S2反问题法是重要的初始设计评估手段。通过选择合理的损失模型并进行验证,得到了适用于大涵道比风扇的S2反问题评估方法,并系统研究风扇关键几何参数对风扇气动效率的影响规律。结果表明:当进口机匣半径增大到一定程度,增大半径对于风扇效率的改善已不明显;当进口轮毂比大于0.295时,风扇效率将急剧下降;流道形式采用等外径或近似等外径设计时,风扇具有更高的效率;而风扇出口尺寸的选择除满足流量系数的要求之外,还应考虑与下游部件的匹配,以提高整个压缩系统的效率。 S2 inverse problem method is an important initial design assessment method. By choosing a reasonable loss model and verifying it, an S2 inverse problem evaluation method suitable for large bypass ratio fans is obtained and the influence of fan critical geometric parameters on the aerodynamic efficiency of fans is studied systematically. The results show that when the radius of inlet casing increases to a certain degree, the increase of radius has no obvious effect on fan efficiency. When the inlet ratio of hub is more than 0.295, the efficiency of fan will decrease drastically. The design of the outer diameter of the fan has a higher efficiency; and the size of the fan outlet in addition to meeting the flow coefficient requirements, but also should be considered with the downstream components to improve the efficiency of the entire compression system.