轴流压气机转子叶尖间隙流动结构的数值研究

为进一步加深对轴流压气机转子叶尖间隙内泄漏流/涡流动结构的认识，针对某台用于高压压气机低速模拟的四级重复级大尺度轴流压气机上的转子，采用定常数值方法开展了详细的研究。首先用已有的试验结果校核了计算方法的可靠性，随后研究了设计点工况下端区复杂流动结构和流动损失的机理，最后比较了无叶尖间隙和不同叶尖间隙大小的轴流压气机转子端区流动结构的差别，以及设计点和近失速情况下叶尖泄漏涡结构、泄漏流/主流交界面、端壁堵塞以及端壁损失的区别。结果表明，在62.5%间隙高度以下的叶尖区域内，从前缘叶尖间隙流出的流体会卷吸成叶尖泄漏涡，且随间隙高度的增加其占据的叶尖泄漏涡的位置由内而外；而在62.5%间隙高度以上，从转子前缘间隙内流出的流体不会卷吸成叶尖泄漏涡，随间隙高度的增加流动受叶尖泄漏涡的影响越来越小，更易出现二次及多次泄漏，且所占据的弦长范围也更宽广；设计状态下，叶尖泄漏涡在向下游发展的过程中会逐步膨胀，并与主流强烈掺混，无量纲流向涡量迅速减小，但无量纲螺旋度值显示其仍能保持集中涡的特征。

Numerical Study on Tip Clearance Flow Structure of an Axial Flow Compressor Rotor

This paper presents steady numerical study on a subsonic rotor, to further the knowledge of tip leakage flow/vortex flow structure in the tip clearance of an axial flow compressor rotor. The rotor and its related low-speed large-scale repeating-stage axial compressor are used for the low-speed model testing of a modern high-pressure compressor. The results are first compared with available experimental data to validate the numerical method. Then complex endwall flow structure and flow loss mechanism at the design operation points are studied. Finally, variations of the axial compressor rotor endwall flow structure among no tip clearance and different clearances are investigated. Also comparisons are made for tip leakage vortex structure, the interface of leakage flow and main flow, endwall blockage and loss between the design and near-stall operation points. The results show that flow spilled from the leading edge of the tip clearance will entrain into the tip leakage vortex below 62.5% clearance height, while it doesn't occur for higher positions. The effects of the tip leakage vortex on the flow decrease at higher positions, where secondary leakage flow appears more common and occupies a broader chordwise extent simultaneously. Although tip leakage vortex will expand and mix strongly with the main flow as it propagates downstream, which leads to the rapid reduction of the normalized streamwise vorticity, the value of the normalized helicity shows that the concentrated vortex feature can still be maintained.