Study On Control Methods Of Turbulent Interaction Noise Of Aeronautical Low-pressure Turbine Based On Bionics Principle

With the rapid development of aviation industry and the enhancement of human awareness of environmental protection,aircraft engine noise has become the focus of attention.In the process of aircraft landing,low-pressure turbine turbulent interference noise occupies the dominant position of engine noise.In-depth study of the mechanism of low-pressure turbine turbulent interaction noise and the development of effective noise control strategies can provide reference and basis for engine noise control research.For the last few years,with the in-depth study of bionics,bionic noise reduction techniques imitating owl wing structure with silent flight ability and shark skin protruding structure with drag and noise reduction function have attracted the attention of scholars,noise reduction techniques such as serrated trailing edge,porous trailing edge,riblet and so on have been developed.Based on this,this paper uses large eddy simulation combined with FW-H acoustic equation to analyze the mechanism of turbulent interference noise in low pressure turbine,and explores the influence of static blade serrated trailing edge,cylindrical surface with porous media and small rib protruding structure on turbulent interference noise and noise reduction mechanism.The main studies and conclusions of this paper are as follows:（1）Firstly,the computational accuracy and efficiency of four subgrid models of large eddy simulation（SL,DSL,WALE and KET）in turbulent interaction noise simulation are compared,and the DSL subgrid model with the best effect is determined.Then,the DSL subgrid-scale model is used to identify and locate the noise source,and it is found that the30%length area of the leading edge of the airfoil is the main noise source,and the noise control research will be carried out around this area.（2）The mechanism of turbulent interaction noise is that the upstream wake contains complex vortex structures of various scales,and its unsteady,nonlinear and instability will lead to interaction effect in the downstream blade flow field,which leads to strong turbulent interaction noise.Noise control can start from the source of noise,to reduce the aerodynamic noise by improving the upstream wake,so we explore three noise reduction strategies to improve the upstream wake,namely,trailing edge sawtooth,porous media and riblet.（3）Taking the last stage low-pressure turbine of PW-E~3 engine as the research object,the stator/rotor interaction noise and aerodynamic performance of the low-pressure turbine are studied when the upstream stator trailing edge adopts short and long sawtooth structure under different axial spacing.The upstream stator adopts the sawtooth trailing edge structure,and the microjet generated at the sawtooth root can eliminate the separation bubble at the leading edge of the downstream rotor,thus weakening the unsteady interference effect,improving the aerodynamic performance and reducing the stator/rotor interaction noise.The noise reduction effect of the stator with long serrated trailing edge is better,which can reduce the tonal noise8.7 d B-11.8 d B,and improve the turbine flow rate and total pressure recovery coefficient.The trailing edge of the stator adopts a bionic sawtooth structure,which can not only reduce the interaction noise but also improve the aerodynamic performance.（4）Taking the rod-airfoil model as the research object,the influence of the porous media structure with different PPI and thickness on the turbulent interaction noise and aerodynamic performance is studied,and the noise reduction mechanism is deeply analyzed.The porous medium stabilizes the shear layer on the cylindrical surface to suppress the shedding of vortices,thereby weakening the impact of the wake on the downstream airfoil.Among them,the cylindrical single tone noise can be reduced by 79d B,the airfoil single tone noise can be reduced by 13.22d B,and the broadband noise can be reduced by about 20d B.Compared with PPI,the change of thickness has a greater impact on turbulent interference noise.Porous media can improve aerodynamic performance while reducing the interaction noise of rod-airfoil.（5）The influence of the riblet structure on the turbulent interaction noise and aerodynamic performance is explored.The riblet structure can effectively reduce the shear stress on the cylindrical surface,delay the separation of the boundary layer,and break the large-scale vortex structure shed from the cylindrical surface into small-scale vortex structures,thereby reducing the rod-airfoil turbulence interaction noise.The noise is reduced by 21.36d B,and the airfoil tonal noise is reduced by 10.89d B.The small riblet structure can also effectively reduce the turbulence interaction noise.Porous media and riblet structure can effectively suppress the rod-airfoil turbulent interaction noise,which can provide theoretical basis and guidance for the subsequent application of noise control to the actual low-pressure turbine.