Combustion Regimes in the Chrysler Multi-Air Multi-Fuel Engine, Part 2 - Diesel Micro-Pilot Combustion

This paper is the second of three papers stemming from a dual fuel Chrysler prototype engine which uses both diesel and gasoline direct injection running at near-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 was designed to tolerate high rates of EGR while maintaining combustion stability by using high charge motion intake port and a high energy ignition system. The engine ran on 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. The first paper explored the use of Diesel Assisted Spark Ignited at moderate loads 6.5 bar to 12.7 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. This paper explores the use of DMP at high loads 10.6 to 14.5 bar BMEP. In the Diesel Micro-Pilot mode, a small quantity diesel injection is used to initiate the combustion of a gasoline-air mixture. Testing was accomplished for engine speeds of 2000 RPM and 2400 RPM with boost levels of 180 kPa to 220 kPa. The engine was optimized to operating points using diesel injection timing and diesel percentage of total fuel mass. Results are presented for both brake thermal efficiency and emissions data. The engine produced brake thermal efficiency levels of 40%.