轴流涡轮叶尖泄漏流损失分析及控制

涡轮转子叶尖间隙泄漏流会导致涡轮损失增加，效率降低，为降低叶尖泄漏损失，本论文开展了轴流涡轮叶尖泄漏流的损失及控制的分析研究。研究以典型轴流涡轮为研究对象，应用雷诺平均Navier-Stokes（RANS）方法，研究了轴流涡轮转子叶尖泄漏涡破碎形成的回流现象，并分析了叶尖间隙高度、叶型负荷、机匣相对运动等因素对叶尖泄漏涡损失的影响，探索了机匣沟槽结构在微型轴流式涡轮转子叶尖泄漏涡流动控制的应用。

（1）在叶尖泄漏流的流动现象研究中，以美国通用电气公司Energy Efficient Engine（高效节能发动机， ）第一级高压涡轮动叶为研究对象，分析了不同转速、不同落压比情况下的叶尖泄漏流和叶尖泄漏涡的表现情况。研究表明，当转速较大、落压比较大时，容易发生叶尖泄漏涡的破碎现象，在涡核中心线上能够观察到明显的回流。

（2）在叶尖泄漏流的影响因素研究中，以美国通用电气公司 第一级高压涡轮动叶叶尖叶型为研究对象，研究了不同间隙高度、不同叶型负荷、机匣是否相对运动以及相对运动速度等因素对叶尖泄漏流的影响，研究表明，随着叶尖间隙高度的增加，叶尖泄漏流逐渐增加，泄漏涡增强，损失增加；叶型载荷系数增加，叶顶区域吸力面与压力面的静压差增加，叶尖泄漏流增强，由叶尖泄漏流造成的损失增加；机匣相对运动能够削弱叶尖泄漏涡，间隙区域最大泄漏位置后移，并使叶尖泄漏涡更接近吸力面；机匣相对运动速度越大，对泄漏涡的削弱效果和通道涡的增强越明显。

（3）在叶尖泄漏流的控制研究中，对某微型涡喷发动机的单级轴流式涡轮进行机匣设计，研究分析了不同机匣沟槽结构对其叶尖泄漏流动的影响。结果说明：当全机匣沟槽结构的叶顶浸入沟槽时，封严效果较好；相较于全机匣沟槽结构，后开式机匣沟槽结构的封严效果更好，随着沟槽前缘间隙的增大，封严效果减弱；沟槽深度等于前缘间隙时，封严效果最佳，即泄漏流明显减弱，同时效率减小量较小。

Turbine rotor tip clearance leakage flow will increase turbine loss and reduce efficiency. In order to reduce tip leakage loss, in this paper, an analysis and research on the loss and control of axial turbine tip leakage flow is carried out. Taking typical axial turbines as the research object, the Reynolds-averaged Navier-Stokes (RANS) is used to study the backflow phenomenon formed by the breakdown of the tip leakage vortex of the axial turbine rotor, analyze the effect of the tip clearance height，blade profile load, and casing relative motion on the tip leakage vortex loss, and explore the influence of the casing groove structure in the vortex flow control of the tip leakage of the micro-axial turbine rotor. To study the flow phenomenon of tip leakage flow and tip leakage vortex in axial turbines, the rotor blades of GE3 E first-stage high-pressure turbine are taken as the research object, and the performance of tip leakage flow and tip leakage vortex under different rotational speeds and different drop-pressure ratios are analyzed. The research shows that when the rotating speed is high and the drop-pressure ratio is high, tip leakage vortex is easily broken, and obvious backflow can be observed on the vortex core center line. Taking the rotor tip profile of GE3 E first-stage high-pressure turbine as the research object, the influences of different clearance heights, different blade loads, relative motion of the casing and relative motion speed on the tip leakage flow were studied. The research shows that with the increase of the tip clearance height, the tip leakage flow gradually increases, the leakage vortex increases, and the loss increases; when the blade load coefficient increases, the static pressure difference between the suction surface and the pressure surface in the tip region also increases, so the tip leakage flow is enhanced and the loss caused by the tip leakage flow increases; the relative movement of the casing can weaken the tip leakage vortex, the maximum leakage position in the clearance area is moved back, and the tip leakage vortex is closer to the suction surface; the gr eater the relative movement speed of the casing, the weakening effect of leakage vortex and the enhancement of passage vortex are more obvious. In the control study of tip leakage flow, the casing of a single-stage axialflow turbine of a micro-turbojet engine is partially designed, and the influence of different casing groove structures on the tip leakage flow is studied and analyzed. The results show that when the blade tip of the full casing groove structure is immersed in the groove, the sealing effect is better; compared with the full casing groove structure, the sealing effect of the rear-opening casing groove structure is better. With the increase of the groove leading edge gap, the sealing effect is weakened; when the groove depth is equal to the leading edge gap, the sealing effect is the best, that is, the leakage flow is significantly weakened, and the reduction in efficiency is small.

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