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The tribological property of carbon graphite material filled with different content was studied. Effect of loading, sliding speed, mass fraction of graphite and mass fraction of carbon fiber (CF) on the wear resistance of the composites was investigated. The results show that CF could significantly improve the wear resistance of carbon graphite material composites, especially in high loading. The experimental results show that wear could be reached at the optimum conditions: sliding speed 2.84 m/s, mass fraction of CF 29.6%, mass fraction of graphite 26.7% and loading 200 N. [ABSTRACT FROM AUTHOR]

The thermo-hydrodynamic effect of the non-contact mechanical seal includes the liquid film flow characteristics and heat transfer characteristics of the seal face. It is of great practical significance to study the effects of friction and thermal deformation on the liquid film flow characteristics and heat transfer characteristics of the mechanical seal. This paper obtains the governing equation of the liquid film flow characteristics of the mechanical seal based on the momentum conservation and mass conservation equations, and then studies the thermohydrodynamic effect mechanism of the mechanical seal face through the coupling analysis of the interactions between the mechanical seal ring and the liquid film. The research results show that the mechanical seal face is deformed under the action of friction and mechanical force, and the liquid film flow characteristics of the end face changes. The liquid film pressure of the parallel flow channel increases linearly along the axial direction, and the liquid film pressure of the non-parallel flow channel exhibits a non-linear increase in a "convex" or "concave" direction; the leakage rate of the parallel flow channel is the smallest, followed by that of the convergent flow channel and then that of the divergent one. The liquid film bearing capacity of the convergent channel is the largest and that of the divergent one is the smallest. Overall, the performance of the parallel flow channel is the most stable. When the mechanical seal face is only subjected to the friction of the liquid film, the larger the angular frequency, the smaller the thickness of the liquid film, and the more heat generated by the friction. The heat transfer coefficient of the rotating ring is much greater than that of the stationary ring, so the heat absorption of the former is also significantly higher than that of the latter. The research results can provide theoretical reference for the study of the non-contact mechanical seal mechanism and the practical application of the thermo-hydrodynamic effect. [ABSTRACT FROM AUTHOR]

A hydraulically controllable mechanical seal for a nuclear reactor coolant pump (RCP) is under development. Its purpose is to correct excessive or insufficient leakage through RCP seals, a current expensive problem. The non-rotating seal face contains an annular cavity, filled with pressurized fluid. By changing the pressure within the cavity, the deformation and geometry of the face can be changed. Since the face geometry determines the thickness of the lubricating film between the two seal faces and the leakage rate, the leakage rate can be controlled. Simulations indicate that the hydraulically controllable seal provides sufficient control to address many abnormal leakage rate scenarios. [ABSTRACT FROM AUTHOR]

Considering the effect of viscosity - temperature relationship and cavitation of micro-scale film,the influencing factors on hydrodynamic lubrication performance of upstream pumping mechanical seal were investigated based on the theory of hydrodynamic lubrication. N - S equation, energy equation ,viscosity - temperature equation and vapor transport equation were solved with the finite volume method by using Fluent software , which was performed to analyze the influence of the viscosity - temperature and cavitation effect on hydrodynamic lubrication failure of the film. The research demonstrates that it will lead to the significant difference of the temperature field by considering the coupling of temperature and viscosity. When the film thickness decreases and the rotating speed rises , cavitation regions and viscous friction heat increases , the opening force of the film is also enhanced. However , the growth rate is restricted to the cavitation regions and viscous friction heat , and the opening force begins to decline to a certain extent , and thereby being insufficient to open the surfaces of the seals and leading to the failure of automatic adjustment function and severe wear , lubrication failure occurrs. Through comprehensive research on the influences of viscosity - temperature and cavitation effect on hydrodynamic lubrication performance , the theories of failure and design of upstream pumping mecha- nical seal are further developed. [ABSTRACT FROM AUTHOR]

Surface texturing the friction faces of a mechanical seal reduces friction as well as leakage and wear, where dimples machined on the surface enhance the formation of a full lubricating film in the seal interface. Numerical simulation is used to determine the optimal surface texturing for the investigated operating conditions of the seal. The geometry of the dimples introduced in the model assume a perfect shape, but machining causes the dimple shapes to be imperfect in terms of the roughness in the dimples, absence of sharp angles, deformed boundaries, and so on. The effect of the real geometry must be considered to confirm that surface texturing will provide the desired results. In the present work, surface texturing is performed using low-temperature plasma coupled with a thermo-chemical surface treatment on stainless steel sealing rings. The real dimple shapes are analysed and considered within the hydrodynamic lubrication model. The influence of different types of defects is studied. It is shown that there is a limit above which surface imperfections dispel the texture's positive effects. Controlling the dimple shapes is important when performing surface texturing. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a novel approach through the Meshfree weak-strong method based on radial basis function, to calculate the distribution of dimensionless pressure of T-groove dry gas seal (T-DGS). In order to avoid a singularity and improve the accuracy of results, linear polynomials were added into the radial basis interpolation and described gas film stress of T-DGS in the form of explicit function characterization. The opening force, gas film stiffness and leakage rate were obtained by the Matlab calculation program. Compared with the related literature, the error was less than 5%, indicating the feasibility of the simulation. The systematic simulation was used to analyze the multi-parameters for T-DGS under different working conditions. The results revealed the influence mechanism of the pressure, rotational speed, groove depth, film thickness and groove number on the sealing performance. By means of the 3D distribution diagrams of the sealing dynamic and static pressure, we found that dry gas seal could well adapt to high speed condition and the formation mechanism of dry gas seal opening force. [ABSTRACT FROM AUTHOR]

Considering the tilt of the seal ring, the transient vibration response analysis model of the non-contact mechanical seal is presented. The model is consisted of the transient Reynolds equation, the equation of motion and the equation for solving the high order nonlinear dynamic coefficients of seal. The relative error of the high order nonlinear film force to the linear film force is also obtained. With Euler method, the characteristic parameters of the transient vibration response are obtained, which include the axial vibration displacements and the angle-swing of the static ring. The 14 nonlinear force and 14 nonlinear overturning moment dynamic coefficients for the non-contact mechanical seal are calculated. The results show that the influence of the damping effects of the sealed fluid between the seal gap on the axial vibration displacements and the angle-swing is linear. The film thickness distribution changes with the axial vibration of seal, which will lead to static ring swing, and the swing also can cause the axial vibration of the seal. With the increase of the nonlinear order, the relative error of the nonlinear film force decreases. All of the nonlinear film forces, the non-linear stiffness coefficient and damping coefficient decrease with the seal film thickness increases. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The change in surface topography caused by friction and wear influences the wear properties and service life of mechanical seal. To investigate the wear properties of mechanical seals and obtain the variation in surface topography, it is practical to carry out accelerating experiments by increasing the load, speed, or temperature of the medium than safe life tests in the field device. Based on the assumption that the same fractal roughness corresponds to the same wear properties, the pi theorem was introduced to derive the relationship of wear under experimental and actual conditions. By providing detailed values of constants in the pi theorem through accelerating experiments, a fractal model was established to predict the life expectancy of mechanical seals. Under the state of mixed friction, measured values of surface topography for experimental stationary rings and data on a mechanical seal ring's service life in the field device were in accordance with those of the model. The establishment of the fractal model provides conditions for the performance study of long-period operating mechanical seals. [ABSTRACT FROM PUBLISHER]

A new pump-out hydrodynamic mechanical seal with self-pumping effect is presented based on centrifugal pump's working principle. Results of parametric study show that both of the opening force and leakage rate increase with increasing medium pressure, channel diameter, spiral angle and width ratio of groove to ridge; The opening force increases with decreasing groove number and length ratio of groove to dam while the leakage rate decreases slightly; There exits an optimum groove depth that obtains higher opening force along with lower leakage rate. Moreover, the new mechanical seal can be used in conditions with larger pressure difference. [ABSTRACT FROM AUTHOR]

TThe friction characteristics of a mechanical seal for rotary blood pumps were investigated to evaluate the volume percentage of blood in the sealing face. These mechanical seals separate blood and cooling water, so the fluid film in the sealing face is composed of two different solutions. Therefore, the volume percentage of each solution is not known. In the experiments, various viscosities of an ethylene glycol solution were used as a substitution for blood, and the friction characteristics were compared for different Ra values for the seat rings: 0.009 and 0.088 μm. These friction characteristics were investigated based on the two different assumptions: a completely mixed state and a completely separated state. As a result, the volume percentage of the sealed fluid in the completely mixed state was larger than that in the completely separated state. In fact, it was considered reasonable that the practical state in the sealing face was between two states. For example, the volume percentage of the sealed fluid showed 65-73% at a viscosity of the sealed fluid of 3.53 mPa·s and at a rotational speed of 3000 min-1. Additionally, it was found that smaller volume percentage of the sealed fluid was evaluated for 0.088 μmRa than for 0.009 μmRa.

Liquid hydrogen (LH2) is excellent in extensive storage and transportation systems, such as being used as fuel in highly efficient liquid-rocket engines. To consider the use of LH2 required for future hydrogen-energy systems, this paper presents a topical review of previous cryogenic tribology studies on the research and development of the bearings and shaft seals for LH2 turbopumps. Cryogenic tribology studies were conducted for the LE-5/LE-7 rocket engines of the Japanese H-2 rocket as well as for an advanced ultra-high-speed LH2 turbopump. The tribo-chemical formation of CaF2/FeF2 film due to the reduction power of LH2 showed excellent self-lubrication, resulting in a sound wear condition within the turbopump bearing. A new hybrid ceramic bearing with Si3N4 balls, which bearing had a single-guided retainer, tested excellently at an ultra-high speed of 120,000 rpm (3 million DN) in LH2. Seal performance for the floating-ring seals using Ag-plated metal seal-rings at ultra-high speeds was also tested.

It is considered that cavitation plays an important role in maintaining the sealing performance of mechanical seals. However, there are not any studies that demonstrated how to control cavitation regions and take advantage of them to improve the sealing performance of mechanical seals. In this study, we have tried to demonstrate that the cavitation rings could be formed and maintained by taking advantage of the laser-textured surface. Furthermore, the effects of the cavitation rings on the frictional characteristics were also investigated. As a result, it was found that the sharp edge of the laser-textured surface could act as the geometric barrier to prevent the gas-liquid interface migration. Eventually, the gas-liquid interface maintained the steady fluid flow along the rows of dimples as the cavitation rings. Furthermore, it was also found that the friction coefficient of the textured surface fluctuated less than that of the plain surface.

Friction and wear tests were conducted for two kinds of material combinations: a DLC-coated and sintered-graphite-carbon material combination, and a non-coated and sintered-graphite-carbon material combination, for comparison. DLC showed a higher friction coefficient than non-DLC materials. Carbon transfer films were only observed at certain places on the DLC surfaces, while most non-DLC surfaces were coated with those films. However, for DLC specimens, the high friction was found to be attributable to the transfer-film area but not non-transfer-film area (i.e. DLC itself). The sintered-graphite-carbon specimens having slid on DLC had little oriented surface layers due to anti-adhesion and amorphous properties of DLC while those having slid on non-DLC were strongly oriented to the sliding direction. Thus, the surface orientation was necessary for sintered carbon graphite to indicate low friction when sliding on its transfer film, and the high friction of DLC was due to the sliding between the little oriented sintered graphite carbon and the transfer film.

The dynamic stability of the non-contacting mechanical seal (NMS) under variable working conditions is a vital factor for the reliable operation of rotating equipment. This paper presents a transient dynamic model to investigate the parametric response of liquid oxygen lubricated NMS under inlet pressure disturbance, which comprehensively considers asperity contact, micro-clearance lubrication and dynamic motion of a flexible mounted ring. Meanwhile, various forms of rub-impact phenomenon and dynamic instability caused by excitation overload are also analyzed. Lastly, an experimental research is proposed with diverse sensors to monitor the parameter data under pressure disturbance. In addition, the characteristics of acoustic emission signals when rub-impact of friction pair occurs are further investigated and processed, including various impact forms and location method. • A transient dynamic model considering rub-impact of liquid film seal is proposed. • Three types of rub-impact and instability caused by excitation overload are analyzed. • Overall response consists of mutation, transition and periodic fluctuation stage. • Different acoustic emission (AE) signals correspond to various rub-impact forms. • The rub-impact frequency obtained by AE sensor is equal to the rotating frequency. [ABSTRACT FROM AUTHOR]

Non-contacting face seals are applied in highly efficient devices in which safety and reliability are required the most. Meeting the requirements is possible due to some detailed research and analyses of physical processes related to the flow of the medium (fluid) through the radial gap, to the heat transfer in the sealing knot or to the thermoelastic strains which are undergone by the wear rings. Establishing and developing mathematical models which describe the above mentioned phenomena allow more and more detailed results of analyses to be achieved. This paper presents the results of the comparative studies for two different mathematical models that describe the same phenomenon, i.e. heat transfer in non-contacting face seals (type: face to face). The results of the research allow to determine which solution provides some more detailed glimpse of the described physical phenomenon and might be applicable to non-contacting face seals.

Ti-8.4 vol% M-47.4 vol% TiC (M: Cr, Mo, W) alloys were prepared through P/M technology and their microstructures and mechanical properties were investigated. It was noted that TiC grain size of W alloy was much smaller than that of both Cr alloy and Mo alloy. Smaller diffusion coefficient of M in β-Ti phase and smaller absolute value of Helmholtz standard free energy of formation of MC were thought to suppress TiC grain growth. It was found that hardness and transverse-rupture strength of W alloy were much higher than those of both Cr alloy and Mo alloy. The occurrence of numerous shallow cracks on the rubbing surface of cemented carbide was studied by using an apparatus simulated mechanical seal. If the Vickers indentation tests were conducted on the rubbing surface where the crack spacing was large, indentation cracks with almost the same length as the neighboring pre-cracks could be formed by the tensile residual surface stress. Thermal and elastic-plastic analyses shows that thermo-cracking mechanism cannot explain why cracks run perpendicular to the direction of sliding and that the dynamical action of a high contact stress together with a high tangential force plays a very important role in the occurrence of cracks. [ABSTRACT FROM AUTHOR]

The paper presents a mathematical model of a heat transfer process for non-contacting face seals. For a slewing ring (rotor), a time fractional Fourier law obtained from fractional calculus was applied. Heat exchange in the stator was described using Laplace’s equation. Heat flux generated in the medium layer separating the rings is discharged first to a working ring and the to a surrounding medium. Distribution of temperature fields in sealing rings was determined with the use of analytical methods, using integral transformation method. The fractional heat conduction equation (for the rotor) was considered in the light of the case 0 < α ⩽ 2 with the special attention paid to α = 1 for the classical heat conduction equation. The proposed way of solving is very broad and involves many theoretical and practical problems, which were taken into account and described in the work. Finally, numerical results are presented graphically for various values of both operational and geometric parameters and order of fractional derivative. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High-performance engineering polymers are potential candidate materials for mechanical seals, especially in corrosive environments and environments where substantial shock and vibration loads are present. This study addresses the friction and wear performances of polyamide-imide (PAI) sliding against tungsten carbide (WC) in seawater for seal applications. The experimental setup consists of two nominally flat rings rotating against each other to simulate the contact in mechanical seals. Three types of experiments were performed, i.e., measurement of friction and wear in a series of 8-h tests, measurement of the friction coefficient as a function of speed and load and measurement of PV (pressure times velocity) limit. Test results show that at lightly loaded conditions WC/PAI seal rings in seawater can reach hydrodynamic lubrication with ultra-low friction coefficient and wear rate. [ABSTRACT FROM AUTHOR]

The end face deformation of the flexible ring of mechanical seals influenced by the O-ring was analyzed in numerical simulation method based on ANSYS platform. The combined contact model of isolated bodies for the flexible ring and the O-ring was established by transforming nonlinear constraint between them into interface force. The results indicated that the end-face deformation of the flexible ring was directly influenced by the fractional compression of the O-ring and the radial taper of the sealing face increased with increasing fractional compression. The excessive fractional compression had unfavorable effect on sealing performance of mechanical seals in view of face deformation. The elasticity modulus of the material of the flexible ring had a great effect on its deformation. [ABSTRACT FROM AUTHOR]

This work presents an experimental study on the lubrication characteristics of the magnetofluid film in a spiral groove mechanical seal to reveal how the magnetic field affects the hydrodynamic effect of magnetofluid. The experiments are carried out based on the non-contact mechanical seal experimental rig and the influences of the magnetic field intensity and the rotational speed on the film thickness, friction torque, characteristic temperature and magnetofluid depletion are investigated experimentally. By numerically analyzing the film pressure distribution, it is revealed that the hydrodynamic pressure increases with the increasing magnetic field intensity. Using an appropriate closing force, it is feasible to control the seal capacity of the seal by regulating the current intensity in the magnetic field generator. [ABSTRACT FROM AUTHOR]

Lubrication reduces the friction between the interfaces of sliding surfaces in the mechanical seals that operate for extended period of time. Due to environmental issues caused by mineral oil-based lubricants, the use of organic based vegetable oils had increased worldwide due to the nontoxic and biodegradable characteristics. In this work an experimental study was carried out by employing a seal pair of tungsten carbide and resin impregnated carbon mechanical seals, its frictional behaviour was studied under the eco-friendly lubricant from the class of vegetable oils — soybean oil and canola oil with an eco-friendly solid lubricant i.e. boric acid powder. An experimental setup was designed and fabricated to study the frictional characteristics of the seal for varying normal load and constant speed. The friction characteristics was studied under unlubricated conditions, independent paraffin oil, soybean oil, canola oil lubricating modes and finally 1 wt.%, 3 wt.% and 5 wt.% of boric acid powder mixed individually with soybean and canola oil. After all running-in test of all lubricating conditions, 5 wt.% of boric acid powder mixed with soybean oil had contributed a hybrid tribofilm and resulted in the lowest friction coefficient value in the range of 0.06–0.07. [ABSTRACT FROM AUTHOR]