Numerical and Experimental Investigations of the Three-Dimensional-Flow Structure of Tandem Cascades in the Sidewall Region
Numerical and Experimental Investigations of the Three-Dimensional-Flow Structure of Tandem Cascades in the Sidewall Region
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DOI：
10.1115/1.4026880
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发表时间：
2014-07
影响因子：
2
通讯作者：
M. Böhle;T. Frey
中科院分区：
文献类型：
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作者：
M. Böhle;T. Frey
串联叶片可能上级单叶片，特别是当需要大转向角时。这在公开文献中有很好的记载，迄今为止，已经对串列叶栅的二维流动进行了许多研究。然而，关于侧壁附近流动的信息少得多。因此，出现了这样的问题，即在侧壁附近应如何选择串列叶栅的几何形状，以使大转角时的流动损失最小化。本文研究了两个大转弯串列叶栅侧壁区域的三维流场。第一串列叶栅的前叶片选择了大间距比（（t/l）1=1.92）。第二串列叶栅具有较小的前叶片间距比（（t/l）1=1.0）。两个叶栅的总间距比相同，t/l=0.6。流动现象，如拐角失速的三维边界层侧壁附近，使用数值和实验方法进行检查。应用Lieblein和Lei的经验相关性。两个串联叶栅的流动拓扑结构进行了解释，并确定了损失开始的位置。此外，对侧壁附近的流动，给出了实验所得的油膜图和数值模拟所得的流线图，并进行了讨论。最后，考虑了气动载荷分配和前后叶片间距比等设计准则。对雷诺数为8× 10 ~ 5时流动转向约50 °的串列叶栅进行了试验。串列叶栅由NACA 65叶片组成，叶片带有圆弧线，展弦比为B/l=1.0。
Tandem blades can be superior to single blades, particularly when large turning angles are required. This is well documented in the open literature and many investigations have been performed on the 2D-flow of tandem cascades to date. However, much less information on the flow near the sidewalls is available. Thus, the question arises as to how the geometry of a tandem cascade should be chosen near the sidewall in order to minimize the flow losses for large turning angles. The present work examines the 3D-flow field in the region of the sidewall of two high turning tandem cascades. A large spacing ratio was chosen for the forward blade of the first tandem cascade ((t/l)1=1.92). The second tandem cascade possessed a smaller spacing ratio for the forward blades ((t/l)1=1.0). Both cascades had the same total spacing ratio of t/l=0.6. Flow phenomena, such as the corner stall of the 3D boundary layer near the sidewall, are examined using both numerical and experimental methods. The empirical correlations of Lieblein and Lei are applied. The flow topology of both tandem cascades is explained and the locations of loss onset are identified. In addition, oil pictures from experiments and streamline pictures of the numerical simulations are shown and discussed for the flow close to the sidewalls. Finally, design rules such as the aerodynamic load splitting and the spacing ratio of the forward- and aft-blades, etc. are taken into account. The examinations are performed for tandem cascades designed for flow turning of approximately 50 deg at a Reynolds number of 8×105. The tandem cascades consist of NACA65 blades with circular camber lines and an aspect ratio of b/l=1.0.