The complex operating state of aeroengines has an impact on the performance of finger seals. However, little work has been focused on the issue and the dynamic performance of finger seals is also rarely studied. Therefore, a distributed mass equivalent model considering working conditions is proposed in this paper for solving the existing problems. The effects of the fiber bundle density and the preparation direction of the fiber bundle of a C/C composite on the dynamic performance of a finger seal are investigated in rotor tilt based on the proposed model. The difference between the C/C composite finger seal performances under the rotor precession and nutation tilt cases is also investigated. The results show that the fiber bundle density and the preparation direction of the fiber bundle have an influence on the dynamic performance of the finger seal as rotor tilt is considered, and the dynamic performance of the finger seal is different in the two kinds of tilting modes. In addition, a novel method for design of finger seals is presented based on the contact pressure between finger boots and the rotor. Finger seals with good leakage rates and low wear can be acquired in this method

Purpose: The carbon/carbon (C/C) composite finger seal experiment was performed on a high-speed seal tester. The purpose of this paper is to investigate the leakage and wear characteristics of C/C composite finger seal under various operating conditions. Design/methodology/approach: Static, dynamic, endurance and post endurance tests were carried out. For static and performance tests, the pressure differential changed from 0.1 to 0.6 MPa and the rotor speed varied from 1,000 to 9,000 r/min. Two endurance tests were conducted for 4 h, with each mounting two finger seals. The seal leakage was monitored by mass flowmeters, and the wear depth was measured and calculated by using three-dimensional profilometer. Findings: Results showed that the seal leakage increases with pressure differential but decreases with rotor speed. Leakage rate is lower when speed is decelerated than that with the speed stepped up. During a time history, material removal caused by wear has significant influence on leakage data causing higher leakage than the results before endurance test. Particular interest is that the uneven wear characteristic on finger foot bottom was firstly revealed, showing severe wear in foot heel area than that in foot toe. Originality/value: This study could provide experimental guidance for finger seal designers. Additionally, the uneven wear characteristic of finger foot was firstly revealed, which showed the necessity of further theoretical research on finger seal wear.

The application of C/C composites in finger seals can effectively solve the problem of seal wear due to its excellent tribological and mechanical behaviors. However, the designable characteristics of composites, such as the density and orientation of fabric on the friction plane, have a very important influence on the tribological properties and service life of sealing materials. In order to obtain a better material design scheme for the C/C composite on the finger seal, it is necessary to conduct research on the tribological properties and wear mechanism of the C/C composite based on the working conditions of the finger seal. Therefore, a reciprocating tribo-tester was used to conduct the test by abrading the C/C composite disk with a pin made of 1045,080M46. The effects of material density, fabric orientation, and load and sliding velocity on the tribological properties and wear mechanism of the C/C composite were studied. The results show that the friction coefficient and wear rate of the composite with a perpendicular orientation (non-woven cloth perpendicular to the friction plane) were lower than those with a parallel orientation (non-woven cloth parallel to the friction plane). The tribological properties with higher density are better than those of material with a lower density. The friction coefficient of low-density material increases with the load, whereas it decreases gradually with high-density material. The wear rate increases with the load for two-density materials. With the increase in the sliding velocity, the friction coefficient decreases. The wear rate of low-density material decreases significantly, whereas it changes little with high-density material. The influence of the sliding velocity on the friction and wear properties of the C/C composite is greater than that of the load. This study provides a feasible material design idea for effectively alleviating the wear of finger seals.

This paper presents a numerical method for simulating progressive wear of the carbon-fiber-reinforced carbon matrix composite used in rotary gas seals due to high experimental cost. In this study, the carbon-fiber-reinforced carbon matrix composite wear rates are experimentally measured, and a formula for the carbon-fiber-reinforced carbon matrix composite wear rates and material design parameters (orientation angles and densities) and operating parameters (load and velocities) is fitted as an input to the wear simulation. A finite element incremental wear simulation procedure for the pin-on-disk wear problem is presented by calculating the local nodal wear rate and wear direction and by introducing the Arbitrary Lagrangian Eulerian adaptive meshing method. In the procedure, the relation between the anisotropy of carbon-fiber-reinforced carbon matrix composite and the varied orientation angle is considered. Results show that the calculated wear volume agrees well with the experimental data. And then the numerical methodology is utilized to investigate the effects of time, orientation angle and operating conditions on the disk wear. The developed numerical methodology could be applied to other sliding wear problems in engineering machinery.

Due to the high speed and high pressure operating conditions, wear between the finger seal and the rotor is inevitable, and this leads to an increase of leakage clearance and becomes an important factor affecting the seal life. The theory of anisotropic elasticity was employed to describe the mechanical characteristics of the seal material. An improved Archard wear model was proposed to calculate the nodal wear rate, and the local wear direction was also determined. The wear simulation model and procedure were established based on the Arbitrary Lagrangian Eulerian adaptive mesh strategy. The effects of material density, fabric orientation, pressure differential and rotor speed on the wear characteristics of finger seal and the change of leakage clearance caused by wear loss were studied. The results show that the wear first occurs at the heel area of the finger foot bottom and gradually extends to the toe area. C/C (carbon fibre reinforced carbon matrix) composite finger seal with higher material density has smaller leakage clearance and wear depth. With the increase of fabric orientation angle, the wear depth in the heel area of finger foot is smaller, and the circumferential wear area is narrower. The average wear depth of finger seal decreases with the orientation angle. When the orientation angle is 0, the seal leakage clearance is smaller. The increase of pressure differential not only aggravates the seal wear, but also expands the wear area, and also increases the average contact pressure and leakage clearance. Increasing the rotor speed make the wear depth of the heel area of finger foot gradually increase, but the wear area becomes narrower. The average contact pressure decreases and the average leakage clearance increases. This study provides a theoretical method and basis for the prediction and evaluation of the wear life and performance of C/C composite finger seal.