亚声速扩压叶栅中弯叶片积叠规律的研究

Study on Stacking Rules of Bowed Blade in Subsonic Compressor Cascade

关键词:  扩压叶栅  环形叶栅  弯曲叶片  数值仿真

Key words:  Compressor cascade  Annular cascade  Bowed blade  Numerical simulation

摘要:

为了探索负荷径向非对称分布的环形扩压叶栅中弯曲叶片造型参数的选取规律，通过数值模拟的方式，对比研究了不同弯高和正弯角对两种不同分离形态的环形扩压叶栅气动性能和流道内旋涡结构的影响。研究结果表明，随着弯叶片正弯角的增大，尾缘附近的一对集中脱落涡增强并向叶展中部靠拢，随之造成了集中脱落涡和壁角涡之间区域的损失降低，同时叶展中部的总压损失增大。在集中脱落涡尚未形成的叶栅中，弯叶片则是主要作用于流道中部的尾缘脱落涡，但作用效果相对较弱。在一定的弯叶片弯高下，扩压叶栅存在最佳弯角，研究所采用的50%弯高的CDA叶栅在进口条件2下的最佳弯角约为25°，并且相同的弯叶片正弯角对叶片展向负荷较高的一端作用效果更显著。当弯叶片正弯角较大(或接近于最佳弯角)时，叶片展向负荷较高的一侧在弯叶片作用下损失峰值增加更为明显，因而在保持弯叶片的周向相对偏移一致的前提下，最佳弯高在叶展中部偏向于负荷较低的一侧。换言之，最佳弯高应偏向于扩压因子展向不均匀度更大的一侧。

Abstract:

In order to explore the selection law of bowed blade design parameters in annual compressor cascades with radial asymmetrical distribution of loading，by numerical simulation，the effects of different bowed heights and positive angles on aero-performance and vortex structure in flow passages of two annual cascades with different kinds of separation were analyzed for comparative study. The results show that，with the increase of positive bowed angle，a pair of concentrated shedding vortexs near trailing edge are enhanced and the cores of them get close to the middle span，which makes the loss decrease near the region between concentrated shedding vortex and corner vortex，while the loss of middle span gets thickened. In cascades where concentrated shedding vortexs have not yet formed，the impact of bowed blade is mainly on trailing edge shedding vortex in the midspan. However，the impact is relatively unapparent. With a certain bowed height，there exists a best bowed angle，the best bowed angle of CDA cascade used in this study is nearly 25° with 50% bowed height in inlet 2. And the same positive bowed angle has a more significant effect on the higher loading side along the spanwise. While the positive bowed angle is relatively large，or approaches the best bowed angle，the loss peak of the higher loading side along the spanwise increases dramatically under the action of bowed blade，which makes the best bowed height bias toward the lower loading side along the spanwise on the assumption of same circumferential relative displacement. Or to put it another way，best bowed height should bias toward the side with higher diffusion factor unevenness along the spanwise.