PI: Ron Matthews, University of Texas.
CFD codes for piston engine simulations generally assign the adiabatic flame temperature to the numerical cell in closest vicinity to the spark gap of the actual engine, which forces a flame to propagate away from this cell. Although this is satisfactory for operating conditions under which spark ignition is not challenging, it is inadequate for engines that operate under conditions under which ignition is problematic, such as high dilution with either high exhaust gas recirculation rates or excess air, high compression ratios, and high boost pressures. Because natural gas has an Octane rating that is off the top of the Octane Rating scale, natural gas engines have both high compression ratios and high boost pressures and generally operate with dilution in order to meet emissions constraints. While some engine simulations have taken steps to incorporate the transient electrical energy input during the spark discharge process, they remain inadequate for determining whether spark ignition is possible. Prior research at UT has shown that the specifics of the transient input of electrical energy into the spark gap and its conversion to thermal energy are important. The objective of the proposed project is to develop a comprehensive numerical model to accurately simulate the impact of combustion chamber flow dynamics and the transient response of the ignition circuit characteristics on spark kernel and early flame kernel development, especially for operating conditions under which ignition is challenging for a natural gas engine. This model is to be integrated into the Converge®CFD software package that is widely used for piston engine simulations.