Effect of Cetane-Coupled Pilot Injection Parameters on Diesel Engine Combustion and Emissions

The effects of cetane number (CN) coupled with pilot injection ratio and pilot injection timing on the combustion and emission characteristics of a four-cylinder diesel engine were investigated. The results showed that as the pilot injection ratio increases, the peak cylinder gas pressure (CGP) increases, and the peak of heat release rate (HRR) increases accordingly; the coupled CN increases, the brake specific fuel consumption (BSFC) decreases, and the brake thermal efficiency (BTE) increases; CO and HC emissions increase; and NOx emissions increase. In addition, the number concentration and total mass of particulate matter (PM) decrease with the increasing pilot injection ratio. Only when the pilot injection ratio reaches 20% does the fuel produce pilot injection heat release. The ignition delay time (ID) and combustion duration (CD) are redefined for the pilot injection heat release operating conditions. With the delay of the pilot injection timing, the peak CGP increases, the coupled CN increases, the BTE increases, the BSFC decreases, CO and HC emissions increase, and NOx emissions decrease. With the delay of the pilot injection timing, the number concentration and total mass of PM decrease. In addition, no pilot injection heat release was generated for any of the five fuels at pilot injection timings from 30 degrees CA BTDC to 45 degrees CA BTDC.

Automated summary

This study investigated the effects of cetane number, pilot injection ratio, and pilot injection timing on the combustion and emission characteristics of a diesel engine. The results showed that increasing the pilot injection ratio and cetane number improved combustion efficiency and thermal efficiency, but led to higher CO, HC, and NOx emissions. Additionally, increasing the pilot injection ratio reduced the concentration of particulate matter.