Evaluation of injection and ignition schemes for the ultra-lean combustion direct-injection LPG engine to control particulate emissions

The experimental results reveal that the fully stratified injection strategies indicate an improvement of approximately 18% in thermal efficiency, but combustion fluctuation was observed owing to stratification. Moreover, simultaneous reductions in the NOX (Nitric Oxides) and CO (Carbon monoxide) emissions were observed (when compared to homogeneous stoichiometric combustion) while increasing the particulate matter emission. In order to stabilize the combustion and reduce the level of soot, a multi-charge ignition was introduced to the selected injection strategies (LBM1 and LBM2). Multi-charge ignition successfully reduces particulate mass by about 10% and secures the combustion stability slightly; however, it increases the particle number concentration.