Browse Publications Technical Papers 2011-01-0886

Effect of First Cycle Fuel Injection Timing on Performance of a PFI Engine during Quick Start for HEV Application 2011-01-0886

Idle stopping is one of the most important fuel saving methods for hybrid electric vehicle (HEV). While the enriched injection strategy which was employed to ensure reliable ignition of first cycle will leads to even more fuel film stayed in the intake port, all of the liquid film will evaporate randomly and interfere the mixture air-fuel ratio of the followed cycles. The fuel transport of the first cycle should be enhanced to reduce the residual fuel film, and then the control of the cycle-by-cycle air-fuel ratio will become easier and the combustion and HC emissions will also be better.
In this paper the mixture preparation characteristics of the unfired first cycle, as well as the combustion and HC emissions characteristics of the fired first cycle under various injection timing strategies such as close-valve injection, mid-valve injection, and open-valve injection were investigated.
The results show that, under the cold start process, open-valve injection should not be applied for the quickly start-up mode of the hybrid engine due to first-cycle misfire at all the given injection pulse width. While for hot start process, whether quickly start-up or not, three injection modes have similar combustion and HC emissions. Due to the high frequency start/stop of the hybrid engine, the coolant temperature was higher than the surrounding at the most of the time, mid- or open-valve injection could be used to increase the fuel transport.


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