离心压气机近失速工况叶尖流场特征及泄漏涡面涡模型

Flow Characteristics of a Centrifugal Compressor in near Stall Condition and Rolling up Vortex Model of Tip Leakage Vortex

为研究航空微型涡轮发动机离心压气机的失速机理,采用数值模拟的方法,对压气机在设计点和近失速点的流场特征进行了研究,并对叶尖泄漏涡进行了建模。结果表明:在近失速工况下,更多的来自轮毂处的低能流和二次流会汇入叶轮通道近壁面的低速区,使得叶尖的堵塞加重,泄漏涡轨迹的偏转及其卷吸作用可能是造成这种现象的原因。通过在压气机机匣外侧引入虚拟镜像涡的方法,应用机翼涡对的不稳定性理论和面涡模型对泄漏涡建立了模型。应用该模型对本文研究的离心压气机以及三个国内外具有典型代表性的压气机进行了预测,表明模型得到的频率同计算和实验结果具有较好的吻合性,对德国宇航院压气机的预测频率与其实际频率的误差仅为2.8%。总体而言,当间隙高度较大时,模型的预测更为准确。

To study the stall mechanism of air centrifugal compressor in micro turbine engine, a numerical simulation method is employed. By comparing the flow field characteristics of design point with near stall point and establishing a tip leakage vortex model, results show that in near stall condition, more low-energy flow from hub and secondary flow gather in the low momentum zones, making blockage more serious. Tip leakage vortex may play an important role in this phenomenon due to the deflection of its track and its entrainment effect. Besides, by introducing the virtual mirror vortex outside the casing, trailing vortex instability theory and rolling up vortex model can thus be used to analyse the tip leakage vortex. This model is applied to the compressor studied in this paper and three domestic and foreign typical compressors, and as a result the model frequency of each compressor are in good agreement with the CFD and experiment results. The relative deviation between the predicted frequency and the experiment frequency even reaches to 2.8% when the model is used for a compressor made by the German Aerospace Center, certifying the validity of the model. In general, as the height of tip gap in- creases, the prediction of leakage vortex model turns out to be more aecurate.