连续可变气门升程系统对增压直喷发动机燃油经济性影响的研究

Influence of Continuously Variable Valve Lift System on Fuel Economy of Turbocharged Gasoline Direct Injection Engine

为了深入分析连续可变气门升程(continuously variable valve lift,CVVL)系统对增压直喷(turbo-charged gasoline direct injection,TGDI)汽油发动机燃油经济性影响,通过对2 000 r/min下0.2 MPa和1.2 MPa及5 000 r/min下0.2 MPa和1.2 MPa这4个典型工况点的台架测试,对比分析了可变气门升程和可变气门正时(variable valve timing,VVT)对比油耗(brake specific fuel consumption,BSFC)的影响规律。结果表明:低负荷工况,比油耗随进气VVT提前和排气VVT推迟线性下降;降低气门升程,增加节气门开度,进气VVT可以进一步提前,排气VVT可以进一步推迟,从而形成米勒循环,使比油耗进一步降低。高负荷工况,气门全升程时比油耗更低,比油耗随进气和排气VVT提前而下降,但进气VVT对比油耗影响较小。

In order to deeply analyze the influence of continuously variable valve lift(CVVL) system on the fuel economy of a turbocharged gasoline direct injection engine(TGDI), the effects of variable valve lift and variable valve timing(VVT) on brake specific fuel consumption(BSFC) were experimentally compared and analyzed at four typical working conditions of 0.2 MPa and 1.2 MPa at 2 000 r/min and 5 000 r/min. The results show BSFC at low load conditions decreases linearly with the advance of intake VVT and the delay of exhaust VVT. Reducing intake and exhaust valve lifts and increasing the throttle opening can further advance the intake VVT and further postpone the exhaust VVT. This forms the Miller cycle and BSFC is further reduced. At high load conditions, BSFC at the maximal intake valve lift is lower than that at a smaller lift, and BSFC decreases with the advances of intake VVT and exhaust VVT.