米勒循环对增压直喷汽油机性能影响的仿真分析

Simulation Analysis of Miller Cycle on Performance of Supercharged Direct Injection Gasoline Engine

摘要:

以一台面向混合动力开发的米勒循环发动机为研究对象，建立了基于130°包角进气凸轮轴的一维流体动力学模型。采用该模型仿真分析了进气门开启时刻（IVO）、排气门关闭时刻（EVC）独立调节、联合调节下米勒循环对发动机性能的影响。结果表明：随着米勒循环加深，低负荷下，进气道废气重吸收质量增加，充量系数降低，泵气损失（PMEP）减小，比油耗（BSFC）降低；中负荷下，充量系数增大，泵气损失显著减小，50%累积放热率的曲轴转角（CA50）减小，比油耗降低；高负荷下，比油耗激增。进排气门联合调节可进一步改善发动机的性能，最佳油耗点的热效率提高了0.43%。

Abstract:

In this paper， the Miller cycle process of hybrid engine is mainly studied. A one-dimensional hydrodynamic model of intake camshaft with 130° wrap angle is established. The effect of Miller cycle realized by independent and joint adjustment of inlet valve opening （IVO） and exhaust valve closing （EVC） on engine performance is simulated and analyzed. It is shown that with the deepening of Miller cycle， under low load conditions，the intake exhaust gas reabsorption mass increases， the volumetric coefficient and pump mean effective pressure （PMEP） decreases， and the brake specific fuel consumption （BSFC） decreases； under medium load condition， the volumetric coefficient increases， the pump mean effective pressure decreases significantly，the crankshaft angle corresponding to 50% heat release rate （CA50） decreases， and the brake specific fuel consumption decreases； under high load conditions，the brake specific fuel consumption increases sharply. The combined regulation of IVO and EVC can further improve the engine performance and increase the thermal efficiency at the best fuel consumption point by 0.43%.