基于无凸轮式配气型线的汽油机低负荷性能研究

Low-Load Performance of Gasoline Engine Based on Non-Cam Valve Pattern

为探究无凸轮式配气型线对汽油机低负荷工况下的性能影响,提高充气效率,降低换气损失,在考虑气门响应延迟与落座冲击的前提下,首先设计了7组无凸轮式进气门型线,得到下止点后10°～100°范围内的多个进气晚关角(θIVC),将无凸轮式进气型线代入汽油机整机模型中进行计算,当充气效率最大时,进一步设计了排气早开角(θEVO)在下止点前10°～60°范围内的6组无凸轮式排气型线。分析了1 000r/min,50%负荷时,无凸轮式配气型线对汽油机性能的影响。结果表明:采用无凸轮式进气型线且当θIVC为20°ABDC时,充气效率相比原机提高9.52%;该进气相位下,进一步设计无凸轮式排气型线并优化θEVO,当θEVO为40°BBDC时,总排气损失最小,指示扭矩相比原机提升约16.88%,当θEVO为50°BBDC时,燃油经济性最佳,燃油消耗率达到260.18g/(kW·h),相比原机降低14.91%。采用无凸轮式配气型线,合理优化组合进排气相位,能够有效提高充气效率,降低排气损失,改善发动机动力性和经济性。

In order to explore the influence of non-cam valve pattern on the low-load performance of engine,improve volumetric efficiency and reduce gas exchange loss,7 sets of intake profiles were designed by considering the valve response delay and seating impact and multiple intake late closing angles between 10°and 100°ABDC were acquired.Importing non-cam intake profile into gasoline engine model,6 sets of non-cam exhaust profiles were designed when the charging efficiency was the highest and the exhaust early opening angle is between 10°and 60°BBDC.In the conditions of 50%load at 1 000 r/min,the influence of non-cam valve pattern on gasoline engine performance was further researched.The results indicated that the charging efficiency increased by 9.52%when the intake late closing angle was 20°ABDC.The non-cam exhaust profiles were adopted and the exhaust early opening angles were optimized at the same intake phase.At 40°BBDC,the total exhaust loss was the least and the indicated torque increased by 16.88%.At 50°BBDC,the fuel economy was optimal and BSFC was 260.18 g/(kW·h)which improved by 14.91%.Accordingly,adopting the non-cam valve pattern and optimizing the intake and exhaust phase could effectively increase the charging efficiency,reduce the exhaust loss and improve the power and economy of engine.