Theoretical study was conducted on a regulated two stage turbocharging system (R2S) for diesel engine based on the equivalent turbocharger concept, from which mathematic expressions for equivalent turbine flow area and equivalent turbocharger efficiency of the R2S system were derived. Equivalent turbine flow area is influenced by the ratio of bypass mass flow rate to the total exhaust mass flow rate. Besides the bypass ratio, and equivalent turbocharger efficiency is also determined by the ratio of isentropic enthalpy drop of the two stage turbines. Equivalent turbine flow area can be used to analyze the regulating ability of the R2S system. To meet the regulating ability requirement, appropriate matching between the two turbochargers for the R2S system is determined using the equivalent turbine flow area expression. The expression of equivalent turbocharger efficiency gives a criterion to the R2S system matching based on economic view, that is, giving more exhaust energy conversion at the stage with higher turbocharger efficiency. In addition, a computational study was carried out on the characteristics of the R2S system and the applications of equivalent turbocharger model on matching and optimization of the R2S system.%应用等效增压器概念对柴油机可调二级增压系统进行了理论研究.建立了可调二级增压系统的等效增压器模型,得到了基于旁通流量比的等效涡轮流通面积表达式和基于旁通流量比与涡轮焓降比的等效增压器效率的表达式.等效涡轮流通面积表达式可用来分析可调二级增压系统的调节能力,并根据期望的调节能力匹配合适的高低压级涡轮增压器组合.等效增压器效率表达式从经济性角度给出了可调二级增压系统的匹配准则:排气能量分配与效率的相适应.最后,利用算例分析了可调二级增压系统的特性并介绍等效增压器概念在匹配与优化上的具体应用.
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