A Simple Model for Scuffing Risk Evaluation of Point Contact Under Mixed Lubrication

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Zhijian Wang ◽  
Qingtao Yu ◽  
Xuejin Shen ◽  
Xiaoyang Chen
Keyword(s):  
Surface Roughness ◽  
Point Contact ◽  
High Viscosity ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Large Radius ◽  
Film Properties ◽  
Boundary Film ◽  
Boundary Films ◽  
High Viscosity Oil

This paper developed a point-contact mixed lubrication (ML) model, incorporating thermal effect, the asperity elasto-plastic deformation and the boundary film properties, to evaluate the relative severity of contact condition. Then, based on the integrity of boundary films and the sharp increase of the friction coefficient, the possibility of the occurrence of scuffing was evaluated. The model was verified with published experimental data. A systematic parametric analysis was made to investigate the influences of surface roughness, contact geometry, and the lubricant properties on contact performance. The results suggest that low surface roughness and high-quality boundary film can effectively improve the scuffing resistance under current operating conditions, while high-viscosity oil and large-radius curvature are not as much effective especially when the components work under high-sliding and high–temperature conditions.

Relating Surface Roughness to Subsurface Stress

2005 ◽  
Author(s):  
A. Martini ◽  
S. B. Liu ◽  
B. Escoffier ◽  
Q. Wang
Keyword(s):  
Surface Roughness ◽  
Stress Field ◽  
Point Contact ◽  
Surface Characteristics ◽  
Operating Conditions ◽  
Surface Design ◽  
Dry Contact ◽  
Subsurface Stress ◽  
The Relationship ◽  
Machined Surfaces

Understanding and anticipating the effects of surface roughness on subsurface stress in the design phase can help ensure that performance and life requirements are satisfied. The specific approach taken in this work to address the goal of improved surface design is to relate surface characteristics of real, machined surfaces to subsurface stress fields for dry contact. This was done by digitizing machined surfaces, simulating point contact numerically, calculating the corresponding subsurface stress field, and then relating stress results back to the surface. The relationship between surface characteristics and subsurface stress is evaluated using several different approaches including analyses of trends identified through stress field visualization and extraction of statistical data. One such approach revealed a sharp transition between cases in which surface characteristics dominated the stress field and those in which bulk, or global contact effects dominated the stress. This transition point was found to be a function of the contact operating conditions, material properties, and most interestingly, the roughness of the surface.

Numerical Solution of Mixed Thermal Elastohydrodynamic Lubrication in Point Contacts With Three-Dimensional Surface Roughness

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Xiaopeng Wang ◽  
Yuchuan Liu ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Thickness Variation ◽  
Wide Range ◽  
Film Lubrication

Elastohydrodynamic lubrication (EHL) is a common mode of fluid-film lubrication in which many machine elements operate. Its thermal behavior is an important concern especially for components working under extreme conditions such as high speeds, heavy loads, and surfaces with significant roughness. Previous thermal EHL (TEHL) studies focused only on the cases with smooth surfaces under the full-film lubrication condition. The present study intends to develop a more realistic unified TEHL model for point contact problems that is capable of simulating the entire transition of lubrication status from the full-film and mixed lubrication all the way down to boundary lubrication with real machined roughness. The model consists of the generalized Reynolds equation, elasticity equation, film thickness equation, and those for lubricant rheology in combination with the energy equation for the lubricant film and the surface temperature equations. The solution algorithms based on the improved semi-system approach have demonstrated a good ability to achieve stable solutions with fast convergence under severe operating conditions. Lubricant film thickness variation and temperature rises in the lubricant film and on the surfaces during the entire transition have been investigated. It appears that this model can be used to predict mixed TEHL characteristics in a wide range of operating conditions with or without three-dimensional (3D) surface roughness involved. Therefore, it can be employed as a useful tool in engineering analyses.

On the Behavior of Friction in Lubricated Point Contact With Provision for Surface Roughness

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
H. Sojoudi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Type Curve ◽  
Lift Off

This paper presents a simple approach to predict the behavior of friction coefficient in the sliding lubricated point contact. Based on the load-sharing concept, the total applied load is supported by the combination of hydrodynamic film and asperity contact. The asperity contact load is determined in terms of maximum Hertzian pressure in the point contact while the fluid hydrodynamic pressure is calculated through adapting the available numerical solutions of elastohydrodynamic lubrication (EHL) film thickness formula for smooth surfaces. The simulations presented cover the entire lubrication regime including full-film EHL, mixed-lubrication, and boundary-lubrication. The results of friction, when plotted as a function of the sum velocity, result in the familiar Stribeck-type curve. The simulations are verified by comparing the results with published experimental data. A parametric study is conducted to investigate the influence of operating condition on the behavior of friction coefficient. A series of simulations is performed under various operating conditions to explore the behavior of lift-off speed. An equation is proposed to predict the lift-off speed in sliding lubricated point contact, which takes into account the surface roughness.

Measurement and Modelling of Boundary Film Properties of Polymeric Lubricant Additives

1996 ◽  
Vol 210 (1) ◽  
pp. 1-15 ◽  
Author(s):  
G Guangteng ◽  
M Smeeth ◽  
P M Cann ◽  
H A Spikes
Keyword(s):  
Polymer Solutions ◽  
Control Volume ◽  
Point Contact ◽  
Solid Surfaces ◽  
Bulk Solution ◽  
Surface Layers ◽  
Film Properties ◽  
Volume Analysis ◽  
Boundary Film ◽  
20 Nm

Experimental work using ultrathin film interferometry has shown that some polymer solutions in oil form much thicker films at slow speeds in rolling, concentrated contacts than predicted from elastohydrodynamic (EHD) theory. This behaviour can be interpreted as resulting from the polymers forming adsorbed, surface layers of enhanced concentration on the two solid surfaces. Such layers, which are typically 20 nm thick, would be significantly more viscous that the bulk solution and thus produce thicker EHD films. This concept has been supported by modelling the elastohydrodynamic point contact using control volume analysis with a layered surface viscosity. The film thickness behaviour predicted computationally using this technique is quite similar to that found experimentally using polymer solutions.

scholarly journals Prospects for production of viscous fluid by electric shaft-driven vane pumps (ESP)

2020 ◽  
Vol 21 (1) ◽  
pp. 66-80
Author(s):  
Sharifjan R. Ageyev ◽  
Evgeny Yu. Druzhinin ◽  
Rustam S. Kamaletdinov
Keyword(s):  
Viscous Fluid ◽  
Oil Production ◽  
High Viscosity ◽  
Operating Conditions ◽  
Speed Regulation ◽  
Design Changes ◽  
Electric Shaft ◽  
Design Selection ◽  
Special Approach ◽  
High Viscosity Oil

The article deals with the prospects of developing significant world reserves of high-viscosity oil. Its production requires specific equipment and technologies, selection of efficient equipment, as well as a special approach in its operation. At the same time it is necessary to take into account the influence of high viscosity on the main characteristics of pumps and on the operating conditions of the equipment in the well. The reasons for unstable operation of the ESP at start-up after long stops are described. The methods of recalculation of characteristics of pumps for oil production of common design are offered. Some results of researches of such pumps on viscous liquid and recommendations on calculation of a flowing part are provided. The possibilities of pumps with open impeller stages and with increased shaft speeds are determined. Additional reasons for decreasing the characteristics of the pump on the viscous fluid, results of the test of stage assembly with measurement of average circumferential components of flow rates at different viscosity of the pumped fluid are given. The possibility of using helico-axial pumps is also considered. Application of modern programs and methods of equipment selection and operation, ESP rotor speed regulation, liquid temperature regulation in tubing and automation of the whole oil production process is recommended. Possible design changes of the ESP in the process of tubing production for the purpose of increasing their efficiency in comparison with the serial pumps are specified. The article can be useful for specialists in design, selection and operation of equipment for high-viscosity oil production.

scholarly journals Analysis of the process of corrosion destruction of settling tanks for preparation of high-viscosity oil to transport through main oil pipelines

2019 ◽  
pp. 52-58
Author(s):  
Dmitry V. Novitskiy
Keyword(s):  
Oil And Gas ◽  
Salt Content ◽  
Settling Tank ◽  
High Viscosity ◽  
Operating Conditions ◽  
Metal Corrosion ◽  
Factors Affecting ◽  
Internal Surfaces ◽  
Oil Pipelines ◽  
High Viscosity Oil

Most of accidents and failures of vertical steel tanks are related to metal corrosion of their shells and equipment. The choice of optimal corrosion protection to extend the life of such tanks is impossible without an understanding of the mechanisms of its origin and development, as well as the degree of influence of operational factors on these mechanisms.Of particular interest is the study of corrosion processes taking place in tanks to prepare for the transport of high-viscosity oils operating in the specific conditions of the Far North. The complex effect of factors such as temperature, total salt content of bottom water, the concentration of corrosion inhibitors, demulsifiers, and mechanical impurities on the rate of corrosion processes is not fully understood to date.This article analyzes the process of corrosion destruction of settling tanks for the preparation of high-viscosity oil to transport through main oil pipelines using the example of the RVS-5000 of the park of input tanks of the Yareganeft oil and gas department. Analysis of operating conditions made it possible to identify factors affecting corrosion processes and to identify potentially the most dangerous zones of contact between media entering the reservoir and the shell metal, the bottom and roof of the tank. The study have showed that the greatest interest is the study of the effect of the presence of mechanical impurities in the fluid supplied to the settling tank on the intensity of corrosion processes on the internal surfaces of the tank in potentially dangerous areas.

The behaviour of heavily loaded line contacts with transverse roughness

1999 ◽  
Vol 213 (4) ◽  
pp. 309-320 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Surface Roughness ◽  
Full Range ◽  
Numerical Results ◽  
Operating Conditions ◽  
Entrainment Velocity ◽  
Original Surface ◽  
Line Contacts ◽  
Transverse Roughness ◽  
Inlet Length

In heavily loaded, piezoviscous contacts the surface roughness tends to be flattened inside the conjunction by any relative sliding of the surfaces. However, before it is flattened, the roughness affects the inlet to the contact, producing clearance variations there. These variations are then convected through the contact, at the entrainment velocity, producing a clearance distribution that differs from the original surface. The present paper explores this behaviour and establishes how the amplitude of the convected clearance varies with wavelength and operating conditions. It is shown that the primary influence is the ratio of the wavelength to the inlet length of the conjunction. Where this ratio is large, the roughness is smoothed and there is little variation in clearance under the conjunction. Where the ratio is small, significant variations in clearance may occur but the precise amplitude and phasing depend on the ratio of slide to roll velocities and on the value of a piezoviscous parameter, c. The numerical results agree closely with existing solutions but extend these to cover the full range of operating conditions.

A Transient 3D CFD Model of a Progressive Cavity Pump

2016 ◽  
Author(s):  
K. R. Mrinal ◽  
Md. Hamid Siddique ◽  
Abdus Samad
Keyword(s):  
Oil And Gas ◽  
Complex Geometry ◽  
Transient Behavior ◽  
Oil And Gas Industry ◽  
High Viscosity ◽  
Solid Content ◽  
Operating Conditions ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Flow Variables

A progressive cavity pump (PCP) is a positive displacement pump and has been used as an artificial lift method in the oil and gas industry for pumping fluid with solid content and high viscosity. In a PCP, a single-lobe rotor rotates inside a double-lobe stator. Articles on computational works for flows through a PCP are limited because of transient behavior of flow, complex geometry and moving boundaries. In this paper, a 3D CFD model has been developed to predict the flow variables at different operating conditions. The flow is considered as incompressible, single phase, transient, and turbulent. The dynamic mesh model in Ansys-Fluent for the rotor mesh movement is used, and a user defined function (UDF) written in C language defines the rotor’s hypocycloid path. The mesh deformation is done with spring based smoothing and local remeshing technique. The computational results are compared with the experiment results available in the literature. Thepump gives maximum flowrate at zero differential pressure.

Sign in / Sign up

Export Citation Format

Share Document