Numerical Study On Unsteady Aerodynamics Of Axial Flow Transonic Fan/Compressor

Rotor-stator interactions between adjacent blade rows is an inherent unsteady phenomenon in multi-stage fan/compressor.It mainly includes wake,potential and shock wave interference,which affects the unsteady aerodynamic variation of blade surface and reduces blade life in severe cases.In this paper,the unsteady aerodynamic forces of blades in an axial-flow transonic compressor are studied by using the self-developed CFD program NUAA-Turbo 2.0,and the mechanism of the influence of rotor-stator interactions on the unsteady aerodynamic forces of compressor blades is analyzed.Firstly,unsteady aerodynamic changes on blade surface caused by two-dimensional rotor-stator and IGV-rotor interactions are studied on the compressor rotating surface by using two numerical methods of detached vortices and high-precision schemes.The results show that,in the case of rotor-stator interactions,the unsteady aerodynamic force of the rotor blade is mainly caused by the potential interference of the downstream stator,mainly near the trailing edge,and the pressure fluctuation amplitude of the pressure surface is larger than the suction surface;The unsteady aerodynamic force of the stator blade is caused by the potential interference and wake interference of the upstream rotor,and the wake interference affects the whole stator blade,while the potential interference mainly affects near the leading edge of the stator.In the case of IGV-rotor interactions,the unsteady aerodynamic force on the IGV surface is caused by the leading edge shock wave and potential interference of the downstream rotor,and the shock wave interference is the main factor;the unsteady aerodynamic force of the rotor blade is caused by the wake interference and potential interference of the upstream IGV,and the wake interference is the main factor.Then,the unsteady aerodynamic distribution and magnitude of blades under rotor-stator interactions and IGV-rotor interactions in a three-dimensional high-load fan are studied by using the unsteady URANS numerical calculation method.The influence of compressor operating conditions and axial spacing on the unsteady aerodynamic force of blades is also studied.The results show that,for the rotor-stator interactions,the pressure fluctuation amplitude of the rotor trailing edge and stator leading edge forward swept regions is larger,and the surface unsteady aerodynamic force of the downstream stator blade is much larger than that of the upstream rotor;The unsteady aerodynamic force of the stator blade at the near choking point is larger than that at the near design point,while the influence of rotor blade is not significant;With the decrease of the axial spacing,the unsteady aerodynamic force of stator blade increases while that of stator blade decreases.For IGV-rotor interactions,the unsteady aerodynamic force of the IGV is affected by the leading edge shock wave of the downstream rotor,and the overall surface mean unsteady aerodynamic force is larger than that of the rotor;The unsteady aerodynamic force of the rotor near choking point condition is smaller than that of near design point,while the unsteady aerodynamic force of the IGV varies little between the two working conditions;With the decrease of the axial spacing,the amplitude of pressure fluctuation on the blade surface and the whole of the guide vane and rotor increases.