Static and dynamic characteristics of a Rayleigh-steps mechanical seal with reverse steps

2021 ◽  
pp. 135065012110658
Author(s):  
Yunlei Wang ◽  
Jiu Hui Wu ◽  
Lushuai Xu ◽  
Hongjun Liu
Keyword(s):  
Film Thickness ◽  
Optimization Design ◽  
Frictional Torque ◽  
Stable Operation ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Angular Misalignment ◽  
Damping Coefficients ◽  
Cavitation Phenomenon ◽  
Stiffness And Damping

This paper presents a Rayleigh-steps mechanical seal with reverse steps (RS-MS), and the governing equation was solved by the finite difference method (FDM). The effects of angular misalignment, working condition parameters, and film thickness on sealing performance were discussed, including the opening force, cavitation ratio, leakage rate, frictional torque, stiffness and damping coefficients. The results indicate that the cavitation phenomenon in the reverse step groove can restrain the leakage, while it also affects the stability of the seal. The angular misalignment makes the seal have greater stiffness and damping coefficients. The stiffness and damping coefficients decrease rapidly with the increase of the film thickness, and the dynamic stability of the mechanical seal decreases with the increase of the film thickness, which is not conducive to the stable operation of the seal. The research results can guide the optimization design of mechanical seals.

The Rotordynamic Coefficients of Mechanical Seals Having Two Flexibly Mounted Rotors

1991 ◽  
Vol 113 (4) ◽  
pp. 795-804 ◽  
Author(s):  
J. Wileman ◽  
I. Green
Keyword(s):  
Degrees Of Freedom ◽  
Reynolds Equation ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Rotordynamic Coefficients ◽  
Damping Coefficients ◽  
Rotating Shafts ◽  
Stiffness And Damping ◽  
Three Degrees Of Freedom ◽  
Degenerate Cases

The Reynolds equation is derived for a mechanical seal in which both elements are flexibly mounted to rotating shafts. Stiffness and damping coefficients for the fluid film are calculated for the three degrees of freedom of each element based upon a small perturbation analysis. The analogous coefficients for simpler configurations (e.g., flexibly mounted rotor, flexibly mounted stator) contained in the literature are shown to be obtainable as degenerate cases of the more general results presented in this work.

Liquid Film Features Analysis on Mechanical Seals with Micro-Pore Face by CFD

2011 ◽  
Vol 354-355 ◽  
pp. 575-578
Author(s):  
Wei Zheng Zhang ◽  
Shu Rong Yu ◽  
Yan Wang ◽  
Xue Xing Ding
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Optimization Design ◽  
Theoretical Data ◽  
Least Square ◽  
Liquid Film Thickness ◽  
Stable Operation ◽  
Mechanical Seals ◽  
Film Stiffness ◽  
The Relationship

The six kinds of different models were simulated by FLUENT software under certain circumstances. As a result, their pressure distributions and liquid film opening force with different thickness were obtained. The relationship between liquid film thickness and opening force was obtained by least square fitting. And then the relationship between stiffness and liquid film thickness was calculated and analyzed. The result shows that: seal opening force and liquid film stiffness decrease as the liquid film thickness increase, this simulation results is identical with the theoretical data. In larger film thickness range, the opening force is larger, and so was the liquid film stiffness, which provide the basis for seal optimization design and the stable operation.

Sinusoidal Three-Lobe Bearings—Optimization and Stability Charts

1980 ◽  
Vol 102 (4) ◽  
pp. 416-424 ◽  
Author(s):  
W. E. ten Napel ◽  
R. Bosma
Keyword(s):  
Film Thickness ◽  
Stability Parameters ◽  
Stability Regions ◽  
Damping Coefficients ◽  
Optimum Position ◽  
Minimum Film Thickness ◽  
Stiffness And Damping

In contradistinction to the commonly used segmented three-lobe bearing, another type of bearing, i.e., the sinusoidal three-lobe bearing has been investigated in this paper. The main advantage of this bearing is that it can very easily be manufactured. Special attention has been paid to problems of optimization with regard to minimum film thickness and friction, respectively. Stiffness and damping coefficients have been calculated as well as stability regions and stability parameters. Additionally, the optimum position of the oil grooves has been investigated.

Static and Dynamic Analysis of Multileaf Foil Journal Bearings Considering Misalignment Effects

1997 ◽  
Author(s):  
D. Sudheer Kumar Reddy ◽  
S. Swarnamani ◽  
B. S. Prabhu
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Performance Characteristics ◽  
Frictional Torque ◽  
Static And Dynamic Analysis ◽  
Foil Bearing ◽  
Deformation Equation ◽  
Load Carrying ◽  
Static Performance ◽  
Stiffness And Damping

Abstract In the present work the analysis of gas lubricated multileaf journal bearing has been presented. The two dimensional compressible Reynolds equation was solved to establish the pressure field in the clearance space of the bearing. Elastic deformation equation is coupled with the Reynolds equation to get the foil deflections and change in film thickness. The effect of bearing misalignment on foil bearing performance characteristics has been presented. The problem has been formulated using incremental finite element method. The effect of bearing misalignment on static performance characteristics like load carrying capacity, frictional torque, minimum film thickness and on dynamic characteristics in terms of stiffness and damping coefficients have been presented.

scholarly journals Research on the Dynamic Characteristics of Mechanical Seal under Different Extrusion Fault Degrees

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1057
Author(s):  
Yin Luo ◽  
Yakun Fan ◽  
Yuejiang Han ◽  
Weqi Zhang ◽  
Emmanuel Acheaw
Keyword(s):  
Film Thickness ◽  
Dynamic Characteristics ◽  
Fluid Film ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Rotating Speed ◽  
Analysis Process ◽  
Fluid Film Thickness ◽  
Object Of Study ◽  
Fault Mechanism

In order to explore the dynamic characteristics of the mechanical seal under different fault degrees, this paper selected the upstream pumping mechanical seal as the object of study. The research established the rotating ring-fluid film-stationary ring 3D model, which was built to analyze the fault mechanism. To study extrusion fault mechanism and characteristics, different dynamic parameters were used in the analysis process. Theoretical analysis, numerical simulation, and comparison were conducted to study the relationship between the fault degree and dynamic characteristics. It is the first time to research the dynamic characteristics of mechanical seals in the specific extrusion fault. This paper proved feasibility and effectiveness of the new analysis method. The fluid film thickness and dynamic characteristics could reflect the degree of the extrusion fault. Results show that the fluid film pressure fluctuation tends to be more intensive under the serious extrusion fault condition. The extrusion fault is more likely to occur when the fluid film thickness is too large or too small. Results illustrate the opening force is affected with the fluid film lubrication status and seal extrusion fault degrees. The fluid film stiffness would not always increase with the rotating speed growth. The seal fault would occur with the increasing of rotating speeds, and the leakage growth fluctuations could reflect the fault degree.

Gas-Expanded Lubricant Performance and Effects on Rotor Stability in Turbomachinery

2014 ◽  
Author(s):  
Brian K. Weaver ◽  
Timothy W. Dimond ◽  
Jason A. Kaplan ◽  
Alexandrina Untaroiu ◽  
Andres F. Clarens
Keyword(s):  
Film Thickness ◽  
Power Loss ◽  
High Speed ◽  
Turbine Generator ◽  
Generator System ◽  
Polyol Ester ◽  
Damping Coefficients ◽  
Wide Range ◽  
Bearing Stiffness ◽  
Stiffness And Damping

Gas-expanded lubricants (GELs) are tunable mixtures of synthetic oil and carbon dioxide that enable dynamic control of lubricant viscosity during bearing operation. This control can help reduce bearing power loss and operating temperatures while also providing direct control over bearing stiffness and damping, which can enhance rotordynamic performance. In this work, the bearing and rotordynamic performance of two representative high-speed machines was evaluated when different lubricants, including GELs, were supplied to the machine bearings. The machines chosen for this analysis, an 8-stage centrifugal compressor and a steam turbine-generator system, represent a wide range of speed and loading conditions encountered in modern turbomachinery. The fluids compared for machine performance were standard petroleum-based lubricants, polyol ester synthetic oils, and polyol ester based-GELs. The performance simulations were carried out using a thermoelastohydrodynamic bearing model, which provided bearing stiffness and damping coefficients as inputs to finite element rotordynamic models. Several bearing performance metrics were evaluated including power loss, operating temperature, film thickness, eccentricity, and stiffness and damping coefficients. The rotordynamic analysis included an evaluation of rotor critical speeds, unbalance response, and stability. Bearing performance results for the compressor showed a 40% reduction in power loss at operating speed when comparing the GEL to the petroleum-based lubricant. The GEL-lubricated compressor also exhibited lower operating temperatures with minimal effects on film thickness. GELs were also predicted to produce lower bearing stiffness when compared to standard fluids in the compressor. Rotordynamic results for the compressor showed that the fluid properties had only minor effects on the unbalance response, while GELs were found to increase the stability margin by 43% when compared with standard fluids. The results from the turbine-generator system also demonstrated increases in low-speed bearing efficiency with the use of GELs, though at higher speeds the onset of turbulent flow in the GEL case offset these efficiency gains. Rotordynamic results for this system showed a contrast with the compressor results, with the GELs producing lower stability margins for a majority of the modes predicted due to increased bearing stiffness in the high-speed turbine bearings and negative stiffness in the lightly loaded, low-speed pinion bearings. These results suggest that GELs could be beneficial in providing control over a wide range of machine designs and operating conditions and that some machines are especially well suited for the tunability that these fluids impart.

Measurements of Static and Dynamic Load Performance of a 102 MM Carbon-Graphite Porous Surface Tilting-Pad Gas Journal Bearing

2021 ◽  
Author(s):  
Luis San Andres ◽  
Jing Yang ◽  
Ryan McGowan
Keyword(s):  
Dynamic Load ◽  
Load Capacity ◽  
Stable Operation ◽  
Specific Load ◽  
Damping Coefficients ◽  
Supply Pressure ◽  
Air Supply ◽  
Frequency Independent ◽  
Stiffness And Damping ◽  
Gas Bearing

Abstract Aerostatic journal bearings with porous tilting pads enable shaft support with minute drag power losses. To date archival information on the static and dynamic load performance of this bearing type is scant. Thus, the paper presents measurements conducted with an air bearing with diameter 102 mm and comprising four tilting pads made of porous carbon-graphite, each with length = 76 mm. At ambient temperature of 21°C, as the air supply pressure into the bearing pads increases, so does the bearing aerostatic specific load that reaches 58% of the pressure difference. With a supply pressure of 7.8 bar(a), the test bearing static stiffness = 13.1 MN/m, is independent of both shaft speed and static load. While operating with shaft speeds = 6 krpm and 9 krpm and under specific loads to 115 kPa and 101 kPa respectively, dynamic load experiments with excitation frequencies up to 342 Hz show the test bearing supplied with air at 7.8 bar(a) has frequency independent stiffness and damping coefficients. For rotor speeds equaling 0, 6 and 9 krpm, the bearing direct stiffnesses range from 13.6 MN/m to 32.7 MN/m as the specific load increases from 0 kPa to 115 kPa. The direct damping coefficients are as large as 5.8 kN·s/m. The test porous gas bearing reached its intended load capacity, demonstrated a dynamically stable operation and produced force coefficients mainly affected by the pads' pivot supports and the magnitude of air supply pressurization.

Gas-Expanded Lubricant Performance and Effects on Rotor Stability in Turbomachinery

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Brian K. Weaver ◽  
Timothy W. Dimond ◽  
Jason A. Kaplan ◽  
Alexandrina Untaroiu ◽  
Andres F. Clarens
Keyword(s):  
Film Thickness ◽  
Power Loss ◽  
High Speed ◽  
Turbine Generator ◽  
Generator System ◽  
Low Speed ◽  
Damping Coefficients ◽  
Wide Range ◽  
Bearing Stiffness ◽  
Stiffness And Damping

Gas-expanded lubricants (GELs) are tunable mixtures of synthetic oil and carbon dioxide that enable dynamic control of lubricant viscosity during bearing operation. This control can help reduce bearing power loss and operating temperatures while also providing direct control over bearing stiffness and damping, which can enhance rotordynamic performance. In this work, the bearing and rotordynamic performance of two representative high-speed machines was evaluated when different lubricants, including GELs, were supplied to the machine bearings. The machines chosen for this analysis, an eight-stage centrifugal compressor and a steam turbine-generator system, represent a wide range of speed and loading conditions encountered in modern turbomachinery. The fluids compared for machine performance were standard petroleum-based lubricants, polyol ester (POE) synthetic oils, and POE-based GELs. The performance simulations were carried out using a thermoelastohydrodynamic bearing model, which provided bearing stiffness and damping coefficients as inputs to finite element rotordynamic models. Several bearing performance metrics were evaluated including power loss, operating temperature, film thickness, eccentricity, and stiffness and damping coefficients. The rotordynamic analysis included an evaluation of rotor critical speeds, unbalance response, and stability. Bearing performance results for the compressor showed a 40% reduction in power loss at operating speed when comparing the GEL to the petroleum-based lubricant. The GEL-lubricated compressor also exhibited lower operating temperatures with minimal effects on film thickness. GELs were also predicted to produce lower bearing stiffness when compared to standard fluids in the compressor. Rotordynamic results for the compressor showed that the fluid properties had only minor effects on the unbalance response, while GELs were found to increase the stability margin by 43% when compared with standard fluids. The results from the turbine-generator system also demonstrated increases in low-speed bearing efficiency with the use of GELs, though at higher speeds the onset of turbulent flow in the GEL case offset these efficiency gains. Rotordynamic results for this system showed a contrast with the compressor results, with the GELs producing lower stability margins for a majority of the modes predicted due to increased bearing stiffness in the high-speed turbine bearings and negative stiffness in the lightly loaded, low-speed pinion bearings. These results suggest that GELs could be beneficial in providing control over a wide range of machine designs and operating conditions and that some machines are especially well suited for the tunability that these fluids impart.

Improvements to the Analysis of Gas Foil Bearings: Integration of Top Foil 1D and 2D Structural Models

2007 ◽  
Author(s):  
Luis San Andre´s ◽  
Tae Ho Kim
Keyword(s):  
Film Thickness ◽  
Gas Turbines ◽  
Load Capacity ◽  
Structural Models ◽  
Underlying Structure ◽  
Fe Model ◽  
Foil Bearings ◽  
Damping Coefficients ◽  
Minimum Film Thickness ◽  
Stiffness And Damping

Gas foil bearings (GFBs) find widespread usage in oil-free turbo expanders, APUs and micro gas turbines for distributed power due to their low drag friction and ability to tolerate high level vibrations, including transient rubs and shaft misalignment, static and dynamic. The static load capacity and dynamic forced performance of GFBs depends largely on the material properties of the support elastic structure, i.e. a smooth foil on top of bump strips. Conventional models include only the bumps as an equivalent stiffness uniformly distributed around the bearing circumference. More complex models couple directly the elastic deformations of the top foil to the bump underlying structure as well as to the hydrodynamics of the gas film. This paper details two FE models for the top foil supported on bump strips, one considers a 2D shell anisotropic structure and the other a 1D beam-like structure. The Cholesky decomposition of the stiffness matrix representing the top foil and bump strips is performed off-line prior to computations coupling it to the gas film analysis governed by Reynolds equation. The procedure greatly enhances the computational efficiency of the numerical scheme. Predictions of journal attitude angle and minimum film thickness for increasing static loads and two journal speeds are obtained for a GFB tested decades ago. 2D FE model predictions overestimate the minimum film thickness at the bearing centerline, while underestimating it at the bearing edges. Predictions from the 1D FE model compare best to the limited tests data; reproducing closely the experimental circumferential wavy-like minimum film thickness profile. The 1D top foil model is recommended due to its low computational cost. Predicted stiffness and damping coefficients versus excitation frequency show that the two FE top foil structural models result in slightly lower direct stiffness and damping coefficients than those from the simple elastic foundation model.

Fuzzy Comprehensive Evaluation Method for Mechanical Seal Risk Assessment of Centrifugal Pumps

2011 ◽  
Vol 474-476 ◽  
pp. 1283-1287
Author(s):  
Ying Jie Hao ◽  
Bo Qin Gu
Keyword(s):  
Evaluation Method ◽  
Comprehensive Evaluation ◽  
Fuzzy Comprehensive Evaluation ◽  
Risk Level ◽  
Stable Operation ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Centrifugal Pumps ◽  
Fuzzy Comprehensive Evaluation Method ◽  
Comprehensive Evaluation Method

A failure analysis of mechanical seals of centrifugal pumps was presented with fuzzy comprehensive evaluation method. Both failure probability and failure consequence were analyzed to evaluate the risk grade of the mechanical seals. The potential risk level of a mechanical seal was estimated by the application of risk matrix. The proposed fuzzy comprehensive evaluation method can be used to judge the reliability of mechanical seals and provide an important reference for the safe and stable operation of centrifugal pumps.

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