| As the core aerodynamic component of aeroengines,the development goal of high-performance compressor make it continue to develop in the direction of high efficiency,high load,and supersonic or transonic.With the increase of the load of compressor,the flow separation in the transsonic stage becomes more serious.Low-energy fluids accumulate in the corner region of the suction side of the stator blade,causing the corner region to separate and induce a stall.The shock wave will cause the suction surface of the rotor to separate more easily under its induction,and the increased interaction among the balde tip leakage flow/vortex,shock wave and radial vortex will worsen the flow environment and induce compressor stall and surge.Therefore,controlling the secondary flow in the compressor through appropriate methods,weakening the flow separation,and improving the flow environment are of great significance to improve performance of the compressor.In this paper,the NASA Stage 37 transonic stage is taken as the research object.Through the numerical simulation method,the effect of the non-axisymmetric endwall on the aerodynamic performance of the transonic compressor is studied.The characteristics of internal flow structure of the typical cases with significant modification effect under different working conditions are analyzed in detail.Through comparison with the flow field of the prototype compressor,the mechanism of the effect of the non-axisymmetric modification of the endwall of the rotor and stator on the aerodynamic performance of the compressor is revealed.First,on the basis of maintaining the prototype of the rotor endwall,the effects of different modification parameters of the upper and lower endwalls of the stator on the stage performance are studied.By comparing the changes of the flow characteristics of the stator,the flow control mechanism of the non-axisymmetric modification of the stator endwall is analyzed.The results show that the modification of the stator casing has a greater impact on the near-design and near-surge conditions of the poor tip corner flow region,while the modification of the hub has a significant effect on the performance of the compressor in the clogging condition.The convex warpage in the middle of the endwall of the casing expands the flow area of the tip and weakens the separation of the blade tip corner,so that the peak efficiency of the near design condition is increased by 0.25% compared with the prototype.The increase in the warpage height causes the low-energy fluid condensed at the casing to increase and migrate to the corner area,blocking the tip flow channel,aggravating the separation of the corner,resulting in decline in stage performance.In the near-surge condition,the endwall form of the convex pressure side and the concave suction side of the tail of the stator casing causes local acceleration of the airflow in the concave area of the suction s ide corner,resulting in the reduction of low-energy fluid in the blade tip corner and the improvement of flow condition.In the clogging condition,the convex and concave warping forms of the front part of the stator hub affect the blade root shock structure.The upward convex shape enhances the shock wave and the pressure expansion ability is improved.The pressure is increased by 0.015 compared with the prototype,but the separation of the corner of suction side near hub is increased so that he efficiency is reduced by up to 1.2%.The concave shape is opposite to the convex shape,the separation of the hub corner disappears basically,the clogging of the blade root area is greatly relieved,and the efficiency is improved by 0.5% compared with the prototype..Secondly,maintaining the prototype of the endwall of stator,the effect of the non-axisymmetric modification of the rotor hub on the performance of the compressor in the stage environment was further studied.By analyzing and comparing the flow field structure of the typical cases,the mechanism of the modification of the rotor hub affecting the compressor performance is revealed.The results show that the convex or concave in the middle of the rotor hub will reduce or increase the flow rate,which will change the working range of the whole stage.In the near design conditions,the concave warpage in the middle of the hub strengthens the shock wave in the blade root area,enhances the compression ability,and the total pressure ratio increases.However,the secondary flow in boundary layer of the hub endwall and the suction surface is intensified,the separation area of the suction side is enlarged.The increase in the radial vortex size enhances the entrainment of low-energy fluids and thus aggravates the flow channel blockage,resulting in lower efficiency than prototype.The warped form of the convex on the pressure side and the concave on the suction side weakens the shock wave at the root of rotor blade,limiting the compression capacity,reducing the boundary layer separation loss and shock wave loss,and improving the peak efficiency of the compressor.In the stall and near-surge conditions,the shock waves of the axial cases of the rotor hub middle convex are weakened to varying degrees,and the total outlet pressure reduce.The radial and lateral secondary flow in boundary layer of the rotor suction side and hub are weakened,the development of radial vortices is hindered,thus the stage efficiency is improved.As the warpage height increases,only the convex warpage in the middle of the rotor hub improves the efficiency of stage in surge point,because the shock wave becomes weaker and the flow condition in the upper half of the bade is significantly improved.The stator inlet environment is greatly affected by the modification of rotor hub,the angle of attack in root region increases,causing the separation of the hub suction side corner to increase,but the intake angle in upper half of the stator is significantly reduced so that the large separation at the corner of blade tip near suction side is greatly reduced,thus the efficiency is significantly improved. |
PDF Full Text Request