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

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 degrees 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. (C) 2019 Elsevier Ltd. All rights reserved.