Experimental investigation on combustion characteristics and influencing factors of PODE/methanol dual-fuel engine

Abstract

PODE/methanol dual-fuel combustion mode was conducted on a four-cylinder common-rail engine with PODE direct injection and methanol intake fumigation. This study is aimed to investigate the effects of methanol substitution ratio (MSR), injection timing and inlet temperature on in-cylinder combustion, emission characteristics and fuel economy of dual-fuel engine. Results show that with the increase of MSR, the ignition delay of dual-fuel engine is prolonged, and the COV increases. At medium and small loads, the peak combustion pressure decreases, and the combustion phase is delayed. At high load, the peak values of heat release rate and combustion pressure increase, combustion duration is shortened, and slight knock occurs at 40% MSR. Dual-fuel mode has benefits in reduction of NOx and soot, while increases NO2 and HCHO emissions. With the delay of injection timing, combustion duration is first prolonged and then shortened. The excessive delay of injection timing leads to increased fluctuation of combustion pressure, and partial misfire occurs. With the increase of inlet temperature, the peak values of heat release rate and combustion pressure increase significantly, combustion duration is shortened, and the COV increases. At the inlet temperature of 65 °C, methanol spontaneous combustion occurs near TDC, and thermal efficiency increases to 44.6%.