Potentials of Air-EGR Dilution for Improving Performance of a High Compression Ratio Spark-Ignition Engine Fueled with Methanol

The effects of air and exhaust gas recirculation (EGR) dilution of a spark ignition engine fueled with methanol under different loads were studied by experiment in this paper. Such as ignition delay, combustion center (CA50), IMEP, break thermal efficiency (BTE) and other parameters were investigated to assess the combustion performance. And discussed in depth the balance between NOx emissions and economic performance represented by brake specific fuel consumption (BSFC). The results showed that combustion progress such as ignition delay, combustion duration and CA50 were more sensitive on the changes of EGR, introducing EGR under the same dilution rate prolonged combustion process. Air-EGR dilution showed the best improvement of IMEP and break thermal efficiency, except the optimal area, increasing EGR rate will decreased IMEP and BTE. Air-EGR dilution strategy showed the best improvement on BSFC than air dilution than EGR dilution. Under light load and high load, when the lowest BSFC was obtained, NOx emissions were less than 0.5 g/kWh with air-EGR dilution strategy.

Automated summary

The effects of air and exhaust gas recirculation (EGR) dilution on a methanol-fueled spark ignition engine were investigated under different loads. Various parameters, such as ignition delay, combustion center, IMEP, and BTE, were studied to evaluate the combustion performance and the balance between NOx emissions and brake specific fuel consumption (BSFC). The results showed that EGR significantly impacted combustion progress and introducing EGR extended the combustion process. Among the different dilution strategies, air-EGR dilution exhibited the best improvement in IMEP and BTE, while increasing the EGR rate decreased both IMEP and BTE. Moreover, the air-EGR dilution strategy demonstrated the best enhancement in BSFC and reduced NOx emissions below 0.5 g/kWh under light and high loads.