A rapid compression machine (RCM) has been designed and built for investigating the autoignition characteristics of bio-derived jet and diesel fuels. The RCM has been designed with a particular emphasis on versatility, so that non-volatile fuels may be tested in a premixed gas phase, as a fuel spray, or as an aerosol in an oxidizing bath gas. A blend of these test approaches provides insight into fundamental fuel kinetics and empirical knowledge of fuel performance in practical combustion systems.A significant portion of this work is dedicated to the optimization of the RCM, and to the development of test methods and data analysis protocols. The RCM is pneumatically-driven and hydraulically-stopped, and it employs a creviced piston that promotes formation of an adiabatically-compressed core of gas. A novel approach to gas-phase charge preparation has been used in which premixtures are prepared directly in the test chamber by use of a fuel injector. Characterization experiments with JP-8 jet fuel confirm this new direct test chamber (DTC) charge preparation protocol is a viable approach for measuring high-fidelity gas-phase ignition delay data. The DTC approach enables efficient gas-phase testing of non-volatile fuels that may not otherwise be tested with the traditional large batch mixture test approach. For fuels that lack sufficient volatility for testing via the DTC approach, two alternatives have been developed. The fuel injector may be used for fuel spray ignition studies which yield practical data with regard to the coupled spray evaporation and ignition processes that are relevant to engines. A second approach volumetrically fills the test chamber with a fuel aerosol and oxidizing bath gas before undergoing wet compression in the RCM to vaporize the fuel. The compression process yields a gaseous mixture of fuel, oxidizer and diluent gases that undergo autoignition. Fuel aerosols are introduced to the RCM through a poppet valve that has been optimized using computational fluid dynamics simulations to enhance mixture formation in the test chamber. Characterization experiments with ethanol have been completed which demonstrate experimental repeatability for the aerosol ignition tests.Bio-derived (camelina seed- and tallow-derived) alternative jet fuels, referred to as hydrotreated renewable jet (HRJ) fuels have been studied using the DTC approach. The large amount of paraffinic content in the HRJ fuels and lack of aromatic compounds relative to conventional JP-8 jet fuel leads to enhanced ignition quality. Ignition delay measurements are made at low compressed temperatures (625 K ≤ Tc ≤ 730 K), compressed pressures of pc = 5, 10, and 20 bar, and equivalence ratios of 0.25, 0.5 and 1.0 in air. The camelina and tallow HRJ fuels exhibit similar autoignition characteristics, but the two fuels can be distinguished under stoichiometric conditions. Kinetic modeling is conducted with a 2-component surrogate (10 % n-dodecane/90 % 2-methylundecane) to evaluate the potential to predict ignition behavior of the HRJ fuels. Modeling results indicate that the surrogate fuel can only provide useful predictions at a limited set of conditions (pc = 5 bar and stoichiometric), and that the agreement of the model and experimental data improves with decreasing compressed pressure.The RCM facility has also been used to study the spray ignition behavior of petrodiesel and fatty acid alkyl esters (i.e., biodiesel) with varying alkyl chain lengths (methyl vs. butyl) and degrees of unsaturation imparted by using different feedstock oils (soy vs. canola). These tests have been conducted at the low temperatures (676 K ≤ Tc ≤ 816 K) and reduced oxygen concentrations (12 % and 18 %) relevant to low temperature combustion schemes in advanced diesel engines. On average, the biodiesel (canola-derived methyl esters) ignited 23 % faster than diesel under similar test conditions. The biodiesel tests demonstrate that even relatively small changes in molecular structure lead to modest changes in spray ignition behavior when coupled to evaporation.
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