建立某增压CNG发动机仿真模型，验证模型的准确性。设计了进气晚关角为0°的无凸轮式进气型线并使节气门全开，模拟分析了转速1 600 r/min、进气管压力120 kPa时，无凸轮式进气型线对该发动机进气性能的影响，并与原机进行对比。结果表明：该工况下，采用无凸轮式进气型线，进气门在下止点关闭时，能够有效防止进气回流，发动机充量系数相比原机提高1.70%，指示功率相比原机提高1.29%，燃油消耗率相比原机降低2.88%，由进气过程进气道及缸内速度场切片和一维仿真数据可知，循环进气量提高1.45%，进气更为充分；进气压力与转速升高时，无凸轮式进气型线对应的最佳进气晚关角也应增大。

The simulation model of a boosting CNG engine was established and the accuracy of the model was verified. The camless intake profile with an intake late closing angle of zero degree was designed and the throttle was fully open. Then the effects of camless intake profile on engine intake performance were simulated and analyzed at 1 600 r/min with the intake manifold pressure of 120 kPa. The results show that camless intake profile can avoid intake backflow effectively when the intake valve closes at BDC. Meanwhile, the volumetric efficiency increases by 1.7%, the indicated power increases by 1.29% and the brake specific fuel consumption decrease by 2.88% after using the camless intake profile. According to the slicing of intake process and incylinder velocity field and 1D simulation data, the intake mass per cycle increases by 1.45% and it is more beneficial. In addition, the optimal intake closing angle corresponding to the camless intake profile also increases with the increase of intake pressure and engine speed.