Experimental investigation on performance, combustion and emission characteristics of a common-rail diesel engine fueled with polyoxymethylene dimethyl ethers-diesel blends

Abstract

Polyoxymethylene dimethyl ethers (PODE) was blended with diesel fuel at volume ratio of 10%, 20% and 30% in the preparation of PODE-diesel blend fuels (marked as P10, P20 and P30). The volatility and oxidation characteristics of blend fuels, and the thermal parameters were analyzed using thermogravimetric method and Coast-Redfern integral method respectively. Also, the effects of PODE-diesel blends on the performance, combustion and emission characteristics were carried out on a 4-cylinder turbocharged intercooled common-rail diesel engine. The results show that P10, P20 and P30 have good stability at room temperature, and also the kinematic viscosity of PODE-diesel blends gradually decreases with increasing PODE blending ratio and temperature. Also with the increase of the blending ratio of PODE, the activation energy of blend fuels decreases and the comprehensive combustion index improves. When the diesel engine is fueled with PODE-diesel blends, the ignition delay period is shortened, shifting the rate of heat release and the rate of pressure rise curves forward. This increment in PODE blending ratio increases the maximum in-cylinder pressure and improves the brake thermal efficiency. The blend fuel has little impact on NOX emissions, however, it can significantly improve HC, CO and smoke emissions. Compared with pure diesel fuel, the smoke emissions of P10, P20 and P30 at full load are reduced by 27.6%, 41.5% and 47.6%, respectively. PODE-diesel blends therefore could reduce particle number concentration and particle mass concentration in diesel exhausts, shifting the distribution peak to small particle sizes. Compared with pure diesel fuel, the peak number concentration of accumulation-mode particles (50nm<Dp<1000nm) of P10, P20 and P30 decrease by 15.97%, 32.28% and 43.79%, respectively. This indicates that PODE as one of the emerging alternative fuels has the potential to achieve high efficient and clean combustion for diesel engines.