Fluid-structure Interaction Study Of Brush Seals Bristle Flutter Based On The Energy Method

Brush seal,as an advanced dynamic seal between rotor and stator.Brush seal plays an important role in improving the ratio of pressure,thrust and fuel consumption of aero-engine.In recent years,with the development of aero-engine in the direction of high parameters,there are still some problems in the application of brush seal.In condition of high differential pressure,bristle flutter phenomenon seriously affect the sealing performance and working life of brush seal.Therefore,this paper studies the flutter problem of bristle in brush seal from three aspects of theory,numerical simulation and experiment respectively.In the aspect of theoretical research,the large length-diameter ratio bristle was simplified as cantilever beam model.The steady-state energy formula of bristle under unsteady aerodynamic force was constructed based on energy method.According to the characteristics of the fluid-structure interaction of brush seals,the transient energy formula of the brush seal was constructed and validated.In numerical research,a method for analyzing flutter characteristics of bristle based on fluid-structure interaction was adopted,and a transient three dimensional two-way fluid-structure interaction numerical solution model considering the unsteady aerodynamic motion deformation of bristle was established.The calculation results of numerical model were compared and verified with those of theoretical and experimental.On the basis of the above analysis,the deformation law of the bristle was analyzed using the method of unsteady aerodynamic work,and the influence of the structure parameters of brush seal on the bristle flutter was further investigated.In the aspect of experimental research,flutter phenomenon of bristle were studied by designing and building a brush seal test bench and single/multistage brush seal experimental parts.The accuracy of the test bench were verified by comparing of results between experimental test and numerical analysis.The results of this paper are as follows.The pressure drop at the gaps between bristles is obvious.The jet flow is produced in the gap between the free end of bristle and rotor surface,while the flow is weak at the root of bristle.Therefore,the effective leakage area of bristle increases gradually from top to bottom,and so does the fluid flow.The bending deformation of bristle is related to the energy absorbed by itself.Under the action of fluid,the bristle oscillates,and the energy reaches the maximum value at the maximum deformation.However,the power of the bristle is zero when the bending deformation of bristle attain maximum,and the bristle is no longer absorbing the energy from fluid at the moment.The decrease of the height of back plate and the length of bristle and the increase of the diameter of bristle all reduce unsteady aerodynamic work,and it is helpful to restrain the bristle flutter.Furthermore,the variation of the gap between bristles and axial gap of back plate have little influence on the bristle flutter.