Dynamic Analysis of Spiral-Groove Rotary Seal Ring for Wet Clutches

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Yi M. Zhao ◽  
Ji B. Hu ◽  
Chao Wei
Keyword(s):  
High Speed ◽  
Friction Torque ◽  
Step Response ◽  
Asperity Contact ◽  
Seal Ring ◽  
Spiral Groove ◽  
Rotary Seal ◽  
Lubrication Performance ◽  
Bearing Force ◽  
Time Marching

A tribo-dynamic model of a spiral-groove rotary seal ring is developed through coupling lubrication and dynamic equations. Effects of centrifugation, hydrodynamics, cavitation, and asperity contact are considered. To represent real rough surfaces, asperity contact is described by a statistics-based model. A global time marching scheme is developed to obtain the motion of seal ring and key parameters such as bearing force, friction torque, and leakage rate. Dynamic behaviors and seal characteristics of spiral-groove rotary seal ring under real and step change oil filling conditions are analyzed. The result shows that the rotary seal ring operates steadily under real conditions and has fast and stable step response. It is also indicated that the seal ring can achieve full film lubrication under high speed conditions through the oil filling and dispersing stage. The steady lubrication performance is experimentally validated.

scholarly journals Non-Hertzian Elastohydrodynamic Contact Stress Calculation of High-Speed Ball Screws

2021 ◽  
Vol 11 (24) ◽  
pp. 12081
Author(s):  
Tiewei Sun ◽  
Min Wang ◽  
Xiangsheng Gao ◽  
Yingjie Zhao
Keyword(s):  
Contact Stress ◽  
Calculation Method ◽  
High Speed ◽  
Contact Region ◽  
Friction Torque ◽  
Wear Depth ◽  
Asperity Contact ◽  
Stress Calculation ◽  
Elastohydrodynamic Contact ◽  
The Asymmetry

In order to eliminate the calculation error of the Hertzian elastohydrodynamic contact stress due to the asymmetry of the contact region of the helix raceway, a non-Hertzian elastohydrodynamic contact stress calculation method based on the minimum excess principle was proposed. Firstly, the normal contact stresses of the screw raceway and the nut raceway were calculated by the Hertzian contact theory and the minimum excess principle, respectively. Subsequently, the Hertzian solution and the non-Hertzian solution of the elastohydrodynamic contact stress could be determined by the Reynolds equation under different helix angles and screw speeds. Finally, the friction torque test of the double-nut ball screws was designed and implemented on a self-designed bed for validation of the proposed method. The comparison showed that the experimental friction torque was the good agreement with the simulated friction torque, which verified the effectiveness and correctness of the non-Hertzian elastohydrodynamic contact stress calculation method. Under the large helix angle, the calculation accuracy of asperity contact stress for the non-Hertzian solution was more accurate than that of the Hertzian solution at the contact region of ball screws. Therefore, the non-Hertzian elastohydrodynamic contact stress considering the asymmetry of the raceway contact region could more accurately analyze the wear depth of the high-speed ball screws.

Optimization of Groove Geometry for Thrust Air Bearing According to Various Objective Functions

2008 ◽  
Author(s):  
Hiromu Hashimoto ◽  
Masayuki Ochiai ◽  
Tadashi Namba
Keyword(s):  
Film Thickness ◽  
Optimum Design ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Optimization Method ◽  
Friction Torque ◽  
Air Bearings ◽  
Objective Functions ◽  
Spiral Groove ◽  
Air Film

Grooved thrust air bearings are widely used to support high-speed, low-loaded shafts in many rotating systems because of their low friction, noiseless operation, and simple structure. Several types of groove geometries, such as straight line, spiral, and herringbone, are commonly used in actual applications. Among them the spiral groove is mainly used. However, as far as the authors know, there is no theoretical evidence that the spiral groove is an optimized groove geometry in all possible groove geometries. This paper describes the optimum design for the groove geometry of thrust air bearings according to various objective functions, such as air film thickness, bearing torque, dynamic stiffness of air film, and combinations of same. In an optimum design, groove geometries are expressed by the third degrees of spline function, and sequential quadratic programming is used as the optimization method. We found that groove geometry optimizing air film thickness or friction torque takes the form of a spiral groove. The geometry optimizing the dynamic stiffness is the modified spiral groove. Some numerical results are compared with the measured data, and good agreements can be seen between them.

Optimization of Groove Geometry for a Thrust Air Bearing According to Various Objective Functions

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Hiromu Hashimoto ◽  
Tadashi Namba
Keyword(s):  
Film Thickness ◽  
Optimum Design ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Optimization Method ◽  
Friction Torque ◽  
Air Bearings ◽  
Objective Functions ◽  
Spiral Groove ◽  
Air Film

Grooved thrust air bearings are widely used to support high-speed, low-loaded shafts in many rotating systems because of their low friction, noiseless operation, and simple structure. Several types of groove geometries, such as straight line, spiral, and herringbone, are commonly used in actual applications. Among these, the spiral groove is mainly used. However, as far as the authors know, there is no theoretical evidence that the spiral groove is the most optimized groove geometry in all possible groove geometries. This paper describes the optimum design for the groove geometry of thrust air bearings according to various objective functions such as air film thickness, bearing torque, dynamic stiffness of air film, and other similar combinations. In an optimum design, groove geometries are expressed by the third degree of spline function, and sequential quadratic programming is used as the optimization method. It is understood that the groove geometry for optimizing air film thickness or friction torque takes the basic form of spiral groove geometry. The geometry design for optimizing the dynamic stiffness is the modified spiral groove. Numerical results are compared with the measured data, and good agreements can be seen between them.

Comparison of Motion Characteristics of High Performance CNC Rotary Tables

2010 ◽  
Author(s):  
Muditha K. M. Dassanayake ◽  
Masaomi Tsutsumi
Keyword(s):  
High Performance ◽  
Closed Loop ◽  
Friction Torque ◽  
Step Response ◽  
Rotary Table ◽  
Direct Drive ◽  
Drive Motor ◽  
Fluctuation Frequency ◽  
Motion Characteristics ◽  
Accuracy And Repeatability

In this paper, the motion performances of the two rotary tables which are driven by roller gear cam and direct drive motor are measured and compared. The table with roller gear cam was controlled in semi-closed loop and full-closed loop methods while the other was controlled only in full-closed loop method. In the measurements, the positioning accuracy and repeatability, rotational fluctuation, frequency response, step response and etc of the systems were measured. All these tests were carried out without any kind of compensation methods such as pitch error or cogging torque compensation etc. Three rotary encoders for rotary table with roller gear cam and one rotary encoder for rotary table with direct drive motor were used for measurements. Furthermore, the simulations were carried out by mathematical models and the results were compared with measured results. The comparison shows that the measured and simulated results have a good agreement. From the simulation results, the friction torque was identified and also compared. The results imply that though both the tables show high performances, the performances of the rotary table driven by roller gear cam are comparatively higher than that of rotary table driven by direct drive motor.

scholarly journals Influence of the Lubrication Oil Temperature on the Disengaging Dynamic Characteristics of a Cu-Based Wet Multi-Disc Clutch

2021 ◽  
Vol 11 (23) ◽  
pp. 11299
Author(s):  
Liangjie Zheng ◽  
Biao Ma ◽  
Man Chen ◽  
Liang Yu ◽  
Qian Wang
Keyword(s):  
Dynamic Characteristics ◽  
Hydrodynamic Lubrication ◽  
Friction Pair ◽  
Automatic Transmission ◽  
Friction Torque ◽  
Asperity Contact ◽  
Uniformity Coefficient ◽  
Lubrication Oil ◽  
The Impact ◽  
First Time

Clutch disengaging dynamic characteristics, including the disengaging duration and the variations of friction pair gaps and friction torque, are crucial to the shifting control of an automatic transmission. In the present paper, the influence of lubrication oil (ATF) temperature on disengaging dynamic characteristics is investigated through a comprehensive numerical model for the clutch disengaging process, which considers the hydrodynamic lubrication, the asperity contact, the heat transfer, the spline resistance, and the impact between the piston and clutch hub. Moreover, the non-uniformity coefficient (NUC) is proposed to characterize the disengaging uniformity of friction pairs. As the ATF temperature increases from 60 °C to 140 °C, the clutch disengaging duration shortens remarkably (shortened by 55.1%); besides, the NUC sees a decreasing trend before a slight increase. When the ATF temperature is 80 °C, the distribution of friction pair gaps is most uniform. During the disengaging process, the increase of ATF temperature not only accelerates the change of the lubrication status between friction pairs but also contributes to the decrease of contact torque and hydrodynamic torque. This research demonstrates for the first time, evidence for clutch disengaging dynamic characteristics with the consideration of ATF temperature.

Effects of Rotational Inertia and Bearing Force on Stability of Permanent Maglev Rotator

2012 ◽  
Vol 150 ◽  
pp. 50-56
Author(s):  
Kun Xi Qian ◽  
Z.H. Xu ◽  
H. Wang
Keyword(s):  
Negative Correlation ◽  
High Speed ◽  
Magnetic Force ◽  
Measuring System ◽  
Rotational Inertia ◽  
Rotating Speed ◽  
Stable Suspension ◽  
Minimal Speed ◽  
Bearing Force ◽  
Magnetic Rings

The authors’ former works demonstrated that a passive magnetic (PM) rotator supported merely by PM bearings has a minimal speed, above which it can stabilize its equilibrium, under the function of a so-called Gyro-effect. It is unclear, however, by which factors is this minimal speed determined. This paper investigated the factors affecting the minimal stable speed of permanent maglev rotator, namely, the rotating inertia and PMB force. Two novel permanent maglev turbine models were designed: Model A---one stator and three rotors which have the same size but different rotational inertias; Model B---one rotor and one stator, but the stator has been devised with three different passive magnetic bearings: 1. a pair of small magnetic rings; 2. a pair of big magnetic rings; and 3. both of the two pairs of magnetic rings. Four Hall sensors distributed evenly at the turbine’s stator were used to detect the rotor’s eccentricity, and the speed sensor measured rotating speed. The calculated models of rotor’s eccentricity were established respectively for the two turbine models; the rotor’s eccentricity measuring system was built up and the rotor’s eccentricity of the two turbines was measured. The experimental data demonstrated that the rotational inertia of three rotors in the model A is 6.293×10-5 kg•m2, 1.074×10-4 kg•m2 and 2.081×10-4 kg•m2 respectively, and the corresponding minimal speed for suspension are 4597rpm, 3030rpm and 2222rpm respectively; in the model B, the magnetic force between the stator and rotor in the three cases is 92.12N, 123.48N, 212.66N respectively, corresponding to the minimal speed for suspension---3730rpm, 3120rpm and 2195rpm respectively. The results exhibited that same as the permanent maglev heart pump, permanent maglev turbines also have gyroscopic effect, which makes the rotors maintain stable suspension. And the minimal speed for suspension has a negative correlation with the rotor’s rotational inertia, namely, the bigger the inertia of the rotor, the smaller the required speed for suspension; the minimal speed for suspension also has a negative correlation with the magnetic force between the stator and rotor, that is, the larger the magnetic force, the smaller the rotating speed for suspension. Smaller minimal speed means better stability of the system, thereafter larger inertia or larger bearing force means better stability; besides, larger difference between minimal speed and performance speed of the rotator means better stability, it’s suggested permanent maglev be applied in high speed rotary machines.

scholarly journals Plasma skimming efficiency of human blood in the spiral groove bearing of a centrifugal blood pump

2020 ◽  
Author(s):  
Daisuke Sakota ◽  
Kazuki Kondo ◽  
Ryo Kosaka ◽  
Masahiro Nishida ◽  
Osamu Maruyama
Keyword(s):  
Red Blood Cells ◽  
Human Blood ◽  
Blood Cells ◽  
High Speed ◽  
Blood Pump ◽  
Spiral Groove ◽  
Centrifugal Blood Pump ◽  
Plasma Skimming ◽  
Ridge Area ◽  
Spiral Groove Bearing

Abstract This work investigates the plasma skimming effect in a spiral groove bearing within a hydrodynamically levitated centrifugal blood pump when working with human blood having a hematocrit value from 0 to 40%. The present study assessed the evaluation based on a method that clarified the limitations associated with such assessments. Human blood was circulated in a closed-loop circuit via a pump operating at 4000 rpm at a flow rate of 5 L/min. Red blood cells flowing through a ridge area of the bearing were directly observed using a high-speed microscope. The hematocrit value in the ridge area was calculated using the mean corpuscular volume, the bearing gap, the cross-sectional area of a red blood cell, and the occupancy of red blood cells. The latter value was obtained from photographic images by dividing the number of pixels showing red blood cells in the evaluation area by the total number of pixels in this area. The plasma skimming efficiency was calculated as the extent to which the hematocrit of the working blood was reduced in the ridge area. For the hematocrit in the circuit from 0 to 40%, the plasma skimming efficiency was approximately 90%, meaning that the hematocrit in the ridge area became 10% as compared to that in the circuit. For a hematocrit of 20% and over, red blood cells almost completely occupied the ridge. Thus, a valid assessment of plasma skimming was only possible when the hematocrit was less than 20%.

scholarly journals Effects of bushing profiles on the elastohydrodynamic lubrication performance of the journal bearing under steady operating conditions

2019 ◽  
Vol 20 (2) ◽  
pp. 207 ◽  
Author(s):  
Chongpei Liu ◽  
Bin Zhao ◽  
Wanyou Li ◽  
Xiqun Lu
Keyword(s):  
Journal Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Parabolic Profile ◽  
Leakage Flow Rate ◽  
Lubrication Performance ◽  
Load Carrying ◽  
Edge Wear ◽  
Flow Rate Change

The bushing profiles have important effects on the performance of journal bearing. In this article, the effects of plain profile, double conical profile, and double parabolic profile on the elastohydrodynamic lubrication of the journal bearing under steady operating conditions are investigated. The journal misalignment and asperity contact between journal and bushing surface are considered, while the modification of the bushing profiles due to running-in is neglected. Finite element method is used for the elastic deformation of bushing surface, while the numerical solution is established by using finite difference method and overrelaxation iterative method. The numerical results reveal that the double parabolic profile with appropriate size can significantly increase the minimum film thickness and reduce the asperity contact pressure and friction, while the maximum film pressure, load-carrying capacity, and leakage flow rate change slightly under steady operating conditions. This study may help to reduce the edge wear and prolong the service life of the journal bearing.

Effects of double parabolic profiles with groove textures on the hydrodynamic lubrication performance of journal bearing under steady operating conditions

2020 ◽  
Vol 21 (3) ◽  
pp. 301
Author(s):  
Chongpei Liu ◽  
Wanyou Li ◽  
Xiqun Lu ◽  
Bin Zhao
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Lubricating Oil ◽  
Asperity Contact ◽  
Adiabatic Flow ◽  
Lubrication Performance ◽  
Load Carrying ◽  
Edge Wear ◽  
Journal Misalignment

The textures on the bushing surface have important effects on the performance of journal bearing. In this study, the effects of double parabolic profiles with groove textures on the hydrodynamic lubrication performance of journal bearing under steady operating conditions are investigated theoretically. The journal misalignment, asperity contact and thermal effects are considered, while the profile modifications due to running-in are neglected. The Winkler/Column model is used to calculate the elastic deformation of bushing surface and the adiabatic flow hypothesis is adopted to obtain the effective temperature of lubricating oil. The numerical solution is established by using finite difference and overrelaxation iterative methods, and the rupture zone of oil film is determined by Reynolds boundary conditions. The numerical results reveal that the double parabolic profiles with groove textures with proper location and geometric sizes can increase load carrying capacity and reduce friction loss under steady operating conditions, which effectively overcome the drawbacks of double parabolic profiles. This novel bushing profile may help to reduce the bushing edge wear and enhance the lubrication performance of journal bearing.

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