Comparison of the Load-Carrying Performance of Mechanical Gas Seals Textured With Microgrooves and Microdimples

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Liping Shi ◽  
Xiuying Wang ◽  
Xiao Su ◽  
Wei Huang ◽  
Xiaolei Wang
Keyword(s):  
Reynolds Equation ◽  
Hydrodynamic Pressure ◽  
Area Density ◽  
Low Area ◽  
Optimal Load ◽  
High Area ◽  
Load Carrying ◽  
Small Clearance ◽  
Gas Seals ◽  
Film Stiffness

The effects of microgrooves and microdimples on the load-carrying performance of mechanical gas seals are compared in this study. Numerical model based on the Reynolds equation for compressible Newtonian fluid is utilized to investigate the load-carrying performance including the hydrodynamic pressure, the load-carrying force, and gas film stiffness of the gas seals. The results indicate that both microgrooves and microdimples can improve the load-carrying performance of mechanical gas seals, particularly under a small clearance condition. Furthermore, different texture patterns achieve optimal load-carrying performance at different area density, seal clearance, and depth: microgrooves with a low area density can obtain higher load-carrying force and gas film stiffness than the dimple patterns, but with high area density, elliptical dimples yield better load-carrying performance than the groove patterns.

Stiffness and Efficiency Optimization of a Hydrostatic Laser Surface Textured Gas Seal

2006 ◽  
Vol 129 (2) ◽  
pp. 407-410 ◽  
Author(s):  
Y. Feldman ◽  
Y. Kligerman ◽  
I. Etsion
Keyword(s):  
Reynolds Equation ◽  
Surface Texturing ◽  
Laser Surface ◽  
Laser Surface Texturing ◽  
Narrow Gap ◽  
Mechanical Seals ◽  
Gas Leakage ◽  
Dimensionless Analysis ◽  
High Area ◽  
Film Stiffness

Microdimples generated by laser surface texturing (LST) can be used to enhance performance in hydrostatic gas-lubricated mechanical seals. This is achieved by applying microdimples with high area density over a certain portion of the sealing dam width adjacent to the high-pressure side, leaving the remaining portion untextured. The textured portion provides an equivalent larger gap that results in converging clearance in the direction of pressure drop and hence, hydrostatic pressure buildup, similar to that of a radial step seal. A mathematical model based on the solution of the Reynolds equation for compressible Newtonian fluid in a narrow gap between two nominally parallel stationary surfaces is developed. A detailed dimensionless analysis of the texturing parameters is performed to achieve maximum gas film stiffness with minimum gas leakage.

Accuracy analysis of narrow groove theory for spiral grooved gas seals: A comparative study with numerical solution of Reynolds equation

2018 ◽  
Vol 233 (6) ◽  
pp. 899-910
Author(s):  
Wanjun Xu ◽  
Jiangang Yang
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
Reynolds Equation ◽  
Compressible Fluids ◽  
Accuracy Analysis ◽  
Performance Parameters ◽  
Typical Performance ◽  
Gas Seals ◽  
Film Stiffness

This study examined the accuracy of narrow groove theory for spiral grooved gas seals. Designed for compressible fluids, a finite difference method was proposed to solve the two-dimensional compressible Reynolds equation. The predictions of narrow groove theory were compared with those of the Reynolds equation. The typical performance parameters including gas film force, leakage, gas film stiffness, and torque were analyzed. The results show that the predictions of narrow groove theory generally agree with those of finite difference method when the number of grooves is more than eight. The gas film force, leakage, and gas film stiffness were slightly overestimated by narrow groove theory, with better accuracy for gas film force, leakage, and torque than for gas film stiffness. Although some cases showed deviation for gas film stiffness of as much as 52%, most deviations can be effectively ignored. Therefore, it is feasible to use narrow groove theory for qualitative analysis such as groove shape optimization. The present analysis provides the optimum groove parameters for the investigated seal.

Hydrodynamics and Sonic Flow Transition in Dry Gas Seals

2014 ◽  
Author(s):  
Azam Thatte ◽  
Xiaoqing Zheng
Keyword(s):  
Linear Partial Differential Equation ◽  
Hydrodynamic Pressure ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Spiral Groove ◽  
Local Pressure ◽  
Choked Flow ◽  
Gas Seals ◽  
Film Stiffness

Dry gas seals (DGS) are widely used in turbomachinery applications. They are recently being also recommended for sealing novel super critical CO2 turbomachinery space. However, these seals can render interesting behavior under certain operating conditions which needs to be carefully monitored so that intended level of dynamic characteristics can be achieved. The ability of these seals to maintain low leakage by riding at small clearances makes them an attractive solution where secondary flows need to be minimized. To understand the significance of some of the key design features of these seals, in this work an analysis on a gas lubricated spiral groove dry gas seal is presented. Equations in polar coordinates governing the compressible flow through the DGS gap and a numerical method to solve such non-linear partial differential equation is presented. The resulting sets of equations are solved for hydrodynamic pressure distribution and the axial separation force and the film stiffness at the rotor-stator interface is calculated. A detailed study on key spiral groove features is then performed to investigate the effect of spiral angle, groove depth, groove pitch and dam width ratio on the hydrodynamic pressure generation capacity, film stiffness and hence on overall performance of the DGS. Another important phenomenon that can occur in DGS under high operating pressure is the sonic transition. It is shown that choked flow under such conditions can take place over the dam section of the seal which manifests itself into large local pressure and temperature variations and can result into dynamic instabilities.

scholarly journals Comparative study of spherical dimple and bump effects on the tribological performances of journal bearing

2018 ◽  
Vol 233 (1) ◽  
pp. 139-157 ◽  
Author(s):  
Chao Gui ◽  
Fanming Meng
Keyword(s):  
Friction Force ◽  
Carrying Capacity ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Load Carrying Capacity ◽  
Transform Method ◽  
Cavitation Effect ◽  
Fast Fourier Transform Method ◽  
Load Carrying

In the present study, tribological performances of journal bearings with the representative spherical dimples and bumps are compared numerically. In doing so, the hydrodynamic pressure of the lubricant is solved by the Reynolds equation considering the lubricant cavitation effect. Meanwhile, the elastic deformation is calculated by the continuous convolution fast Fourier transform method. The enhanced load-carrying capacity and the reduced friction force occur only when the dimples are located at pressure rising part of the bearing. The bumps located at the pressure falling part can enhance the load-carrying capacity but increase the friction force. The above dimple and bump effects change at the varied feature sizes and intervals.

A High Performance Journal Bearing With Controlled Elastic Deflection

1995 ◽  
Vol 117 (4) ◽  
pp. 702-708 ◽  
Author(s):  
A. K. Tieu ◽  
N. O. Freund
Keyword(s):  
Thermal Effects ◽  
High Performance ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Hydrodynamic Pressure ◽  
Hydrodynamic Analysis ◽  
Elastic Deflection ◽  
Load Carrying ◽  
Bearing Load ◽  
Generalized Reynolds Equation

A thermo-elasto-hydrodynamic analysis of an undercut journal bearing is presented whereby elastic deflection is introduced in a certain area of the bearing surface. The hydrodynamic pressure is computed from the generalized Reynolds equation, which takes into account thermal effects on viscosity. This is accomplished by solving the full energy equation for temperature. The elastic deflection is obtained from the elasticity equation. This study is then complemented with an elasto-hydrodynamic analysis of the full bearing. The controlled elastic deflection increases the bearing load carrying capacity and reduces friction.

The Effect of Journal Bearing Misalignment on Load and Cavitation for Non-Newtonian Lubricants

1986 ◽  
Vol 108 (4) ◽  
pp. 645-654 ◽  
Author(s):  
R. H. Buckholz ◽  
J. F. Lin
Keyword(s):  
Reynolds Equation ◽  
Numerical Solutions ◽  
Journal Bearings ◽  
Surface Boundary ◽  
Film Rupture ◽  
Aspect Ratios ◽  
Free Surface Boundary Condition ◽  
Load Carrying ◽  
Boundary Location ◽  
Surface Boundary Condition

An analysis for hydrodynamic, non-Newtonian lubrication of misaligned journal bearings is given. The hydrodynamic load-carrying capacity for partial arc journal bearings lubricated by power-law, non-Newtonian fluids is calculated for small valves of the bearing aspect ratios. These results are compared with: numerical solutions to the non-Newtonian modified Reynolds equation, with Ocvirk’s experimental results for misaligned bearings, and with other numerical simulations. The cavitation (i.e., film rupture) boundary location is calculated using the Reynolds’ free-surface, boundary condition.

Numerical Analysis of Dry Gas Face Seals With Spiral Groove and Inner Annular Groove

2008 ◽  
Author(s):  
Xu-Dong Peng ◽  
Li-Li Tan ◽  
Ji-Yun Li ◽  
Song-En Sheng ◽  
Shao-Xian Bai
Keyword(s):  
Reynolds Equation ◽  
Geometric Parameters ◽  
Axial Stiffness ◽  
Face Seal ◽  
Optimization Principle ◽  
Face Seals ◽  
The Face ◽  
Gas Face Seal ◽  
Film Stiffness ◽  
Spiral Grooves

A two-dimensional Reynolds equation was established for isothermal compressible gas between the two faces of a dry gas face seal with both spiral grooves and an inner annular groove onto the hard face. The opening force, the leakage rate, the axial film stiffness and the film stiffness to leakage ratio were calculated by finite element method. The comparisons with the sealing performances of a typical gas face seal only with spiral grooves onto its hard face were made. The effects of the face geometric parameters on the static behavior of such a seal were analyzed. The optimization principle for geometric parameters of a dry gas face seals with spiral grooves and an inner annular groove was presented. The recommended geometric parameters of spiral grooves and circular groove presented by optimization can ensure larger axial stiffness while lower leakage rates.

scholarly journals A comparison between soil loss evaluation index and the C-factor of RUSLE: a case study in the Loess Plateau of China

2012 ◽  
Vol 16 (8) ◽  
pp. 2739-2748 ◽  
Author(s):  
W. W. Zhao ◽  
B. J. Fu ◽  
L. D. Chen
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Soil Loss ◽  
Drainage Network ◽  
Land Use Patterns ◽  
Low Area ◽  
Use Patterns ◽  
High Area ◽  
Land Use Types

Abstract. Land use and land cover are most important in quantifying soil erosion. Based on the C-factor of the popular soil erosion model, Revised Universal Soil Loss Equation (RUSLE) and a scale-pattern-process theory in landscape ecology, we proposed a multi-scale soil loss evaluation index (SL) to evaluate the effects of land use patterns on soil erosion. We examined the advantages and shortcomings of SL for small watershed (SLsw) by comparing to the C-factor used in RUSLE. We used the Yanhe watershed located on China's Loess Plateau as a case study to demonstrate the utilities of SLsw. The SLsw calculation involves the delineations of the drainage network and sub-watershed boundaries, the calculations of soil loss horizontal distance index, the soil loss vertical distance index, slope steepness, rainfall-runoff erosivity, soil erodibility, and cover and management practice. We used several extensions within the geographic information system (GIS), and AVSWAT2000 hydrological model to derive all the required GIS layers. We compared the SLsw with the C-factor to identify spatial patterns to understand the causes for the differences. The SLsw values for the Yanhe watershed are in the range of 0.15 to 0.45, and there are 593 sub-watersheds with SLsw values that are lower than the C-factor values (LOW) and 227 sub-watersheds with SLsw values higher than the C-factor values (HIGH). The HIGH area have greater rainfall-runoff erosivity than LOW area for all land use types. The cultivated land is located on the steeper slope or is closer to the drainage network in the horizontal direction in HIGH area in comparison to LOW area. The results imply that SLsw can be used to identify the effect of land use distribution on soil loss, whereas the C-factor has less power to do it. Both HIGH and LOW areas have similar soil erodibility values for all land use types. The average vertical distances of forest land and sparse forest land to the drainage network are shorter in LOW area than that in HIGH area. Other land use types have shorter average vertical distances in HIGH area than that LOW area. SLsw has advantages over C-factor in its ability to specify the subwatersheds that require the land use patterns optimization by adjusting the locations of land uses to minimize soil loss.

Analysis of misaligned water-lubricated polymer bearing with axial grooves

2019 ◽  
Vol 71 (3) ◽  
pp. 411-419 ◽  
Author(s):  
Fangrui Lv ◽  
Chunxiao Jiao ◽  
Donglin Zou ◽  
Na Ta ◽  
Zhu-shi Rao
Keyword(s):  
Carrying Capacity ◽  
Hydrodynamic Pressure ◽  
Maximum Pressure ◽  
Load Carrying Capacity ◽  
Misalignment Angle ◽  
Content Type ◽  
Load Carrying ◽  
Polymer Bearing ◽  
Journal Misalignment ◽  
Practical Implications

Purpose The purpose of this paper is to analyze the lubrication behavior of misaligned water-lubricated polymer bearings with axial grooves. Design/methodology/approach A lubrication model considering journal misalignment, bush deformation and grooves is established. In dynamic analyses of shaft systems, bearings are usually simplified as supporting points. Thus, an approach for solving the equivalent supporting point location is presented. The influence of misalignment angle and groove number on film thickness, hydrodynamic pressure distribution, load-carrying capacity and ESP location is investigated. Findings As the misalignment angle increases, the location of the maximum pressure and ESP are shifted toward the down-warping end, and the load-carrying capacity of the bearing decreases. In comparison to the nine-groove bearing, the six grooves bearing has a higher load-carrying capacity and the ESP is located closer to the down-warping end for an equivalent misalignment angle. Practical implications The results of this study can be applied to marine propeller shaft systems and other systems with misaligned bearings. Originality/value A study on the lubrication behavior of misaligned water-lubricated polymer bearings with axial grooves is of significant interest to the research community.

scholarly journals Analytical Study of Non-Recessed Conical Hole Entry Hybrid/Hydrostatic Journal Bearing with Constant Flow Valve Restrictor

2020 ◽  
Vol 37 (3−4) ◽  
Author(s):  
Prashant Govindrao Khakse ◽  
Vikas M. Phalle
Keyword(s):  
Journal Bearing ◽  
Angular Distance ◽  
Maximum Pressure ◽  
Constant Flow ◽  
Double Row ◽  
Element Analysis ◽  
Load Carrying ◽  
Conical Bearing ◽  
Film Stiffness ◽  
Flow Valve

The present work studies the analysis of a non recessed hole entry conical hybrid/hydrostatic journal bearing adjusted for constant flow valve (CFV) restriction. The paper provides effectiveness between the conical bearings with hole entry operating in hybrid and hydrostatic mode. The Reynolds formulae, for the flow of fluid through the mating surfaces of a conical journal and bearing, are numerically worked out in both the modes considering the finite element analysis (FEA) and the necessary boundary preconditions. Holes in double row are marked on conical bearing circumference to accommodate the CFV restrictors, the angular distance between two holes are 30o apart from the apex. Qualitative features of the conical journal bearing system with hole entry have been elaborated to analyze bearing performance for radial load variation Wr = 0.25-2. Numerical results obtained from the present study indicate that load carrying capacity of conical bearing, operating in hydrostatic mode, is enhanced by the maximum pressure, direct fluid film damping and direct film stiffness coefficients vis-a-vis corresponding hybrid mode.  

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