Research On Complex Wave System And Leakage Flow Of High Reaction 1+1/2 Counter-rotating Turbine

1+1/2 counter rotating turbine is a counter rotating turbine without guide vanes,which is mainly composed of high-pressure stage stationary blades,high-pressure stage rotor blades and low-pressure stage rotor blades.The flow field inside the high-pressure stage rotor blade is complex,especially the interaction of tip leakage flow,expansion wave and shock wave at the top of the blade makes the flow more complex,which also constitutes the main source of aerodynamic loss of the high-pressure stage rotor blade.Therefore,it is necessary to study the internal flow field of high pressure rotor blade in detail.First of all,according to the design requirements of a project,this paper carries out one-dimensional aerodynamic design of the vaneless counter rotating turbine,and derives the correlation formula between the key parameters and the turbine efficiency,power ratio and other performance indicators,so as to facilitate the rapid design of the counter rotating turbine.On the basis of one-dimensional aerodynamic design,the three-dimensional aerodynamic design of 1+1/2 counter rotating turbine is completed and numerical simulation is carried out.Then,taking the tip clearance of high pressure rotor blade as a variable,the interaction between leakage vortex and wave system in the tip clearance of high pressure rotor blade under the condition of 1% blade height and 2% blade height is analyzedWith the increase of clearance height,the flow range of tip leakage flow increases,which is mainly manifested in that the higher the clearance is,the closer the starting position of tip leakage flow is to the throat of high pressure rotor blade,the larger the influence range of tip leakage vortex,and the closer the suction side of cascade passage along the flow direction.With the increase of clearance,the outlet pressure of high pressure turbine increases,the intensity of trailing edge expansion wave and shock wave increases,and the interaction between reflected shock wave and wake of internal wake and external wake increases.The reflected shock wave emitted by the high pressure disturbance source propagates to the surface of the separated blades,thickens the boundary layer and forms a "barrier" to prevent the expansion ability of the expansion wave on the pressure side of the trailing edge.When the gap height is different,the internal wake wave and the pressure side expansion wave will interact with the leakage flow: the internal wake wave will change the leakage flow trajectory,reduce the influence area of the leakage vortex,and the leakage vortex will make the shock wave and the expansion wave deflect upstream;When the gap height increases,the external wake acts on the leakage vortex,and the flow trajectory of the leakage vortex changes.At the same time,the shock intensity decreases and the propagation ability to the downstream decreases.Finally,the relationship between leakage flow and wave system in high pressure turbine rotor blade at different operating conditions of speed and back pressure is analyzed.It is found that the leading factor of leakage vortex is still the tip clearance height,and the outlet back pressure and speed have little effect on leakage vortex.When the gap is higher and the expansion ratio is smaller,the shock wave at the trailing edge of the cascade will deform,resulting in the turning of the countercurrent direction.At the same time,the primary compression wave or shock wave will appear at the exit,which increases the mixing loss between the leakage vortex and the exit shock wave.