Combustion Regimes in the Chrysler Multi-Air Multi-Fuel Engine, Part 1 - Diesel Assisted Spark Ignited

This paper is the first of three papers stemming from a dual fuel Chrysler prototype engine which uses both diesel and gasoline direct injection running at stoichiometric conditions, as part of a project to explore the viability of incorporating an engine platform which utilizes low temperature combustion regimes into a modern automotive application. The combustion system used high rates of EGR while maintaining combustion stability by using high charge motion intake port and a high energy ignition system. The engine ran highly dilute SI combustion at low loads, Diesel Assisted Spark Ignition at medium loads and a transition to Diesel Micro Pilot ignition at medium to high load. This paper explores diesel assisted spark ignited combustion at medium loads 6.5 bar to 12.7 bar BMEP. The second paper will explore the use of diesel micro-pilot ignition at high loads 10.6 bar to 14.5 bar BMEP and the third paper to be published in 2024 will explore fuel property effects (mainly Cetane and Octane) through the use of alternative fuels. In the diesel assisted spark ignited combustion regime combustion is initiated via a spark while using a diesel injection to provide a low octane fuel source early in combustion. Results were obtained at speed/load points ranging from 1500 to 3200 RPM and boost levels ranging from 95 to 200 kPa. Spark timing, diesel injection timing, and exhaust gas recirculation percentage were crucial variables affecting the performance of the engine. Brake thermal efficiency levels above 39% were possible at numerous operating conditions.