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.

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.

scholarly journals Influence of Floating Ring Seal Working Condition Parameters on the Dynamic Characteristics of Transient Gas Film

2021 ◽  
Vol 2108 (1) ◽  
pp. 012087
Author(s):  
Lishan Xu ◽  
Weizheng Zhang ◽  
Junjie Lu ◽  
Zhu Liu
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Spiral Groove ◽  
Low Leakage ◽  
Ring Seal ◽  
Stiffness And Damping Coefficient ◽  
Small Perturbation Method ◽  
Stiffness And Damping

Abstract The high requirements for sealing performance in high-speed rotating machinery has led to the design of floating seal with annular spiral groove that offer the advantages of low leakage and extended stability. However, efforts to model the dynamic performance of these floating seal have suffered from the great complexity of the flow field. The present work addresses this issue by establishing a transient Reynolds formulation of a floating seal with annular spiral groove in a rotating coordinate system based on the small perturbation method. In addition, the influence of radial eccentricity and film thickness on the solution divergence and calculation accuracy is calculated. The dynamic stiffness and dynamic damping matrixes are built. Then the variation rules of the dynamic stiffness and damping coefficient of the gas film with structure and working conditions are investigated in detail. The results show that the floating ring seal is more suitable for the service conditions of small film thickness, low pressure, high speed and large eccentricity. Accordingly, the results obtained lay a theoretical foundation for evaluating real-world applications of floating ring seal.

scholarly journals Analysis of the dynamic characteristics of downsized aerostatic thrust bearings with different pressure equalizing grooves at high or ultra-high speed

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110180
Author(s):  
Ruzhong Yan ◽  
Haojie Zhang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Rotation Speed ◽  
Dynamic Stiffness ◽  
Simulation Method ◽  
Perturbation Amplitude ◽  
Thrust Bearings ◽  
Supply Pressure ◽  
Ultra High Speed ◽  
Air Film

This study adopts the DMT(dynamic mesh technology) and UDF(user defined functions) co-simulation method to study the dynamic characteristics of aerostatic thrust bearings with equalizing grooves and compare with the bearing without equalizing groove under high speed or ultra high speed for the first time. The effects of air film thicness, supply pressure, rotation speed, perturbation amplitude, perturbation frequency, and cross section of the groove on performance characteristics of aerostatic thrust bearing are thoroughly investigated. The results show that the dynamic stiffiness and damping coefficient of the bearing with triangular or trapezoidal groove have obvious advantages by comparing with that of the bearing without groove or with rectangular groove for the most range of air film thickness, supply pressure, rotation speed, perturbation amplitude, especially in the case of high frequency, which may be due to the superposition of secondary throttling effect and air compressible effect. While the growth range of dynamic stiffness decreases in the case of high or ultra-high rotation speed, which may be because the Bernoulli effect started to appear. The perturbation amplitude only has little influence on the dynamic characteristic when it is small, but with the increase of perturbation amplitude, the influence becomes more obvious and complex, especially for downsized aerostatic bearing.

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.

High-Speed Rotor With Air Bearings Mounted on Flexible Supports: Test Bench and Experimental Results

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
G. Belforte ◽  
F. Colombo ◽  
T. Raparelli ◽  
V. Viktorov
Keyword(s):  
High Speed ◽  
Test Bench ◽  
Dynamic Stiffness ◽  
Experimental Results ◽  
Air Bearings ◽  
Stability Threshold ◽  
Air Turbine ◽  
Flexible Supports ◽  
The Stability ◽  
Rotational Response

A test bench for rotors supported by air bearings floating on O-rings is designed in order to study the whirl phenomenon and characterize the stability threshold with damping elements mounted on bearings. The work includes a description of the test bench and some preliminary experimental results. A rotor of 1kg mass and 37mm diameter is rotated up to 75,000rpm by an air turbine machined on the rotor. Capacitance probes, placed in two radial planes, allow orbit scanning of both the rotor and the bushing at different rotating speeds and suitable load devices permit measurement of the static and dynamic stiffness of the rotor-bearing system. Curves of rotational response using rubber O-rings of three different materials are shown and compared. Also presented are the Fourier spectra of the signals for rotor displacement. The phenomenon of whirl instability is shown in terms of whirl frequency and orbit amplitudes of the rotor and bearings. The effects of both supply pressure and angular velocity on the stability threshold are shown.

Thermohydrodynamic Study of Multiwound Foil Bearing Using Lobatto Point Quadrature

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Kai Feng ◽  
Shigehiko Kaneko
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Three Dimensional ◽  
Iteration Process ◽  
Element Model ◽  
Air Bearings ◽  
Foil Bearing ◽  
Wide Range ◽  
Air Film

The applications of foil air bearings have been extended for use in a wide range of turbomachineries with high speed and high temperature. Lubricant temperature becomes an important factor in the performance of foil air bearings, especially at high rotational speeds and high loads or at high ambient temperature. This study presents a thermohydrodynamic (THD) analysis of multiwound foil bearing, in which the Reynolds’ equation is solved with gas viscosity as a function of temperature that is obtained from the energy equation. Lobatto point quadrature is utilized to accelerate the iteration process with a sparse mesh across film thickness. A finite element model of the foil is used to describe the foil elasticity. An iterative procedure is performed between the Reynolds equation, the foil elastic deflection equation, and the energy equation until convergence is achieved. A three-dimensional temperature prediction of air film is presented, and a comparison of THD to isothermal results is made to emphasize the importance of thermal effects. Finally, published experimental data are used to validate this numerical solution.

2925 Optimum Design of High-Speed Spiral Grooved Air Film Thrust Bearingswith Experimental Verifications

2005 ◽  
Vol 2005.4 (0) ◽  
pp. 301-302
Author(s):  
Hiroshi HARA ◽  
Hiromu HASHIMOTO ◽  
Masayuki OCHIAI
Keyword(s):  
Optimum Design ◽  
High Speed ◽  
Air Film

An Experimental Study on a High-Speed Rotor Supported by Air Bearings Mounted on O-Rings

2006 ◽  
Author(s):  
G. Belforte ◽  
T. Raparelli ◽  
V. Viktorov ◽  
F. Colombo
Keyword(s):  
High Speed ◽  
Test Bench ◽  
Dynamic Stiffness ◽  
Air Bearings ◽  
Stability Threshold ◽  
Supply Pressure ◽  
Air Turbine ◽  
Fourier Spectra ◽  
The Stability ◽  
Bearing System

A test bench on rotors supported on air bearings floating on O-rings has been designed in order to study the whirling phenomenon and individuate the stability threshold with the presence of damping elements mounted on the bearings. The work contains description of the test bench and the first experimental results. A rotor of 1 kg mass and 37 mm diameter is rotated up to 75000 rpm by an air turbine manufactured on the rotor. Capacitance probes, placed in two radial planes, allow to scan the orbits of both the rotor and the bushing at different rotating speeds and proper load devices make it possible to measure the static and dynamic stiffness of the rotor-bearing system. Diagrams on the rotating response using different kinds of rubber O-rings are presented and compared, with also indications on the Fourier spectra of the signals relative to the rotor displacement. The phenomenon of whirling instability is showed, with considerations on the whirling frequency and on the orbit amplitudes of the rotor and the bearings. The effect of both supply pressure and angular velocity on the stability threshold is showed.

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