Experimental and computational studies of the effects of natural gas composition variables on autoignition delay times will be carried out under simulated diesel engine conditions in a constant-volume combustion vessel. Onset of heat release and flame lumino-sity will be measured for experimental determination of these delay times. In addition, the HCT program (an existing one-dimensional hydrodynamic, chemical, and thermal computer code) will be used to study the theoretical dependence of this delay time on natural gas composition. Model predictions will be checked against the experimental results. Finally, a Cooperative Fuel Research (CFR) single-cylinder Diesel engine will be modified to burn compressed natural gas (CNG) and efficacy of these modifications will be studied. Natural gas is an attractive alternative fuel to diesel fuel since it has a low emissions potential and is readily available. However, under compression ignition conditions, natural gas has poor ignition characteristics relative to diesel fuel. Better understanding of the ignition characteristics of natural gas and their dependence on gas composition (which is somewhat variable) are needed to facilitate the use of this fuel in compression ignition engines.
