Authors: Y Shiao L V Dat
Publish Date: 2012/10/02
Volume: 13, Issue: 6, Pages: 885-893
Abstract
Variable valve timing VVT and cylinder deactivation CDA are promising methods in reducing fuel consumption and emission at part load in SI engines An SI engine which uses electromagnetic valvetrain EMV will eliminate flow restriction from the throttle valve and produce higher indicated mean efficiency pressure IMEP due to the disabling of some of the working cylinders at part load Therefore pumping loss can be significantly reduced at partload conditions In addition duration and timing of valve events are variably controlled at different operating conditions This contributes to the improvement of engine efficiency In this study a dynamic model of an unthrottled SI engine has been developed to simulate the engine cycle The model uses an EMV system that allows valvetrain control and cylinder deactivation techniques to be carried out in simulation flexibly The simulated results find the optimal valve timing for different engine speeds The optimal timing of intake valve closing depends on engine speed linearly while the intake valve opening insignificantly influences engine performance Additionally this study also shows that cylinder deactivation modes can be successfully applied in improving engine efficiency at different engine loads Different cylinder deactivation strategies have been applied for the full range of engine loads It is concluded that the twocylinder deactivation mode 50 CDA considerably improves fuel consumption at low engine load Meanwhile onecylinder deactivation 25 CDA is an optimal fuel economy mode at medium engine load With proper uses of VVT and CDA strategies the efficiency of an SI engine can be increased more than 30 at low engine load and 117 at medium engine load
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