Study On Aerodynamic Performance Of Turbine Sector Cascades With Adjustable Geometry

In the future,aviation weapon platforms will develop in the direction of full airspace,wide speed domain,super maneuver,etc.,which requires the power system to maintain stable and efficient operation under partial load in a wide range.Variable geometry turbine technology is one of the keys to support the power system to achieve a wide range of variable load operation.A common technical measure for variable geometry turbines is to use a guide vane adjustment mechanism to control the throat area of the turbine guide,and then control the flow to adapt to the changes in the engine's operating conditions.In order to ensure that the angle of the guide vane is continuously adjustable within a certain range,it is necessary to reserve appropriate clearances in the upper and lower end wall regions of the vane,which will cause the tip leakage flow and its interaction with the secondary flow in the end zone,which not only causes the flow The field structure is more complex and will cause additional flow losses.In addition,the guide vane adjustment mechanism will cause leakage flow turbulence in the tip clearance,further increasing the complexity of the above problem.Therefore,studying the flow mechanism of variable geometry turbines and mastering the loss laws are of great significance to the further development of variable geometry turbine technology.This paper firstly carried out a test study on a turbofan cascade with adjustable guide vanes for a certain type of engine.The design of the fan-shaped cascade test piece was designed using UG software.In order to facilitate the control of the angle of the inlet guide vane,this article uses a connecting rod structure and a dial to adjust the guide vane.On this basis,the design of the experimental cascade aerodynamic parameter collection scheme was completed.In the aerodynamic test,this paper specifically carried out the flow field parameter measurement under different angle of attack schemes(7°,-3°,-7°)and different isentropic outlet Mach numbers(0.65,0.75,0.85),focusing on analysis The typical flow structure of cascade outlet flow field and the distribution rule of cascade performance parameters are presented.On the basis of systematically obtaining the experimental data of this set of cascades,the numerical simulation method of geometry adjustable turbine fan cascades was verified.Based on the verified numerical method,this paper then carried out the numerical study of a certain engine variable geometry turbine fan cascade.In order to better reveal the characteristics of variable geometry turbine tip leakage flow,this paper uses the same blade geometry to conduct the numerical simulation of the flow loss characteristics of the gapless guide vane and the full gap guide vane(without considering the adjustment mechanism in the guide vane gap).On this basis,the flow field characteristics and the loss mechanism of the adjustment mechanism in the gap are further studied,and the flow characteristics of the gapless guide vane and the full gap guide vane are compared and analyzed.The results show that the existence of the gap will cause leakage flow,and the leakage flow will cause a large change in the flow field of the cascade flow channel,causing large losses;the presence of the rotating shaft can suppress the leakage flow to a certain extent and reduce the leakage vortex,At the same time,additional bypass losses will occur.