scholarly journals Analysis of The Influence of The Critical Speed of Thermoelastic Instability of Transfer Case on The Torque Transmission

2021 ◽  
Author(s):  
Yu Ming WANG ◽  
Liqing CHEN ◽  
Xiutian LIANG ◽  
Hongliang LI
Keyword(s):  
Critical Speed ◽  
Friction Pair ◽  
Stable Region ◽  
Lubricating Oil ◽  
Engineering Practice ◽  
Oil Viscosity ◽  
Thermoelastic Instability ◽  
Oil Film ◽  
Transfer Case ◽  
Torque Transmission

Abstract Based on the thermoelastic instability theory, the variation trend of film thickness on the surface of transfer case friction pair is studied, and the basic process in which the thickness of lubricating oil film changes due to thermoelastic instability was obtained. According to this process, the critical speed of transfer case friction pair is used to reflect transfer torque stability. Based on above, firstly, the dynamic simulation model of the transfer case is established from which the dynamic characteristic equation of the transfer case under the combined action of asperity torque and viscous torque is obtained. Secondly, according to the result that the thickness of the transfer case lubricating oil film is affected by the joint action of lubricating oil pressure, contact pressure and thermal expansion, the condition of thermoelastic instability of the transfer case torque transmission is discussed. The result shows that the critical speed of the thermoelastic instability increases correspondingly with the increase of the thickness of the oil film. The critical curve divides the engagement process into the stable region at the upper part of the curve and the unstable region at the lower part of the curve, so as to calculate the thermoelastic instability region of the torque transfer of the transfer case. Finally, in order to further analyze the influence of thermoelastic instability on the characteristics of the transfer case, three factors, namely the surface roughness of the friction plate, the lubricating oil viscosity and the thermal conductivity of the dual steel disc, are mainly selected for analysis, and the thermoelastic instability is taken into account. The conclusion is expected to be used in the engineering practice of torque distribution control of the transfer case.

Numerical Simulation on Oil-Flow-State of Gap Oil Film in Sector Cavity Multi-Pad Hydrostatic Thrust Bearing

2010 ◽  
Vol 37-38 ◽  
pp. 743-747
Author(s):  
Xiao Dong Yu ◽  
Xiu Li Meng ◽  
Hui Jiang ◽  
Xiao Zhong Lou ◽  
Bo Wu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Laminar Flow ◽  
Critical Speed ◽  
Thrust Bearing ◽  
Lubricating Oil ◽  
Good Effect ◽  
Critical Flow ◽  
Flow State ◽  
Oil Film ◽  
Oil Flow

Hydrostatic thrust bearing lubrication is significantly affected by the oil flow state of gap oil film, but it can not be measured by experiment and analysis. For this problem, the oil flow state of gap oil film in sector cavity multi-pad hydrostatic thrust bearing during rotation was simulated by using computational fluid dynamics, lubricating theory, and Finite Element Method. Laminar model and κ-ε turbulence model were adopted to model incompressible steady equations, and the equations were discreted by using Finite Volume Method and Second-order Finite Difference. By comparing the calculated results of numerical simulation and semi-empirical theoretical equation, the numerical simulation is proved feasible in oil film state analysis parameter prediction, which can overcome the deficiency of single model and get good effect. Streamlines and velocity vectors show that the lubricating oil flow in the resistive oil edges and oil cavities are laminar flow under the conditions of speed and flow in less than a certain value, while the flow and speed are more than a certain value, the lubricating oil flow in the resistive oil edges is also laminar flow, but the lubricating oil flow in the oil cavities is turbulent flow, then determines critical flow and critical speed. The critical flow and critical speed were determined, it provides a theoretical basis of the temperature field and thermal field deformation calculation.

scholarly journals Viscosity Effect on Stiffness of Non-conventional (Five Tilted Pads) Journal Bearing

2018 ◽  
Vol 25 (3) ◽  
pp. 53-57
Author(s):  
Mohammed Oawed Atteaa Alhassany ◽  
Ali Khalid Aldulaimy
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Cross Coupling ◽  
High Viscosity ◽  
Lubricating Oil ◽  
Coupling Coefficients ◽  
Oil Viscosity ◽  
Viscosity Change ◽  
Oil Film ◽  
Stiffness Coefficients

In this tribological study, we highlight the effect of lubricating oil viscosity in the Multi-pads hydrodynamic journal bearings generate important improvement in characteristics of stiffness and stability in the high speed turbomachines. Depending on viscosity of oil film (three values) variation for five tilted pads bearing, each pad is pivoted and is facilitated to be tilted with small angles, by using Matlab program, we calculate the oil film thickness for convergence layer. We applied Reynold’s equation and solved it’s numerically by using finite difference method with 5 nodes technique to find the pressure distributed on each node in the mesh of tilted pad, then calculate stiffness coefficients. Results show that there is clear effect on stiffens with viscosity change. The increase in value of Krr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is14.33 MN/m, while the increase in Krr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 11.37 MN/m. the increase in value the of Kss (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is5.921 MN/m, while increase in Kss value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is9.55 MN/m respectively. the increase in value of Ksr (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) is 8.95 MN/m, while the increase in Ksr value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is 14.41 MN/m respectively. the increase in value of Krs (for n = 0.3) between viscosity (0.04 Pas. s) and viscosity (0.058 Pas. s) are 5.08 MN/m, while the increase in Krs value between viscosity (0.058 Pas. s) and viscosity (0.087 Pas. s) is8.19 MN/m respectively. The values of the dominate principal coefficients Krr is greater than that of Ksr, also The values of the principal coefficients Kss is greater than that of cross coupling Krs for all values of viscosity that studied. From this result, we can conclude the side effect of cross coupling coefficients (Ksr ,Krs) can be overcome by great values for principal coefficient (Krr, Kss) respectively, so we can get good improvement instability for this bearing by variation the viscosity. After that, we regarded to use high viscosity lubricant in multi-pad journal bearing to improve the performance and stability by controlling the stiffness coefficients.

The Simple Model of the Oil Film Thickness between Piston Ring and Cylinder

2010 ◽  
Vol 97-101 ◽  
pp. 1239-1242
Author(s):  
De Liang Liu ◽  
Hui Biao Lu ◽  
C.G. Sun
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engine ◽  
Piston Ring ◽  
Reynolds Equation ◽  
Combustion Engine ◽  
Friction Pair ◽  
Internal Combustion ◽  
Theoretical Research ◽  
Lubricating Oil ◽  
Oil Film

Piston ring-cylinder is one of the most important friction pair of internal combustion engine，the lubricating state between them has decided internal combustion engine lubrication quality. So the theoretical research to the lubricating characteristics of the piston-ring group, especially the calculation of the lubricating oil film thickness is very important. The oil film thickness between piston-ring and cylinder is studied by calculation method. The calculation program is developed with average Reynolds equation taken the surface topography, viscosity-temperature effect, viscosity-pressure effect, extrusion effect and other factors into account. The position of oil outlet point is preinstalled, the full lubrication is assumed, and the Reynolds equation is solved by full pivot element gausses elimination approach, so the iterative course and calculation workload are reduced, and a great lot of the calculating time is saved, the oil film thickness of full period can be more accurately predicted by the ordinary PC within 30 minutes, which can supply quick effective evidence for next calculation and analysis.

Study on oil starvation at the oil seal edge of the oil film of hydrostatic bearing with double rectangular cavity

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shiqian Ni ◽  
Yanqin Zhang ◽  
Zhen Quan
Keyword(s):  
Temperature Rise ◽  
Friction Pair ◽  
Operating Conditions ◽  
Rectangular Cavity ◽  
Lubricating Oil ◽  
Heat Accumulation ◽  
Content Type ◽  
Oil Film ◽  
Hydrostatic Bearing ◽  
Side Flow

Purpose When the clearance oil film of hydrostatic bearing friction pair is in critical lubrication state, the phenomenon of zero flow of local lubricating oil will aggravate the oil film temperature rise, which needs to be solved. Design/methodology/approach In this paper, the critical lubrication parameter equation and the oil film temperature rise mathematical model are derived for the new type q1-205 double rectangular cavity hydrostatic bearing. Based on a combination of theoretical analysis, simulation and experimental verification, this paper analyzes the flow characteristics and temperature rise characteristics of the lubricating oil when the hydrostatic bearing is in a critical lubrication state under different operating conditions and finally obtains the critical lubrication state of the oil film. Findings This study found that the numerical simulations and the derived formulas agree with the results. When the oil film is in critical lubrication, the cross-section side flow of the oil side is almost zero. The heat cannot be taken away in time, resulting in the local temperature rise of the oil film, which causes serious heat accumulation. Originality/value It is concluded that the operating condition parameters corresponding to the critical lubrication state provide a theoretical basis for the selection of actual hydrostatic bearing operating conditions, which is of great scientific significance.

Analysis on Influence of Oil Film Thickness on Temperature Field of Heavy Hydrostatic Bearing in Variable Viscosity Condition

2011 ◽  
Vol 239-242 ◽  
pp. 1418-1421 ◽  
Author(s):  
Yan Qin Zhang ◽  
Xiao Qiu Xu ◽  
Xiao Dong Yang ◽  
Hong Mei Li ◽  
Hui Jiang ◽  
...  
Keyword(s):  
Temperature Field ◽  
Film Thickness ◽  
Temperature Rise ◽  
Variable Viscosity ◽  
Lubricating Oil ◽  
Engineering Practice ◽  
Flow State ◽  
Oil Film ◽  
Hydrostatic Bearing ◽  
Nc Machine

According to the problem of the influence of oil film thickness on temperature rise for heavy hydrostatic thrust bearing during operation， build viscosity-temperature equation of lubricating oil film and mathematics model of oil film temperature rise of heavy hydrostatic bearing with multiple oil pads, simulate the temperature field of hydrostatic bearing with sector cavity under various oil film thickness using FVM(finite volume method), and reveal the influence law of oil film thickness of temperature rise for hydrostatic bearing. The results show that temperature distribution of hydrostatic bearing is much the same under various oil film thicknesses, but the influence of oil film thickness of temperature rise for hydrostatic bearing is greater. The results of numerical calculations actually response flow state inside hydrostatic bearing ，offer theoretical foundation for the design of hydrostatic bearing in engineering practice, and have important significance in improving operation stability of NC machine.

Research and Development of Overloading Velocity Jump Line Contact Elastohydrodynamic Lubrication Testbed

2015 ◽  
Vol 713-715 ◽  
pp. 182-186
Author(s):  
Nai Ming Miao
Keyword(s):  
Working Conditions ◽  
Friction Pair ◽  
Elastohydrodynamic Lubrication ◽  
Lubricating Oil ◽  
Glass Block ◽  
Contact Friction ◽  
Line Contact ◽  
Oil Film ◽  
Experimental Apparatus ◽  
Velocity Jump

To research the lubricating property of line contact elastohydrodynamic lubrication under the working conditions of overloading velocity jump, based on the optic elastohydrodynamic experimental apparatus developed by the research group, an measuring equipment applicable to the oil film thickness and shape under the condition of overloading velocity jump is designed and developed. This testbed is mainly composed of glass block reciprocating motion system, ball or roller rotary rolling system, loading system, speed regulating system, light source system and image acquisition system. The motion part replaces the slider-crank mechanism with kad-screw mechanism and is driven by stepper motor, so as to realize the different working conditions of velocity jump. The developed platform was adopted to carry out the velocity jump line contact elastohydrodynamic lubrication test by the driving of the stepping motor, investigating the influence of line contact friction pair on the lubricating oil film at the moment of acceleration under the overloading working condition.

Summary of Research on Oil Film Temperature Characteristic of Hydrostatic and Hydrodynamic Thrust Bearings

2021 ◽  
Vol 14 ◽  
Author(s):  
Yanan Feng ◽  
Xiaodong Yu ◽  
Zelin Han ◽  
Shihao Li ◽  
Bangyao Tang ◽  
...  
Keyword(s):  
Temperature Rise ◽  
Thrust Bearing ◽  
Friction Pair ◽  
Dynamic Pressure ◽  
Operational Reliability ◽  
Lubricating Oil ◽  
Research Directions ◽  
Oil Film ◽  
Specific Research ◽  
Thrust Bearings

Background: In order to explore the temperature rise and distribution of the micro-gap lubricating oil film of the hydrostatic and hydrodynamic thrust bearing, further solve the problem of thermal deformation of the friction pair of the hydrostatic and hydrodynamic support and improve the operation accuracy and stability of the hydrostatic and hydrodynamic thrust bearing. Objective: Combined with the theory of dynamic and static pressure bearings, the problem of lubricating oil film temperature rise is analyzed, and specific research directions are proposed. It is hoped that it will be helpful to improve the research of bearing stability and provide a theoretical basis for the structural design and operational reliability of heavy hydrostatic bearings. Methods: This article summarizes the research status of the oil film temperature rise of hydrostatic and hydrodynamic thrust bearings, especially focusing on the influence of hot oil carrying on the temperature rise of the lubricating oil film, and finally the specific research directions and methods of the oil film temperature rise are prospected. Conclusion: Aiming at the research hotspots of lubricating oil film temperature rise and distribution, based on the analysis of the principle of hydrostatic and dynamic pressure bearings, the domestic and foreign literature on the influence of the micro-gap lubricating oil film temperature rise and distribution of hydrostatic and hydrodynamic thrust bearings is collected and analyzed. The research shows that although some research results have been made in this area, due to current research methods and angle analysis still have certain limitations, so the study of the oil film temperature rise is not comprehensive, and further detailed discussion and analysis are still needed.

Cause Analysis and Improvement of the Oil-Film Oscillation of the Centrifugal Compressor

2012 ◽  
Vol 479-481 ◽  
pp. 1297-1302
Author(s):  
Hong Wei Chen ◽  
Rong Jie Wang
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Critical Speed ◽  
Lubricating Oil ◽  
Cause Analysis ◽  
Oil Film ◽  
Relative Eccentricity ◽  
Improvement Measures

The paper starts from the reasons of the Centrifugal Compressor’s oil-film oscillation in one factory of Longyan, and thinks oil-film oscillation is the typical one of faults of the high-speed glide bearing and happens at about two times of the critical speed. It also summarizes the features of the oil-film oscillation, analyzes the reason, and finds out that the problem is related to the load, critical speed, the relative eccentricity of the bearing, lubricating oil and the bearing’s load amount. Finally it puts forward HHT detecting methods which can accurately find the problem earlier, and proposes improvement measures which have been proved simple, convenient, and practical after half year’s experiment.

Thermal elastohydrodynamic lubrication characteristics and optimisation of the ball-type tripod universal joint

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuqin Yang ◽  
Xiaojie Han ◽  
Mingqing Si
Keyword(s):  
Elastic Modulus ◽  
Film Thickness ◽  
Temperature Rise ◽  
Elastohydrodynamic Lubrication ◽  
Lubricating Oil ◽  
Universal Joint ◽  
Oil Viscosity ◽  
Content Type ◽  
Oil Film ◽  
Lubrication Characteristics

Purpose This paper aims to study the influence of three-column groove shell radius, ball radius, lubricating oil viscosity and elastic modulus on the thermal elastohydrodynamic lubrication (TEHL) characteristics and optimisation of the ball-type tripod universal joint. Design/methodology/approach The point contact TEHL model of the joint was developed, and the multi-grid method was used to solve it. The influence of three-column groove shell radius, ball radius, lubricating oil viscosity and elastic modulus on the lubrication characteristics was analysed. Further, the optimisation of the joint TEHL performance was carried out by the Kriging approximation model combined with the multi-objective particle swarm optimisation (MOPSO) algorithm. Findings The research results show that increasing groove shell radius and ball radius can effectively increase the oil film thickness, and decrease the oil film pressure, as well as the temperature rise. Decreasing elastic modulus can reduce the oil film temperature rise and pressure, and increasing viscosity can effectively increase the oil film thickness. The optimised minimum oil film thickness increases by 33.23% and the optimised maximum oil film pressure and maximum temperature rise decrease by 11.92% and 28.87%, respectively. Furthermore, the relative error of each response output is less than 10%. Originality/value This study applies TEHL theory to the tribological research of the ball-type tripod universal joint, and the joint’s lubrication performance is improved greatly by the Kriging model and MOPSO algorithm, which provides an effective measure to raise the joint’s working efficiency.

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