Content uploaded by I. Etsion
Author content
All content in this area was uploaded by I. Etsion on Aug 11, 2015
Content may be subject to copyright.
Analytical and Experimental Investigation of Laser-Textured Mechanical Seal Faces
Abstract
An analytical model is developed to predict the relation between the opening force and operating conditions in a mechanical seal with laser textured microsurface structure in the form of micropores. The model is valid for any desired shape of the micropores. An optimization is performed for spherical shape micropores evenly distributed on one of the mating rings face to maximize the opening force and fluid film stiffness. Results of a parametric study are presented showing the effect of the main design parameters on the seal performance. Some results of an experimental investigation with water-lubricated seal rings are also shown and compared with the theoretical model. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Toronto, Ontario, Canada, October 26–28, 1998
... In modern tribology, theoretical and experimental research shows that friction and wear on a surface can be reduced by using textured features [12,13]. In the late 1990s, Etsion et al. [14] introduced a micro pit on the mechanical seal surface and observed a reduction in friction and wear with the presence of textures and an extended service life compared to an untextured surface. Costa and Hutchings [15] investigated line grooves, circular dimples, and chevron texture in the hydrodynamic lubrication film and achieved the maximum film thickness and better tribological properties for chevron texture. ...
The herringbone texture exhibited excellent tribological performance to minimize friction and wear. However, the application of this texture in the development of grooved thrust bearings is limited. Therefore, in this study, an attempt was made to design an oil-lubricated herringbone grooved thrust bearing for high-speed locomotive turbochargers. The designed bearing accommodates the axial load generated due to the pressure difference between the turbine and compressor wheel. The bearing design starts with applying Newton’s second law to predict the thrust load acting on the locomotive turbocharger rotor. The thrust load is calculated analytically and is found to be 4.54 kN for a design rotor speed of 1,00,000 rpm. Further, the herringbone grooved thrust bearing has been modeled numerically using non-linear Reynolds equation. The modified Reynolds equation is discretized using the finite volume method (FVM) and solved by successive over-relaxation (SOR) methodology to determine the static characteristics over the bearing surface. The developed HGTB is found to have a suitable load-carrying capacity of 4.6 kN, frictional torque of 0.25 N.m, and power loss of 2.98 kW. Further, a parametric analysis has been carried out to study the influence of design parameters such as the number of grooves, helix angle, angular groove width, groove depth, and speed on load-carrying capacity, frictional torque, and power loss.
In order to improve the opening and stability of the Compliant Foil Face Gas Seal (CFFGS) under high-speed conditions, this paper proposes a new CFFGS structure with super-elliptical hole textures on the foil end face. It also establishes its theoretical model of aeroelastic coupling lubrication and solves the above model using the finite difference method, and an original binary representation method for the position of the hole texture arrangement scheme is proposed. Systematically investigated, the influence law of the hole texture arrangement scheme on the steady-state performance of the seal is identified, and its mechanism of influence is made clear. The optimized design of the structural parameters of the texture structure and the foil end face is further carried out under the optimal arrangement scheme of the hole texture with the maximum opening force and gas film stiffness as the target. The outcomes demonstrate that when the texture is set in the seal and face’s slope section, the seal’s opening and stability are obviously improved. Furthermore, within the scope of parameter research, when the super-elliptical coefficients n1 and n2 are 4, the transverse semi-axis a of super-elliptical texture is 2.5 mm, the longitudinal semi-axis b of super-elliptical texture is 4 mm, the wedge height δh is 14–20 μm, and the compliance coefficient α is 0.02–0.03, the CFFGS with super-elliptical hole texture has better all-around sealing performance.
Surface texture technology is a method to improve the tribological properties of friction pairs. In this study, a cylindrical texture is designed in cage pocket, and then the volume of fluid model and the multi-reference frame method are used to investigate the oil volume fraction inside the bearing cavity, the pressure and oil distribution on the ball surface, and the oil distribution on the inner/outer raceway. The results show that the cylindrical texture in cage pocket is helpful to increase the oil volume fraction inside the bearing cavity, improve the pressure distribution on the ball surface, and increase the oil content on the ball surface. The cage pocket texture helps the ball to carry more lubrication oil in the high-speed rotation process, which increases the oil content of the outer raceway and improves the oil-air lubrication effect of the ball. This study proposes a new texture arrangement in cage pocket of angular contact ball bearings, and introduces the mixed mesh method to divide the fluid domain of bearing. Through comparative study, the cage pocket texture is helpful to improve the oil-air lubrication efficiency.
Friction control is the most fundamental and important issue in the field of tribology. In recent years, friction control technology, which aims to reduce the energy loss in mechanical systems to address global environmental issues, has received significant attention. Friction control involves minimizing the friction coefficients and maintaining high frictional forces, such as in power transmissions and brakes. Surface texturing plays a crucial role in controlling the friction of tribological elements. In the future, technologies for active friction control at the interface between living organisms and artifacts will be indispensable for realizing a collaborative society with the coexistence of humans and robots. This article reviews the role and key findings of surface texturing and outlines its potential and future trends.
Hydro-viscous drive (HVD) plays a significant role in smoothly transferring torque and flexibly regulating the velocity of the disks. By hydro-viscous drive, we mean that the viscous shear stress of the thin oil film between a multi-layer assembly of rotating parallel disks is generated to transmit torque and power. The laminar-to-turbulent transition is an extremely complicated issue due to the combined effects of squeeze and shear on the oil film within the microscale friction pair system. Hence, a comprehensive and thorough analysis of flow instability in fluid-thermal-solid interaction of tribodynamic behavior is highly desirable. Following a brief introduction of fundamentals of HVD, this paper provides an overall review on the instability mechanisms for three types of canonical flow dynamic models, i.e., plane squeeze flow, plane shear flow, and rotating-disk flow. The effects of various aspects of wall conditions and working media, such as surface microstructure, and temperature-dependent viscosity, on flow instability are then summarized, which can serve as a reference and guidance for optimizing the design of friction pair systems. Based on the review of the former progress, this paper not only explores the in-depth mechanisms regarding the laminar-to-turbulent transition in microchannel flow, but also provides the possibility of bridging the gap between flow instability and tribodynamic behavior.
In the process of machine and mechanical operation, it is inevitable to face problems such as friction and wear. At present, there are many solutions to solve the problems. As a very effective method, surface texturing has been applied in many projects. In recent years, surface texturing has made great achievements in the study of friction pair surface, which is of great significance to improve the tribological properties of friction pair surface. In this paper, the author reviews the main research results of surface texturing in controlling friction in recent years and points out the research purpose and development status of surface texture. The preparation of texturing is summarized and analyzed from two aspects: shape and size control accuracy and surface quality. The research on the anti-friction mechanism of texture is reviewed, and the three states of dry friction, fluid lubrication, and boundary lubrication are analyzed, respectively. The optimization of morphology and parameters was discussed, and the optimal parameter range was obtained. Finally, the above aspects of the full text are summarized, and the problems faced by all aspects are put forward. Combined with the actual situation of the current research, the future development prospect of surface texture technology is prospected.
Description
41 papers provide a comprehensive overview of the problems and new technologies in hydraulic systems associated with hydraulic fluids and their interaction with component design, component metallurgy, and the design of the hydraulic system itself.
Six sections cover: Theory, Mechanism and Simulation • Failure Analysis • Materials • Components--Seals, Valves and Rolling Element Bearings • Fluids
Major issues addressed include:
• The effect of fluid chemistry on component failure as the result of oxidation, wear debris, viscosity loss, generation of corrosion by-products, and yellow metal wear.
• Metallurgy of the material, including material pair effects and physical properties.
• The effect of surface finish.
• Modeling wear mechanisms as a function of material pair contact loading, speed, and other factors.
• Dynamic versus static wear.
• Wear mechanisms including rolling contact fatigue, cavitation, lubrication failure, abrasive wear, and others, in addition to combinations of these mechanisms.
• Methods of failure analysis focusing on strategies to identify root caused of failure.
• Hydraulic component design and metallurgy of bearings, gears, slippers, and end-plates.
A partially porous mechanical face seal is analyzed. The Reynolds equation is solved analytically and the pressure distribution, leakage, and dynamic coefficients are presented in closed form analytical expressions. It is shown that a partially porous seal has an axial stiffness even in cases of flat parallel faces when solid face seals have no such stiffness at all. A comparison is made between optimally designed partially porous and coned face seals. It is shown that the former give substantial improvement. Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in New Orleans, Louisiana, October 24-27, 1993
A mathematical model is developed to allow performance prediction of all-liquid noncontacting mechanical seals with regular microsurface structure in the form of hemispherical pores. Seal performance such as the equilibrium face separation, friction torque and leakage across the seal are calculated and presented for a range of sealed pressure, pore size and pore ratio of ring surface area. An optimum pore size is found that depends on the other variables and corresponds to maximum axial stiffness and minimum friction torque. Also, a critical pore size is found above which seal failure is possible.
Observations of load support from various shapes of microasperities placed on the surface of a rotary-shaft face seal indicate that all are comparable in this respect and generally follow the theory developed previously for cylindrical asperities. Both positive (protrusions) and negative (valleys) asperities produce similar load support, developing stable hydrodynamic lubricant films of the order of 10−5 in. for linear velocity of at least 50 in./sec, lubricant viscosity as low as 1 cp, and loads of the order of 100 pounds or higher. Variations in the film thickness with these parameters is predicted by the theory developed on the basis that an effective small tilt exists on the tops of the asperities. Leakage from microasperity-lubricated seals on the average follows the predictions of Poiseuille flow, with the exception that a significant effect of rotor rotation is observed. For a leakage channel height of 10−4 in., leakage was typically of the order of 0.2 in.3 /hr for a pressure drop of 10 psi across the seal.
The purpose of this paper is to present a computational algorithm capable of automatically handling cavitated regions in liquid-lubricated bearings. The emphasis is on the ease with which numerical solutions of the appropriate equations can be handled. The objective is to show how to reduce the programming complexity for treatment of cavitation to the point where designers will deem the effort worthwhile.
The location of both rupture and reformation boundaries in liquid film bearings is important in determining overall performance characteristics. Finite difference approximations have been most widely used in the numerical analysis of hydrodynamic bearings, and the problem of determining cavitation interfaces may be trivial or extremely complex depending upon the physical model adopted. For some situations finite element analysis may offer an advantage and this possibility is investigated.
The production of mechanical seal rings made of silicon infiltrated silicon carbide (SiSiC) is described with emphasis on the effect of different topographies on their performance. In particular, attention is given to optimization of the design of the seals for achieving the elastohydrodynamic effect between the sealing faces, and optimization of the microstructure of the sealing face material with regard to starting and stopping behavior, elastohydrodynamic service, loss of static torsional moment, and running friction behavior. The design is optimized by development of a new forming process, and the material behavior is adjusted to operational demands through the use of finite element analysis and sophisticated test technology.