Influence of hydrogen fraction and injection timing on in-cylinder combustion and emission characteristics of hydrogen-diesel dual-fuel engine

In order to achieve low-carbon, high-efficient and clean combustion for internal combustion engines, hydrogen -diesel dual-fuel combustion mode (HDDF) was conducted on a 4-cylinder common-rail diesel engine. This research investigated the effects of hydrogen substitution ratio (HSR) and diesel injection timing (DIT) on in -cylinder combustion and emission characteristics of HDDF engine at 20% and 40% loads. The results show that with the increase of HSR, the maximum combustion pressure of HDDF engine shows a decreasing trend, and the peak phase gradually advances. The overall trends of COVIMEP and combustion duration increase. The NO, CO2, CO, Soot and HC emissions all decrease, while NOx emissions first decrease and then increase. At 20% load and HSR = 30% conditions, CO2 emission decreases by 14.96% compared to baseline engine. With the advance of DIT, the maximum combustion pressure of HDDF engine increases, the ignition delay and combustion duration become longer, and COVIMEP shows a downward trend. The NO2, NO, CO2 and NOx emissions and BTE increase, while both CO and HC decrease. When the DIT is advanced from-2 degrees CA ATDC to-10 degrees CA ATDC, the BTE of HDDF engine increases from 28.8% to 31.3%.