Analysis Of Passive Control On Tip Leakage Flow Of The Driving Shaft On Variable Geometry Guide Vanes

The existing research of variable geometry turbine(VGT) mainly focuses on the cycleof the unit and the characteristics of VGT, the attention on flow and vortex structure insideVGT have been paid little. these research have neglected the influence on the tip clearanceflow and vortex structure, which have been caused by the driving shaft fixed on adjustableguide vanes.because of which, loss in adjustable guide vanes will be change. In order toresearch effects of the driving shaft on the adjustable guide vanes and to control the tipleakage flow by means of adjusting the size and location of the adjustable guide vanes in tipplatform, it is practical and researchful significant.In order to know effects of the driving shaft on the old research in VGT, numericalsimulation about the adjustable guide vanes of a variable geometry power turbine wasperformed, which have been fixed driving shaft. According to the analysis of the result, Theflow characteristics of endwalls and blade surfaces for the vanes and the structures of3D flowfield were also presented, on which the influence caused by driving shaft have been research.Especially the change of tip clearance flow and the generation, evolution of the tip leakagevortex are analyzed in detail in the paper. Besides, the difference of aerodynamic parametersand the loss distribution in the guide vanes was also studied between the guide vanes fixed thedriving shaft and the vanes without shaft. The proposed research ensures the flow fieldstructure and loss of the adjustable guide vane, shows the influence of the driving shaft on theflow field of adjustable guide vanes, and provides reference for3D geometry design of theadjustable guide vane. The result showed that the installation of the driving shaft can beeffective to control the tip leakage flow, effect the generation, evolution of the tip leakagevortex, and to reduce the tip leakage loss and mass weighted average total pressure losscoefficient at outlet.Subsequently, another important study in the proposed research is to control the tipleakage flow maximatily by means of adjusting the size and location of the adjustable guidevanes in tip platform. numerical simulation about the adjustable guide-vane was performed,which is fixed on the driving shaft with different sizes and different location. Revealed theeffect of sizes and locations changing of the driving shaft to the turbine performance by comparing the fluid detail about controlling tip clearance flow and the generation, evolutionof the tip leakage vortex, as well as mass weighted average total pressure loss coefficient andmass weighted average flow angle at outlet. The result showed that the location changing ofthe driving shaft can preferably effect the generation, evolution of the tip leakage vortex. theinstallation of the driving shaft at20%~50%chord is perfect for the blade researched in thethesis. the diameter of the driving shaft can also control tip clearance flow effectively, but itshould been considered based on tip chord. The ratio of the diameter to tip chord is theparameter need to be considered, when choosing the diameter of the driving shaft.