Endwall Contouring Using Continuous Diffusion: A Breakthrough Method and its Application to a Three-Stage High Pressure Turbine
Endwall Contouring Using Continuous Diffusion: A Breakthrough Method and its Application to a Three-Stage High Pressure Turbine
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连续扩散端壁轮廓：突破性方法及其在三级高压涡轮机中的应用
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
K. Lu
中科院分区：
文献类型：
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作者：
M. Schobeiri;K. Lu
高压涡轮的叶片具有相对较小的展宽比，这会在轮毂和叶尖附近产生主要的二次流区。轮毂和叶尖涡系引起的二次流产生阻力，导致二次流损失增加，从而降低级效率。鉴于技术的高度成熟度和涡轮机空气动力效率的现状，只有通过大量的研发工作才能实现重大的效率改进。相比之下，气动效率的适度提高可以通过减少上述寄生旋涡的影响来实现。引入了适当的非轴对称端壁轮廓，减少了由压力和吸力面之间的压差引起的二次流动效应。同样，附加前缘圆角会降低马蹄铁漩涡的强度。虽然适当的端壁轮廓设计需要特别注意，但前缘圆角的设计是直接的。在本文中，我们提出了一种基于物理的方法，使研究人员和工程师能够为任何类型的叶片设计端壁轮廓，而不考虑叶片载荷、反作用力、级载荷和流量系数。详细介绍了该设计方法，并将其应用于德克萨斯A&M大学涡轮性能与流动研究实验室(TPFL)三级研究涡轮的第二级转子。对包括二次流在内的流场进行了全面的数值计算，结果表明设计合理的端壁外形对效率有积极的影响。结果还表明，设计不当的外形会对涡轮机效率造成不利影响。将效率计算的数值结果与参考非等高型水轮机的实验效率进行了比较。版权所有©2011由ASME
Blades of high pressure turbines have a relatively small aspect ratio that produce major secondary flow regions close to the hub and tip. The secondary flows caused by a system of hub and tip vortices induce drag forces resulting in an increase of secondary flow losses and thus a reduction of stage efficiency. Given the high level of technological maturity and the current state of turbine aerodynamic efficiency, major efficiency improvement, if any, can be achieved only by significant R&D effort. In contrast, moderate increase in aerodynamic efficiency is attainable by reducing the effect of parasitic vortices such as those mentioned above. Introducing an appropriate non-axisymmetric endwall contouring reduces the secondary flow effect caused by the pressure difference between pressure and suction surfaces. Likewise, attaching leading edge fillets reduces the strength of horse shoe vortices. While an appropriate endwall contouring design requires special care, the design of the leading edge fillet is straight forward. In this paper we present a physics based method which enables researchers and engineers to design endwall contours for any arbitrary blade type regardless of the blade loading, degree of reaction, stage load and flow coefficients. A thorough step-by-step design instruction is followed by its application to the second rotor of the three-stage research turbine of Turbomchinery Performance and Flow Research Laboratory (TPFL) of Texas A&M University. Comprehensive numerical calculations of the flow field including the secondary flow show the positive impact of an appropriately designed endwall contouring on the efficiency. The results also show, how an inappropriately designed contour can be detrimental to turbine efficiency. The numerical result of the efficiency calculations is compared with the experimentally obtained efficiency for the reference non-contoured turbine.Copyright © 2011 by ASME