叶尖小翼对涡轮叶片叶尖泄漏流气动性能作用机理的研究

In high pressure turbines, the pressure difference between the blade pressure side and the suction side drives the flow across the tip gap, causing tip leakage flow. The tip leakage flow reduces the work produced by the turbine and creates a loss. The tip leakage flow also distorted the flow down stream of the turbine, so it has a negative effect on the aerodynamic performance of the high pressure turbine. Using winglets on the tip can reduce the driving pressure difference across the tip, thus reducing the tip leakage flow. Experimental and numerical methods will be used in this project to study the effects of the tip leakage flow on the aerodynamic performance of the tip leakage flow of the winglet tip. The aim of the project is to investigate the effects of the winglet on the driving pressure difference on the aerodynamic performance of the tip leakage flow; the fluid mechanics of the flow around the winglet of the tip and the tip leakage vortex due to the mixing of the tip leakage flow and the flow in the main passage. The loss mechanism of the tip leakage flow will be discussed. The tip geometry with a combined design of winglet and squeaelr will also be investigated. The geometric parameters of the winglet and squealers will be changed to further understand the effects of these geometries on the aerodynamic performance of the winglet tip. The effects of relative endwall motion between the tip and the casing on the aerodynamic performance of the tip leakage flow will be investigated.The aerodynamic performance of the tip leakage flow of the winglet tip (and winglet-squealer tip) will also be studied for cases where the main flow is transonic, and the effects of compressibility will be examined.

高压涡轮叶片的压力面和吸力面间存在压力差。该压力差驱动气流流过涡轮转子叶片叶尖与机匣之间的间隙，形成叶尖泄漏流动。叶尖泄漏流减少了涡轮所做的功，造成流动损失并影响到下游流场的均匀性，对涡轮的性能产生不利影响。在叶尖采用小翼的设计，可以降低驱动叶尖泄漏流的压力差，从而减少叶尖泄漏流。本项目拟通过实验和数值模拟的方法，研究在高压涡轮叶片叶尖上采用小翼对叶尖泄漏流气动性能的作用机理。具体将研究叶尖小翼结构对驱动叶尖泄漏流的压力差作用；叶尖间隙内和叶尖附近流体的空气动力学特性；叶尖泄漏流和主流掺混后形成泄漏涡的特性及其对下游流场的影响；叶尖泄漏流损失的机理；在叶尖小翼上使用肋结构的作用；叶尖小翼（和肋）几何参数对泄漏流气动性能影响的规律和机理；叶尖和机匣间相对运动对叶尖泄漏流气动性能的影响机理；以及跨音速情况下，气体可压缩性对叶尖泄漏流气动性能的影响。

高压涡轮叶片的压力面和吸力面间存在压力差。该压力差驱动气流流过涡轮转子叶片叶尖与机匣之间的间隙，形成叶尖泄漏流动。叶尖泄漏流减少了涡轮所做的功，造成流动损失并影响到下游流场的均匀性，对涡轮的性能产生不利影响。在叶尖采用小翼的设计，可以降低驱动叶尖泄漏流的压力差，从而减少叶尖泄漏流。本项目拟通过实验和数值模拟的方法，研究在高压涡轮叶片叶尖上采用小翼对叶尖泄漏流气动性能的作用机理。. 本项目研究了高压涡轮动叶的空气动力学性能研究了针对双肋叶顶的气动和传热性能，分析了肋高和肋宽等几何条件的作用机理。研究表明，肋过高的话会降低肋之间涡系对泄漏流的阻碍能力，从而增大叶顶泄漏流损失；肋宽对叶顶泄漏流气动性能的影响较小。基于流动特性，还研究了肋高和肋宽对叶顶传热特性的作用。. 本项目还研究了叶顶和端壁间相对运动的作用，发现相对运动形成的通道内的刮削涡是叶顶区域流动损失的重要来源，叶顶双肋之间的刮削涡会影响叶顶的流动特性。. 在研究叶顶小翼对流动机理作用的基础上，本项目发展了一种新型的叶顶小翼设计技术。该设计技术可以有效降低叶顶附近的叶顶泄漏流损失。这种小翼几乎完全抑制了通道中刮削涡的发展，从而极大提高了涡轮的效率。和双肋相比，经过优化的采用小翼的叶顶可以将泄漏流损失系数降低23%，且叶顶表面积仅增加了20%。基于涡轮级的数值模拟表明，采用该小翼的叶顶将涡轮的级效率提高了0.6-1%（不同的湍流模型）。该设计在大尺寸低速叶栅台对采用肋翼结构叶顶的空气动力学性能进行了验证。研究采用了试验和数值模拟的方法，研究了五种不同叶顶几何形状在三个叶顶间隙条件下的作用。研究表明，采用小翼结构的叶顶设计有效抑制通道中的二次涡系，提高了涡轮效率。