Wear Characteristics And Thermal Protection Analysis Of C/C Composite Finger Seal

As a new type of dynamic seal structure,finger seal has a good application prospect because of its flexibility and low leakage.In recent years,its wear life and high temperature thermal protection as a low friction material have become the focus of attention.Based on this,the wear mechanism of finger seal and the thermal protection of C/C composite finger seal are systematically studied,which can provide research reference for promoting the long life design and high temperature application value of finger seal.The main research contents and conclusions are as follows:1)In order to analyze the wear mechanism of finger seal and build its wear calculation model,combined with the working mechanism of finger seal,the mathematical model of the contact interface between finger seal and friction pair was established,and the finite element model of the contact wear between single asperity on the bottom surface of finger seal shoe and the pair was established from the micro level The calculation method of wear depth and the determination principle of wear direction were established,which provided a theoretical basis for the interpretation of macro wear behavior of finger seal and the construction of model.2)Based on Archard wear model,the calculation formula of finger seal wear is obtained,which is embedded into UMESHMOTION subroutine in ABAQUS.Combined with ale adaptive grid technology,the stress wear coupling behavior of finger seal rotor working is simulated,and the macro model of finger seal rotor wear analysis is established,A new technique for calculating the wear loss of C/Ccomposite finger seal is proposed.The results show that the average wear depth of the bottom node of the finger shoe is positively correlated with the pressure difference,speed and radial runout of the rotor.At the same time,the wear process results show that the root of the finger shoe is worn first,and with the extension of time,the average wear depth of the bottom node of the finger shoe is positively correlated with the pressure difference,speed and radial runout of the rotor,The wear area gradually shifts to the middle of the sole,and the front of the sole is worn at last,that is,the root of the finger seal is worn seriously while the front is worn lightly.In addition,the wear simulation results show that the average wear depth of the optimized finger seal is only 1/4 of that of the non optimized structure when the working pressure difference is 0.3MPa and the rotor speed is 10000 r/min.3)Aiming at the problem of oxidation analysis of C/C composite finger seal in high temperature application environment(400℃),high temperature oxidation resistance was studied by adding thermal protection coating on the surface.Graphene oxide coating(rGO)was prepared by reducing graphene oxide on the finger seal surface of C/C composite based on the photothermal effect of high repetition rate femtosecond laser.The controllable preparation of rGO coating was realized by adjusting the operating parameters of the laser.The microstructure of the coating on the finger seal surface of C/C composite was evaluated by SEM.It was found that the pores of the fiber braided structure of C/C composite were filled and covered by the coating on the finger seal surface with rGO coating,and the surface roughness was improved obviously.The common edge chipping caused by machining was obvious on the finger seal surface without coating The surface of carbon fiber is rough.At the same time,the results of high temperature bench test of finger seal show that some areas of finger seal surface coated with rGO coating are relatively flat,with small voids.There are large oxidation voids and traces of fiber fracture on the uncoated finger seal surface.The energy spectrum analysis shows that the carbon element of uncoated finger seal decreases and the oxygen element increases,indicating that there is obvious oxidation reaction.It is verified that rGO coating can improve the thermal oxidation performance of finger seal.