A Reduced Order Model For Aerodynamic Response Of Blades Excited By Back Flow

Aviation turbojet engines are the main power equipment for modern aircraft and are the pearl of modern industrial technology.With the development of the aviation industry,the internal dynamic and static leaf stages of the turbojet engine are getting higher and higher,which leads to more complex internal air flow,and the interference of dynamic and static leaves and flutter phenomena.Aeroengines with long service life,good safety and high reliability are required to fully understand the mechanical behavior of the dynamic and static blades under this condition.This brings great difficulties to the development of aero-engines.High-performance parallel numerical simulation is the main method to study the internal flow of the engine and the fluidsolid coupling vibration of the engine,which greatly reduces the work difficulty of the aeroengine design research and provides great help to the engine designer.However,highperformance parallel numerical simulation has a large workload and is not suitable for daily work.To solve this problem,this paper establishes a rapid analysis model of the aerodynamic vibration of the upstream blade excited by the back flow,and provides a new idea for studying the aeroelastic vibration of the upstream blade under dynamic and static interference conditions.The main work and conclusions of this paper are as follows:1)Based on the harmonic balance method,Volterra series method and linear autoregressive method(ARX),this paper studies the aerodynamic response of the blade in the upstream of the turbine blade in the dynamic and static blade interference of aero turbine engine.Based on the principle of system identification,the blade aerodynamic reduction model based on harmonic balance method,Volterra series method and linear autoregressive equation method(ARX)was established to describe and study the aerodynamic response of blade under excitation of back flow.2)According to the two-dimensional calculation example,the aerodynamic step-down model based on the harmonic balance method is very accurate when describing a single back pressure excited blade;When describing the single exit flow direction angular excitation blade,the aerodynamic peak deviation of the blade is slightly larger,but the aerodynamic change of the outlet flow direction angular excitation blade can be described completely;When describing the whole back flow excitation blade,there is a significant phase deviation in the blade aerodynamic force,so it can not describe blades' aerodynamic force accurately;Therefore,the blade aerodynamic reduction model based on the harmonic balance method can still describe the aerodynamic changes of the blade excited by the back flow.This method can be used to study the aerodynamic response of the blade driven by the back flow.3)According to the two-dimensional example,when the aerodynamic model of blade reduction based on the Volterra series is used to describe the aerodynamic response of the upstream blade excited by a single back pressure variation,the aerodynamic equilibrium position is obviously biased,and the amplitude deviation is also obvious,but basically this model can describe the aerodynamic changes of the blade;When describing a single outlet flow direction angular excitation blade,there is a small equilibrium position and response amplitude deviation,but basically it can describe the aerodynamic change of the blade;The accuracy of the model is high when describing the aerodynamic response of the upstream blade to the back flow;Especially in the face of random gust excitation,the aerodynamic reduced-order model has a very high accuracy,indicating that the model can accurately describe the aerodynamic response of the blade during random wind excitation.The reduced-order model based on the Volterra series method can describe the aerodynamic changes of the blade excited by the back flow,and has a higher accuracy for the random wind excitation of the blades.Therefore,the Volterra series method can be used to study the aerodynamic response of the back flow excited blades.4)According to the two-dimensional example,when the ARX-based blade aerodynamic ROM is used to describe a single back pressure-excited blade,the blade peak aerodynamic response has a larger peak error,but the overall description of the blade aerodynamic response is still relatively accurate;When describing the single exit flow angular excitation blade,the model has an initial oscillation with a large error,and the model with the exception of the initial oscillation has high accuracy;When describing the full-back flow excitation blade,the accuracy of the model is higher.Whether it is the blade aerodynamic peak error or oscillation error is lower than the single back pressure or outlet flow angle reduction model.Therefore,the ARX method can be used to study the aerodynamic response of the propeller blades driven by the back flow.