Numerical research on the performance, combustion and energy flow characteristics of gasoline-powered vehicle under WLTC

Abstract

In order to evaluate and improve the performance of a vehicle equipped with a gasoline engine, an integrated model of the vehicle coupling with a detailed engine model was established to investigate the performance, combustion and energy distribution under the Worldwide Harmonized Light duty Test Cycle (WLTC) of cold start. The results show that 2.3–3.2 kW of brake power is required for the automatic transmission under idling conditions. Brake thermal efficiency mainly ranges from 17.71% to 31.94% apart from the rapid deceleration conditions and exhibits poor fuel economy under low-speed phase. Combustion phase of 50% mass fraction burnt (CA50) is usually delayed in case of knocking combustion under higher speed conditions. Moreover, it is delayed to 65 °CA at the initial stage of cold start for fast light-off of three-way catalyst (TWC), but 10–90% combustion duration (CA10-90) is not very sensitive to the cold start. The heat cumulated in the engine structure is obvious at the initial stage and up to 37.39% but finally occupies 4.93%. The proportion of heat transfer loss to coolant increases after 300 s and finally occupies 22.71%. Exhaust gas loss mainly ranges from 0.91 kW to 28.42 kW and its proportion first decreases and then increases to 26.46%. After 1160 s, it exhibits higher growth rate. Pumping loss varies from 0.1 kW to 2.67 kW and occupies 2.2% in the total energy. Furthermore, the findings in the paper can be applied to evaluate and optimize the energy distribution by changing different technologies or strategies in the future.