Effects of injection and spark timings on combustion, performance and emissions (regulated and unregulated) characteristics in a direct injection methanol engine

Abstract

Methanol is a promising low-carbon fuel for internal combustion engines. Increasing the compression ratio combined with direct injection (DI) is an important technology to realize methanol's potential for carbon reduction. In this work, experimental investigations into the effects of injection timing and spark timing (ST) on combustion, performance, and emissions characteristics were carried out on a high compression ratio DI SI methanol engine. The experiments were performed at two intake pressure of 65 kPa and 87 kPa and a constant engine speed of 1500 rpm. The ignition delay and burn duration were slightly reduced with retarding SOI. However, the volumetric efficiency and combustion efficiency decreased rapidly with retarding SOI. The trade-off relation between the effect of SOI on NO and CO emissions was notable. However, methanol and formaldehyde emissions increased simultaneously with retarding SOI. ST retarding could mitigate the NO and CO emissions at the expense of deterioration in heat release rate, thermal efficiency, methanol and formaldehyde emissions. Overall, the combustion stability was good with all SOIs and STs but the combustion efficiency and emissions deteriorated with retarding SOI. A range of −270 to −240 °CA aTDC would be optimal for SOI to obtain good performance.