采用连续可变气门正时控制的发动机效率研究

Research on engine efficiency using continuous variable valve timing control

针对不同负载条件下发动机循环输出效率较低问题,设计了连续可变气门正时控制系统,并对其输出效率进行仿真验证。创建了节气门控制和连续可变气门正时控制P-V简图,分析各自工作过程。建立不可逆条件下发动机循环效率方程式,比较节气门控制和连续可变气门正时控制的发动机输出效率表达式,并且给出了发动机燃油经济性计算方程式。采用仿真实验对发动机不同负荷情况下的输出效率进行仿真验证,与传统节气门控制的发动机输出效率进行比较。结果显示:不可逆性条件下发动机输出效率较低,在满载条件下,发动机采用节气门控制和连续可变气门正时控制,输出效率差别不大;在小负荷条件下,采用节气门控制的发动机,输出效率较低,而采用连续可变气门正时控制的发动机,输出效率较大。不可逆性对发动机工作循环的输出效率产生强烈影响,在小负荷条件下,采用连续可变气门正时控制,能够节约发动机燃油的消耗,并且随着膨胀比指数的增大,输出效率就会降低。

For the low cycle output efficiency of engine under different load conditions,a continuous variable valve timing control system is designed and its output efficiency is verified by simulation.The P-V diagrams of throttle control and continuous variable valve timing control are created and their working processes are analyzed.The engine cycle efficiency equation under irreversible conditions is established.The engine output efficiency expressions of throttle control and continuous variable valve timing control are compared,and the fuel economy calculation equation of the engine is given.The output efficiency of the engine under different loads is simulated and verified by simulation experiments.The output efficiency of the engine controlled by traditional throttle is compared with that of the engine controlled by traditional throttle.The results show that the output efficiency of the engine is low under irreversible conditions.Under full load conditions,the engine adopts throttle control and continuous variable valve timing control,and the output efficiency has little difference.Under low load conditions,the engine with throttle control has lower output efficiency,while the engine with continuous variable valve timing control has lower output efficiency.The output efficiency of the engine is high.Irreversibility has a strong impact on the output efficiency of engine working cycle.Under the condition of small load,continuous variable valve timing control can save fuel consumption,and with the increase of expansion ratio index,the output efficiency will decrease.