某8缸柴油机脉冲增压排气管布置对排气干扰的影响

Effect of pulse exhaust pipe layout on exhaust interference of an 8-cylinder diesel engine

为解决某直列8缸脉冲增压柴油机各缸排气干扰问题,设计4种排气管布置形式,利用GT-Power软件搭建柴油机模型,分析排气管布置形式对排气干扰的影响,并进行优化和试验验证。结果表明:排气管的布置形式和发火顺序是产生排气干扰的主要因素,各缸扫气不均匀是排气干扰的直接原因,在25%额定负荷时过量空气系数异常降低;4排管结构、增压器双流道、单个流道排气间隔曲轴转角为180°的排气管布置型式在低负荷工况下排气压力会高于进气压力,各缸形成均匀排气干扰;排气门开启曲轴转角由120°推迟至140°后,过量空气系数由1.82提高至2.15,低速性能明显改善。

To solve the problem of exhaust interference in each cylinder of a certain inline 8-cylinder pulse turbocharged diesel engine,four types of exhaust pipe arrangements are designed.A diesel engine model is built using GT-Power software to analyze the effect of exhaust pipe arrangements on exhaust interference,and optimization and experimental verification are carried out.The results show that the layout and firing sequence of the exhaust pipes are the main factors of exhaust interference,and uneven sweeping of each cylinder is the direct cause of exhaust interference.The arrangement of exhaust pipes with a 4-row pipe structure,dual turbocharger channels,and a single channel exhaust interval with a crankshaft angle of 180°will result in higher exhaust pressure than intake pressure under low load conditions,resulting in uniform exhaust interference for each cylinder.At 25%rated load,the excess air coefficient abnormally decreases.After delaying the opening angle of the exhaust valve crankshaft from 120°to 140°,the excess air coefficient increases from 1.82 to 2.15,and the low-speed performance is significantly improved.