Research On Aerodynamic Optimization Of The High-loaded Transonic Fan And The Flow Diagnosis With Vorticity Dynamics

With the design requirement of morden aeroengines for high through-weight ratio,high throughflow and high efficiency,the compression system is required to develop towards higher stage load,less stage numbers and wider range of stability.However,the constant increasing of load level must cause higher Mach number at the rotor tip and,in the blade passage,lead to some technological bottlenecks ugently needed to be solved,such as intense adverse pressure gradient and large-scale boudary layer separation.Therefore,based on the deep understanding of physical mechanism for the blade passage flow of transonic fans,carrying out the research on aerodynamic optimization methods for high-loaded fans/compressors and developing them,and dipping out advanced diagnosis methods for blade passages become essential techinical ways to develop advanced compression system of the aeroengines with the high-through-weight feature.In terms of high-loaded transonic fans,morden aerodynamic optimization technologies integrated with CFD approaches was applied and an relevant aerodynamic optimization platform was built to conduct the research on aerodynamic optimization and flow diagnoses.Subsequently,on the basis of the optimization result,in combination with the theory of vortex dynamics,the underlying dynamics property for the aerodynamic performance expansion of transonic fans was revealed in order to provide flow-geometry relating rules in the blade passage for further improving overall performance of the high-loaded transonic fan.Through successively adopted one-dimensional,quasi-three-dimensional and three-dimensional design methods,the initial aerodynamic design of a high-loaded transonic fan was completed.Meanwhile,the initial geometric structure of the blade passage and aerodynamic parameters in it are obtained.It is revealed that,compared with the fans of the same type,the fan initially obtained has a higher aerodynamic performace and lays the foundation for further aerodyanmic optimization.Based on the initial design of the high-loaded transonic fan,an aerodynamic optimization platform was built.Subsequently,including the camber line curvaure control method,endwall profile optimization method and blade geometry angle control method,multiple opimization methods were applied to complete the aerodynamic optimization of the high-loaded transonic fan.In this process,the internal mathematical-physical mechanism for different optimization methods to adjust the geometric structures of the blade passage and to improve the optimziation performace of overall fans was discussed.The relating rules between the geometry of the blade passage and aerodynamic parameters in it was analysed.The final optimziation result produces a new fan stage with total pressure ratio of 2.504,adiabatic efficiency of 88.59% and mass flow rate over 26kg/s at the design point as well as favorable flow structures for the rotor and stator blade passage.Briefly speaking,the camber line curvature control method is able to control the shock wave structure,weaken the boundary layer separation and reduce the scale and strength of secondary flow.As a result,the throughflow capability of the fan stage is improved and the range of stability is widen.The endwall profile optimization method can compressively utilize the deceleration-diffusion characterastics of high-loaded transonic fans to solves the bottleneck problem during the optimization process caused by the boundary layer separation in the pressure surface of the rotor blade and affecting the fan-stage performace improvement.The blade geometry angle control method is implemented by reasonablely adjusting the geometry angle at the inlet and outlet of the rotor/stator blade.Through this way,it solves the mathemetical-physical relation of the geometry-flow vector matching and improves the flow-guiding and-adjusting charaterastics.As a consequence,the overall aerodynamic performance of the high-loaded transonic fan stage is improved.On the basis of the final optimization result of the high-loaded transonic fan and integrated with the theory and analysis methods of vortex dynamics,the research on vortex dynamics flow diagnosis methods was conducted.This is aimed at further analysing the relating rule between mathematical-physical parameters and flow phenomenon in the blade passage,such as shock wave,boundary layer,secondary flow and etc,and further investigating the vortex structure in the blade passage.It is revealed that there are various mathematical-physical parameters in vortex dynamics(helicity,boundary voticity flux,radial vorticity and etc.)which can be used in the internal flow analysis of transonic fans,even all other types of turbomechinary with different throughflow forms.From the underlying transport principle of dynamics parameters of flow motion,the parameters in vortex dynamics discribe the key flow information deeply and from multi angles,such as the mechanism of flow loss generation,the relating rule between shock wave and the dual vectors in its adjacent region and the separation of boundary layer.This is essential for turbomachinary to carry out the research on internal flow and improve its performance.Additionally,the new vortex identification method provides the vortex structure identification in blade passages of turbomachinery with new technology and is significant for research and application.