Mechanical Face Seals Research Articles

Heat transfer study of mechanical face seal and fin by analytical method

Heat transfer investigation of the mechanical device such as fin and mechanical face seals is crucial for the development of these elements in different applications. In this study, two analytical approaches (collocation and numerical methods) are used to study the thermal performance of fin and mechanical face seal in various operating conditions. In the mechanical face seal, the influence of significant parameters (thermal conductivity, operating temperature and heat convection coefficient) are investigated. In the fin study, the stretching and shrinking of the fin with different cross section are comprehensively discussed. Our findings reveal that the performance of these elements significantly varies in different operating conditions.

Thermohydrodynamic analysis on herringbone-grooved mechanical face seals with a quasi-3D model

A quasi-3D thermohydrodynamic model was introduced to analyze the seal performance of a herringbone-grooved mechanical face seal. In the model, the heat conduction equations of the seal rings and the energy equation of the lubrication film were solved simultaneously by the streamline upwind/Petrov–Galerkin finite element method. The Reynolds equation and the temperature equations were iteratively solved to obtain the liquid film pressure and the temperature distribution. A parameterized study was conducted to analyze the influence of the herringbone grooves’ geometry on the opening force, leakage rate, friction coefficient, and temperature rise. The results show that the hydrodynamic analysis overestimates the opening force because the viscous heat reduces the dynamic viscosity. The longer and narrower inner spiral groove gives the smaller leakage rate and the longer outer spiral groove with a smaller spiral angle shows the larger opening force.

Thermal analysis of mechanical face seal using analytical approach

In this paper, analytical methods are applied to investigate the influences of significant factors on the temperature distribution of mechanical face seals as key component of the mechanical instruments. In this study, collocation and numerical methods are used to solve the thermal equation of the mechanical face seal in various operating conditions. This work also focuses on the role of material of mechanical seal on temperature distribution to reveal this factor in the performance of the mechanical face seal. The effect of various parameters (thermal conductivity, operating temperature and heat convection coefficient) on the temperature distribution of mechanical face seals has been studied in different boundary temperatures. The results show that thermal radiation has extensively influenced on the temperature distribution of the mechanical seal. It can be found that thermal radiation of the surface seal significantly reduces the temperature and the performance of the seal highly increases. Moreover, the results depict that mechanical face seal with Hastelloy X material performs with high efficiency in high temperature operating conditions.

A leakage channel model for sealing interface of mechanical face seals based on percolation theory

Abstract Leakage channels of contact mechanical face seals have significant influence on sealing performance. The porosity of initial sealing interface is obtained based on the fractal parameters of rotating and stationary rings firstly. The effects of fractal parameters, material properties and face pressure on porosity of sealing interface are revealed, and then the percolation assumption for single grid model of sealing interface is proposed. Finally, a leakage channel model based on the volume porosity of sealing interface is established and investigated accordingly. The proposed research is expected to provide the basis for the explanation of leakage and optimum design of contact mechanical face seals.

Dynamic modeling of an eccentric face seal including coupled rotordynamics, face contact, and inertial maneuver loads

Mechanical face seals are constitutive components of turbomachines, which in turn can be constitutive to other systems (e.g. aircraft). Furthermore, the rotating element of a face seal is inextricably coupled to the turbomachine via a flexible mount, and the stationary seal element is coupled to the rotating seal element via the fluid film existing between the seal faces. Consequentially, understanding interactions between the seal and turbomachine is important for quantifying seal performance and improving its design. With few exceptions, previous works study the face seal dynamics independent from the rotordynamics. In addition, most prior investigations consider only angular and axial seal dynamics and neglect eccentric (i.e. lateral) deflections of the seal element(s). For the first time, this work develops a comprehensive and novel model of a mechanical face seal in the inertial reference frame including coupled rotordynamics and inertial maneuver loads of the overall system. The model is developed for a general seal geometry where both seal elements, stationary and rotating, are flexibly mounted and allowed to undergo angular, axial, and eccentric deflections. In addition, the seal model presented here accounts for transient operation, fluid shear forces, seal face contact, friction, and thermoelastic deformation. Finally, various faults due to manufacturing imperfections, component flaws, and/or installation errors can be accounted for by incorporating static angular misalignment of both seal elements, dynamic angular misalignment of the rotating seal element, eccentric rotating imbalance, and axial offset of the rotating seal element center of mass. Throughout this work, the equations of motion developed are valid for both steady-state and transient operation. This comprehensive model significantly advances the state of the art in mechanical face seal dynamic modeling and represents a pivotal step towards analyzing seal performance regarding a broad diversity of realistic problems.

Steady-State Response of a Flexibly Mounted Stator Mechanical Face Seal Subject to Dynamic Forcing of a Flexible Rotor

Mechanical face seals are constitutive components of much larger turbomachines and require consideration of the system dynamics for successful design. The dynamic interplay between the seal and rotor is intensified by recent trends toward reduced clearances, higher speeds, and more flexible rotors. Here, the “rotor” consists of the flexible shaft and the rotating seal seat. The objective here is to, for the first time, determine how the rotor affects the seal performance and vice versa. Thresholds can then be established beyond which the rotor influences the seal but not vice versa (i.e., the rotordynamics can be sent to the seal analysis as an exogenous input). To this end, a model of a flexibly mounted stator face seal is provided including the coupled dynamics of the flexible rotor. The model accounts for axial and angular deflections of the rotor and seal. Coupled rotordynamics are modeled using a lumped-parameter approach including static and dynamic rotor angular misalignments. For expediency, linearized expressions for fluid forces are used, and the resulting steady-state equations of motion are solved analytically to investigate how rotor inertia, speed, and angular misalignment influence the coupled seal dynamics. Importantly, results from the study reveal that in some operating regimes, neglecting the rotordynamics implies healthy seal operation when instead intermittent rub exists between the faces. This work also shows that when the rotor inertia is much larger than the seal inertia, the rotordynamics can be solved separately and used in the seal model as an external input.

Study on the nonlinear transient response for the non-contact mechanical face seal

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.

Probe model of wear degree under sliding wear by Rk parameter set

A probe model of wear degree under a sliding wear is established by using the Rk parameter set referring to ISO 13565-2. Four wear degrees are defined as peak-region, core-region, valley-region and deep scratch periods. The Rk parameter set serves as wear-degree-evaluation indexes. A surface-surface dry sliding experiment of silicon-carbide and carbon-graphite (widely used in mechanical face seals) discs is performed on a rotational tribological tester to demonstrate the new model. The results show that the Rk-parameter-set probe can qualitatively assess wear degree. Furthermore, the possibility of quantitative analysis is also rendered by analyzing the evolution of the relative change of Rvk and the relative wear depth as the test duration increases.

Frictional surface performance enhancement using carbon nano-species derived from carbides

Carbide Derivative Technologies Inc has developed a process that enhances the frictional surface performance of components, using carbon nano-species derived from carbides. Described as ‘not a coating’, it converts the carbon already sintered into the carbide, without adding a dissimilar material that can be prone to delamination. This process, which removes the silicon and promotes the growth of carbon species at the surface, such as nano-crystalline diamond, does not add any dimension, which enables it to be performed on finished components such as mechanical seal faces, bearings, bushings or shafts. Here, we take a look at this technology and how it can be applied.

7톤급 터보펌프 기계평면실의 성능 시험 연구

7톤급 터보펌프 기계평면실의 성능 시험 연구

A new telemetry system for measuring the rotating ring's temperature in a tribological test rig for mechanical face seals

This paper presents the development, installation and application of a new wireless telemetry system for measuring the rotating ring's temperature of mechanical face seals. This new thermometric chain has been integrated in a preexisting tribological test rig, used in laboratory to characterize the dynamic, acoustic and thermal behavior of mechanical face seals.Before use, the new telemetry system has been subjected to calibration, validation as well as mechanical and electrical verification. Furthermore, the measuring uncertainty of the thermometric chain has been evaluated according to the Guide to the expression of uncertainty in measurement.

Impact Phenomena in a Noncontacting Mechanical Face Seal

Noncontacting mechanical face seals are often described as unpredictable machine elements, gaining this moniker from numerous instances of premature and unexpected failure. Machine faults such as misalignment or imbalance exacerbate seal vibration, leading to undesirable and unforeseen contact between the seal faces. A hypothesis explaining the high probability of failure in noncontacting mechanical face seals is this undesired seal face contact. However, research supporting this hypothesis is heuristic and experiential and lacks the rigor provided by robust simulation incorporating contact into the seal dynamics. Here, recent developments in modeling rotor–stator rub using rough surface contact are employed to simulate impact phenomena in a flexibly mounted stator (FMS) mechanical face seal designed to operate in a noncontacting regime. Specifically, the elastoplastic Jackson–Green rough surface contact model is used to quantify the contact forces using real and measurable surface and material parameters. This method also ensures that the seal face clearance remains positive, thus allowing one to calculate fluid-film forces. The seal equations of motion are simulated to indicate several modes of contacting operation, where contact is identified using waveforms, frequency spectra, and contact force calculations. Interestingly, and for the first time, certain parameters generating contact are shown to induce aperiodic mechanical face seal vibration, which is a useful machine vibration monitoring symptom. Also for the first time, this work analytically shows a mechanism where severe contact precipitates seal failure, which was previously known only through intuition and/or experience. The utility of seal face contact diagnostics is discussed along with directions for future work.

Development of low-cost deformation-based micro surface texturing system for friction reduction

Surface texturing as a means for enhancing tribological properties of mechanical components has been under intensive investigation over the last two decades. Many methods have been proposed to create surface texture of various patterns and geometries. However, among all these methods, deformation-based micro-surface texturing is least studied. It has many advantages over other methods that could lead to immediate industry application, including high productivity, high geometry fidelity and low cost. In the current work, a simple but effective incremental micro embossing system based on a commercially available press has been developed to create micro surface textures of various shapes and depths with accuracy up to 5 μm. The friction coefficients of the textured surfaces have been tested at different loadings and speeds with various lubricants to demonstrate their friction reduction capability. It has been observed that at high speed conditions, the friction reduction is achieved by the hydrodynamic lift. Interestingly, at the low speed conditions, the micro-surface texture is still capable of reducing the friction, thanks to its lubricant retention and debris entrapment capability. A micro surface textured mechanical face seal demonstrator has been built to further evaluate the micro surface texture created by incremental embossing method. A reduction of 20% in torque friction has been consistently achieved, which is on a par with that of the laser surface texturing method.

A Parametric Study on Friction Instabilities in Mechanical Face Seals

ABSTRACTThe present article aims to analyze and evaluate how dynamic parameter design influences the behavior of mechanical face seals and improves their performance by detecting undesirable phenomena like stick–slip and ringing. Those phenomena occur in situations of boundary lubrication.A new lumped parameter model is proposed to study mechanical face seals used in automotive cooling water pumps in order to examine how dynamic parameters such as mass, moment of inertia, and stiffness are involved in stick–slip phenomena. The aim of this work is to provide a practical design tool to predict stick–slip conditions and to choose the optimal mechanical specifications. Numerical simulations demonstrate how the critical service conditions vary with design parameters and permit tabulation of the results.

Self-adaptive surface texture design for friction reduction across the lubrication regimes

Surface texturing has been shown to reduce friction and improve durability in mechanical face seals and metal forming operations, and lightly loaded thrust bearings. However, the success has been limited to conformal contacts and low load high speed operating conditions, i.e. hydrodynamic lubrication dominated regime. Both experiments and numerical simulations have shown that textural patterns, under higher loading and/or slower speeds may increase friction and even cause the lubrication film collapse. Specific designs of surface texture pattern, as its shape, depth and density, are required for different lubrication regimes. Our own study has shown (Hsu et al 2014 J. Phys. D: Appl. Phys. 47 335307) that large/shallow dimple reduces friction in hydrodynamic lubrication regime, whereas small/deep dimple shows benefit in mixed/boundary lubrication regimes (if the textural designs can provides hydrodynamic/hydrostatic lift forces to reduce the machine loading). In considering an engine component typically experiences duty cycles that may cross various lubrication regimes, a multiscale surface texture design appears attractive. This type of mixed shape texturing combines textures designed for low load, high speed operating conditions and the textures that are designed for high load, low speed operations. In this paper, two types of multiscale surface texture designs are presented. Ball-on-three-flats (BOTF) wear tester (under high loading conditions) is used to evaluate the performance of these multiscale texture designs along with the baselines of un-textured surfaces under the same surface preparation procedures. Two texture designs with only a single shape dimples are included in the study. Results suggest that multiscale surface texture design not only further reduces friction in comparison to the textures with single shape dimples, but also shows the effectiveness across hydrodynamic regimes to the mixed lubrication regimes.

A Mixed Thermoelastohydrodynamic Lubrication Analysis of Mechanical Face Seals by a Multiscale Approach

This article presents an improvement to a previous multiscale approach used to model the mixed lubrication regime in a mechanical face seal. The physical mechanisms considered by the improved model are the surface roughness effects on the fluid film lubrication, the thermal deformations, and the heat transfer in the seal rings due to viscous and dry friction. The developed numerical model determines the pressure distribution by taking into account the effect of cavitation and contact asperity between the surfaces. Heat dissipation, heat transfer, and deformations are computed from the heat dissipated at the seal interface by a finite element technique. The multiscale model significantly reduces computation time while maintaining the accuracy of the results. The results obtained through a parametric study show that there are different operating zones where the lubricating film thickness is controlled by the roughness height or by the thermal effect.

Study of the fluid film vaporization in the interface of a mechanical face seal

This paper presents numerical simulations of the effect of an increase in feeding temperature on a mechanical seal operating with water. A transient numerical model using the homogeneous fluid theory was developed to analyze the vaporization of the fluid film in a mechanical seal interface. Heat transfer in the contiguous solids and faces deformations are considered. After a validation of the model by comparison with experiments, a parametric study is presented. For moderate temperature rise, the vaporization of the fluid in the contact has no significant effect on the seal performance. However, above a temperature threshold, the mechanical seal can exhibit unstable behavior which can be detrimental for its life expectancy.

Experimental and CFD investigations of carbon/SS316 mechanical face seals under different lubricating conditions

Purpose – The purpose of this paper is to test mechanical face seals made of carbon/SS316 with different coolants for evaluating its tribological performance. The reliability of a mechanical seal mainly depends on the seal materials and the type of coolant used for the lubrication. Design/methodology/approach – Compressed air, vacuum and nitrogen are the main coolants utilized for the experimental work, and the obtained results are compared with the dry running case for a specified period. The experimental results are also validated with the computational fluid dynamics (CFD) simulation results. Findings – The results shows that the sealing pressure, sliding speed and materials used would be the predominant factors for the seal design. Over compressed air, vacuum and nitrogen cooling techniques were found to be more efficient. Originality/value – The experimental results are also validated with the CFD simulation results. This paper also emphasizes the usage of vacuum as a cooling medium in industries, which will enhance the seal life at an economical cost over nitrogen.

Techniques for calculating the hydrodynamic characteristics of mechanical face seals with gaps of complex forms

This paper presents numerical and analytical techniques for calculating the hydrodynamic characteristics of mechanical face seals with gaps of complex forms that feature tapering and undulation. The numerical technique is developed using the finite volume method and takes into account inertial forces. With the tapering and undulation parameters of the clearance taken equal to zero, the analytical expressions obtained for the working fluid leakage through the gap of complex form are reduced to well-known relations. The techniques developed are applicable to both hydrodynamic and contact face seals.

Improving Bearings Thermal and Tribological Performance with Built-In Heat Pipe

A recent experimental investigation revealed that a mechanical face seal with built-in heat pipe can significantly reduce the interfacial contact temperature (Xiao and Khonsari in J Eng Tribol 228(5):498–510, 2014). Further experimental tests are set up to investigate the effect of thermal and lubrication characteristics in a thrust-bearing configuration with built-in heat pipes either in the stationary or in the rotating component. During the tests, the rotating disk slides against the stationary disk in an oil reservoir filled with SAE 10 engine oil. Both disks are made of heat-treated stainless steel 17-4 PH with the same hardness. Rubbing face temperature and surface friction coefficient are measured from both the heat pipe and conventional disk pair and the conventional disk pair. The test results show that both the heat pipe stationary and rotating disks are capable of reducing the temperature and friction coefficient.