| With the development of compressor tend to high load,there exists strong crosswise secondary flow in cascade flow passage and they will induce serious corner separation phenomenon,resulting in adverse effect on the performance of the compressor.At present,the flow control method is always applied to suppress corner separation.Vortex generator,as a passive flow control technology,has been widely applied in the flow separation of the outflow and gained good results.Therefore,it is of great significance for the development of high-performance compressor to carry out the research of using vortex generator to control corner separation.A numerical simulation was conducted to study a plane cascade internal flow field through the commercial software Fluent.This paper explored the mechanism of vortex generator controlling separation control and investigated the impacts on cascade internal flow field of the geometrical parameters and installation site and amount of vortex generators.In addition,it is studied that how the vortex generators effect the compressor internal flow field at non-design incidence and analyzed the final control effects at different incidence.Study on the control mechanism of the corner separation using vortex generators shows that the vortex generator placed inside the cascade can resist the crosswise flow of air,making it more difficult for the low energy fluid to accumulate in the suction corner region.The stream-wise vortex generated by the vortex generator is opposite to the passage vortex,which can block the passage vortex in the middle of the pitch,inhibit the development of the passage vortex toward the suction side and weaken the strength of the passage vortex.Moreover,the downwash action of the stream-wise vortex on the suction side can entrain the high energy fluid into the corner area,activated the boundary layer fluid.The effects of the geometrical parameters of vortex generators on corner separation were investigated.Longer and higher vortex generators can product stronger stream-wise vortex,but they also result in larger additional flow losses.The vortex core height of stream-wise vortex is same as height of vortex generator.The stream-wise vortex generated by too high vortex generator cannot interact with the near-wall boundary layer,thus,it will not get good control effect.The effects of the installation site and amount of vortex generators on corner separation were investigated.If the installation angle ? of vortex generator is too large,it will cause the flow separation in the area between vortex generator and the suction side,resulting in the more serious crosswise secondary flow and total pressure loss.In order to effectively activate boundary layer fluid of suction side corner region and prevent the development of passage vortex toward the suction side,the installation site of the single vortex generator should not be too far away from the leading edge and the suction side.If a plurality of vortex generator is arranged in the flow passage in a way of moving along axial direction and gradually toward the pressure side,it can expand the blocking range of crosswise secondary flow and the successively generated stream-wise vortex will weaken the passage vortex continuously.However,multiple vortex generators will also generate more additional flow losses at the middle of the pitch.The study of controlling corner separation using vortex generator at different incidence shows that the crosswise secondary flow and corner separation in the cascade is becoming stronger and stronger and the total pressure loss increases rapidly with the increasing of incidence.The control effect of vortex generator on corner separation will strengthen with the increase of incoming flow incidence.At the incidence of-4°,the total pressure loss coefficient is reduced by 2.7% compared with the prototype cascade,and the total pressure loss coefficient is 16.3% lower than that of the prototype cascade when the incidence reach 8°. |
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