Operating a heavy-duty direct-injection compression-ignition engine with gasoline for low emissions

A study of partially premixed combustion (PPC) with non-oxygenated 91 pump octane number¹ (PON) commercially available gasoline was performed using a heavy-duty (HD) compression-ignition (CI) 2.44 l Caterpillar 3401E single-cylinder oil test engine (SCOTE). The experimental conditions selected were a net indicated mean effective pressure (IMEP) of 11.5 bar, an engine speed of 1300 rev/min, an intake temperature of 40°C with intake and exhaust pressures of 200 and 207 kPa, respectively. The baseline case for all studies presented had 0% exhaust gas recirculation (EGR), used a dual injection strategy a -137 deg ATDC pilot SOI and a -6 deg ATDC main start-of-injection (SOI) timing with a 30/70% pilot/main fuel split for a total of 5.3 kg/h fueling (equating to approximately 50% load). Combustion and emissions characteristics were explored relative to the baseline case by sweeping main and pilot SOI timings, injection split fuel percentage, intake pressure, load and EGR levels. The results from these tests produced low engine-out NOx and PM emissions. Interestingly, with EGR rates over 20%, both NOx and PM were simultaneously reduced while maintaining or even lowering indicated specific fuel consumption (ISFC). The results presented in this paper demonstrate promising in-cylinder emissions reductions from the use of gasoline in HD CI engines.