3-D Computations to Improve Combustion in a Stratified-Charge Rotary Engine - Part III: Improved Ignition Strategies

A three-dimensional combustion model for a direct-injection stratified-charge rotary engine is used to identify modifications to the engine that should lead to better indicated efficiency. The engine has a single spark plug positioned alongside a single-hole pilot injector in a cavity located after the minor axis and a five-hole main injector that is located before the minor axis. It is predicted that a second ignition source located upstream of the main injector will lead to an increase in indicated efficiency of 6-8% if it ignites the mixture consistently. The computations were made at high and low engine speeds and loads, covering a significant part of the practical operating range of the engine. It is also predicted that the gain in efficiency of the engine with two ignition sources would be 7-10%, instead of 6-8%, if a two-hole pilot injector is also used instead of the one-hole pilot. Measurements made after the computations showed that indeed ignition from the second ignition source was not reproducible. However, in those cycles in which ignition occurred, with two igniters the efficiency increased by about the predicted amounts.