离心压气机叶顶泄漏涡轨迹数值模拟及失速预测

以级压比为4.1的Krain叶轮为研究对象,数值研究流量、转速和叶顶间隙对叶顶泄漏涡(TLV)轨迹和主流/叶顶泄漏流交界面(ITLMF)位置的影响。数值结果表明:流量减小、转速升高和叶顶间隙减小,使叶顶泄漏涡轨迹远离吸力面、主流/叶顶泄漏流交界面向上游移动。将主流与叶顶泄漏流的相互作用简化为一股自由来流与一股逆向壁面射流的相互作用,并对叶顶泄漏流速度进行模化。利用主流/叶顶泄漏流动量平衡原则确定交界面位置,采用Zhao模型预测叶顶泄漏涡轨迹,并建立叶顶泄漏流的有效起始位置与叶顶间隙的关系,从而建立亚声速离心压气机失速预测模型。结果表明,模型预测值与CFD预测值符合较好,方均根误差低于2.42%。 

Numerical simulation of tip leakage vortex trajectory and stall prediction for centrifugal impeller

The Krain impeller with total pressure ratio of 4.1 was taken as the research object. The effects of mass flow rate, rotational speed and tip clearance on the tip leakage vortex (TLV) trajectoryand the interface between the tip leakage flow and the main flow (ITLMF) were numerically investigated. Results showed that the decrease of mass flow rate, the increase of the rotational speed and the decrease of the tip clearance made the TLV trajectory move away from the suction surface and the ITLMF move upstream. By simplifying the main flow and tip leakage flow interaction as the free-stream and counter-flow wall jet interaction, a subsonic centrifugal impeller stall-onset prediction model was developed. In this model, the momentum balance analysis was applied to identify the position of main flow/tip leakage flow interface. The tip leakage flow velocity was modeled. Zhao’s model was used to predict the TLV trajectory. The relationship between the virtual origin of tip clearance jet and the tip clearance was determined. Results showed that the stall point predicted by current model agreed well with CFD, with the root mean square error was below 2.42%.