Simulation study on in-cylinder combustion and pollutant generation characteristics of PODE/methanol blends

Abstract

In order to cooperative control particulate matter (PM) and nitrogen oxides (NOx) emissions from compression ignition engines, the coal-based oxygenated fuels polyoxymethylene dimethyl ethers (PODE) and methanol are selected as diesel alternative fuels. The numerical model of in-cylinder combustion is established by CFD simulation platform coupling PODE/methanol chemical reaction mechanism and then in-cylinder combustion and pollutant generation of PODE/methanol blends under various methanol ratios, fuel injection parameters and intake pressures conditions are calculated and analyzed. Results show that compared with pure PODE, the maximum combustion pressures of the blends with 30% methanol increases by 3.7%, the combustion duration is shortened by 1.2°CA, and NOx emissions decrease by 16.1%. Soot emission of the blends decreases with the increase of methanol ratio. Both the advance of injection timing and the increase of injection pressure lead to the increased peak values of in-cylinder pressure and temperature of the blends, the advance of combustion heat release starting point, the reduction of combustion duration and the increase of NOx emissions. However, soot emission shows an overall downward trend. The increment in intake pressure significantly reduces the in-cylinder temperature and the emissions of NOx and soot, which effectively alleviates the trade-off relationship between NOx and soot.