4

6

Time [s]
(e) PR=0.5

86

8

10

Figure 6.17 Cont‟d

-7.4
-7.6

Pressure [psi]

-7.8
S1
S2
S3
S4

-8
-8.2
-8.4
-8.6
-8.8
0

2

4

6

8

10

Time [s]
(f) PR=0.4
Figure 6.17 Cont‟d

At small opening ratios, h/D=5.4% and 10.8%, PS2 is larger than PS3,
which is larger than PS4, and PS1 is less than PS4. These pressures oscillate with
small amplitude at some average mean value. This can happen in region F with
flow pattern F. As the opening ratios increases, unstable flow appears at PR=0.7
and is seen at high pressure ratios shown in Fig.6.17 (a), (b), and (c). This
unstable flow can be observed in region H with combination of flow pattern F and
G or other flow patterns. At small pressure ratios, on the other hand, pressures
oscillate with small amplitude without sudden pressure increases or decreases in
Fig. 6.17 (d), (e), and (f). Since PS3 is larger than PS1 and PS4 and PS2 are almost

87

the same, the flow pattern I can be observed in region I. These similar trends
can be observed at other opening ratios.
6.5 Noise
In order to compare the sound pressure levels as measured at each
microphone location over the range of pressure ratios tested, an example set of
measurements made at h/D = 5.44% is tabulated in Table 6.3 with background
noise in Table 6.2. Major differences are not observed at each channel and
overall dBA variations are between 120 and 150 for each opening. At PR=70%,
the maximum value of dBA is found for each valve. For all openings the
maximum sound pressure level was found between PR=0.7 and 0.8. In this
pressure ratio range, a loud whistling sound was produced by the bypass valve.

Table 6.2 Short seat background noise

dBASS

CH1
CH2
CH3
CH4
119.19 119.83 120.77 119.52
SS: Short Seat

Table 6.3 Short seat noise at each channel at h/D=5.44%
PR
99
90
80
70
60
50
40

CH1
119.34
135.79
134.67
141.84
138.78
139.72
132.42

CH2
120.90
127.73
134.47
142.53
137.58
136.40
131.95

88

CH3
122.94
128.81
134.75
141.16
137.15
137.20
131.31

CH4
117.38
125.80
135.65
145.46
141.57
140.80
133.58

6.6 Vibration
In Fig.6.18, A1 means an accelerometer connected to channel 1 on the
LX-120;

the

same

naming

convention

is

followed

for

the

remaining

accelerometers. Accelerometer results of New LRCO short seat at h/D=16.32%
is shown in Fig.6.17 as an example. The maximum amplitudes are found at
around 4000 Hz. As pressure ratio decreases, peaks are observed at low
frequency range from A3 and at high frequency range from A2 and A4. This
phenomenon is observed at other opening ratios. .

25
A1
A2
A3
A4
A5

Amplitude (m/s2)

20

15

10

5

0

0

1000

2000

3000

4000

5000

6000

Frequency (Hz)
(a) PR=0.9
Figure 6.18 Vibration at different pressure ratios at h/D=16.32%

89

60
A1
A2
A3
A4
A5

Amplitude (m/s2)

50

40

30

20

10

0

0

1000

2000

3000

4000

5000

6000

Frequency (Hz)
(b) PR=0.8
Figure 6.18 Cont‟d

30
A1
A2
A3
A4
A5

Amplitude (m/s2)

25

20

15

10

5

0

0

1000

2000

3000

Frequency (Hz)
(c) PR=0.7
90

4000

5000

6000

Figure 6.18 Cont‟d

40
A1
A2
A3
A4
A5

35

Amplitude (m/s2)

30
25
20
15
10
5
0

0

1000

2000

3000

4000

5000

6000

Frequency (Hz)
(d) PR=0.6
Figure 6.18 Cont‟d

180
A1
A2
A3
A4
A5

160

2

Amplitude (m/s )

140
120
100
80
60
40
20
0

0

1000

2000

3000

Frequency (Hz)
(e) PR=0.5
91

4000

5000

6000

Figure 6.18 Cont‟d

400
A1
A2
A3
A4
A5

350

2

Amplitude (m/s )

300
250
200
150
100
50
0

0

1000

2000

3000

4000

Frequency (Hz)
(f) PR=0.4
Figure 6.18 Cont‟d

92

5000

6000

CHAPTER 7
COMPARISON OF THE OLD VALVE AND NEW VALVES
7.1 Mass Flow Rate
To compare the mass flow capacity of the three valves, mass flow rates
are compared at the same pressure ratio and area ratio. Area ratio is defined as
valve passage areas (AV) that are divided by the minimum area (AM) in the seat.
Fig.7.1 shows mass flow rate versus area ratio at PR=0.9. Mass flow rates of the
LRCO long seat are slightly larger than those of the old valve and LRCO short
seat between about 0.3 and 0.6 in the area ratio. As the valve passage area
increases, the old valve has greater mass flow than the LRCO long seat, and
mass flow through the LRCO long seat is larger than that through LRCO short
seat. This trend is also observed at PR=0.7 as shown in Fig.7.2. Between about
0.4 and 0.8 in the area ratio, mass flow rates in both the LRCO long seat and
LRCO short seat are slightly larger than that of the old valve. At a large valve
passage area, on the other hand, the old valve has more mass flow than the
LRCO long seat and the LRCO short seat. This trend continues at PR=0.5 in
Fig.7.3.

93

0.3
Old Valve
LRCO Long Seat
LRCO Short Seat

Mass Flow Rate(kg/s)

0.25

0.2

0.15

0.1

0.05

0.2

0.4

0.6

0.8

1

1.2

1.4

Area Ratio(AV/AM)
Figure 7.1 Mass flow rates versus Area Ratio (AV/AM) at PR=0.9

0.3
Old Valve
LRCO Long Seat
LRCO Short Seat

Mass Flow Rate(kg/s)

0.25

0.2

0.15

0.1

0.05

0.2

0.4

0.6

0.8

1

1.2

1.4

Area Ratio(AV/AM)
Figure 7.2 Mass flow rates versus Area Ratio (AV/AM) at PR=0.7

94

0.3
Old Valve
LRCO Long Seat
LRCO Short Seat

Mass Flow Rate(kg/s)

0.25

0.2

0.15

0.1

0.05

0.2

0.4

0.6

0.8

1

1.2

1.4

Area Ratio(AV/AM)
Figure 7.3 Mass flow rates versus Area Ratio (AV/AM) at PR=0.5

7.2 Flow Axisymmetry
The change in α on the inner ring of the hemispherical plug with the old
seat (OS) and the LRCO plug with the long seat (LS) and the short seat (SS) at
h/D=5.4% is shown in Fig.7.4. The red line represents α of the hemispherical
plug with the old seat. The inner ring of the LRCO plug with the long seat and the
short seat are the blue and green lines respectively. The inner ring of the
hemispherical plug is non-axisymmetric between PR=0.45 and PR=0.6 and then
becomes axisymmetric. The inner ring of LRCO plug with either the long seat or
the short seat is axisymmetric over the entire range of pressure ratios.
Fig.7.5 shows α of the outer ring of the hemispherical plug with the old
seat and the LRCO plug with the long seat and the short seat at h/D=5.4% with

95

the same color-scheme as Fig.7.4. The hemispherical plug outer ring α varies
randomly as pressure ratio increases. However, with either the long seat or the
short seat, α of the outer ring of the LRCO plug remains almost constant until
PR=0.6 and then begins to decrease.
Fig.7.6 shows α of the old seat, the long seat, and the short seat at
h/D=5.4%. Similar to what was seen in Fig.7.6, the flow in the old seat is very
non-axisymmetric compared to the long seat and the short seat in the low
pressure ratio range from PR=0.4 to 0.7. The general trend for three seats is that
they tend to axisymmetric in the high pressure ratio range.
As the opening ratio increases, the old valve and the LRCO plug with
either the long seat or the short seat behave similarly. Non-axisymmetry in the
inner ring of the hemispherical plug is observed until h/D=21.7%. After that
opening ratio, the flow is axisymmetric over the entire pressure ratios. The LRCO
plug‟s inner ring with either the long seat or the short seat is also axisymmetric
from the small opening to the fully open position. A similar trend is observed in
the outer ring for all three seats. The outer ring of all three plug-seat
combinations becomes axisymmetric as the opening ratio increases. However,
the three seats behave differently from the inner ring and the outer ring of two
plugs. One general trend of α for all three seats is that a peak is observed in the
high pressure ratio range; as an example sees Fig.5.14 which is the long seat
with the LRCO plug in the fully open position.

96

0.06
Inner ring with OS
Inner ring with LS
Inner ring with SS

0.05



0.04

0.03

0.02

0.01

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 7.4 A plot of α versus PR on the inner ring at h/D=5.4%

0.08
Outer ring with OS
Outer ring with LS
Outer ring with SS

0.07
0.06



0.05
0.04
0.03
0.02
0.01
0
0.4

0.5

0.6

0.7

0.8

0.9

PR
Figure 7.5 A plot of α versus PR on the outer ring at h/D=5.4%

97

1

0.12
Old seat
Long seat
Short seat

0.1



0.08

0.06

0.04

0.02

0
0.4

0.5

0.6

0.7

0.8

0.9

1

PR
Figure 7.6 A plot of α versus PR on the seat at h/D=7.6%

7.3 Flow Instability
Pressure oscillation on the plug and seat for the old valve and new valves
is compared at h/D=10.8% in Fig.7.7~Fig.7.15. In those figures, the x-axis is time
(second) and the y-axis is gauge pressure (lb/in2). The plug taps are PL1 ~ PL8,
which correspond to the tap locations shown in Fig.2.4 (a) and S1~S4 indicate
tap locations on the seat as shown in Fig.2.4 (b). Fig.7.7 shows gage pressure
oscillations on the inner ring of the hemispherical plug of the old valve. At PR=0.9
in Fig.7.7 (a), there is a background oscillation super-posed on the trace for the
old valve. This super-posed pressure oscillation is also observed in the inner ring
of the LRCO plug with either the long seat in Fig.7.8 (a) or the short seat in
Fig.7.9 (a). As the pressure ratio decreases, sudden changes in the amplitude of
the pressure oscillation are observed in the inner ring of the hemispherical plug in

98

Fig.7.7 (b). On the other hand, pressures on the inner ring of the LRCO plug with
either the long seat or the short seat oscillate at average mean values shown in
Fig.7.8 (b) and Fig.7.9 (b) respectively. Pressures on PL2 and PL3 are grouped
in high pressure oscillation while pressures on PL1 and PL4 are in low pressure
oscillation. At the lowest pressure ratio, PR=0.4, the inner ring of the
hemispherical plug for the old valve in Fig.7.7(c) has the similar pressure
oscillation as at PR=0.9 while the inner ring with either the long seat or the short
seat has clearly separated pressure oscillation trends in Fig.7.8(c) and Fig.7.9 (c).

-1.2

Pressure [psi]

-1.4
-1.6
PL1
PL2
PL3
PL4

-1.8
-2
-2.2
-2.4
-2.6

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.7 Gage pressure oscillations on the inner ring of the hemispherical
plug with the old seat at different pressure ratios (PR) at h/D=10.8%

99

-4

Pressure [psi]

-4.5
PL1
PL2
PL3
PL4

-5

-5.5

-6

-6.5

0

2

4

6

8

10

Time [s]
(b) PR=0.7
Figure 7.7 Cont‟d

-8.6

Pressure [psi]

-8.8
-9
PL1
PL2
PL3
PL4

-9.2
-9.4
-9.6
-9.8

0

2

4

6

Time [s]
(c) PR=0.4
Figure 7.7 Cont‟d

100

8

10

-1.9
-2

Pressure [psi]

-2.1
-2.2

PL1
PL2
PL3
PL4

-2.3
-2.4
-2.5
-2.6
-2.7

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.8 Gage pressure oscillations on the inner ring of the LRCO plug
with the long seat at different pressure ratios (PR) at h/D=10.8%

-6.4

Pressure [psi]

-6.5
-6.6
PL1
PL2
PL3
PL4

-6.7
-6.8
-6.9
-7

0

2

4

6

Time [s]
(b) PR=0.7
Figure 7.8 Cont‟d
101

8

10

-9.4

Pressure [psi]

-9.6
PL1
PL2
PL3
PL4

-9.8

-10

-10.2

-10.4

0

2

4

6

8

10

Time [s]
(c) PR=0.4
Figure 7.8 Cont‟d

-1.7
-1.8

Pressure [psi]

-1.9
-2

PL1
PL2
PL3
PL4

-2.1
-2.2
-2.3
-2.4
-2.5

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.9 Gage pressure oscillations on the inner ring of the LRCO plug
with the short seat at different pressure ratios (PR) at h/D=10.8%

102

-5.9
-6

Pressure [psi]

-6.1
-6.2

PL1
PL2
PL3
PL4

-6.3
-6.4
-6.5
-6.6
-6.7

0

2

4

6

8

10

Time [s]
(b) PR=0.7
Figure 7.9 Cont‟d

-8.8

Pressure [psi]

-9
-9.2
PL1
PL2
PL3
PL4

-9.4
-9.6
-9.8
-10

0

2

4

6

Time [s]
(c) PR=0.4
Figure 7.9 Cont‟d

103

8

10

The stability of the pressure distribution on the outer ring of the two plugs
behaves both similarly and dissimilarly to that of the inner ring depending upon
pressure ratio. At PR=0.9 and 0.7 in Fig.7.10 (a) and (b) respectively, clear
pressure changes are observed on the outer ring of the hemispherical plug,
which are different from those seen on the LRCO plug with either the long seat in
Fig.7.11 (a) and (b) or the short seat in Fig.7.12 (a) and (b). The outer ring of the
LRCO plug with two seats is more stable than the hemispherical plug with the old
seat. At a lower pressure ratio, PR=0.4, any pressure changes are not observed
in two outer rings with seats shown in Fig. 7.10 (c), Fig7.11(c), and Fig. 7.12 (c).
Therefore, they are all stable.

-1.4

Pressure [psi]

-1.6
-1.8
PL5
PL6
PL7
PL8

-2
-2.2
-2.4
-2.6
-2.8

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.10 Gage pressure oscillations on the outer ring of the hemispherical
plug with the old seat at different pressure ratios (PR) at h/D=10.8%

104

-5

Pressure [psi]

-5.5
PL5
PL6
PL7
PL8

-6

-6.5

-7

-7.5

0

2

4

6

8

10

Time [s]
(b) PR=0.7
Figure 7.10 Cont‟d

Pressure [psi]

-7

-7.5
PL5
PL6
PL7
PL8

-8

-8.5
0

2

4

6

Time [s]
(c) PR=0.4
Figure 7.10 Cont‟d

105

8

10

-0.7

Pressure [psi]

-0.8
-0.9
PL5
PL6
PL7
PL8

-1
-1.1
-1.2
-1.3
-1.4

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.11 Gage pressure oscillations on the outer ring of the LRCO plug
with the long seat at different pressure ratios (PR) at h/D=10.8%

-1.2

Pressure [psi]

-1.4
-1.6
PL5
PL6
PL7
PL8

-1.8
-2
-2.2
-2.4
-2.6

0

2

4

6

Time [s]
(b) PR=0.7
Figure 7.11 Cont‟d
106

8

10

-1.6

Pressure [psi]

-1.8
PL5
PL6
PL7
PL8

-2

-2.2

-2.4

-2.6

0

2

4

6

8

10

Time [s]
(c) PR=0.4
Figure 7.11 Cont‟d

-0.6

Pressure [psi]

-0.7
-0.8
PL5
PL6
PL7
PL8

-0.9
-1
-1.1
-1.2
-1.3

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.12 Gage pressure oscillations on the outer ring of the LRCO plug
with the short seat at different pressure ratios (PR) at h/D=10.8%

107

Pressure [psi]

-1.5

PL5
PL6
PL7
PL8

-2

-2.5

0

2

4

6

8

10

Time [s]
(b) PR=0.7
Figure 7.12 Cont‟d

-1.2

Pressure [psi]

-1.4
-1.6
PL5
PL6
PL7
PL8

-1.8
-2
-2.2
-2.4
-2.6

0

2

4

6

Time [s]
(c) PR=0.4
Figure 7.12 Cont‟d

108

8

10

Clear pressure increases and decreases are also observed on the old
seat shown in Fig.7.13. The pressure increases suddenly and stays there for a
while. The pattern of pressure oscillations on the seat is similar to the inner ring
and outer ring of the hemispherical plug. On the other hand, the sudden
increases and decreases are not observed in the long seat in Fig.7.14 and the
short seat in Fig.7.15. High pressures on PL 2 and PL3 are grouped together and
behave similarly. Low pressures on PL1 and PL4 are also grouped together and
oscillate around some average mean values with a small amplitude. Therefore,
the long seat and the short seat are more stable than the old seat.

Pressure [psi]

-1

-1.5
S1
S2
S3
S4

-2

-2.5

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.13 Gage pressure oscillations on the old seat at different
pressure ratios (PR) at h/D=10.8%

109

-3.5

Pressure [psi]

-4
-4.5
S1
S2
S3
S4

-5
-5.5
-6
-6.5
-7

0

2

4

6

8

10

Time [s]
(b) PR=0.7
Figure 7.13 Cont‟d

-6

Pressure [psi]

-7
S1
S2
S3
S4

-8

-9

-10

-11

0

2

4

6

Time [s]
(c) PR=0.4
Figure 7.13 Cont‟d

110

8

10

-1.8
-1.9

Pressure [psi]

-2
-2.1

S1
S2
S3
S4

-2.2
-2.3
-2.4
-2.5
-2.6

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.14 Gage pressure oscillations on the long seat at different
pressure ratios (PR) at h/D=10.8%

-6.5
-6.6

Pressure [psi]

-6.7
-6.8

S1
S2
S3
S4

-6.9
-7
-7.1
-7.2
-7.3

0

2

4

6

Time [s]
(b) PR=0.7
Figure 7.14 Cont‟d

111

8

10

-10

Pressure [psi]

-10.2
S1
S2
S3
S4

-10.4

-10.6

-10.8

-11

0

2

4

6

8

10

Time [s]
(c) PR=0.4
Figure 7.14 Cont‟d

-1.6

Pressure [psi]

-1.8
S1
S2
S3
S4

-2

-2.2

-2.4

-2.6

0

2

4

6

8

10

Time [s]
(a) PR=0.9
Figure 7.15 Gage pressure oscillations on the short seat at different
pressure ratios (PR) at h/D=10.8%

112

-5.5

Pressure [psi]

-6
S1
S2
S3
S4

-6.5

-7

-7.5

0

2

4

6

8

10

Time [s]
(b) PR=0.7
Figure 7.15 Cont‟d

-9.2

Pressure [psi]

-9.4
S1
S2
S3
S4

-9.6

-9.8

-10

-10.2

0

2

4

6

Time [s]
(c) PR=0.4
Figure 7.15 Cont‟d

113

8

10

7.4 Non-axisymmetric Unstable Flow
Non-axisymmetric unstable flow causes unbalanced pressure distribution
along the plug and seat, which results in valve vibration. If that happens, the plug
can be broken in a short period of time by large pressure oscillation amplitude or
in a long period of time by small pressure oscillation. There are three possible
cases for the valve failure. The first case is that if the pressures on the half of the
plug facing towards the inlet are always higher than the other side of the plug, the
plug will experience lateral vibration, and crack will initiate from the higher
pressure side. The second case is that if higher backpressure in the seat occurs,
the seat will force the flow back to the plug and the plug will vibrate in the vertical
direction. The last case is the combination of the lateral and vertical vibration.
When the seat is non-axisymmetric at PR= 0.5 at h/D=5.44%, the flow is
unstable. The plug will be pushed by higher pressures on P6 and P7 toward the
opposite side from the inlet pipe so the plug will experience vibration in the lateral
direction. At the same time, higher backpressures on the seat push the flow back
to the inner ring. This causes the plug to vibrate in the vertical direction. Except
for PR=0.5, the seat does not push the flow back to the inner ring because
pressures on the inner ring are larger than the seat. Thus, the plug‟s vibration is
caused in the lateral direction by P6 and P7 until about PR=0.93. The
combination of lateral and vertical vibration continue to be observed at PR=0.5
and 0.6 at h/D=10.88%, and from PR=0.6 to 0.9 at h/D=16.32%. After
h/D=16.32%, pressures on the inner ring are always larger than the seat so
vertical vibration no longer appears. In the short seat, the vertical vibration can

114

be observed more often than the long seat. From the small opening to
h/D=21.7%, pressures on the seat are larger than the inner ring at PR=0.4, 0.5,
and 0.6. From h/D=27.2% to the fully open (h/D=65.3%), pressures on the short
seat are larger than the inner ring over the entire pressure ratio. If the valve fails,
it would occur at these pressure ratios and opening heights where pressures on
the seat are larger than the inner ring.

7.5 Noise and Vibration
The background noise of the old valve and each channel‟s noise at
h/D=5.44% are tabulated in Table 7.1 and Table 7.2 respectively. Comparing
them with the noise of the long seat in Table 5.2 and 5.3 and the short seat in
Table 6.2 and 6.3, major differences are not observed at each channel for each
of the three valves. Also, major differences are not found in vibration results in
the three valves.
Table 7.1 Old valve background noise

dBAOV

CH1
CH2
CH3
CH4
125.49 126.54 126.07 124.84
OV: Old Valve

Table 7.2 Old valve noise at each channel at h/D=5.44%
PR
99
90
80
70
60
50
40

CH1
119.84
127.22
136.10
142.31
138.02
139.55
134.49

CH2
120.29
127.89
135.98
142.61
138.90
138.44
134.20

115

CH3
120.78
128.79
136.99
144.17
137.53
139.14
134.01

CH4
121.41
128.09
136.80
144.50
139.24
141.85
135.58

CHAPTER 8
CONCLUSION AND FUTURE WORK

The new governor valves are designed to reduce flow non-axisymmetry
and instability. The newly designed governor valves are tested to investigate the
relationship between plug and seat under the same conditions as the previous
valve test. In this experiment, four microphones and five accelerometers were set
up to study the new valve‟s interaction with fluid in addition to the static pressure
taps from the previous experiments.
Mass flow rates for the LRCO valves are measured at different valve
openings and pressure ratios. The LRCO valves have less flow capacity than the
old valve (the hemispherical plug valve) at the large valve passage area. At the
small valve passage area, mass flow rates of the LRCO valves are slightly larger
than those of the old valve.
The LRCO valves are deemed to be more axisymmetric than the old valve.
For the LRCO valves, the inner ring is axisymmetric over the entire pressure ratio
tested from the small opening (h/D=5.4%) to the fully opening (h/D=70.7% for the
long seat and 65.3% for the short seat). The outer ring is non-axisymmetric at the
small openings but it becomes axisymmetric at the intermediate and large
openings. The long seat and the short seat, on the other hand, vary depending
on pressure ratios and opening ratios.
The LRCO plug is deemed to be more stable than the hemispherical plug.
Any sudden pressure increases or decreases during the recorded time are not

116

observed. All pressures on the inner ring and outer ring of the plug oscillate at
some average mean values. However, the long seat and the short seat still have
instability. Pressures on the seats oscillate with large amplitudes and their
behavior does not have similar trends as the plug.
Flow patterns and regions are drawn based on experimental results. The
flow is three dimensional in the valve so it is very difficult to visualize the flow
movement. Although the visualized flow patterns and regions in 2D are not very
accurate due to the complicated flow and limited numbers of sensors tested, they
can still help understand the flow phenomena in the valve. These flow patterns
and regions should be studied again and confirmed by CFD work.
Noise and vibration are tested, but the test results are not as good as
expected. Microphones are located near the vacuum pump that makes a loud
noise by motor. Because of that, actual noise generated in the test valve is not
measured accurately. In order to collect more accurate data, some methods to
minimize the vacuum pump noise should be considered. During the test,
vibration of the plug and test chests is observed. Vibration results show peaks at
high frequency but it is difficult to relate them to flow instability. Additional
measurements need to be considered to measure plug‟s lateral and vertical
vibration.

117

BIBLIOGRAPHY

118

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120