scholarly journals Performance Analysis of Hydrodynamic Pressure Finger Seal by Wall Slip Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yan-chao Zhang ◽  
Ting Wang ◽  
Dong-ya Zhang ◽  
Ming-hu Yin ◽  
Ya-hui Cui ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
High Speed ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Hydrodynamic Pressure ◽  
Wall Slip ◽  
Leakage Rate ◽  
Slip Effect ◽  
Wall Surface ◽  
Air Film

Hydrodynamic pressure finger seal1 is a kind of flexible noncontact dynamic sealing device with good application potential. It relies on the ultrathin dynamic pressure film effect produced by the rotation of finger boot and rotor to realize the design of noncontact and low leakage and is suitable for high-speed dynamic sealing parts. However, under the high-speed condition, there is a wall slip effect when the gas flows in the microchannel with a thickness of about 10 μm between the finger boot and rotor, which affects the stability of the dynamic pressure air film and also affects the change of the air film bearing capacity and the leakage rate of the finger seal. Therefore, based on the theory of microflow, the interstitial flow field model of finger seal under fluid dynamic pressure is established, and its slip effect under high speed is analyzed. The results show that the slip ratio of the sealing medium temperature of 500°C and 0.1 MPa conditions reached 27.28%. When considering the slip effect of the wall surface generated by the gas under shear driving, the gas film bearing capacity decreased and the leakage rate increased. When the pressure difference between the upper and lower reaches of the seal is 0.1 MPa, and the rotor line speed is 400 m/s, the gas film bearing capacity decreases by 17.39% after considering the slip effect of the wall surface, and the leakage rate increases by 14.06%. The results provide an important reference for the structural design and leakage control of hydrodynamic finger seal.

Slider Air Bearing Design Enhancements for High Speed Flexible Disk Recording

2005 ◽  
Vol 127 (3) ◽  
pp. 522-529 ◽  
Author(s):  
James White
Keyword(s):  
High Speed ◽  
Numerical Solutions ◽  
Hydrodynamic Pressure ◽  
Flying Height ◽  
Air Bearing ◽  
Mechanical Shock ◽  
Current Effort ◽  
Slider Air Bearing ◽  
Flexible Disk ◽  
Air Film

The current effort was motivated largely by the fact that computing and communication platforms are becoming more portable and mobile with increased demands for both speed and disk storage. This work makes use of an asymmetric opposed slider arrangement to provide both static and dynamic improvements to the recording head air bearing interface for high speed flexible disk applications. The combination of a longitudinally slotted rail opposed by an uninterrupted rail that functions as a noncontact hydrodynamic pressure pad causes the disk to deflect at the submicron level over critical areas of the slider interface. This allows the required static minimum flying height to be focused over the recording transducer while higher clearances are positioned elsewhere, resulting in minimized exposure to contact between slider and disk. The high stiffness and low flying height of the air film at the recording element together with the low stiffness and high flying height of the opposing air film provides a noncontact air bearing interface that is especially immune to mechanical shock. A computer code called FLEXTRAN was developed that provides both static and dynamic numerical solutions of the air bearing interface composed of two opposed gimbal mounted sliders loaded against a high speed flexible disk. Simulations of the asymmetric opposed slider configuration are presented and compared with those of other slider air bearing designs.

Modelling on Predicting Pressure Distribution and Capacity of Foil Thrust Bearing

2018 ◽  
Author(s):  
Zheng Xu ◽  
Fenzhu Ji ◽  
Yu Zhou ◽  
Fanyong Wu ◽  
Shuiting Ding
Keyword(s):  
Bearing Capacity ◽  
Pressure Distribution ◽  
High Speed ◽  
Thrust Bearing ◽  
Rotation Speed ◽  
Air Bearing ◽  
Environment Temperature ◽  
Foil Thrust Bearing ◽  
Cfd Method ◽  
Air Film

Air bearing is future main supporting way of high-speed machinery such as turbocharger, micro gas-turbine engine. Foil bearing is a new type of air bearing which is lubricated by the thin-film air with its self-adapting elastic foil structure. It has many significant advantages such as non-pollution, longer working life, higher reliability, and lower friction loss. Different from foil journal bearing, in present the study of foil thrust bearing is extremely insufficient, especially about how to accurately predict the pressure distribution and efficiently improve the bearing capacity. The pressure distribution prediction of foil thrust bearing air film directly impacts the bearing stiffness and damping design, and then influences bearing capacity. The Reynolds equation commonly used to do such estimation is not accurate enough since the influence of temperature on air property parameters is ignored. The inaccurate prediction leads a catastrophic reduction to the bearing performance. In order to solve this problem, we propose a model to accurately predict the pressure distribution and capacity of foil thrust bearing using CFD method, as well estimating the relationship between air film clearance thickness, rotation speed, environment temperature and the capacity. Firstly, we simulate the pressure distribution of air film and then evaluate the simulation result by constrained experiments. We also correct the simulation by using modified air parameters obtained from experiment. The experimental results indicate our corrected simulation model is accurate with error less than 4%. Secondly, we compare simulation and experiment pressure results under different conditions. The model accuracy sensitivity varies within 10% under different rotation speed, air film clearance thickness and environment temperature. Finally, we use corrected model to analyze capacity impact parameters. We find the capacity of bearing increases with the decreasing of average air film clearance thickness under fixed speed of the thrust disc. The smaller clearance thickness is, the more influence its variation has on the bearing capacity. Meanwhile, the capacity of the bearing decreases with the reducing thrust disc speed under constant clearance thickness, and it decreases more obviously in the lower speed. The capacity reaches its largest under 200 °C and it falls with the increases or decreases of environment temperature. The model in this paper provides important theoretical foundation when designing the stiffness, damping and temperature control of each bearing area.

The Modeling of Rubber Sealing Ring of Fluid Dynamic Pressure and Finite Element Analysis about Stress Based on SolidWorks and ANSYS

2012 ◽  
Vol 215-216 ◽  
pp. 1246-1249
Author(s):  
Juan Zhu ◽  
Long Qing Zou ◽  
Shi Jie Han
Keyword(s):  
Finite Element ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Hydrodynamic Pressure ◽  
Wave Crest ◽  
Hydrodynamic Effect ◽  
Element Analysis ◽  
Rubber Ring ◽  
Finite Element Software ◽  
Sealing Ring

Hydrodynamic seal ring is based on the hydrodynamic effect of rotary shaft seal, Kalsi sealing ring is the typical type of products, and the design of sealing lip adopts unique waveform structure. Based on geometry analysis of the sealing ring, the 3D model of the ring was established by using SolidWorks software, and then the model was introduced into finite element software ANSYS, which was used to analyse stress for the Kalsi of rubber sealing ring. Through the analysis of the stress of rubber ring, the position of the maximum stress value of the rubber seal in hydrodynamic pressure was wave crest (valley) in the edge of the wave side. When the pressure of seal was 10MPa, the maximum value of stress of rubber sealing was up to 6.54MPa.

Subsynchronous Vibrations in Rotating Machinery: Methodologies to Identify Potential Instability

2007 ◽  
Author(s):  
Rahul Kar ◽  
John Vance
Keyword(s):  
Phase Angle ◽  
High Speed ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Rotating Machinery ◽  
Diagnostic Tools ◽  
Study Methods ◽  
Frequency Tracking ◽  
Rotor Bearing ◽  
Bearing System

Rotordynamic instability can be disastrous for the operation of high speed turbomachines in the industry. Most ‘instabilities’ are due to de-stabilizing cross coupled forces from variable fluid dynamic pressure around a rotor component, acting in the direction of forward whirl and causing subsynchronous orbiting of the rotor. However, all subsynchronous whirling are not unstable and methods to diagnose the potentially unstable kind from the benign are critical to the health of the rotor-bearing system. In this study, methods to demarcate between the two are detailed. Orbit shape, “frequency tracking” and agreement of subsynchronous frequencies with known eigenvalues are used as diagnostic tools. It is shown that a change in synchronous phase angle produced by de-stabilizing cross coupled forces can be used as a definitive indicator of incipient instability. Typical signatures of subharmonic vibrations induced from non-linear stiffness of the rotor- bearing system are examined analytically and through experiments.

scholarly journals Analysis of Bearing Capacity of Steel-Concrete Composite Beams Considering Interface Slip Effect

2021 ◽  
Vol 719 (2) ◽  
pp. 022036
Author(s):  
Song Yang ◽  
Fan Chen ◽  
Zubin Ai ◽  
Lingyuan Zhou ◽  
Zhensheng Cao
Keyword(s):  
Bearing Capacity ◽  
Composite Beams ◽  
Slip Effect ◽  
Interface Slip

scholarly journals Droplet impact onto a spring-supported plate: analysis and simulations

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Michael J. Negus ◽  
Matthew R. Moore ◽  
James M. Oliver ◽  
Radu Cimpeanu
Keyword(s):  
High Speed ◽  
Flexible Substrate ◽  
Practical Importance ◽  
Hybrid Approach ◽  
Hydrodynamic Pressure ◽  
Analytical Framework ◽  
Canonical System ◽  
Linear Process ◽  
Plate Motion ◽  
The Impact

AbstractThe high-speed impact of a droplet onto a flexible substrate is a highly non-linear process of practical importance, which poses formidable modelling challenges in the context of fluid–structure interaction. We present two approaches aimed at investigating the canonical system of a droplet impacting onto a rigid plate supported by a spring and a dashpot: matched asymptotic expansions and direct numerical simulation (DNS). In the former, we derive a generalisation of inviscid Wagner theory to approximate the flow behaviour during the early stages of the impact. In the latter, we perform detailed DNS designed to validate the analytical framework, as well as provide insight into later times beyond the reach of the proposed analytical model. Drawing from both methods, we observe the strong influence that the mass of the plate, resistance of the dashpot, and stiffness of the spring have on the motion of the solid, which undergo forced damped oscillations. Furthermore, we examine how the plate motion affects the dynamics of the droplet, predominantly through altering its internal hydrodynamic pressure distribution. We build on the interplay between these techniques, demonstrating that a hybrid approach leads to improved model and computational development, as well as result interpretation, across multiple length and time scales.

Development and Experimental Performance Verification of a Magneto-Aerostatic Bearing for Cartridge of Dental Handpieces

2012 ◽  
Author(s):  
Guan-Chung Ting ◽  
Kuang-Yuh Huang ◽  
Keng-Ning Chang
Keyword(s):  
High Speed ◽  
Ball Bearings ◽  
Aerostatic Bearing ◽  
Operation Conditions ◽  
Air Inlet ◽  
Efficient Performance ◽  
Aerostatic Bearings ◽  
Repulsive Forces ◽  
Radial Loading ◽  
Air Film

Bearings for high-speed rotors are the key component of dental handpieces. The friction induced by conventional ball bearings restricts its speed and reduces its efficiency. In order to significantly improve the efficiency of dental handpieces, a mini-type cartridge that integrates a turbine and a spindle with radial aerostatic bearings and axial passive magnetic bearings has been ingeniously designed and realized. Around the rotating spindle, there is a high-pressured air film built up by a pair of radial aerostatic bearings, and magnet rings are applied to create repulsive forces to axially support the rotating spindle. The high-pressured air film comes from the specifically designed separable orifice restrictors, which can be easily and precisely manufactured. Frictionless bearing effect can be achieved by aerostatic principle, and the magnetic principle is applied to create large repulsive force against the axial working force. A tri-directional air inlet is designed to reduce radial loading force of a spindle during working. The modularized form of the magneto-aerostatic bearing allows it to be easily assembled and replaced in the very compact space of a mini-type cartridge. Through analytical simulations with fluid-dynamics software (CFD) and experiments, the magneto-aerostatic bearing is optimized to bring out efficient performance in its limited space. The experiments have verified that its noise level is 15dB lower than the conventional cartridge with ball bearings, and its startup air pressure is reduced from 0.4 bar to 0.1 bar. Under the same operation conditions, the newly developed cartridge with magneto-aerostatic bearings creates twice higher speed than that of the conventional one.

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.

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

Thermo-Fluid-Dynamic Design of Reciprocating Compressor Cylinders by Fluid Structure Interaction (FSI)

2011 ◽  
Author(s):  
Riccardo Traversari ◽  
Alessandro Rossi ◽  
Marco Faretra
Keyword(s):  
High Speed ◽  
Fluid Dynamic ◽  
Fluid Structure Interaction ◽  
Classical Equation ◽  
Flow Coefficient ◽  
Reciprocating Compressor ◽  
Complex Situation ◽  
Fluid Structure ◽  
Associated Gas ◽  
Structure Interaction

Pressure losses at the cylinder valves of reciprocating compressors are generally calculated by the classical equation of the flow through an orifice, with flow coefficient determined in steady conditions. Rotational speed has increased in the last decade to reduce compressor physical dimensions, weight and cost. Cylinder valves and associated gas passages became then more and more critical, as they determine specific consumption and throughput. An advanced approach, based on the new Fluid Structure Interaction (FSI) software, which allows to deal simultaneously with thermodynamic, motion and deformation phenomena, was utilized to simulate the complex situation that occurs in a reciprocating compressor cylinder during the motion of the piston. In particular, the pressure loss through valves, ducts and manifolds was investigated. A 3D CFD Model, simulating a cylinder with suction and discharge valves, was developed and experimentally validated. The analysis was performed in transient and turbulent condition, with compressible fluid, utilizing a deformable mesh. The 3D domain simulating the compression chamber was considered variable with the law of motion of the piston and the valve rings mobile according to the fluid dynamic forces acting on them. This procedure is particularly useful for an accurate valve loss evaluation in case of high speed compressors and heavy gases. Also very high pressure cylinders, including LDPE applications, where the ducts are very small and MW close to the water one, can benefit from the new method.

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