Transient performance of three phase sequential turbocharging with unequal size turbochargers
In order to improve the part load and transient performance of diesel engine, a three phase sequential turbocharging system with unequal size turbochargers was investigated by experiments in this paper. The performances of load acceptance processes under different speeds of three matching schemes (one small turbocharger, one big turbocharger and small with big turbochargers) were studied first. It is found that the response performance is better with small turbocharger, but the discrepancy of response time reduces as engine speed increased. The three phase switching boundaries of sequential turbocharging system under steady states were obtained according to the principle of optimal fuel efficiency. For speed characteristic, the small, big and small with big turbochargers are sequentially used along with the engine speed increasing from low to medium and high speed. For propeller characteristic, the two, big and two turbochargers are used along with the engine speed increasing from low to medium and high speed. Based on steady states switching strategies, the transient performance and soot emissions during acceleration processes were studied. It is found that the response performance and soot emissions of the sequential turbocharging system are better than those of one turbocharger system. But the switching process of cut in of big turbocharger and cut out of the small turbocharger has adverse effect on response performance, because it takes time for big turbocharger to speed up and for boost pressure to recovery. The switching strategies suitable for transient processes were also investigated. The allowable operation boundary of small turbocharger under steady states was used as small turbocharger switching boundary during transient processes, and two-phase switching strategies (shift between small and big turbocharger) was used instead. The results showed that the transient performance can be improved further by using transient switching strategies. For acceleration process with constant torque, the stagnation time of speed up during cut in and out point is reduced. For acceleration under propeller law, the stagnation phenomenon is more obvious with transient switching strategies, because at least one turbocharger is running when switching with steady state strategies.
Yi Cui Kangyao Deng Zhe Zhang
Shanghai Jiaotong University,China
国际会议
上海
英文
1-8
2013-05-13（万方平台首次上网日期，不代表论文的发表时间）