Numerical Investigation of Blade Lean and Sweep affecting Secondary Flows in an Axial Expansion Turbine

28th IAHR symposium on Hydraulic Machinery and Systems

Neipp, A.^1 ; Riedelbauch, S.^1

Institute of Fluid Mechanics and Hydraulic Machinery, University of Stuttgart, Pfaffenwaldring 10, Stuttgart

70550, Germany^1

关键词: Decisive importance;    Flow optimization;    Numerical investigations;    Operating ranges;    Thermal turbomachinery;    Turbine efficiency;    Turbine performance;    Very low aspect ratios;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/49/6/062026/pdf
DOI  :  10.1088/1755-1315/49/6/062026

来源: IOP

【 摘 要 】

Based on an axial expansion turbine used for energy recovery from working fluids an automated CFD-flow optimization was performed to increase the turbine efficiency without narrowing the operating range. The optimization results showed that even small changes in the optimization target had a significant influence on the lean and sweep of the new blade designs. The resulting blade shapes were extraordinary. The lean and sweep resembled more that of thermal turbomachinery than hydraulic machinery. It became clear that the special blade shapes were a result of the very low aspect ratio of the turbine and the resulting large influence of secondary flows. The blade lean and sweep induce secondary flow structures which are of decisive importance for the turbine performance. The simulation results showed that positive compound lean increases the efficiency and positive compound sweep improves the cavitation behavior of the investigated axial expansion turbine. However the complexity of the occurring secondary flows make an universally valid statement on the effect of blade lean and sweep on the flow behavior of an axial turbine impossible.