A closed-form contact model for gas face seals during the opened operation

2018 ◽  
Vol 70 (6) ◽  
pp. 1110-1118 ◽  
Author(s):  
Songtao Hu ◽  
Noel Brunetiere ◽  
Weifeng Huang ◽  
Xi Shi ◽  
Zhike Peng ◽  
...  
Keyword(s):  
Closed Form ◽  
Rotor Dynamics ◽  
Contact Model ◽  
Strong Impact ◽  
Face Seal ◽  
Content Type ◽  
Face Seals ◽  
The Face ◽  
Nonparallel Plane ◽  
Gas Face Seal

Purpose Face contact has a strong impact on the service life of non-contacting gas face seals; the current research which mainly focuses on the face contact had appeared during the startup or shutdown operation. This paper aims to present a closed-form contact model of a gas face seal during the opened operation. Design/methodology/approach Referring to the axial rub-impact model of rotor dynamics, a closed-form contact model is developed under a nonparallel plane contact condition that corresponds to the local face contact of sealing rings arising from some disturbances during the opened operation. The closed-form contact model and a direct numerical contact model are performed on Gaussian surfaces to compare the contact behavior. Findings The closed-form contact model is in a good agreement with the direct numerical contact model. However, the closed-form contact model cannot involve the influence of grooves on the sealing ends. The error is eliminated in some other types of gas face seals such as coned gas face seals. Besides non-contacting face seals, the closed-form model can be applied to the axial rub impact of rotor dynamics. Originality value A closed-form contact model of a gas face seal is established during the opened operation. The closed-form contact model is validated by a direct numerical contact model. The closed-form contact model also suits for axial rub-impact of rotor dynamics.

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.

Hydrodynamic effect of non-closed elliptical grooves of bi-directional rotation gas face seals

2019 ◽  
Vol 72 (3) ◽  
pp. 369-377 ◽  
Author(s):  
Jing Xie ◽  
Shaoxian Bai ◽  
Chunhong Ma
Keyword(s):  
Inclination Angle ◽  
Convergence Criterion ◽  
Hydrodynamic Effect ◽  
Face Seal ◽  
Content Type ◽  
Lubricating Film ◽  
Sealing Performance ◽  
Face Seals ◽  
Hydrodynamic Mechanism ◽  
Gas Face Seal

Purpose The purpose of this paper is to improve opening performance of bi-directional rotation gas face seals by investigating the hydrodynamic effect of non-closed elliptical grooves. Design/methodology/approach A model of non-closed elliptical groove bi-directional rotation gas face seal is developed. The distribution of lubricating film pressure is obtained by solving gas Reynolds equations with the finite difference method. The program iterates repeatedly until the convergence criterion on the opening force is satisfied, and the sealing performance is finally obtained. Findings Non-closed elliptical groove presents much stronger hydrodynamic effect than the closed groove because of drop of the gas resistance flowing into grooves. Besides, the non-closed elliptical groove presents significant hydrodynamic effect under bi-directional rotation conditions, and an increase of over 40 per cent is obtained for the opening force at seal pressure 4.5 MPa, as same level as the unidirectional spiral groove gas seal. In the case of bi-directional rotation, the value of the inclination angle is recommended to set as 90° presenting a structure symmetry so as to keep best opening performance for both positive and reverse rotation. Originality/value A model of non-closed elliptical groove bi-directional rotation gas face seal is established. The hydrodynamic mechanism of this gas seal is illustrated. Parametric investigation of inclination angle and integrity rate is presented for the non-closed elliptical groove bi-directional rotation gas face seal.

Numerical Modelling of High Pressure Gas Face Seals

2005 ◽  
Author(s):  
Se´bastien Thomas ◽  
Noe¨l Brunetie`re ◽  
Bernard Tournerie
Keyword(s):  
High Pressure ◽  
Thermal Effects ◽  
Operating Conditions ◽  
Compressible Fluids ◽  
Face Seal ◽  
Choked Flow ◽  
Exit Boundary ◽  
Face Seals ◽  
Gas Face Seal ◽  
Comparison With Experimental Data

A numerical model of face seals operating with compressible fluids at high pressure is presented. Inertia terms are included using an averaged method and thermal effects are considered. The real behaviour of gases at high pressure is taken into account. An original exit boundary condition is used to deal with choked flow. The model is validated by comparison with experimental data and analytical solutions. Finally, the influence of the operating conditions on the performance of a high-pressure gas face seal is analysed.

scholarly journals Experimental and numerical study of wavy mechanical face seals operating under pressure inversions

2019 ◽  
Vol 234 (2) ◽  
pp. 247-260 ◽  
Author(s):  
Jérémy Cochain ◽  
Noël Brunetière ◽  
Andrew Parry ◽  
Henri Denoix ◽  
Abdelghani Maoui
Keyword(s):  
Numerical Model ◽  
Numerical Study ◽  
Hydrodynamic Pressure ◽  
Poor Performance ◽  
Force Balance ◽  
Face Seal ◽  
Spring Force ◽  
Face Seals ◽  
The Face ◽  
The Impact

This paper investigates the impact of the face waviness and pressure inversions on the leakage and on the outer fluid entry of mechanical face seals using a numerical model and an experimental setup. The numerical model couples a transient Reynolds equation, an analytical contact model, a force balance solver, and a solver for the thermo-mechanical deformations. The experimental tests on a face seal with low waviness and on a face seal with high waviness provide leakage and outer fluid entry data, which are reproduced by the model. Contrary to the face seal with low waviness, the face seal with high waviness has poor performance and the pressure inversions increase significantly the ingression of outer fluid. The parametric study shows a decrease of leakage with increasing spring force, and an increase of leakage and outer fluid entry with increasing values of waviness amplitude. The higher leakage observed for wavy seals is shown to be due to the higher average film thickness, and to some extent due to the mechanisms associated with waviness: hydrodynamic pressure generation, film squeeze and stretching.

Thermoelastohydrodynamic characteristics of supercritical CO2 spiral groove face seals

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Delei Zhu ◽  
Shaoxian Bai
Keyword(s):  
Critical Temperature ◽  
Peer Review ◽  
Spiral Groove ◽  
Supercritical Regime ◽  
Content Type ◽  
Lubricating Film ◽  
Sealing Performance ◽  
Face Seals ◽  
The Face ◽  
Energy Equations

Purpose The purpose of this study is to determine the sealing performance of face seals by numerical analysis of thermoelastohydrodynamic characteristics of supercritical CO2 (S-CO2) spiral groove face seals in the supercritical regime. Design/methodology/approach The spiral groove face seal was used as the research object. The distribution of lubricating film pressure and temperature was analysed by solving the gas state, Reynolds and energy equations using the finite difference method. Furthermore, the influence law of sealing performance was obtained. Findings Close to the critical temperature of S-CO2, face distortions produced by increasing pressure lead to divergent clearance and resulted in reduced opening force. In the state of S-CO2, the face distortions generated by increasing seal temperature lead to convergent clearance, which enhances the opening force. In addition, near the critical temperature of S-CO2, the opening force may be reduced by 10%, and the leakage rate of the seal sharply increases by a factor of four. Originality/value The thermoelastohydrodynamic characteristics of supercritical CO2 face seals are illustrated considering the actual gas effect including compressibility, heat capacity and viscosity. Face distortions and sealing performance were calculated under different seal pressures and seal temperatures in the supercritical regime, as well as with N2 for comparison. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2020-0169/

Numerical Modelling of High Pressure Gas Face Seals

2005 ◽  
Vol 128 (2) ◽  
pp. 396-405 ◽  
Author(s):  
Sébastien Thomas ◽  
Noël Brunetière ◽  
Bernard Tournerie
Keyword(s):  
High Pressure ◽  
Thermal Effects ◽  
Operating Conditions ◽  
Compressible Fluids ◽  
Face Seal ◽  
Choked Flow ◽  
Exit Boundary ◽  
Face Seals ◽  
Real Behavior ◽  
Gas Face Seal

An axisymetric numerical model of face seals operating with compressible fluids at high pressure is presented. Inertia terms are included using an averaged method and thermal effects are considered. The real behavior of gases at high pressure is taken into account. An original exit boundary condition is used to deal with choked flow. The model is validated by comparison with experimental data and analytical solutions. Finally, the influence of the operating conditions on the performance of a high-pressure gas face seal is analyzed. It is shown that when the flow is choked, the mass flow rate is reduced and the behavior of the seal becomes unstable.

Experimental study on the water lubrication of non-contacting face seals for turbopumps

2014 ◽  
Vol 66 (2) ◽  
pp. 314-321 ◽  
Author(s):  
Zhang Guo-yuan ◽  
Wei-gang Zhao ◽  
Yan Xiu Tian
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Rocket Engine ◽  
Groove Depth ◽  
Liquid Oxygen ◽  
Liquid Rocket Engine ◽  
Face Seal ◽  
Content Type ◽  
Face Seals ◽  
Liquid Rocket

Purpose – A new type of hydrostatic and hydrodynamic non-contacting face seals has been designed to meet the requirements of lower leakage, longer life and more repeatedly start and stop on shaft seals raised by liquid rocket engine turbopumps. And an experimental study on the performance of the face seal in the actual liquid oxygen turbopump was completed where low-viscosity water was selected as the seal fluid for the sake of safety. The paper aims to discuss these issues. Design/methodology/approach – Different performances of face seals under preset conditions were obtained by repeatedly running tests, and the main performance parameters encompass leakage, fluid film pressure between the faces, operating power, face temperature, and so on. Findings – The results indicate that the designed face seal has a smaller amount of leakage, with a minimum value of 3 ml/s. Furthermore, the designed face seal has been proved to demand lower operating power. Since its operating power changes slightly with different sealed fluid pressures, the new seal can be deployed in the harsh working condition with high pressure or with high speed (greater than 20,000 rpm). However, one proviso is that when liquid is employed as the seal fluid, the groove depth should be relatively deeper (greater than 10 μm). Research limitations/implications – In response to future engineering requirements, study on the controllable spiral-groove face seals to improve the current design is being conducted. Originality/value – The advancement of such non-contacting face seals proffers important insights to the design of turbo-pump shaft seal in a new generation of liquid rocket engine with regard to the requirement of frequent start and stop as well as long life on it.

‘Bonbibi’ Could Wait Till Our Boss Decides: Looking at the Changing Face of the Indian Sundarbans

2021 ◽  
pp. 239386172110146
Author(s):  
Prama Mukhopadhyay
Keyword(s):  
Strong Impact ◽  
Interstate Migration ◽  
World Economic Forum ◽  
Fishing Community ◽  
Indian Sundarbans ◽  
Local Perception ◽  
Cultural Life ◽  
Previous Decade ◽  
The Face ◽  
World Economic

Internal migration constitutes a major source of steady flow of population in India, and reports published by the World Economic Forum (WEF),1 2017 state that interstate migration in the country has doubled during 2001–2011, compared to the previous decade.2 In developing countries, such migration is often considered to be an effective way for income diversification for the economically marginalised sections of the society, even though its effect on ‘human development’ is oft debated. This article would engage with this debate and bring out how migration from the Indian part of the Sundarbans to other parts of the country is not only changing the demography of the region but is also having a strong impact on the local perception and attachment towards the deltaic landscape. By bringing in ethnographic details from a village in the Indian Sundarbans, which was predominately inhabited by the fishing community earlier, this article would bring out how traditional occupations like fishing are slowly losing their popularity in the face of the lure of out-migration, as the very identity of the ‘indigenous’ Sundarban fisher folks—who were once rightfully considered to be the true conservator of the forests—is changing. From there, this article would engage with the broader debate of rethinking whether migration can be considered as a positive indicator of development in such ecologically fragile areas like the Sundarban deltas, which used to indeed have a distinct economic, social and cultural life of its own.

Associated change in plantar temperature and sweating after transthoracic endoscopic T2–3 sympathectomy for palmar hyperhidrosis

2001 ◽  
Vol 95 (1) ◽  
pp. 58-63 ◽  
Author(s):  
Han-Jung Chen ◽  
Cheng-Loong Liang ◽  
Kang Lu
Keyword(s):  
Skin Temperature ◽  
Temperature Change ◽  
The Body ◽  
Palmar Hyperhidrosis ◽  
Compensatory Sweating ◽  
Content Type ◽  
Postoperative Changes ◽  
The Face ◽  
The Difference ◽  
Fine Print

Object. Transthoracic endoscopic T2–3 sympathectomy is currently the treatment of choice for palmar hyperhidrosis. Compensatory sweating of the face, trunk, thigh, and sole of the foot was found in more than 50% of patients who underwent this procedure. The authors conducted this study to investigate the associated intraoperative changes in plantar skin temperature and postoperative plantar sweating. Methods. One hundred patients with palmar hyperhidrosis underwent bilateral transthoracic endoscopic T2–3 sympathectomy. There were 60 female and 40 male patients who ranged in age from 13 to 40 years (mean age 21.6 years). Characteristics studied included changes in palmar and plantar skin temperature measured intraoperatively, as well as pre- and postoperative changes in plantar sweating and sympathetic skin responses (SSRs). In 59 patients (59%) elevation of plantar temperature was demonstrated at the end of the surgical procedure. In this group, plantar sweating was found to be exacerbated in three patients (5%); plantar sweating was improved in 52 patients (88.1%); and no change was demonstrated in four patients (6.8%). In the other group of patients in whom no temperature change occurred, increased plantar sweating was demonstrated in three patients (7.3%); plantar sweating was improved in 20 patients (48.8%); and no change was shown in 18 patients (43.9%). The difference between temperature and sweating change was significant (p = 0.001). Compared with the presympathectomy rate, the rate of absent SSR also significantly increased after sympathectomy: from 20 to 76% after electrical stimulation and 36 to 64% after deep inspiration stimulation, respectively (p < 0.05). Conclusions. In contrast to compensatory sweating in other parts of the body after T2–3 sympathetomy, improvement in plantar sweating was shown in 72% and worsened symptoms in 6% of patients. The intraoperative plantar skin temperature change and perioperative SSR demonstrated a correlation between these changes.

More tax on asset gains is likelier than a wealth tax

2021 ◽  
Keyword(s):  
Asset Prices ◽  
Content Type ◽  
Developed Economies ◽  
Support Measures ◽  
Investment Income ◽  
The Future ◽  
The Face ◽  
Fiscal Support ◽  
Wealth Tax

Significance Developed economies have implemented fiscal support measures worth over 16% of their GDP to combat the pandemic's impacts. To pay off the resulting debt and to ensure sufficient revenue in the face of a fragile and uneven recovery, new taxes and higher rates are being considered. Impacts Levying a wealth tax on productive firms risks starving them of capital for the future. If levied too high or too long, people would sell assets to pay, depressing asset prices, reducing investment and prompting outflows. Criticisms of wealth taxes mean that a one-off surcharge on investment income above a certain threshold would be easier and more popular.

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