Overtip Choking and Its Implications on Turbine Blade-Tip Aerodynamic Performance
Overtip Choking and Its Implications on Turbine Blade-Tip Aerodynamic Performance
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DOI：
10.2514/1.b34112
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发表时间：
2011-09
影响因子：
1.9
通讯作者：
Qiang Zhang;Li He
中科院分区：
文献类型：
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作者：
Qiang Zhang;Li He
在发动机典型流动条件下，高压涡轮叶片尖端上的大部分流动是跨音速的。在目前的工作中，通过计算分析了阻塞流行为及其对顶部泄漏流损失产生的影响。采用广泛开发的 RANS 代码（HYDRA）。首先介绍高速线性级联验证案例，并将计算结果与实验数据进行比较，以确定和建立代码预测跨音速涡轮叶片尖端空气动力学损失的能力。然后对从几乎不可压缩到标称跨音速的不同流动条件下的叶片配置进行计算研究，从而能够建立与出口马赫数条件相关的叶尖泄漏损失的定性一致趋势。结果清楚地表明，局部阻塞对顶部泄漏质量流设置了限制器，导致与低速和/或非阻塞条件下的泄漏流结构不同。尖端阻塞的存在有效地阻止了吸力表面侧对尖端上方流动的影响，从而导致传统用于尖端处理和设计的压力驱动机构的故障。清楚地识别并突出了叶片负载和叶尖上方泄漏质量流之间的解耦。此外，负载-泄漏流解耦的实现表明具有相对较低叶尖泄漏损失的高负载叶片设计的可能性。生成并分析高负载叶片，以证明这种设计的可行性，并减少叶尖泄漏损失。
At engine representative flow conditions a significant portion of flow over a high pressure turbine blade tip is transonic. In the present work, the choking flow behavior and its implications on over-tip leakage flow loss generation are computationally analyzed. An extensively developed RANS code (HYDRA) is adopted. Firstly a high speed linear cascade validation case is introduced, and the computations are compared with the experimental data to identify and establish the capability of the code in predicting the aerodynamics losses for a transonic turbine blade tip. The computational studies are then carried out for the blading configuration at different flow conditions ranging from a nearly incompressible to a nominal transonic one, enabling to establish a qualitatively consistent trend of the tip leakage losses in relation to the exit Mach number conditions. The results clearly show that the local choking sets a limiter for the over tip leakage mass flow, leading to a different leakage flow structure compared to that in a low speed and/or unchoked condition. The existence of tip choking effectively blocks the influence of the suction surface side on the over-tip flow, and hence leads to a breakdown of the pressure-driven mechanism, conventionally used in tip treatment and designs. The decoupling between blade loading and over tip leakage mass flow is clearly identified and highlighted. Furthermore, the realization of the loading-leakage flow decoupling indicates a possibility of a high-load blading design with a relatively low tip leakage loss. A high load blading is generated and analyzed to demonstrate the feasibility of such designs with a reduced tip leakage loss.