DCVVT发动机外特性转矩下凹问题的研究

DCVVT发动机耐久性试验中,在转速1 500~2 500 r/min时外特性转矩存在明显下凹,而标定试验过程中外特性转矩无此下凹问题。采用一维仿真和试验验证相结合的方法,证明排气系统管路的不一致造成此发动机转矩的下凹。进一步研究发现,当DCVVT发动机进排气门重叠角大时,发动机的外特性对排气系统前级催化反应器与后级催化反应器之间管路长度的变化很敏感,可采用缩短此段管路长度的方法来避免发动机耐久试验外特性在转速1 500~2 500 r/min时的转矩下凹。

Research in Problem of Up Concave in Characteristics of Output Torque for DCVVT Engine

During durability test for Double Continuously Variable Valve Timing （DCVVT） engine, at rotation speed of 1 500 - 2 500 r/ min, the output characteristics were appeared obviously up concave, while in the rated test, there was no such problem existed. By adopting the method of one dimensional simulation and test validation in combination, it was proved that the up concave of characteristics of engine rotation torque caused by non matches in the pipe routes of emission system. It was researched t＇urther that. when the air gate overlap angels of intake and outlet of DCVVT were large, the output characteristics of engine was very sensitive to the changes in pipe length between front and rear catalytic reactors in emission system. The method of cutting short of this section of pipe can be adopted to avoid up concave in rotation torque, dnring output characteristics test for the engine durability, at speed of 1500 -2 500 r/min.