水轮机模式液力透平流道式导叶的优化

Optimization of runner-type guide vanes of hydraulic turbine in hydraulic turbine mode

由于水轮机模式液力透平级间导叶水头损失占比高达40%,需要对液力透平级间导叶进行研究。在可选的级间导叶中,流道式导叶正反导叶连为一体,流道相对独立,是一种水力性能较好的级间导叶。本文基于水力原动机理论,将水流环量概念贯穿液力透平流道设计全过程,设计了与水轮机模式液力透平转轮相匹配的流道式级间导叶,并采用正交试验的优化算法,对水头影响较大的因素,包括导叶包角φ、正导叶出口角α3、反导叶宽度b_(5)、流道外壁最大直径D_(4),各取4个水平进行正交试验方案的设计。通过CFD数值计算,分析各个方案的性能,找出了各因素对导叶性能的影响规律,在此基础上获得了效率较高的导叶模型,并研究了水力性能、叶片表面压力分布及叶片内部流动规律。研究表明:各个参数对效率的影响力中,b_(5)最大,D_(4)最小;对水头的影响力中,b_(5)最大,φ最小。优化后的模型在设计工况点效率提高了5.83%,应用水头提高了7.15%,级间导叶损失降低了1.16%,导叶表面压力过渡更加均匀,叶片内部水流流态更加平稳,满足液力透平对于高余压液体的能量回收要求。本研究可以为水轮机模式液力透平流道式导叶的选型和优化提供参考。

Further study on interturbine guide vanes is necessary,as they account for up to 40%of the total head loss in hydraulic turbine mode.Among interstage guide vanes available,the runner type is good in hydraulic performance,because it integrates guide vanes and return guide vanes together and its flow passage is relatively independent.Based on the theory of hydraulic prime mover,this paper describes new designs of runner-type vanes that match the turbine mode,with the concept of flow loop running through the whole design procedure of a hydraulic turbine runner.An optimization algorithm of orthogonal tests is adopted to design orthogonal test schemes for four main factors:guide blade angleφ,guide blade outlet angleα3,return guide blade width b_(5),and the maximum diameter D_(4)of the flow passage outer wall;and each is tested at four levels.Influence of each factor on guide blade performances are evaluated through CFD calculations and comparative analysis of the performances in different schemes.On this basis,we achieve a guide blade design of higher efficiency;its hydraulic performance,blade surface pressure distributions,and blade internal flow patterns are analyzed.The results of range analysis show that among the influences of different parameters on efficiency,b_(5)is the largest and D_(4)the smallest;on water head,b_(5)is the largest andφthe smallest.Though optimizing the model,its efficiency is increased by 5.83%at the design point,applied head increased by 7.15%,and interstage guide vane loss reduced by 1.16%.And water flows in the blade passages are more stable.Thus,the optimized model meets the requirements of energy recovery from the high residual pressure liquid in hydraulic turbines,providing a useful design and optimization approach for the runner-type guide vanes of hydraulic turbines.