Investigation On The Aerodynamic Design And Flow Field For A Turbine Rotor With An End Wall Rotating In The Inverse Direction

Current counter-rotating turbines of jet engines usually have one inter-stage plane between which high pressure rotor and low pressure rotor rotates in inverse directions.Such configuration only removes one row of turbine nozzles,and the power imposed on inner shaft is insufficient to drive high bypass ratio fans for 1+1/2 counter-rotating turbines.Multistage vaneless counter-rotating turbine(MVCRT)have multiple counter-rotating planes between neighboring rotors with overhung blades.The power generated by the rotors connected with inner shaft to drive fans is significantly increased and more than one row of nozzles can be reduced in it.As a result,specific fuel consumption decreases and thrust to weight ratio increases for the engines employing such turbines.The new configurations cause new issues due to that the relative rotating speed of a multistage vaneless counter-rotating turbine is much higher than that of a conventional turbine.This paper presents aerodynamic design and flow field analysis of a MVCRT rotor rotating in an inverse direction of the end wall.3D numerical simulation is performed to investigate the internal flow field,especially in the regions near hub and shroud.The corresponding analysis would help to optimize flow field organization and contribute to the improvement of jet engine performance.Main contents of this thesis are as follows:1.An aerodynamic design and numerical simulation of a MVCRT rotor with end wall rotating in an inverse direction is carried out,and the static structural analysis is carried out as well.The result indicates that The flow field of the turbine rotors should be transonic to raise stage work coefficient because of insufficient inlet swirls and limited blade turnings.Larger inlet swirls aids in reducing relative exit Mach numbers and the losses of shock and viscous.Exit swirls increases with inlet axial velocity decreasing,however excessively low inlet axial velocity leads to increase the centrifugal stress at MVCRT blade roots and rotating end wall.Near-casing passage vortex interacts with tip leakage vortex,which results in radial non-uniformities and larger attack angle for subsequent rotor baldes.2.Effect of the rotating speed and direction of the end wall on tip leakage flow and turbine performance is investigated numerically at various tip clearance heights.The numerical results shows that the relative motion of the end wall in an opposite direction of blade rotating obstructs the tip leakage flow and enhances the near-casing secondary flow.As the relative motion speed of the end wall increases,the strength of the tip leakage vortex is weakened,but the passage vortex and shed vortex are enhanced.As a result,the entropy generation is increased near the end wall.The efficiency the turbine rotor rotating in an inverse direction of the end wall drops fester with the increasing of the tip leakage gap at higher relative motion speeds of the end wall.