Optimization of the injection parameters and combustion chamber geometries of a diesel/natural gas RCCI engine

Abstract

This study aims at finding the favorable combinations of the diesel injection parameters and combustion chamber shape of a diesel/natural gas dual fuel engine to achieve lower fuel consumption and pollution emissions. The genetic algorithm NSGA-II coupled with the KIVA-3V code was employed for the multi-objective optimizations. The results show that the straight combustion chamber is effective to reduce the CH4 emission and improve the fuel economy, and the indicated thermal efficiency reaches 50.2% with an injection timing of −16.45 °CA ATDC. The NO emissions are the lowest when the reentrant-type combustion chamber is used, while CH4 emissions and ISFC are higher than the other two types of the combustion chamber. When the injection timing is far away from the top dead center, the NO emissions, CH4 emissions and ISFC are very close to each other for the three types of the combustion chamber. Slightly narrow spray angle is favorable to improve the performance of the dual fuel engine.