建立了Y型和直连型两种典型的二级增压系统旁通结构，利用CFD对其流阻进行了对比。结果表明：当旁通阀全关时，Y型旁通结构流动损失较直连型大，而当旁通阀开启时，Y型旁通结构流动损失较直连型小；对于同种旁通结构，旁通阀的开度越小，损失越大，但是随着开度的增加，由于流过旁通结构的气体质量增加，导致损失相对较大。

The Ytype and straighttype bypass structures for twostage turbocharger were established and their flow resistances were compared by CFD software. The results show that the flow loss of the Ytype structure is larger than that of the straighttype structure when the bypass valve closes fully, but is smaller when the valve opens. For the same bypass structure, smaller opening will lead to greater loss. The flow loss will became relatively larger with the increase of valve opening due to the increase of air mass through bypass valve.