Numerical simulation and experimental investigation on pollutant emissions characteristics of PODE/methanol dual-fuel combustion

Abstract

The current study focuses on the effects of methanol ratio, injection timing and intake temperature on emission performance of a common-rail engine with polyoxymethylene dimethyl ethers (PODE)/methanol dual-fuel combustion mode. Then, the numerical model of dual-fuel combustion is established using CFD software CONVERGE coupled with PODE/methanol chemical kinetic mechanism, and the distribution and evolution characteristics of important radicals, methanol and temperature fields inside cylinder are calculated and analyzed. The results show that the NOx and soot emissions of dual-fuel mode decrease by 12.4% and 26.0% compared with pure PODE at 50% load, but CO and HC emissions increase. With the methanol ratio increasing, the NO and N2O emissions decrease, while the methanol, NO2, HCHO, C2H4, CH4 and C2H6 emissions increase, and the peak HO2 mass of dual-fuel increases by 156.2% compared with pure PODE. With the advance of injection timing and the increase of intake temperature, the generation rate of H and OH radicals in dual-fuel combustion raise, the emissions of NO and NO2 increase, while the emissions of methanol, HCHO, C2H4, CH4 and C2H6 decrease. Therefore, compared with traditional diesel engine, more attention should be paid to the unregulated emissions of NO2, methanol and HCHO for PODE/methanol dual-fuel engine.