’—
!,
7".
,,,,
é
—._——
if, _
7 , , -V
_ ,7 <

,1
__._.—:-
_ ._v , ,
,_7 #,
———-—" ;
é

THE EFFECT OF BACK PRESSURE ON THE
HORSEPOWER OUTPUT OF AN‘ iNTERNAL
COMBUSTEON ENGINE

Thai: for The Dogma 01" M. S.
MICHIGAN STATE COLLEGE
Fredric Joseph Warm“

1951

 

 

 

 

 

 

 

I
'H ‘ .
.’ ‘-
i ‘ ‘
o i
) .‘ ;\
v p _
This is to certify that the t. 1 _
thesis entitled i . ',
The Effect of Back Pressure on the If .I
,Horsepower Output of an Internal
Combustion Engine.
presented by .k
Fredric Joseph Warren 1" f-
! ‘ ‘ '
has been accepted towards fulfillment ~
of the requirements for >
Master of Science degree in Mechanical Engineering ’
r \
Major professor
f t
h'
v
0.159

 

no... - II‘

”I.

r

I

III' oil-- 9. _ -_-I-'." I l --t '-

~I'R

I

‘ I-‘Tr- - It“. iii "I'r'-’- -“‘.‘

5"

'u-I J fi‘l‘l
I I'

Dr
.

 

THE EFFECT OF BACK PRESSURE ON THE HORSEPOWER OUTPUT
OF AN INTERNAL COMBUSTION ENGINE

By
Fredric Joaeph.Warrell

—#

A THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Mechanical Engineering

1951

ACKNOWLEDGEMENT

The author wishes to take this opportunity to thank
Mr. George W. Hobbs of the School of Engineering for his
guidance in this project and Mr. S. A. Olsen for his aid

in performing the eXperimental tests.

3::
3::
2e?!“
14;:
£2
:53

TABLE OF CONTENTS
Page

Introduction . . . . . . . . . . . . . . . . . . . . . . 1
Description of Apparatus . . . a . . . . . . .,. . . . .
Schematic Diagram of Laboratory Arrangement for Test . .

Procedure 0 o O O O O O O O o o o o a o o o a e a o o o

amp-u

Discussion . . . . . . . . . . . . . . . . . . . . . . .
Summary . . . . . . . . . . . . . . . . . . . . . . . . 11
References . . . . . . . . . . . . . . . . . . . . . . . 12
Appendix

Tables . . . . . . . . . . . . . . . l - 12

Curves . . . . . . . . . . . . . . .13 — 26
Sample Calculations . . . . . . . . .27 - 28

INTRODUCTION

The object of this investigation is to determine
the effects of exhaust pressure on the horsepower output
of an internal combustion engine. The torque, since it
is of primary importance in automotive applications, and
the specific fuel consumption, since it is of importance
to the operator of an engine, are also considered.

Some work.has been done in this field, although
much of it is contradictory or inconclusive. Heldt1 claims
that a manifold can be designed so that the peak of the
pressure wave will be out of the manifold when the next
cylinder exhausts. Burgess-Manning2 claims that “tuning“
is neither necessary nor helpful.

Jesse S. Doolittle3 performed similar experiments at
Pennsylvania State College onma two-cycle Diesel engine
and concluded that at loads less than the load which
yields the minimum fuel rate, the effect of back pressure
was negligible. At loads greater than the load which
yielded the minimum fuel rate the effect was greater, due
to the lack of air.

Heldt also expressed a method of evaluating the
horsepower loss due to a muffler. This loss was equal to
the ratio of muffler pressure to indicated mean effective
pressure. Since the amount of residual gas in the cylin-
der is affected by the exhaust pressure and the indicated
mean effective pressure is affected by the amount of

residual gas, this method of evaluation does not seem to

be adequate.

It is hoped that the results of this investigation
will have three effects. First, to correlate the work
which has been done before. Second, to establish cri-
teria for the design of more efficient exhaust manifolds
to obtain better engine performance more economically.
Third, to establish criteria for the design and use of
devices to utilize the energy in the exhaust gases by
predicting their effect on engine performance.

It is believed that the modern internal combustion
engine has been develOped to the point where most of the
losses are relatively small ones. It is further heped
[that this investigation will lend encouragement to those
attempting to discover and to evaluate the effects of
these small losses so that it will be possible to build

engines more economically in the future than it is possible

to bUlld tOdaya

DESCRIPTION OF APPARATUS

1.

2.

3.

Engine -- l9h9 Chevrolet
Serial Number - GAA 8 I 2b I
Number of cylinders - 6
Valve Arrangement -- overhead
Bore -- 3%
Stroke -- 3-3/h
Displacement -- 216.5
Compression Ratio - 6.5 to 1
Dynamometer - General Electric
Serial Number -- 150h076
Range -— 100 HP absorbed O 1050 to 3500 rpm
Current -— Direct 277 amps. and 250 volts
Gate Valve - Jenkins Brothers
Size - 2 inches
WSF -- 125
OWG -- 200
Zenith Mileage Tester -- 160, 150, 150 cc. bulbs
Number —- ME 9H9
Stop'Watch.—- Elgin
Range -- O to 10 min.
Calibration -- 10ths of a second
Manometer - M.S.C.
Fluid - mercury
Range -- O to 20 inches
Calibration -- 10ths of an inch

Test performed at M.S.C. Automotive Laboratories, East

Lansing, Michigan.

-3...

L. OWR Md Q.D..wv1m& rd.

«WORK .P 7d w:\< wrap}. (Neva? $0.016? HON {V

 

 

1 q

4M2 «\Q OW..Q.-....->\.C
WELL... 3 03 ,1ng

\NBVV\\/

 

 

 

 

1)

4

.( U V...

1

1C .§.1.&.0<\Q oi<§hi0p

 

 

X2 «\K. Quirk

 

 

mum k hut). Wit TV?

 

 

 

 

‘ z
_ _m ml «R Q sh.h§...§<

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

km a. max/.63 12> Q

 

 

 

 

 

 

 

 

 

.... a: m J - -_
In L. .\ _ udim brad a CD .179. w.
1|! @ E -

ARTIM
M>>IQ 1.?»qu {m

4N3<Q OER Z0”. M). \rnM. Tm.

slurrxfi. wwfié In SEN

tanned u 45

K2 «R QMKSVS m. >340. O k

PROCEDURE

Three groups of tests were used in order to define
the effects completely and to provide an accuracy check.
All results were corrected to standard atmospheric con-
ditions so that the information could be correlated and
so that it could be applied easily to other engines.

Group I tests were used to find the effect of back
pressure on the shape of the horsepower curve. The
pressure in the exhaust manifold was set at 1000 rpm,
taken as reference speed, by throttling the flow in the
tail pipe with the gate valve. Scale load, fuel time,
and exhaust pressure were read at speeds of 3500, 3200,
2800, 2h00, 2000, and lhoo rpm. Extreme difficulty in
establishing initial back pressures greater than one-half
inches of mercury limited these tests.

Group II tests were run at constant back pressure
over the above range of speed. Scale load and fuel time
were determined. These tests proved to be of more value.

Group III tests were run at constant speed over a
range of back pressures from one-half to six inches of
mercury. Scale load and fuel time were determined. These
tests acted as a check on Group II tests and.proved to be
the easiest tests to calibrate the effect of back pressure
on brake horsepower at constant speed. These tests were
run at full, three-quarter, one-half, and one-quarter

throttle settings.

The engine was calibrated at all throttle openings

-5-

with the gate valve in the tail pipe completely open.
These curves were then corrected by use of the empirical
correction factor determined from the tests of the three
groups.

All tests were run at full load.

DISCUSSION

The Chevrolet engine was chosen for these tests
for two reasons. First, the simple manifold system
facilitated the testing procedures and the arrangement
of the laboratory equipment. Second, since the trend in
modern automotive engines seems to be toward overhead
valves, it was deemed most advisable to use an engine
of this valve arrangement.

A gate valve was chosen to throttle the exhaust flow
since it was felt that this type of valve*would offer the
least resistance to flow when it was wide Open, as in the
calibration tests.

It was originally planned to define also the cyclic
pressure variations in the exhaust system, but the mercury
manometer proved to be too sluggish to measure the rapid
pressure fluctuations without incorporating in it some
type of timing device. Hence, this part of the test was
abandoned and the effect of the mean exhaust pressure only
was investigated. This yields the effect of the back

pressure on the engine as a.whole.

..6..

The peak pressure at any time at any one exhaust
port can be calculated from the physical properties of
the system, and its effect on that cylinder may be eval-
uated from the data of this paper. In this manner, the
effect of back pressure on any part of the engine may be
evaluated.

As a check on the accuracy of this eXperiment, a
curve plotted from the tests of Group I was corrected by
use of the results of Group III tests. This corrected
curve was found to agree closely with a curve plotted from
the data of Group II tests at the appropriate back pressure.

The tests of Group III indicate that both brake horse-
power and torque decrease linearly with back pressure.

Back pressure was also revealed to increase linearly with
speed. Therefore, the torque and the horsepower losses
are linear with respect to speed. This agrees with the
friction horsepower curve which is essentially linear with
respect to speed.

This linear relationship results in a displacement
of the horsepower and torque curves by equal increments
throughout their entire range. This is comparable to
lowering the friction horsepower curve throughout its
entire range by an equivalent amount.

Group III tests also indicate that the rate of decrease
of horsepower with back pressure is equal to 1.1 brake
horsepower per inch of mercury at full throttle. Further-
more, this rate of loss is independent of speed.

-7-

At an initial back pressure of zero inches of mercury
at 1000 rpm., the back pressure builds up at a rate of
0.1095 inches of mercury per 100 rpm. This yields a total
horsepower loss at peak output of 2.168 horsepower, which
is equivalent to a percentage loss of 2.5 per cent in
terms of peak horsepower at zero inches of mercury back
pressure. While this is not of great magnitude, it is
entirely unnecessary if it is considered that more adequate
design will eliminate this loss.

It was also determined that the rate of horsepower
loss was decreased at lesser throttle openings, and that
the rate of build-up of back pressure acted in a like
manner. At one-quarter throttle the decrease in horsepower
due to back pressure is small, but the greater decrease in
horsepower due to throttling induces higher percentage
losses of horsepower - of the order of 13 per cent.

This leads to three conclusions. First, throttling
of the exhaust flow occurs at high outputs. Second,
exhaust manifolds are built oversized rather than designed
to accomodate the flow. Third, since the automobile Oper-
ates at part throttle and.part load conditions, the effect
of back pressure on the horsepower output of a vehicle is
considerable under normal driving conditions and present
design methods. .

Torque is shown to decrease at a rate of 1.? foot-
pounds per inch of mercury at full throttle. At peak
torque of 169.5 foot-pounds at 1600 rpm., the loss due to

- 8 -

this build-up of back pressure is equal to 1.53 foot-pounds,
which is equivalent to a percentage loss of 0.90h per cent.
At peak power output, the loss would be 3.5 foot-pounds, or a
percentage loss of 2.58 per cent. Thus, it is demonstrated
that the high-speed performance of an automotive-type

vehicle suffers from an increase in back pressure for any

one load condition.

It was also demonstrated that the rate of loss of
torque decreases with lesser throttle openings. At one-
quarter throttle the decrease in torque is small and,
coupled with the lesser torque developed, reveals a per-
centage loss of approximately 11 per cent at peak torque.
Therefore, the normal operating performance of an auto-
motive-type vehicle is greatly impaired by poor-design of
the exhaust system.

Brake specific fuel consumption acted in a seemingly
erratic manner, and much more work needs to be done in
order to calibrate fully the influence of back pressure
on this phase of performance. However, the following
trends were noticed:

l. The rate of increase of brake specific
fuel consumption with back pressure is
greater at low speeds.

2. The rate of increase of brake fuel consump-
tion with back pressure is greater at
lesser throttle openings.

3. All changes are linear.

-9...

These trends tend to substantiate the work of A. J.
Blackwood and G. H. Cloud at the Esso Laboratories,
Linden, New Jersey, as reported in the discussion of
Reference 3.

It appears that more work and better design is
needed in this field,than is generally presumed. The air-
craft industry has made some overtures in this direction,
but the more advantageous performance has been credited
to the propulsive effect of the Jet created. The results
of this investigation indicate that the added power may
just as well come from the increased engine performance
due to decreased back pressure.

These results also indicate a need for caution in
designing such devices as turbosuperchargers to utilize
the energy in the exhaust gases. Undoubtedly some advan-
tags can be obtained, but the resulting loss in engine

performance tends to lessen the advantage gained.

-—10-

SUMMARY

2.

3.

Horsepower decreases linearly with increased
back pressure at a rate of 1.1 horsepower per
inch of mercury at full throttle.

Torque decreases linearly with increased back
pressure at a rate of 1.7 foot-pounds per inch
of mercury at full throttle.

The rate of horsepower loss is decreased with
smaller throttle Openings, but the percentage
loss is greatly increased.

The rate of torque loss is decreased.with
smaller throttle openings, but the percentage
loss increases greatly.

The shape of the horsepower and torque curves
are not changed. The curves are simply dis-
placed downward by equal increments throughout
their entire range.

The conclusions of Jesse Doolittle with respect

to fuel consumption were substantiated.

._ 11..

REFERENCES

1. High-Speed Combustion Engines by P. M. Heldt -
P. M. Heldt - Nyack, N. Y. - 19h8.

2. Diesel Exhaust Noise Contrgl - Bulletin uu7 -
Burgess Battery Company, Chicago, Ill. - 19MB.

3. Effect of Variations in Atmospheric Conditions
on Diesel Engine Performance by Jesse S. Doolittle -

ASTM Transactions - February, 19Ul.

-12-

APPENDIX

VARIABLE BACK PRESSURE

C.F. = 1.036
Date: 3-22-51

Warrell

Observers:

Olsen

 

 

Hi .dpm
6 mm

Uhmm

A.moomv made

A.oev Hook
mo oaoao>

osoaoe .aoo

Ammo

coon
mason

2mm
ease

2mm
Hmchoz

2mm OOOH 6
mm HmapHcH

 

514'.
57.
62.

#60

0 136.0 u6o

.5 79.6 151.3 460
9
5

9 166
168.

93.0 45.5

80.0 120.5
00 820
5 73.0 160.5

92.0 62

00 2390 88.

3200 3170 75
2800 2770 83

24
2000 1980

P0 = 0 3500 3090 66.5
l’+00 1420

CONSTANT BACK PRESSURE

 

 

 

Observers: Warrell C.F. = 1.056
Barlow Date: 3-23-51

0 ’7

:3 A m

0' ‘4 o O

a 0:: o
H O O 03 H
g 0 5+ §~a ~a as
.4 o Fwd g3 . r4 0 C) S .
a: :2 on a .40 s g m
o h (>0 tn 0 ()5 *1 0.9
2% 9% mg n :3 >m sa m mm
3500 3500 67.8 81.5 122.9 060 53.0 0.616 1.0
3200 3180 75.5' 82.6 136.9 #60 55.5 0.585 1.0
2800 2810 83.5 80.7 151.3 #60 61.7 0.539 1.0
2#00 2#05 88.0 7#.0 159.3 #60 69.5 0. 522 1.0
2000 2000 92.0 63.# 166.9 #60 81.8 0.17 1.0
3500 3500 66.5 80.1 120.5 #60 50.1 0.669 1.5
3200 3175 7#.5 81.# 135.0 #60 56.3 0.585 1.5
2800 2790 83.3 80.0 151.0 #60 62.2 0.539 1.5
2#00 2390 88.5 7#.0 160.5 #60 70.6 0. 513 1.5
2000 2000 91.5 62.2 165.9 060 8#.2 0. 500 1.5
1#00 1#50 92.0 #6.0 166.9 #60 112.6 0.518 1.5
3500 3#70 65.7 80.1 121.5 #60 53.5 0. 601 2.0
3200 3180 69.7 77.8 128.0 #60 55.7 0.57# 2.0
2800 2730 70.3 67.# 130.0 #60 61.7 0.525 2.0
2#00 2370 71.1 59.3 131.5 #60 69.5 0.516 2.0
2000 1950 91.1 62.# 168.5 310 5#.1 0.506 2.0
l#00 1395 90.1 ##.2 1668 310 76.7 0.513 2.0

CONSTANT BACK PRESSURE

 

 

 

Observers: Warrell C.F. = 1.056

Barlow Date: 3-23-51

o ’7

:3 A m

0‘ $4 0 O

a :10 m
H O 0 ID H
2 o 5* 3" " “h
'32: 3:: '38 E x: 3'73 E E 6a?
o a c>o an 0 c2: .4 a) app
2% 9% ma 0 o bh B m mm
3500 3500 68.0~ 83.7 125.7 #60 5#.1 0.592 2.5
3200 3150 72.0 79.9 133.0 #60 56.3 0.603 2.5
2800 2730 82.9 79.5 153.0 060 63.0 0.532 2.5
2#OO 2#05 86.2 7#.0 159.1 #60 70.5 0.51# 2.5
2000 1985 89.9 62.8 166.0 #60 8#.2 0.507 2.5
1000 1380 88.5 #3.1 163.6 #60 117.5 0.530 2.5
3500 3080 66.6 81.5 123.1 060 52.3 0.625 3.0
3200 3170 7#.7 83.2 138.0 #60 56.3 0.577 3.0
2800 2760 82.6 80.2 152.7 #60 62.1 0.538 3.0
2#00 2385 87.2 73.1 161.1 #60 68.3 0.531 3.0
2000 l9#5 90.1 61.7 166.5 310 5#.7 0.517 3.0
1#00 1370 88.7 43.1 16#.0 310 75.8 0.538 3.0
3500 3005 67.5 81.7 120.8 060 50.3 0.605 3.5
3200 3125 75.3 82.9 139.5 #60 56.7 0.571 3.5
2800 2705 81. 78.5 150.3 060 60.1 0.533 3.5
2000 2390 86.7 72.9 160.3 060 70.0 0.523 3.5
2000 1980 89.0 62.2 165.0 060 83.7 0.515 3.5
1400 1380 88.2 #2.8 162.9 #60 116.0. 0.5#0 3.5

CONSTANT BACK PRESSURE

 

 

 

Observers: Warrell Warrell C.F. = 1.056
Barlow Olsen Date: 3-23-51

0 ’7

:3 A m

U‘ H . 0

$4 00 a)
r... O O m H
g o E" 2" V =0:
8: g 83 fi 38 S E: ad
ca LE 00 0 033 H 0) mp
2 Ba: 01.4 0 >13. E-¢ 00 mm
3500 3050 66.7 80.9 123.1 060 52.3 0.625 0.0
3200 3170 7#.1 82 5 137.0 #60 56.3 0.577 #.0
2800 2815 81.6 8 150.9 #60 62.1 0.538 #.0
2000 2360 88.0 73.0 162.6 060 68.3 0.531 0.0
2000 1970 88.7 .# l6#.0 310 5#.7 0.517 #.0
1000 1385 87.9 02.7 162.2 310 75.8 0.538 0.0

3-28-51

3500 3510 68.5 5 #60 53.5 0.600 1.0
3200 3190 77.5 9 #60 56.2 0.556 1.0
2800 2760 85.6 1 #60 62.3 0.52# 0.8
2000 2000 91.5 0 060 68.5 0.513 0.6
2000 2010 9#.5 .0 #60 80.5 0.505 0.6
1000 1390 95.3 9 310 76.2 0.516 0.5
C.F. = 1.0#1

5.

BACK PRESSURE TEST
CONSTANT SPEED

 

 

 

Observers: Warrell C.F. = 1.001
Olsen Date: 3-28-51
0 0
:5‘ :3.
o 2 0 8
S-c o L. o
s 8 o 9* s a o 5*
2.? ’33 3: '38 a i: t t: ”a '38 E s:
D. :39 ha 00 no 0 C1. 63-. 5% co m 0
U) COD. E-I (Do—1 O U U) me. E4 00.4 D D
3500 t - - 3200 t - -
1 3080 70.3 80.9 127.9 1 3200 77.5 36.0 101.1
1% 3520 69.6 85.1 126.7 12 3155 79.2 86. 6 100.2
2 3060 70.0 80.5 128.1 2 3090 77.1 82. 6 100.3
2} 3000 71.9 85.9 130. 9 25 3150 76.9 80.0 100.0
3 3080 68.0 82.1 123. 8 3 3100 76.0 82.0 139.1
35 3080 67.5 81.5 122.8 35 3110 77.0 83.2 100.0
4 3130 75.8 82.1 138.0
0% 3200 73.0 82.1 133.6
5 3200 73.3 82. 1 133.0
5% 3200 72.5 81.3 132.0
6 3180 73.1 80.133.1
2800 t - - 2000 3 - _
1 2850 80.1 83.1 151.3 1 2360 91.5 70.6 166.6
1% 2800 80.0 81.5 152.9 15 2010 89.8 70.6 163.5
2 2790 83.9 81.0 152.7 2 2000 89.0 70.1 162.7
25 2770 83.7 80.0 152.0 25 2390 88.3 73.0 160.7
3 2780 83.6 80.5 152.2 3 2370 88.8 72.8 161.7
3% 2750 83.5 79.5 152.0 3% 2390 88.3 73.0 160.7
0 2705 82.7 78.7 150. 5 0 2350 87.6 71.3 159.5
0% 2720 83.3 78.3 151. 6
5 2700 82.8 78.3 150. 7
55 2770 83.6 80.2 152.2
6 2780 82.1 79.0 109.5

BACK PRESSURE TEST
CONSTANT SPEED

 

 

 

Observers: Warrell N C.F. = 1.001
Olsen Date: 3-28—51
0 O
:3 :3
. E 0 8”
$4 0 $4 0
=3 . 9 2 2 . B
'8 Mg 0 HO 0. . 0 MID 0 H6 0. o
0 on) :42: 0503 LT: 30 a) on) 23:: 0305 :1: R
Q. 674 kg 00 m o D. «SS-c tag 00 m o
In (DD-o [-i 01.4 D D 0) ma. E" 11);] O O
2000 2 - - 1000 0 1360 90.0 00.2 171.1
1 1900 92.2 61.8 167.8 1 1020 90.0 06.1 171.1
1; 1955 92.7 62.6 168.8 1% 1360 93.5 00.0 170.2
2 1960 92.7 62.8 168.8 2 1390 92.5 00.0 168.0
25 1900 91.8 61.5 167.1 2% 1320 91.0 01.6 166.0
3 1910 92.3 60.9 168.0 3 1350 91.1 02.5 165.8
3% 1920 91.0 60.0 165.7 3% 1320 90.0 01.0 165.5
0 1930 90.0 60.6 165.5 0 1370 91.1 03.1 165.8

 

0’ I.

I'll:

BACK PRESSURE TEST
CONSTANT SPEED — 3/0 THROTTLE

 

 

 

Observers: Warrell C.F. = 1.05
Olsen Date: “-2-51
A O "o
00 :3 (0

mm 8 ‘33 8

H $404 0 o to

g :30 a E4 2v v

a?) Mg 0 0 H6 o On 3H 0 0

an 00):: :5 0303 £0 :13 H0 8 (an

oil ushra $4 :30 o a: C): -4 In

20) mil-v E4 61...“! O O >l’x. B 00

3500 1 3065 58.0 106.3 70.2 310 03.0 0.623
2 3065 57.0 100.5 69.0 310 03.5 0.626
3 3065 56.7 100.0 68.6 310 03.5 0.630
0 3065 56.7 100.0 68.6 310 03.8 0.625
5 3030 56.0 102.5 67.1 310 00.2 0.633

3200 1 3200 60.0 118.0 71.9 310 00.9 0.580
2 3200 60.0 117.1 71.5 310 05.2 0.581
3 3170 65.0 119.1 75.2 310 05.0 0.565
0 3200 63.0 115.6 70.3 310 05.3 0.590
5 3180 63.5 116. 70.0 310 05.3 0.590
6 3130 63.2 116.0 68.9 310 05.5 0.600

2800 1 2785 70.6 129.5 68.6 310 09.7 0.551
2 2770 71.2 130.5 68.6 310 50.3 ‘ 0.505
3 2760 70.5 129.1 67.7 310 50.0 0.551
0 2755 69.0 126.5 66.2 310 50.0 0.560
5 2760 69.3 127.0 66.6 310 50.5 0.559
6 2750 68.2 125.0 65.0 , 310 50.0 0.571

2000 1 2055 70.1 135.9 63.0 310 50.1 0.509
2 2005 70.8 137.0 62.7 310 50.6 0.550
3 2000 73.9 135.5 61.7 310 55.2 0.552
0 2010 '73.5 130.8 61.8 310 55.6 0.506
5 2370 72.1 132.1 59.6 310 56. 0.560

‘1

 

 

'IFI'IIII

BACK PRESSURE TEST
CONSTANT SPEED - PART THROTTLE

 

 

 

Observers: Warrell C.F. = 1.071
Olsen Date: 5—3-51
A 0 I:
ho :3 u:
a: 8‘ $u~ o
0 g 00 0)
r4 ps0 o o m
2 2° . a m w v
'7? “:2 ° "'7 2° .: 5'2 °’ °
86. 3.... a; 88 o o '8': 5 8
zen mmv t—o 00...) o 0 >0. £0 00
3/0 Throttle
2000 1 2060 77.7 106.0 57.2 310 62.0 0.530
2 2070 77.2 105.0 57.1 310 61.7 0.530
3 2060 76.5 103.5 56.3 310 62.7 0.533
0 2000 76.2 103.0 55.5 310 63.3 0.536
5 2010 76.0 102.5 50.6 310 63.5 0.502
1000 1 1055 78.1 106.5 00.6 160 03.5 0.525
2 1090 77.9 106.1 01.0 160 0 .3 0.529
R 1370 76.6 103.8 37. 160 07.9 0.500
1 00 70.7 100.1 38. 160 05.5 0.535
5 1060 75.0 100.7 39.1 160 05.5 0.5 5
1/2 Throttle
2800 1 2730 52.0 98.3 51.0 310 62.1 0.590
2 2735 52.3 98.0 51.0 310 61.0 0.601
3 2700 51.2 96.0 0.1 310 61.0 0.615
0 2700 51.3 96.3 9.0 310 61.8 0.616
5 2730 50.0 9 .8 08.7 310 61.1 0.631
6 2720 50.0 9+.5 08.9 310 62.9 0.603

BACK PRESSURE TEST
CONSTANT SPEED - PART THROTTLE

 

 

 

Observers: Warrell C.F. = 1.071
Olsen Date: 5-3-51
A O f:
00 :3 00
I: 0* hes o
o L. D. 0 0 0
r-I ‘00-. o :2: o m
at, a o o E-t CD 0v v
«40> 31m . l> Fwd . . §r4 o (J
3:» <00>Q : «:8 A $0 r10 5 IL
0:1 QSHvd $05; ()0 o 0 0:: 4H In
200 mmv E—c 01.4 D o >En El 00
1/2 Throttle
2000 1 2305 57.0 107.7 08.1 310 66.8 0.585
2 2050 56.3 105.7 09.3 310 65.2 0.585
a 2370 56.3 105.7 07.6 310 66.5 0.593
2000 56.0 105.1 08.0 310 65.7 0.596
5 2360 55.5 100.1 06.8 310 66. 0.602
6 2360 55.5 100.1 06.8 310 66.9 0.601
2000 1 2000 66.0 123.9 07.2 310 70.2 0.536
2 2000 65.1 122.1 06.6 160 38.0 0.502
3 1970 60.0 120.1 05.1 160 38. 0.560
0 1900 60.5 121.0 00.7 160 39.3 0.552
5 1960 60.7 121.5 05.0 160 39.5 0.501
1000 1 1075 70.7 132.9 37.3 160 50.0 0.520
2 1070 69.8 131.0 36.65 160 08.9 0.502
3 1020 68.9 129.2 30.9 160 50.7 0.508
0 1020 68.0 127.5 30.5 160 50.9 0.553
5 1020 67.0 125.8 30.0 160 52.2 0.506

9.

BACK PRESSURE TEST

CONSTANT SPEED - PART THROTTLE

 

 

 

Observers: Warrell C.F. = 1.071
Olsen Date: 5-3—51=
A 0 ’7
u) s w
n: c: ~0»~ o
o A n. 0:) 0
#4 ps0 o a: o m
2 2° . a m .1 v
«H M01 0 0 H6 0 o 5H 0) 0
SE; 010:: SE; 010 s. h r40 8 It
0 diari n (:0 <5 0 0:: «a 0)
z mmv E4 01...] U 0 >50 5" m
1/0 Throttle
2000 1 2020 16. 6 31.1 11.66 160 80.7 1.031
2 2000 16.7 31.35 12.20 160 80.2 0.990
3 2020 16.3 30.6 11.78 160 79.0 1.038
0 2020 16.3 30. 6 11.78 160 79.2 1.000
5 2015 16.9 31. 7 12.19 160 78.8 1.010
1600 1 1605 31.0 58.9 18.05 160 79. 5 0.660
2 1620 31.0 58.1 17.95 160 80. 9 0.668
3 1600 30. 6 57.0 17.51 160 80. 0 0.689
0 1575 30. 8 57.8 17.35 160 81. 7 0.680
5 1565 30. 8 57.8 17.21 160 81.8 0.689
1200 1 1195 00.3 83.0 18.90 160 88.0 0.580
2 1175 00.9 80.2 18.85 160 88.3 0.580
3 1170 03. 9 82.0 18.35 160 89. 7 0.590
0 1160 03.0 81.5 18.00 160 90. 6 0.595

10.

BACK PRESSURE TEST

VARIABLE B.P.

— PART THROTTLE

 

 

 

Observers: Warrell C.F. = 1.005
Olsen Date: 5-5-51
0 ’7
S m
8 % 8’8 8 85:
H O o In 54
d E" “3 0V V :5 o
C 0 g 0 $3
2 8 '3': .: .: 1.7.: s 2 2m
25 25 83- 8 s :2 a: 3.? 22.
3/0 Throttle
3500 3530 56.9 100.0 70.5 310 02.0 0.629 0.9
3200 3200 65.7 120.9 73.0 310 00.9 0.567 0.8
2800 2790 71.8 181.9 69.7 310 59.9 0.056 0.75
2000 2360 77.5 1 .2 63.3 310 55.7 0.525 0.6
2000 2000 80.7 150.1 56.0 310 60.2 0.516 0.6
1000 1395 80.7 150.1 39.0 310 91.2 0.521 0.20
1/2 Throttle
2800 2775 53.1 '97.5 ,51.7 ‘160 532.1 0.585 0.5
2000 2370 60.1 110.5 50.0 160 30.5 0.563 0.0
2000 2000 66.5 122.1 06.7 160 38.2 0.500 0.0
1000 1390 73.7 135.5 36.0 160 51.1 0.527 0.2
1/0 Throttle
2000 2000 28.6 52.5 20.1 160 69.2 0.697 0.1
1600 1580 39.1 71.9 21.7 160 73.2 0.610 0.1
1000 1185 50.5 92.8 21.0 160 82.1 0.560 0.0

11.

 

TV"-

 

 

12.

 

 

mm “6.50.
a a.

mm 8.5....
mmmo «0

& .mcacmno
oaupoana

 

1.1

0.05

25
50

1.3

0.80

1.5

0.80

75
100

1.7

. 1.1

C 5‘ HF

13.

EFFECT DF‘ EACK PA? Ska/1W5 CN
BRA/(f HORSEF’OWER AT FULL. THRCTTLE

 

 

 

 

3:0 #: 4. i 1% . 1 1 1 L A 1 A
50 CW FJA’EdSL/A'E - 770. 1:: H55.
.2’

10.

 

.77- F'E‘C I
QN EQ/‘trff HQQDE‘PnyE/r A ,° 3.! 72H
/ R
1 P 4.1 _. [352:1
V
{ \4'5‘ 1‘4.

 

71’)

 

 

 

 

 

CBHF’

 

 

 

1'\
.w
1

L)

EFFECT OF BACK PRESSUR’E
Oxv ERA K5 HOPSEPOVVEA’ AT l/jé THPOTTLE

15.

 

57 IF-'

A
I-

(A)
L,‘

L ,1

K.)

 

 

 

0.
_\~ \\\L 2’81 >0
\NNM —_.._ Mk“

\‘ ‘ ~ ngk :)\‘_’)
b
1.
C / .5.‘ .9 4/- :7

:5 «CK PEI-:55 OPE - /N. o F Hg

b1

F'l/W

so

/-0

EF‘F’E’ET‘ or BACK PF’ESSURE
0N BQAK‘E 2707:3572)qu AT /4 rweorrLJr

 

 

 

 

 

 

 

/ r." 3 ‘9’
59555108585— “ //\/. OF— H.’
(‘3)

0‘

F'JW

16.

17.

0/5 PLA :5 MIT/VT o .F H".- ‘88 2‘71); 511/23?
C a 4‘ v E. 5 v ,. 4v 002/1 :55: 8A -: i1
F’FeESS OPE A7‘ FUL L THPOT/‘LE

7O

60

CEi/v'F"

 

4O

 

3 O A L . . ' L

1’00 O /5OC7 2 9’30 3 C Q 30 0C) 350;?

FJW

CBHF’

18.

075722. A CEMEN r or: HOP SEDDWEF?
CURVE. EV INCREAsED BACK
PRESSURE AT % THROTTLE

 

 

 

5 0
7o 8
.4
6
60 .
50 L
4-0 .
30 1.
‘23 A L L 1 J 1
““0 ’5 ""J £97053 £67530 300 _> any.

C E'HF’

 

D/SPL A C‘EMEN 7‘ CF" HJA" SEPO wEQ
Cup? v5 525/ INCREASE/.7 BACK
PRESS um: A T 3;; 7wm0r 7'15

 

19.

 

:3 1

5;) 1.

40 1

3.3 r

(Ex-J A 4 J. A l
a) 0 0 I577») ECG-O E50 0 3 Q 1;: L; .535 2) 0

FJ W

CBHP

BO

#3

D/ 3 1971A :: EMF/v 7‘

La

 

FFES‘SUQE A 7

 

N733
RPM

OF /~10‘?$EPOV\-’ER
CUQ\/EL‘5 EV INCREASED BACK

(/7. THROTTLE.

/‘r"

0

a? f) L) g.)

2500

F~JW

20.

.5 ("2
EL")
7:)
{1
1‘
CD
0
CC
53
4.7
4 _
a L
U .7 ,

 

 

21.

COM/DA Rx 3 ON 555' 7' wgz-gtv
CALCULA TED {1 EXF’E'RV'MENTAL CURVES
A T [C20 ’4: ,1) .

  
   
 
 

 

 

 

 

 

 

 

 

_:_-_:L 1 ”IL A 7‘50
r—
. EXPEF’IMEN rm. 1..
c I/E’VE' C DAV-1’50 TE {:3-
L.
EA :3 K PRES 37/ PE
/ 714.3 " 75 .c 9 a 3 :25; 3.; 3 7 3.3 O .3 .4 5.30
,C‘F'M

PU \A/

7.

TOPS L’E

IOO

 

22.

 

 

 

L
L
L A L L l 4 1 1 A 4

BACK PRESSURE - ”V 0" “(5%.

FUW

 

7,

T'QF?QUE ~

23.

54—550 'r or BACK 9:255 s UF’E
o/v TOQQUE A r % T/yfi’o 7’ 71'. E

/40

x0:-

 

 

 

do 1 4 L 1 L 1 4 1 1 g LA 1
o / 2 3 4 5 A .
8A C K ’9»? ES 9 (JR’E — m: Jr: a;

FJVV

TORQUE — 7‘

”+0

' 120

100 F

80

 

21+.

EFFECT OF‘ BACK ngsrsc/RE
ON Toma/e Ar ’92? HIROTTLE

 

 

A L A .1 L L L L A A. J A

/ 2 3 1+ 5 6
BACK #9533095 - w. or Hg

F'JW

7.

TORQUE- -

£7“ch 7' OF BACK PPESSUPE
0N 7179005 A 7' '4 rHfio r'rL E

25.

 

 

 

 

 

 

I \
/0() P
L-
>—— {’ /(:)Cd
50 _ i
L
60 bk " /{:‘o_._c_>
I
L
40 r
{.2300
4+
20 A L L L 1 L
O / (:3 3 5

540K PRESSURE - W. OF {:5

F'JW

‘ \ 26.
E F/‘EC 7’ OF TH-PO T H. E SE 77-1/VG ON 7345-" A}; ff or
C'HA N G E OF H.195 ED 0 WE»? W" 1‘7" BA CK PAY: .54 IF 5'

 

 

 

 

<3 L
$0
Qk ’ ~
K )
‘I'flg
L.
o 1__ + L _A__
J 85' 5'0 75' /0~9
THPQTTLE OPEN/MG - 9.4
EFFECT or n/Avorng 'SE'TT/NG ON 7"HE RATE or
CHA/VGE OF fOQQUE W/7'H BACK PQESS‘c/QE
2 _
51‘
‘h t“)
{I E ’ r
E
O J 4 L L
0 25 5'0 75 IOO'

x"
7715’? f F1. E o PEN/A's - C7C,

F'JW

27.
SAMPLE CALCULATIONS

1. Correction Factor

CF 3.22522 /§§§_:_la_
B - E / 520

where: 29.92 = standard atmospheric pressure
in inches of mercury.
B = observed barometric pressure in

inches of mercury.

F)
ll

water vapor pressure in inches
of mercury.
520 = standard atmospheric temperature
in degrees Rankine.
T 8 observed dry bulb temperature
in degrees Fahrenheidt.
CF = £2.23 //§__‘Ei = 1.071

2. Corrected Torque
T I CF 1 L x W
where: CF = correction factor
L = brake arm in feet
W = scale load in pounds
T = 1.071 x 1.75 x 68.9 = 129.2 foot—pounds
3. Corrected Brake Horsepower

CBHP = CF 1 W x N
3000

where: CF = correction factor

W scale load in pounds

N 3 r.p.m.

._. __.

28.

3000 = dynamometer constant

CBHP I 1.071 x 68,h x 1&20 = 3b. 9
3000

h. Brake Specific Fuel Consumption

BSFC . 160 x o x 62 b x 600 #/BHP -hr.
(2.55) 3 x £72 8x CBEPx

=.229_______
CBHP x t

corrected brake horsepower

where: CBHP
t = time to consume 160 co. in secs.

BSFC = 970 1_ = 0.5u8 #/BHP - hr.
3b.? x 50.7

‘. Per cent Horsepower Loss

% = 0.1095 x 3200 x 1.1 3 2.168 HP loss

2§%§% x 100 = 2.; %

J
O

nee 16 '5:

 

O,

MICHIGAN STATE UNIVERSITY LIBRARIES

I In; lljlll IIIIIIHIIIII

3 1 3178 0624

'

 

93