Papers by Author: Bo Qin Gu

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Authors: Jian Feng Zhou, Bo Qin Gu
Abstract: The thermo-hydrodynamic effect in the spiral groove mechanical seal was investigated. The coupling analysis of the fluid film and the thermal deformation of sealing rings was carried out, the separation angle obtained, and the shape of the gap between the two deformed end faces determined. The results indicate that the increase of the temperature of the fluid film and the thermal deformation of the sealing rings cause the increase of the leakage rate. There exists a critical rotating speed, when the rotating speed is lower than the critical speed, the bearing force increases with the increase of the rotating speed, and once the rotating speed is higher than the critical speed, the bearing force decreases reversely. The thermal deformation weakens the hydrodynamic effect of the spiral groove mechanical seals.
2455
Authors: Jin Shan Dong, Bo Qin Gu
Abstract: The heat transfer in solid-fluid coupling system relates to not only the heat transfer process in solid and fluid bodies but also the physical quantity exchange through the boundary. Because some boundary conditions, such as heat flux and coefficient of heat transfer, are uncertain, neither solid body nor fluid body can be separated from the coupling system when the thermal coupling analysis is carried out. A coupling analysis method based on numerical simulation codes ABAQUS and FLUENT was put forward to solve the boundary problem. The two simulation codes were controlled by the interface software which was developed to exchange the boundary conditions between solid and fluid models at each iteration step. A copper finned radiator model and its corresponding air model were built by ABAQUS and FLUENT respectively, and the heat elimination process of the radiator under forced convection conditions was investigated. The heat elimination characteristic of an aluminium radiator was also researched. By comparing with the copper radiator, it can be found that the larger the coefficient of heat conductivity is, the higher the heat elimination efficiency is.
635
Authors: Ye Chen, Bo Qin Gu
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.
2691
Authors: Bo Qin Gu, Ye Chen
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.
1243
Authors: Ye Chen, Bo Qin Gu
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.
651
Authors: Lin Liu, Bo Qin Gu, Ye Chen
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.
11
Authors: Yao Feng Zhang, Bo Qin Gu, Yi Ding
Abstract: Three kinds of coating materials, namely Al2O3, Al2O3(87%)-TiO2(13%), and Cr2O3(92%) -TiO2(3%)-SiO2(5%), were plasma sprayed on specimens of 08Cr2AlMo steel. The corrosion performance of the specimens was determined by potentiodynamic polarization test, slow strain rate tensile (SSRT), and scanning electron microscope (SEM). The test results indicate that the plasma sprayed coatings do not show passivation in saturated H2S solution, but they have higher corrosion resistance than the bare 08Cr2AlMo steel. Furthermore, these coatings reduce SCC susceptibility of the steel in saturated H2S solution. The specimens treated by plasma spray have longer fracture time and larger area reduction. The SCC resistance depends largely on coating porosity, coating type and the bond strength between the coating and the substrate. Among the three coatings, the Cr2O3(92%)-TiO2(3%)- SiO2(5%) coating exhibits the lowest SCC susceptibility.
593
Authors: Jian Jun Sun, Bo Qin Gu
Abstract: While the fact that abrasion leads to change of surface topography is taken into consideration, the influence of spring pressure both on leakage rate and on friction characteristic of contacting mechanical seals are investigated by fractal theory. Several GY-70 type mechanical seals are tested. Both theoretic analysis and test results indicate that the friction will be more serious because lubrication medium between two end faces reduces as spring pressure increases, though the increase of the spring pressure may not be enough to change the face friction state of mechanical seal. There is an optimum spring pressure for mechanical seal operation. Under different operating conditions, identical type mechanical seals may possess different spring pressure. Appropriate selection of spring pressure is key to the mechanical seal operation under the best condition.
2990
Authors: Xiu Feng, Bo Qin Gu
Abstract: In this paper, the fractal characterization of the sealing surface topography of metallic gaskets was studied. The influence of the compressive stress on the fractal parameters was also investigated. It’s found that the sealing surface of metallic gaskets is fractal, and its topography can be characterized by the fractal dimension and the scale coefficient. The leakage model of metallic gaskets was established. The research results indicate that the larger the fractal dimension is, and the less the scale coefficient and the non-contact area are, the better the sealing performance of metallic gaskets is.
2977
Authors: Chun Lei Shao, Bo Qin Gu, Ye Chen
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.
643
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