Improving the Efficiency of Low Temperature Combustion Engines Using a Chamfered Ring Land

Abstract

In the present study, a chamfered piston crown design was used in order to reduce unburned hydrocarbon (UHC) emissions from the ringpack crevice. Compared to the conventional piston design, the chamfered piston showed 17–41% reduction in the creviceborne UHC emissions in homogeneous charge compression ignition (HCCI) combustion. Through parametric sweeps 6 mm was identified to be a suitable chamfer size and the mechanism of the UHC reduction was revealed. Based on the findings in this study, the chamfered piston design was also tested in dualfuel reactivity controlled compression ignition (RCCI) combustion. In the tested RCCI case using the chamfered piston the UHC and CO emissions were reduced by 79% and 36%, respectively, achieving 99.5% combustion efficiency. This also improved gross indicated thermal efficiency (gITE) from 51.1% to 51.8% in a 9 bar indicated mean effective pressure (IMEP) RCCI combustion case.