CNG/Methane-Combustion in a Homogeneous-Combustion Radical-Ignition D.I. Diesel Engine

A detailed examination is made of the effects of internally generated “radicals” on the chemical-kinetics mechanism for CNG (compressed natural gas) combustion in a direct-injection (DI) diesel engine operating under ultra-lean fuel conditions at normal diesel compression ratios. The primary generating site for these “radical” chemical species is a set of mini-chambers located within the cylinder head. Explored in this study is the potential for controlling the autoignition timing of the engine by altering the rates of this radical generation process via the temperature management of these chambers. The study suggests that the temperature management of these secondary chambers may help enable the control of the ignition timings in response to engine load changes. The simulation involves the chemical-kinetics of 29 species and 84 chemical reactions solved simultaneously within the mini and main chambers as these chambers interact with each other, with the engine housing and with the manifold (exchanging energy, momentum, mass and chemical species).