To investigate the hard-to-measure complex flow in a squirrel-cage fan, a slice model was established in the present study to perform a partial large eddy simulation calculations on an r-θ sectional flow field instead of the large-scale and time-consuming full three-dimensional flow calculations. The method used to build the slice model was first introduced, and then the model was verified by the results obtained by other models and flow measurements. It is shown that to calculated the correct flow field and detailed vortex evolution, the Courant number of the slice model should be below 1, and the model thickness should be at least 2.4% of the impeller outer diameter. Through this simplified model, vortex evolutions rarely observed in other studies were successfully captured, such as vortex shedding caused by leading-edge separation, periodic backflow in the blade cascade, and vortex cluster traveling across the impeller. The flow separations were also illustrated on the inner surface of the volute tongue, accompanied by tiny and high-frequency eddies. The evolution process and frequency characteristics of these flow patterns were analyzed in detail, providing references for the design and noise reduction of this type of fan.

为了研究鼠笼式风扇中难以测量的复杂流动，本研究建立了切片模型，对r - θ进行了部分大涡模拟计算。截面流场代替了大规模、耗时的全三维流计算。首先介绍了建立切片模型的方法，然后通过其他模型和流量测量得到的结果对模型进行了验证。结果表明，要计算正确的流场和详细的涡流演化，切片模型的库朗数应小于1，模型厚度应至少为叶轮外径的2.4%。通过这个简化的模型，成功地捕捉到了其他研究中很少观察到的涡流演化，例如前缘分离引起的涡流脱落、叶栅中的周期性回流以及穿过叶轮的涡流簇。涡旋舌的内表面也显示了流动分离，伴随着微小的高频涡流。详细分析了这些流型的演变过程和频率特性，为此类风机的设计和降噪提供参考。