Wear Mechanism And Performance Analysis Of C/C Composite Finger Seal

As a new type of flexible sealing device,the finger seal has good application prospects in the fluid sealing part of important equipment such as aero-engine,automobile engine,high-speed gearboxes and turbocharger of heavy constr-uction vehicles.It has attracted more and more attentions and been studied in the field of dynamic sealing recently.However,the contradiction between hy steresis leakage and wear life has been difficult to solve.The unique self-lubricating property and good wear resistance of C/C composite materials are very beneficial to improve the comprehensive performance of finger seal,and is feasible solution to improve the above problems.For this reason,the theoretical analysis and related experimental teclniques are used in this paper.The hysteretic leakage and friction and wear performance of C/C composite finger seal were analyzed comprehensively and systematically.The main research contents and conclusions of this paper are as follows:1.The finite element model of the finger seal was established by ANSYS APDL.The hysteresis rate of the C/C composite finger seal and the contact pressurc between the finger foot and the rotor surface were studied by quasi-dynamic performance analysis.At the same time,the performance analysis of the traditional cobalt-based alloy finger seal under the same conditions was carried out.Accor-ding to the analysis results,the influence of the two materials on the performance of the finger seal was discussed.The results show that the performance characteristics of C/C composite finger seal can be reflected effectively by the quasi-dynamic performance analysis,and its hysteresis rate and averasge contact pressure increase with the increase of upstream and downstream pressure diifference.However,the contact area between C/C composite finger seal and the rotor is larcger,so the contact pressure is small.Therefore,in the structural design of the C/C composite finger seal,while ensuring its hystiresis characteristics,more atteintion can be paid to the low wear characteristics of the friction pairs.2.In order to study the friction mechanism of C/C composite,and look for a good friction pair.The pin-disk friction test of C/C composite for finger seal is designed to study the friction performance between C/C composite and rotor runway coating,according to the typical actual working condition characteristics of the finger seal and the similar principle of PV.The results shows that the friction coefficient of the C/C composite pin-disk is smaller than that of the cobalt-based alloy pin-disk,and the line wear increases with the load increase in the C/C composite pin-disk,but the friction performance of the C/C-Cr3C2 friction pair is more stable.The wear morphology of C/C composite pin-disk were analyzed by SEM scanning electron microscopy.The main wear mechanism was abrasive wear and a small amount of adhesive wear.The cobalt-based alloys produce wear marks on the surface of the disk,but the C/C composite is difficult to form wear marks on the friction surfaces of the disk.3.In order to study the dynamic performance of the C/C composite finger seal,considering the Coulomb friction between the finger element and the aft cover or the finger element and finger element,an equivalent dynamic model of the finger seal was established,and explain the calculation method of each equivalent parameter and the characterization method of the dynamic performance.The ode function of MATLAB is used to solve the equivalent dynamics model,and the dynamic performance of the C/C composite finger seal is analyzed and compared with that of finite element model.The results show that considering the Coulomb friction between the finger element and the aft cover or the finger element and finger element,the displacement response of each finger element is consistent but the degree of hysteresis is inconsistent,and the hysteresis of the first finger element is highest;with the increase of the pressure difference,the hysteresis of the C/C composite finger seal is also increasing.Therefore,the rotor working characteristics and pressure conditions needs to be considered comprehensively for the structural design of finger seal in practical engineering applications.4.The bench performance test between C/C composite finger seal and Cr3C2 coating was carried out.The C/C composite finger seal not only has a smaller leakage,but also has excellent wear resistance compared with the cobalt-based alloy,according to the leakage rate before and after the endurance test and the wear morphology of the finger foot.There is no wear mark on the friction surface of the rotor after 60 hours of durability test,which is in good agreement with the pin-disk friction test.The results show that the C/C composite finger seal has excellent comprehensive performance,which provides an important reference for its friction pairs,structural design and engineering application.