Effects of hydrogen mixing ratio on combustion and emissions of natural gas-diesel dual fuel engine with high natural gas substitution rate

In order to explore the feasibility of natural gas (NG)/diesel dual-fuel engine with high NG substitution rate under medium and low load, the effects of hydrogen (H-2) on the performance and emissions of the engine are studied numerically. The baseline engine is a four-cylinder turbocharged diesel engine, which is modified into a diesel-Natural Gas-Hydrogen ternary fuels engine with port-injected H-2 and NG fuels and direct-injected diesel fuel. The simulation is performed using GT-Power software, and numerical results are validated with the experimental data. The percentage of diesel fuel is set at 10% and 20% (by energy). The engine speed decreases from high speed to medium speed and finally to low speed. The engine load decreases from medium load to low load. The H-2 mixing ratio increases from 10% to 50%. The results show that, with the increase of H-2 mixing ratio, the peak cylinder pressure (PCP), the peak cylinder temperature (PCT), the heat release rate (HRR) and the maximum pressure rise rate (MPRR) increase, while the indicated thermal efficiency (ITE) decreases under all working conditions. Among them, the MPRR increases by 4%similar to 13% at medium load and 1%similar to 2% at low load, but it does not exceed 0.6 MPa/ (degrees) CA. The indicated thermal efficiency decreases by 1%similar to 4% at medium and low load. In terms of emissions, the carbon monoxide (CO) and the hydrocarbons (HC) decrease by 34%similar to 43%, but the nitrogen oxide (NOX) increases by 58%similar to 73%.