Carbon Fibre Brush Seal Leakage And Heat Transfer Characteristics Study

In the core equipment of important fields such as aerospace,sealing components play an irreplaceable role in dynamic gas path sealing.As a new type of sealing structure,the emergence of brush seal overcomes the defects of large leakage and severe wear of the labyrinth seal.The brush sealing device is composed of a brush bundle,a front and rear baffle,and a rotor.Due to the high flexibility and strong ductility of the brush tow,it can allow the rotor to undergo certain radial deformation or jumping.Compared to labyrinth seals,brush seals have the advantages of low wear and leakage in terms of wear characteristics,and have important research value.However,in practical production,the application of brush seals in practical engineering and theoretical research is subject to many limitations due to the problems of increased wear caused by a large amount of frictional heat at high rotational speeds,burning points and hair breakage,as well as difficulties in calculating leakage and heat transfer characteristics.In the face of the above issues,this thesis proposes to replace the traditional high-temperature alloy brush wire with carbon fiber material during the research process,and design the brush seal structure based on the material characteristics.It is hoped that the traditional metal brush seal brush wire will have excellent ductility,flexibility,and excellent sealing performance while solving the problems of hair breakage and burning under high temperature and high-speed conditions.This thesis first explores the calculation methods for end face wear and frictional heat,and then explores the equivalent stiffness coefficient of brush seals considering frictional effects.In the presence of upstream and downstream pressure differences,the equivalent stiffness coefficient of the brush wire will be strengthened to some extent due to the presence of friction.Secondly,research is conducted on numerical calculation methods for brush seals.Based on the flow theory of porous media and the Naviskotos equation,the brush bundle part in brush seals is designated as the porous media region.The key parameters such as equivalent diameter,heat transfer coefficient,porosity and the calculation method of gas resistance to brush tow are determined,so as to establish a finite Metacomputing calculation model for the leakage and heat transfer characteristics of brush seal.We have employed a rigorous methodology that involves the correction of parameters using a comparative analysis between experimental and simulated data.The corrected parameters,including thickness and radial expansion,were then confirmed using the experimental data.This approach allowed us to obtain reliable results and draw meaningful conclusions from our study.We reconstructed our brush seal leakage and heat transfer calculation model by incorporating the revised parameters and compared and analyzed its performance against the original model.The analysis results prove that the theoretical calculation results have a high degree of overlap with the experimental values,Proved the applicability of the established brush seal leakage and heat transfer model.Finally,This thesis presents a study that investigates the influence of various structural and operating parameters of carbon fiber brush seals on their equivalent stiffness coefficient,leakage,and heat transfer characteristics.The calculation results of leakage and heat transfer characteristics show that as the structural and operating parameters of carbon fiber brush seals change,the leakage amount and the highest temperature generated correspondingly change.Its trend of change is similar to that of metal brush seal,but its sealing effect is significantly better than that of metal brush seal.In terms of the calculation results of the equivalent stiffness coefficient of carbon fiber brush seals,the equivalent stiffness coefficient of brush seals shows a decreasing trend with the increase of brush wire arrangement angle and brush wire length,and an increasing trend with the increase of brush wire diameter.Among them,the brush wire diameter has the greatest impact on the equivalent stiffness coefficient of brush seals.In the operating conditions,the change in speed has a relatively small impact on the equivalent stiffness coefficient of the brush wire,and the presence of upstream and downstream pressure differences will strengthen the equivalent stiffness coefficient to a certain extent.The analysis of the above results provides an important theoretical reference for designing high-performance brush seals.