Papers by Author: Ye Chen

Abstract: A new kind of sealing composite material reinforced mainly with carbon and glass hybrid fibers was developed with calendar preparation method. In consideration of the difference of surface behavior, carbon fiber and glass fiber were pretreated by various surface treatment methods, and the effect of these methods on the material properties and interface bonding between fibers and matrix was studied through the transverse tensile test and SEM analysis. The optimum prescription of the sealing composite material was obtained by regression design method, adopting stress relaxation at 300°C as evaluating indicator. The performances of the developed sealing composite material were tested, and the results indicated that the main performances of the material coincided with the requirements prescribed in Chinese national standard and some performances were even better than that of the products of some famous corporations.

Abstract: Centrifugal pump is a kind of important industrial installation for fluid delivery. The research on the unsteady flow in centrifugal pump is very meaningful to reducing vibration. Particle image velocimetry (PIV) system and test pump designed for PIV measurement were introduced. The experimental scheme and the methods of numerical simulation were discussed. PIV technique was used to measure the unsteady velocity field near the volute tongue under the mode of external synchronization. The unsteady pressure field was simulated by using Sliding Mesh (SM) model provided by Fluent. The results show that the velocity and pressure fluctuate periodically with the rotation of impeller. Partial fluid flows back to the impeller passage and the velocity in the inlet of diffusion tube decreases significantly due to shunt effect of the volute tongue. On the section VIII, the magnitude and fluctuation range of velocity show a decreasing trend in radial direction. The fluctuation of circumferential velocity is related to the position of high-speed flow in impeller passage, and the fluctuation of radial velocity is influenced by blade interference and Coriolis force. The static pressure increases and the dynamic pressure decreases in the radial direction of volute. The velocity and the pressure on the section VIII and the outlet total pressure fluctuate intensively when the blade tail end passes the section VIII and the volute tongue. The vibration of pump can be reduced by increasing the volute tongue mounting angle and decreasing the blade outlet mounting angle properly.

Abstract: The temperature-dependent tensile strength is an important indicator used to evaluate combination property of short-fiber-reinforced elastomer matrix composite. Some short-fiber-reinforced elastomer matrix composites are manufactured in the molding preparation process, and the tensile tests of fiber, matrix and the composites are carried out at different temperatures. The fiber length and orientation distributions are statistically analyzed. The influence of temperature on the micromechanical stress distribution and transfer in the composite is investigated, and the thermal stresses in the fiber, matrix and fiber-matrix interface are obtained. Based on the theory of micromechanical stress distribution and transfer of the fibrous composite, the mixture law is modified, and a model for predicting the temperature-dependent tensile strength of this kind of composite is developed. Moreover, the mechanism of the tensile fracture of the composite at various temperatures is discussed. Research indicates that the tensile strength is largely related to the temperature, mechanical performances of the main components of the composite and some microstructural parameters, such as short fiber aspect ratio, volume fraction and orientation distribution. The tensile strength of SFRE decreases with increasing temperature. The tensile strength increases with the increase of fiber length when the fiber length is no larger than critical fiber length. There exists a critical fiber volume fraction where the tensile strength of SFRE reaches the maximum. The tensile fracture of the composite depends largely on the temperature, the bond strength of fiber-matrix interface and the average length of reinforcing short fibers. The temperature-dependent tensile strengths predicted by the presented model are in good agreement with experimental data.

Abstract: Three kinds of coating materials, namely Cr2O3 ceramic, Al2O3-TiO2 ceramic and WC-Co cermet, were screened and sprayed on the surface of valve ball by plasma spraying technology, and two kinds of brush plating materials, namely high speed nickel and nickel tungsten, were also screened and brush plated on the surface of valve seat by electrical brush technology. The microstructure and morphology of the plasma sprayed coatings were analyzed by means of scanning electron microscopy. The tribological properties of the plasma sprayed coatings sliding against the high speed nickel and nickel tungsten layers were investigated on a pin-on-disc friction and wear tester. The microhardness, thermal shock property and bonding strength of the coatings were also tested. The results indicate that the sealing pair composed of the valve ball with the plasma sprayed coating of Al2O3-TiO2 and the valve seat with the brush plating layer of nickel tungsten has the best combination property.

Abstract: The nonlinear finite element method (FEM) was applied to the analysis of the strain distribution in
-shaped seal rings acted by internal pressure or the combined action of internal pressure and axial displacement. The results indicate that the maximum Mises equivalent strain exists at the juncture between the exterior surface of the loop and that of the knuckle when the ring is acted by axial compression displacement and relatively large internal pressure, which is in agreement with the practical work conditions of the rings. According to the plastic limit analysis method, the limit internal pressure should be determined based on the strained condition of the juncture between the exterior surface of the loop and that of the knuckle of the ring by using twifold elastic slope criterion. The formulae for calculating the limit internal pressure of the rings were also derived by regression analysis of the FEM results. These formulae can be used in the limit design and the safety assessment of
-shaped rings.

Abstract: A new kind of sealing composite material reinforced mainly with aramid and pre-oxidized fibers were developed by molding preparation method. The effect of different surface treatment methods of the fibers on the heat resistance of the composite material was studied. The optimum prescription of the sealing composite material was obtained by regression design method. The relationship between the transverse tensile strength of the material after ageing at elevated temperatures and its main ingredients was investigated. The performances of the developed sealing composite material were tested, and the results indicate that the main performances of the material coincide with the requirements prescribed in Chinese national standard and some performances are even better than that of the products of some famous corporations.