Aerodynamic Optimization Design Method And Flow Structure Study For A Transonic Fan

The core design technology of multi-stage fan/compressor always plays an important role in the compression system research of high-load and high-throughflow aero-engines.Many countries invest heavily in high-efficiency,high-load,high-throughflow and high-reliability compression systems to meet the development needs of high thrust-weight ratio aircraft engines.Therefore,it is necessary to understand the internal flow physical mechanism of the multi-stage fan/compressor channel.It is indispensable to explore how to use geometric constraints in the limited space to guide the fluid.The development of the interaction between shock and boundary layer is also need to control properly to achieve high-efficiency heat&thermal conversion.On the base of these,the optimization design technology of compression system will be a nice technical approach that expands the comprehensive performance of modern advanced aero-engines.In this paper,based on the design parameters of the NASA Stage-67 two-stage transonic axial fan with published experimental data,the aerodynamic design of the two-stage transonic fan is studied by one-dimensional,quasi-three-dimensional(Q3D)and three-dimensional design methods.The detailed flow structure parameters and performance parameters in the transonic fan channel are obtained by 3D CFD,and the correlation characteristics between transonic diffuse flow and channel geometric boundary in multi-level environment are analyzed in depth.On this basis,the optimal design method of the two-stage transonic fan channel(endwall/blade)is established,and aerodynamic optimization design research and internal flow diagnosis analysis are carried out.Finally,the aerodynamic performance and flow structure data of the new two-stage transonic fan are obtained.Based on analyzing the endwall geometry and hydrodynamic characteristics of the two-stage transonic fan,a fore-concave and aft-convex hub is proposed on the quasi-three-dimensional level.This hub is verified and analyzed by the Q3 D endwall optimization design platform established in this paper.Not only good results are obtained in three-dimensional environment,but also the flow capacity,total pressure ratio and adiabatic efficiency of the two-stage transonic fan are improved.Based on the endwall-optimized fan,three-dimensional aerodynamic optimization design method and platform are established.The mean line optimization is implemented for the first and second stage rotor.Matching inlet flow angle and the mean line is curried out for the second stage rotor.The optimized results are analyzed in detail.The research results show that the optimization effect of the first-stage rotor optimization scheme is mainly reflected in the non-design speed,especially 70%,80% and 90%.With total pressure ratio consistent with the baseline design,the maximum adiabatic efficiency is obviously improved.The optimization results of the second-stage rotor optimization scheme have advantages at the design speed,but the pressure ratio at the non-design speed are significantly lower than the first-stage rotor optimization scheme.The reason can be summarized as follows.The channel boundary geometric is modified.The shock wave position moves downstream due to adjusting shock structure reasonably.Thereby,the shock intensity at the tip is reduced,which leads to weakening the loss from shock and boundary layer.At the same time,by optimizing the flow angle and mean line of the two rows rotors,the pressure gradient on the blade surface is adjusted,and the aerodynamic load is redistributed,which is beneficial to reduce the strength and scale of the boundary layer separation and to reduce the secondary flow los s.In addition,although the performance of the fan is improved at design point by optimizing single blade,the overall performance of the compression system may not be enhanced under non-design conditions or even non-design speed conditions.Therefore,it is necessary to further analyze the flow and develop more general optimization design techniques to solve the performance expansion problem of multi-stage fan/compressor under all working conditions.