Methane/CNG Combustion in a DI Radical-Ignition Rotary Engine with Low-Heat Rejection

Numerical examination is made of the use of methane in a direct-injection (DI) radial-ignition (RI) diesel rotary-combustion engine (RCE) while operating under ultra-lean fuel conditions at low compression ratios (CR's). The simulated engine is operated with the help of five percent hydrogen as a pilot. Homogeneous combustion under such conditions is made possible by radical species produced in periphery-mounted secondary chambers. The bulk of the mass of the radical species generated by these chambers is used in the subsequent cycle to initiate and control main chamber autoignition. One goal is to see whether DI-RI alone can substantially extend the lean-burn region of this engine to enable low-heat rejection high-power density operations with low NO_x emissions. A detailed examination is made of the effects of internally generated “radicals” on methane combustion chemistry in the RCE. The simulation follows the radical-driven chemical-kinetics, the heat transfer and the pressure-driven mass-species transfer occurring simultaneously in and between the various chambers and the manifold.