Loss Control Research Of Adjustable Guide Vane In Variable Geometry Turbine

With the continuous improvement of the turbine performance requirements, the modernturbine technology develops towards the variable working condition. As an effective means ofvariable working, variable geometry turbine (VGT) has been increasingly applied to aircraftengine, ship gas turbine power and turbo charger, etc. Variable geometry turbine use adjustableguide vanes technology mostly. By changing the low pressure turbine guide vanes’ installationangle to adjust the turbine thermal circulation, the turbine can adapt to the change of workingcondition. However, the adjustable guide vane mechanism bring about the blade tip clearanceand the guide vane rotating drive shaft structure, which cause great changes of the tip fluid flowcondition such as the leakage and the flow around. Leakage flow at adjustable guide vane tipcauses a lot of the loss, which lead to a big decline of turbine efficiency. Therefore, it has veryimportant practical significance and research value to make the research of adjustable guidevanes’ flow field, the drive shaft structure and the variable working condition changing.First of all, to decrease the leakage loss of blade tip, this paper conducts the design of thenew and old different guide blade drive shaft structure. Spherical end wall was used at blade tipin order to minimize the height of clearance between blade tip and the casing. Numericalsimulation of two kinds of shaft structure with the same gap value and also a no tip clearancemodels in an axial flow turbine stage are performed, and aimed at the tip flow field structure, wehave taken a deep research with the different calculation results of the three dimensional flowfield distributions. Then this paper elaborates the forming and development of the tip leakagevortex which formed by leakage flow, and analyses the influence of different schemes on tip flow,leakage vortex and rotor flow field.Finally, aimed at the blade fixed angle changing on the variable working condition, severalmodels of guide vanes which rotate with the degree at-7°,-4°,0°,4°and7°were calculated.Due to using the spherical end wall structure at the blade tip and the casing, the clearance keepsinvariant when the adjustable guide vanes rotating. On the basis of numerical calculation results,this paper analyses the changing of pressure distribution, tip leakage and the loss distributionwhen the vane rotating.