scholarly journals Semi Salix Leaf Textured Gas Mechanical Face Seal with Enhanced Opening Performance

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7522
Author(s):  
Linqing Bai ◽  
Pengcheng Zhang ◽  
Zulfiqar Ahmad Khan
Keyword(s):  
Friction Torque ◽  
Contact Friction ◽  
Textured Surface ◽  
Face Seal ◽  
Textured Surfaces ◽  
Positive Effects ◽  
Mechanical Face Seal ◽  
Gas Face Seal ◽  
Hydrodynamic Effects ◽  
The Impact

Seal performance of a novel gas mechanical face seal with semi salix leaf textures was introduced and theoretically investigated with the purpose of enhancing hydrostatic and hydrodynamic opening performance. First, a theoretical model of a laser surface textured gas mechanical face seal with semi salix leaf textures was developed. Second, the impact of operating and texturing parameters on open force, leakage, and friction torque was numerically investigated and has been discussed based on gas lubrication theory. Numerical results demonstrate that the semi salix leaf textured gas face seal has larger hydrostatic and hydrodynamic effects than the semi ellipse textured seal because of the effect of the inlet groove. All semi salix leaf textured surfaces had better open performance than the semi ellipse textured surface, which means that the inlet groove plays an important role in improving open performance and consequently decreasing contact friction during the start-up stage. Texturing parameters also influenced the seal performance of thee semi salix leaf textured gas face seal. When the inclination angle was 50°, the radial proportion of the inlet groove was 0.8, the dimple number was 9, and the open force resulted in the maximum value. This research has demonstrated the positive effects of the applications of a semi salix leaf textured gas mechanical face seal that combines the excellent hydrostatic and hydrodynamic effects of groove texture and the excellent wear resistance of microporous textures.

scholarly journals ECOLOGICALLY BASED APPROACH TO COASTAL DEFENCE DESIGN AND PLANNING

2011 ◽  
Vol 1 (32) ◽  
pp. 50 ◽  
Author(s):  
Barbara Zanuttigh ◽  
Inigo Losada ◽  
Richard Thompson
Keyword(s):  
Standard Procedure ◽  
Combined Method ◽  
Ecological Data ◽  
Positive Effects ◽  
Environmental Friendly ◽  
As Species ◽  
Hydrodynamic Effects ◽  
The Impact ◽  
Selection Of

Sustainability of coastal areas requires the development of a standard procedure for the selection of equitable defence solutions and the design optimization of existing defences in order to minimize the impact on the environment and maximize positive effects such as species biodiversity and structure colonization. The aim of this paper is to propose a combined method, based on numerical simulations and on collection of ecological data in the field, to provide indications for an environmental friendly construction of breakwaters. This method is applied and tested against the case study of Elmer, UK, where information on existing species and their abundance related to hydrodynamic effects induced by the breakwaters

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

2017 ◽  
Vol 232 (6) ◽  
pp. 732-748
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Dynamic Modeling ◽  
Equations Of Motion ◽  
Center Of Mass ◽  
Contact Friction ◽  
Face Seal ◽  
Transient Operation ◽  
Angular Misalignment ◽  
The Face ◽  
Mechanical Face Seal ◽  
Constitutive Components

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.

The Influence of Surface Patterning on the Thermal Properties of Textured Thrust Bearings

2017 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Surrogate Model ◽  
Load Capacity ◽  
Computing Time ◽  
Friction Torque ◽  
Fluid Film ◽  
Design Parameters ◽  
Textured Surface ◽  
Textured Surfaces ◽  
Thrust Bearings ◽  
Lubricated Contacts

Contact performance can be enhanced by using textured surfaces. These are also found to have influences on lubricated contacts. The effects of textured surface on lubricated contacts has been widely investigated over the past twenty years. The property of lubricated contacts has been found to play an important role on the performance of fluid film bearings. According to the previous study, the introduction of dimples on the inner surfaces of parallel thrust bearings can improve the load capacity and reduce the friction. Since the friction loss is mostly converted to thermal energy and then increase the temperature, textured surface is expected to have a positive effect on the thermal property of the thrust bearings. A procedure to find the optimal partially texture geometry, which minimize the temperature inside the bearing film, is presented in this study. A parallel sector-pad thrust bearing is simulated by a 3D computational fluid dynamics model. The stationary surface of the bearing is textured with dimples while the rotor surface is flat. The results of the baseline model have been validated by the experimental data from the literature. The temperature and pressure distribution on the bearing pad are presented. In this study, two types of dimples, including rectangular and elliptical, are compared together. A parametric study is conducted to investigate the influence of the texture geometries. In this study, the length of the major axis (width), the length of the minor axis (length), dimple depth, circumferential space between two dimples, radial space between two dimples, radial extend and circumferential extend are selected as design parameters. A surrogate model is used to reduce the computing time of CFD analysis. Based on the surrogate model, a multi-objective optimization scheme is used to navigate the design space and find the optimal texture structure that provides a lower maximal temperature inside the fluid film, higher load capacity, and lower friction torque. The optimal radial extent of the texture is around 80% of the pad radial length for both cases. The optimal length of the elliptical dimples in the circumferential direction is about 30% larger than the value of the rectangular dimples. In the final optimal design, the maximal temperature reduces 1.1% and 1.3% for rectangular and elliptical dimples while the load capacities are maintained at the same level.

Near-Contact Laser Surface Textured Dry Gas Seals

2004 ◽  
Vol 126 (4) ◽  
pp. 788-794 ◽  
Author(s):  
A. D. McNickle ◽  
I. Etsion
Keyword(s):  
High Speed ◽  
Friction Torque ◽  
Laser Surface ◽  
Face Seal ◽  
Lower Face ◽  
Turbine Engine ◽  
Potential Benefits ◽  
Gas Seals ◽  
Gas Face Seal ◽  
Face Temperature

A new concept of a near-contact gas seal is experimentally investigated. A simulated gas face seal for a high-speed gas turbine engine is used for the investigation. A baseline conventional contacting-type seal is compared with an identical seal that was laser surface textured (LST) to turn it into a near-contact gas seal. Results show the potential benefits of the new concept in terms of smoother running, lower friction torque, and lower face temperature at 12,000 RPM over a range of face loading.

scholarly journals Effects of the shape of surface micropores on the performance of a face seal

1970 ◽  
Vol 38 ◽  
pp. 25-31 ◽  
Author(s):  
M Mahbubur Razzaque ◽  
M Tanvir Rahman Faisal
Keyword(s):  
Pore Size ◽  
Hydrodynamic Pressure ◽  
Control Area ◽  
Friction Torque ◽  
Face Seal ◽  
Cylindrical Pores ◽  
Face Seals ◽  
Mechanical Face Seal ◽  
Performance Surface ◽  
Pore Depth

 A mathematical model is developed for the prediction of performance of a mechanical face seal with regular microstructure on its surface in the form of pores. Pores of right circular cylindrical, hemispherical and exponential profiles have been considered. A two dimensional steady state Reynolds equation is solved to get the hydrodynamic pressure distribution on an imaginary control area around a single pore. Consequently, the seal performance parameters such as seal clearance, friction torque and leakage across the seal are calculated. A parametric analysis is done for right circular cylindrical pores for a range of sealed pressure, pore size and pore ratio. Increase of pore ratio improves the seal performance up to a pore ratio of 12%, beyond which no improvement of the seal performance is possible. The optimum pore size depends on the sealed pressure as well as on the pore profile. Through a comparison of the performance of face seals with different pore profiles hemispherical pores are recommended for enhancement of performance. For any pore profile, the seal performance improves with the increase of pore depth as long as the depth is less than 1.5 times of the pore radius. Keywords: Face seal, seal performance, surface micropore, pore profile, pore ratio.DOI: 10.3329/jme.v38i0.897 Journal of Mechanical Engineering Vol.38 Dec. 2007 pp.25-31  

Income Diversification and Bank Efficiency in Vietnam

2017 ◽  
pp. 52-67
Author(s):  
Sang Nguyen Minh
Keyword(s):  
Regression Model ◽  
Commercial Banks ◽  
Banking System ◽  
Operational Efficiency ◽  
Commercial Banking ◽  
Tobit Regression ◽  
Income Diversification ◽  
Positive Effects ◽  
Study Results ◽  
The Impact

This study uses the DEA (Data Envelopment Analysis) method to estimate the technical efficiency index of 34 Vietnamese commercial banks in the period 2007-2015, and then it analyzes the impact of income diversification on the operational efficiency of Vietnamese commercial banks through a censored regression model - the Tobit regression model. Research results indicate that income diversification has positive effects on the operational efficiency of Vietnamese commercial banks in the research period. Based on study results, in this research some recommendations forpolicy are given to enhance the operational efficiency of Vietnam’s commercial banking system.

Impact of Digitalization on Service Work in Knowledge-Intensive Business Services: An Empirical Study in Tax Consultancies

2019 ◽  
Vol 3 (4) ◽  
pp. 209-222
Author(s):  
Philipp K. Görs ◽  
Henning Hummert ◽  
Anne Traum ◽  
Friedemann W. Nerdinger
Keyword(s):  
Work Engagement ◽  
Service Work ◽  
Psychological Consequences ◽  
Business Services ◽  
Knowledge Intensive Business Services ◽  
Positive Effects ◽  
Knowledge Intensive ◽  
The Impact ◽  
Positive Effect ◽  
Special Case

Digitalization is a megatrend, but there is relatively little knowledge about its consequences for service work in general and specifically in knowledge-intensive business services (KIBS). We studied the impact of digitalization on psychological consequences for employees in tax consultancies as a special case of KIBS. We compare two tax consulting jobs with very different job demands, those of tax consultants (TCs) and assistant tax consultants (ATCs). The results show that the extent of digitalization at the workplace level for ATCs correlates significantly positively with their job satisfaction. For TCs, the same variable correlates positively with their work engagement. These positive effects of digitalization are mediated in the case of ATCs by the impact on important job characteristics. In the case of TCs, which already have very good working conditions, the impact is mediated by the positive effect on self-efficacy. Theoretical and practical consequences of these results are discussed.

HOW CLIMATE CHANGE CAN INFLUENCE THE AGRICULTURE IN UKRAINE: A REVIEW

2020 ◽  
Author(s):  
N. Maidanovych ◽  
Keyword(s):  
Climate Change ◽  
Crop Yields ◽  
Soil Surface ◽  
Winter Period ◽  
Negative Consequences ◽  
Resource Saving ◽  
Impact Of Climate Change ◽  
Positive Effects ◽  
Average Annual Temperature ◽  
The Impact

The purpose of this work is to review and analyze the main results of modern research on the impact of climate change on the agro-sphere of Ukraine. Results. Analysis of research has shown that the effects of climate change on the agro-sphere are already being felt today and will continue in the future. The observed climate changes in recent decades have already significantly affected the shift in the northern direction of all agro-climatic zones of Europe, including Ukraine. From the point of view of productivity of the agro-sphere of Ukraine, climate change will have both positive and negative consequences. The positives include: improving the conditions of formation and reducing the harvesting time of crop yields; the possibility of effective introduction of late varieties (hybrids), which require more thermal resources; improving the conditions for overwintering crops; increase the efficiency of fertilizer application. Model estimates of the impact of climate change on wheat yields in Ukraine mainly indicate the positive effects of global warming on yields in the medium term, but with an increase in the average annual temperature by 2 ° C above normal, grain yields are expected to decrease. The negative consequences of the impact of climate change on the agrosphere include: increased drought during the growing season; acceleration of humus decomposition in soils; deterioration of soil moisture in the southern regions; deterioration of grain quality and failure to ensure full vernalization of grain; increase in the number of pests, the spread of pathogens of plants and weeds due to favorable conditions for their overwintering; increase in wind and water erosion of the soil caused by an increase in droughts and extreme rainfall; increasing risks of freezing of winter crops due to lack of stable snow cover. Conclusions. Resource-saving agricultural technologies are of particular importance in the context of climate change. They include technologies such as no-till, strip-till, ridge-till, which make it possible to partially store and accumulate mulch on the soil surface, reduce the speed of the surface layer of air and contribute to better preservation of moisture accumulated during the autumn-winter period. And in determining the most effective ways and mechanisms to reduce weather risks for Ukrainian farmers, it is necessary to take into account the world practice of climate-smart technologies.

INFLUENCE OF GREENHOUSE SHADING AND DIFFERENT NUTRIENT MANAGEMENT PRACTICES ON ALLEVIATING HEAT STRESS, IMPROVING PLANT NUTRIENTS STATUS, FLOWERING GROWTH AND YIELD OF TOMATO

2020 ◽  
Vol 51 (4) ◽  
pp. 1001-1014
Author(s):  
Sulaiman & Sadiq
Keyword(s):  
Heat Stress ◽  
Management Practices ◽  
Nutrient Management ◽  
Block Design ◽  
Nutrient Status ◽  
Growth And Yield ◽  
Reproductive Growth ◽  
Positive Effects ◽  
Nutrition Programs ◽  
The Impact

The experiment was conducted in a greenhouse during 2017 and 2018 growing seasons to evaluate the impact of the shading and various nutrition programs on mitigating heat stress, reducing the use of chemical minerals, improving the reproductive growth and yield of tomato plant. Split-plot within Randomized Complete Block Design (RCBD) with three replications was conducted in this study. Shading factor was allocated in the main plots and the nutrition programs distributed randomly in the subplots. Results indicate that shading resulted in the decrease of daytime temperature by 5.7˚C as an average for both seasons; thus a significant increasing was found in leaf contents of macro nutrients (Nitrogen, Phosphorous, and Potassium), and micro nutrients (Iron, Zinc and Boron), except the Iron content in 2018 growing season. Furthermore, shading improved significantly the reproductive growth and tomato yield. Among the plant nutrition programs, the integrated nutrient management (INM) including the application of organic substances, bio inoculum of AMF and 50% of the recommended dose of chemical fertilizers; lead to the enhancement of nutrients content, reproductive characteristics and plant yield. Generally, combination of both shading and INM showed positive effects on plants nutrient status and persisting balance on tomato flowering growth and fruits yield.

The Impact of Ultraviolet Radiation on Barrier Function in Human Skin: Molecular Mechanisms and Topical Therapeutics

2019 ◽  
Vol 25 (40) ◽  
pp. 5503-5511 ◽  
Author(s):  
Abdulaziz Alhasaniah ◽  
Michael J. Sherratt ◽  
Catherine A. O'Neill
Keyword(s):  
Ultraviolet Radiation ◽  
Barrier Function ◽  
Molecular Mechanisms ◽  
Transepidermal Water Loss ◽  
Protective Effects ◽  
Barrier Dysfunction ◽  
Epidermal Barrier ◽  
Positive Effects ◽  
Terrestrial Mammals ◽  
The Impact

A competent epidermal barrier is crucial for terrestrial mammals. This barrier must keep in water and prevent entry of noxious stimuli. Most importantly, the epidermis must also be a barrier to ultraviolet radiation (UVR) from the sunlight. Currently, the effects of ultraviolet radiation on epidermal barrier function are poorly understood. However, studies in mice and more limited work in humans suggest that the epidermal barrier becomes more permeable, as measured by increased transepidermal water loss, in response UVR, at doses sufficiently high to induce erythema. The mechanisms may include disturbance in the organisation of lipids in the stratum corneum (the outermost layer of the epidermis) and reduction in tight junction function in the granular layer (the first living layer of the skin). By contrast, suberythemal doses of UVR appear to have positive effects on epidermal barrier function. Topical sunscreens have direct and indirect protective effects on the barrier through their ability to block UV and also due to their moisturising or occlusive effects, which trap water in the skin, respectively. Some topical agents such as specific botanical extracts have been shown to prevent the loss of water associated with high doses of UVR. In this review, we discuss the current literature and suggest that the biology of UVR-induced barrier dysfunction, and the use of topical products to protect the barrier, are areas worthy of further investigation.

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