Combustion of a spark-ignition methanol engine during cold start under cycle-by-cycle control

The effects of ambient temperature, intake air preheating, additional liquefied petroleum gas (LPG) injected into the inlet port, and methanol injection timing on the cold-start first cycle firing behavior of an electronically controlled inlet port methanol injection spark-ignition (SI) engine were investigated under a single-cycle fuel injection strategy. The results showed that the ambient temperature significantly affects the start firing behavior of the engine. When the ambient temperature is below 16 degrees C, the methanol engine can not be started reliably without auxiliary start aids even at the large amount of methanol injected per cycle. Using a glow plug to heat the engine inlet manifold and additional LPG injected into the inlet port result in a reliable firing of the engine. The amount of methanol injected per cycle for the reliable firing during the cold start of the engine reduces obviously, and the cold-start performance improves significantly with the rise in ambient temperature. If the fuel injection timing is controlled reasonably at the engine cold start, it is possible to ensure the most fuel-air mixture to enter the cylinder on time, to realize the ideal concept of the next cycle combustion after fuel injection. Optimal control on the fuel injection timing improves the cold-start reliability and reduces the cold-start HC emissions from the engine.