Research on the effect of different test cycles on low temperature emissions and fuel consumption of Light plug-in hybrid cars

Based on a plug-in hybrid car equipped with a 1.5L turbocharged direct injection gasoline engine, this paper studies the emission and fuel consumption characteristics of the prototype vehicle under three different cycle conditions, WLTC city, WLTC and CLTC-P. The results show that for the four pollutants: CO, THC, NMHC and NOx, WLTC city cycle emissions are the largest, WLTC cycle emissions are the smallest, CLTC-P cycle emissions are the middle. For N2O, WLTC cycle has the largest combined emissions, CLTC-P cycle combined emissions are the smallest, and WLTC city cycle combined emissions are the center. The combined fuel consumption under WLTC city conditions is approximately 1.3 times the combined fuel consumption under the complete WLTC cycle. The combined fuel consumption under CLTC-P conditions is approximately 1.25 times that of the complete WLTC cycle. The first phase of each cycle is the phase with the highest emissions and fuel consumption.

Effect of piston shape design on the scavenging performance and mixture preparation in a two-stroke boosted uniflow scavenged direct injection gasoline engine

Compared to a four-stroke engine, the two-stroke engine doubles firing frequency and has favourable power-to-weight or power-to-volume ratio as well as engine downsizing to improve the overall powertrain fuel economy. In order to overcome the shortcomings of the conventional cross-flow or loop scavenged two-stroke engines, a two-stroke boosted uniflow scavenged direct injection gasoline engine was designed and its performance was analysed. In this study, three-dimensional computational fluid dynamics simulations were performed to understand the impact of the piston shape design on the scavenging process, in-cylinder flow formation, turbulence level and subsequent fuel/air mixing process in the boosted uniflow scavenged direct injection gasoline engine. Both single injection and split injection strategies were investigated to study the interactions between piston designs and fuel injection strategies to achieve stoichiometric mixture around the spark plug. The results show that the optimised piston with the same opening timing for all scavenge ports could achieve much better scavenging performance than the baseline piston design. In particular, the shallow pistons, that is, Piston #1 and Piston #4, could produce stoichiometric mixture around the spark plug with relatively lower inhomogeneity and higher turbulence kinetic energy around top dead centre when implementing the split injection strategy with start of injection timing at 250/310 °CA.