Effects of Adding Ethanol to Natural Gas-Air Mixture on Combustion and Emissions of Natural Gas-Diesel Dual Fuel Engine Based on GT-Power

To resolve power reduction and engine knock, we investigate the influence of adding ethanol to the natural gas (NG)-air mixture on the combustion and emissions of NG-diesel dual-fuel (NDDF) engines by numerical analysis. The baseline engine is a 4-cylinder diesel engine. NG and ethanol fuels are injected into the intake port, while diesel fuel is injected directly into the cylinder. The simulation is performed using GT-Power software, and the results are validated using experimental data. The engine speeds are set at 1000, 1800, and 2800 rpm. The engine loads are set at 50% and 75%. The diesel injection ratios are 10% and 20%. The ethanol substitution rate (ESR) varies from 0% to 60% with an interval of 10%. The results indicate that combustion and emissions are improved with the increase in ESR. First, the engine knock is reduced since the maximum pressure rise rate (MPRR) decreases. Second, the power performance and economy performance of the NDDF engine is improved because the indicated thermal efficiency (ITE) and brake mean effective pressure (BMEP) increase. In addition, although the emissions of the NG-ethanol-diesel ternary-fuel engine are higher than that of NDDF engines, some emissions, such as nitrogen oxide (NOx) emissions and carbon monoxide (CO) emissions, are lower than that of pure diesel engines. This suggests that the addition of ethanol can improve the power and economic performance of NDDF engines.