Numeric Investigation Of The Influences Of The Rim Seal Gas To The Aerodanamic Performance Of The Mainstream On The High-pressure Turbine

The hot gas in mainstream of the high-pressure turbine can be ingested into the stator-rotor wheel space.The overheating of turbine disks results in the uncontroled deformation and fatigued of the cavity.Sealing flow on turbine is the key solution to this problem.The fuction of sealing flow is to prevent the high temperature gas from ingressing into the cavity and cool the cavity through the compressed cooling air from the compressor.The paper researches the effects of the parameter(injected angle and massflow ratio etc.) of rim sealing flow and(axial location and width of axial gap) of the axial gap for the mainstream aerodynamic perf ormance.Based on the axial gap,various geometries of the rim seal are designed and thire effects on the mainsteam are discussed.The typical three rim seal geometries:axial seal,compound seal and seal with cavity are designed by UG software.The seal mesh is geneated by ICEM sofware and the mainstream m esh is generated by NUMECA software.The numerical calculation is progressed by the ANSYS CFX 14.5.In order to ensure the accuracy of the calculation results,the paper analys es the mesh independence and checks the dependability of the numerical method.Rim seal reduces the stage rate of the turbine and the efficiency of the rotor,meanwhile increases the total pressure coefficent of the stator.The sealing flow injects into the mainstream,striking the mainstream flow in the bourdary layer,thus the local mainstream flow is changed and the mainstream flow separates at the outlet of the rim seal.The sealing flow influences the development of the passage vortex in the stator and the rotor,resutling in the change of the flow structure of the endwall and inducing the mixing loss.Aiming at the research target,the results of the n umerical calculation illustrate that the effects of the sealing flow for the mainsteam reflect mainly on the root and the suction of the rotor.As the sealing flow ratio increases,stage rate and rotor efficiency decrease.However,the total pressure loss coefficient increase.The load of the root of the rotor and the ability of working reduce.Besides,the influence range of the secondary flow in the rotor increase s and the aerodynamic performance of the stage is weakened.However,the cooling effects become better.The influence of the sealing flow ratio for the mainstream is not evident.Besides,axial gap with wider distance from the leading edge of the rotor and more narrow gap can benefit the mainstream aerodynamic performance.Axial gap with nearer distance from the leading edge of the rotor and more narrow gap can have better cooling effects on the hub and suction of the rotor.Under the same rim sealing flow ratio,the compound seal and seal with cavity show better aerodynamic performance and higher load of the root of the rotor.There are more mainstream gases ingressed into the cavity at the pressure surface.As the the rim sealing flow ratio increases,there are fewer mainstream gases ingressed into the cavity.The cooling gas which is injected into the mainstream from the compound seal and the seal with cavity is closer to the wall.Under the large rim sealing flow ratio,the cooling gas has less impact on the mainstream.When the rim sealing flow ratio increases to a ce rtain extent,the negative incidence appears at the entrance of the rotor.Among the several rim seals,the negative incidences of the compound seal and the seal with cavity are smaller.Considering the turbine total parameters and the detailed analysis of th e flow field structure,it reveals that compound seal and seal with cavi ty have less impact on the aerodynamic performance of the turbine,but better cooling effect on the rotor comparing with the other two rim seals under the studied rim sealing flow ratio.The aerodynamic performance changes little when it has cavity in the rim seal.