Experimental Evaluation of Pilot and Main Injection Strategies on Gasoline Compression Ignition Engine—Part 2: Performance and Emissions Characteristics

Abstract

Internal combustion (IC) engines play an important role in the global economy by powering various transport applications. However, it is a leading cause of urban air pollution; therefore, new combustion strategies are being developed to control emissions. One promising advanced low-temperature combustion (LTC) technology is gasoline compression ignition (GCI). This experimental study assesses the performance of a two-cylinder engine, emissions, and exhaust particulate characteristics using G80 (80% v/v gasoline and 20% v/v diesel) blend operating in GCI mode vis-à-vis baseline conventional diesel combustion (CDC) mode using diesel. The effects of double pilot injection, Pilot-1 proportion (10–30%), and main injection timing were investigated on the GCI combustion. Experiments were performed at different engine loads (3, 4, and 5 bar brake mean effective pressure [BMEP]) at a constant engine speed (2000 rpm). GCI combustion showed higher brake thermal efficiency (BTE) than CDC mode at medium loads. Hydrocarbon (HC) and carbon monoxide (CO) emissions increased in GCI mode, but oxides of nitrogen (NOx) were reduced than the baseline CDC mode. High pilot ratio and late main injection timing tests showed higher HC and CO emissions in the GCI mode at low engine loads. The GCI mode engine emitted higher nucleation mode particles and nanoparticles than baseline CDC mode at high engine loads. Using a triple injection strategy, GCI engines simultaneously reduced NOx and particulate matter (PM) emissions, especially at high loads. Controlling these emissions in baseline CDC mode engines is otherwise quite challenging.