Effect of diesel/PODE/ethanol blends on combustion and emissions of a heavy duty diesel engine

Polyoxymethylene dimethyl ethers (PODE) is a promising alternative fuel for diesel engine with high cetane number, high oxygen content and no C-C bond, which is beneficial for achieving clean combustion. Furthermore, PODE can be employed as a co-solvent for alcohol/diesel blends, and stabilizes the miscibility of ethanol/diesel blends. In this study, the effects of ethanol/diesel/PODE blends on the combustion and emissions characteristics were studied in a six-cylinder heavy duty diesel engine. The experimental results show that blending ethanol and PODE into diesel can accelerate the combustion rate in late combustion stage at all loads. Blending PODE and ethanol to diesel, the BSFC of blends increase and the BTE of blends are basically same as that of D100 at low and medium loads. As the load increases, the reduction of HC and soot emissions of blends compared with D100 weaken, and the growth of NOX emissions of blends compared with D100 increase. The performance and emissions of different fuels were also evaluated based on the World Harmonized Stationary Cycle (WHSC) test cycle. As the blending ratio of PODE and ethanol increase, the weighted BSFC increases significantly, but the weighted equivalent BSFC increase slightly. The weighted HC emissions decrease and the weighted NOX emissions increase with ethanol/diesel/PODE blends. Blending PODE and ethanol can reduce the weighted CO emissions; however, as the blending ratio of ethanol increases, the decrease trend of weighted CO emissions get weakened, and DPE15 even exhibits increasing trend compared to D100, which is attributed to the increasing CO emissions at cold idle condition. With the blending ratio of PODE and ethanol increasing, the weighted soot emissions are reduce apparently, and the highest reduction ratio is 86.9% for DPE15 fuel.