Investigation of the effect of hydrogen addition on the combustion and emissions performance of high compression ratio liquid methane gas (LMG) Engine

To investigate the effect of hydrogen addition on the combustion and emission performance of a high-compression-ratio liquid methane gas (LMG) engine under continuously varying loads, this study considered an inline 6-cylinder 4-valve single-point injection spark ignition liquefied natural gas (LNG) engine as an object to comprehensively discuss the combustion process, engine performance, and emissions characteristics under different loads and speeds at different hydrogen energy share (HES) by means of coupled experiments and simulations. The results show, with an increase in hydrogen concentration, the brake-specific fuel consumption (BSFC) of the LMG engine showed a decreasing trend, the peak cylinder pressureincreased significantly, the maximum pressure rise rate also increased significantly, and the location of 50 % mass fraction burned (MFB) was advanced significantly. In terms of emissions, with the gradual increase in the hydrogen energy ratio, the NO_X emissions show an increasing trend and HC emissions showed a decreasing trend. With the increase in HES the location of peak combustion temperature (LPCT) advanced approximately 43.08 %. However, although the addition of hydrogen significantly increased the combustion rate of the LMG, the knocking became more intense as a result, and the tendency increased sharply when the HES increased from 12 % to 20 %.