Studies On Leakage Characteristics And Structure Optimization Of Aeroengine Brush Seal

Brush seal is a new kind of aero-enging seal with excellent sealing performance.When it replaces the traditional tooth labyrinth seal,the internal air leakage and fuel loss of the engine can significantly reduce.However,the brush is composed of thousands of filaments,so it is difficult to study the leakage flow details by an experimental method due to its complicate structure.In addition,the brush material is easily bent and broken during high temperature service,which seriously affects its sealing performance and service life.This paper focuses on the leakage calculation simulation and structural optimization of brush seals,and preliminarily explores the influence of heat treatment process on the mechanical properties of brush materials.The purpose of this paper is to provide technical support for the development of highperformance aeroengine brush seals.First,along the circumference of rotor,a two-dimensional staggered bundle model of cross section of brush bundle is established.The pressure distribution of the air among the brush wires is obtained by CFD simulation.The air flow characteristics are analyzed and the working mechanism of the brush seal is clarified.In order to simplify the model,compared the pressure and velocity distribution of air among the different brush wires models,with 1,2,3,and 6 rows along the circumferential direction of the rotor.And it turns out that the simulation results of the 3 rows brush wire model are more accurate.The effects of differential pressure,number of brushes along the axial direction of the rotor,and filament diameters on the sealing performance are studied.Based on the two-dimensional model,a three-dimensional staggered tube bundle slice model is established.The leakage amount of air,under different pressure conditions,through the three-dimensional burshes model is calculated by CFD simulation,and the results agree well with the experimental data.The air pressure and velocity distribution in the threedimensional model are described,and the working principle of the sealing structure is analyzed.The effects of different geometric parameters,such as the protective height of the rear baffle,and the axial distance between the brush tow and the rear baffle,on the sealing performance under different pressure differences are studied.After comparing the pressure distribution on the rear baffle surface under different conditions,it is found that increasing the axial distance between the brush tow and the rear baffle reasonablely can greatly reduce the hysteresis effect.A new brush seal structure with double front baffles and three cavity is proposed,which mainly includes: double front baffle and sandwich cavity,cavity between front baffle and brush tow,brush tow,rear baffle,and cavity between brush tow and rear baffle.The flow distribution of the airflow in the model under the 0.2MPa pressure difference is simulated by CFD.After comparing the amount of air leakage through the new brush seal and the conventional brush seal under different pressure differences,it is found that the new brush seal can effectively alleviate the hysteresis.And sealing performance of new brush seal structure is better than other low-hysteresis brush seals at present.The effects of different heat treatment on the mechanical properties and microstructure of brush material GH4145 superalloy is studied preliminarily.It is found that the strength and plasticity of brush material after aging at 680? for 2h is better.The microstructure of the alloy is compared and analyzed under different aging temperature and aging time.