Abstract: In order to study the aerodynamic characteristics of an compressor intermediate duct with a large mean radius change to length ratio，three-dimensional numerical simulation investigations of the duct(ΔR/L=0.5)flow and loss are undertaken. The results show that there is a strong adverse pressure gradient at the inner wall，and boundary layer separations happen at the corner of hub and struts，and with the effects of complex flow such as layer separations and layer migrations，the total pressure loss of the duct is 3.8%，while loss in the hub 25% mass flow is 2.7%，the mid 50% mass flow is 1.9%，and the casing 25% mass flow is 11.7%. Further study shows that the duct flow is sensitive to the change of Mach number and the thickness to chord ratio of struts，especially loss in the hub 25% mass flow increases sharply，while Mach number increases from 0.25 to 0.48，loss in the hub 25% mass flow rises by 52%，and while the thickness to chord ratio of struts increases from 0.16 to 0.27，the loss rises by 93%.

Key words: Numerical simulation；Large radius change to length ratio；Flow separation；Total pressure loss；Vorticity

摘要： 为了进一步揭示大径向落差长度比中介机匣的气动特性，采用全三维数值模拟方法对径向落差长度比ΔR/L=0.5的中介机匣的流动与损失特征进行了研究。结果表明大径向落差长度比中介机匣通道内轮毂面存在较大的逆压梯度，支板-轮毂角区容易发生流动分离，加之附面层迁移等复杂流动的影响，导致中介机匣的总压损失较大为3.8%，轮毂25%流量层，主流50%流量层及机匣25%流量层的总压损失分别为2.7%、1.9%和11.7%。进一步的研究发现中介机匣流场对马赫数和支板厚度弦长比的变化较为敏感，特别是轮毂面附近的总压损失会随马赫数和支板厚度弦长比的增大显著增加，马赫数从0.25增大到0.48时，轮毂面总压损失相对增大52%；支板厚度弦长比从0.16增加到0.27时，轮毂面总压损失相对增大93%。

关键词: 数值模拟；大径向落差长度比；流动分离；总压损失；涡量；