Effect of injection strategy on cold start firing, combustion and emissions of a LPG/methanol dual-fuel spark-ignition engine

Abstract

The spark ignition (SI) methanol engine is particularly difficult for cold start at low ambient temperature. Adding liquefied petroleum gas (LPG) can ensure a successful cold start of SI methanol engine. Based on a single-cycle fuel injection strategy, the effects of the amount and injection timings of methanol and LPG per cycle were experimentally investigated on cold start firing and emissions of a LPG/methanol dual-fuel SI engine. The results show that the minimum amount of LPG injected per cycle is the key factor to determine the reliable firing of LPG/methanol engines at low ambient temperatures. In order to form an ideal mixture in the firing cycle, 300 °CA injection interval between methanol and LPG is feasible to be used. Fuel injection parameters have great influences on the HC emissions, which are 74.4% lower under critical firing than that of misfiring mode. By altering injection parameters, unburned methanol shows opposite tendencies with formaldehyde emissions and similar tendencies with HC emissions.