A review on performance, combustion and emission of diesel and alcohols in a dual fuel engine

In recent years, diesel vehicles have made a considerable contribution to the total emissions of vehicle pollutants. In view of stringent emission regulations, it is meaningful to look for clean, renewable and sustainable fuels and the correct utilization technology. One effective approach is application of diesel and alcohols dual fuel (DADF) engines, which can achieve the maximum substitution of alcohols to diesel without requirement for mutual solution and meanwhile reduce the emissions of major pollutants. In this study, three combustion modes of DADF engine are firstly introduced and comparatively analyzed, and then the combustion and emission characteristics of DADF engine are compared with those of pure diesel engine, and finally, the effects of alcohol injection strategy, substitution ratio and type of pilot fuel on the combustion and emission characteristics of DADF engine are summarized. The results show that the DADF engine can reduce both particulate matter (PM) and nitrogen oxides (NOx) emissions in conventional dual fuel (CDF) mode, especially under high load conditions; compared to the CDF mode, the engine has a longer ignition delay (ID) and poorer combustion stability in reaction controlled compression ignition (RCCI) mode, with a significant reduction in NOx and soot emissions and an increase in hydrocarbon (HC) and carbon monoxide (CO) emissions; compared to a pure diesel engine, the DADF engine has increased maximum cylinder pressure (Pmax), heat release ratio (HRR) and ID, shortened combustion duration (CD), increased HC and CO emissions, but reduced soot emissions; the combustion process of the engine is also improved when biodiesel and polyoxymethylene dimethyl ether (PODE) are used as pilot fuels.