Numerical Study of Single Pad Externally Adjustable 120° Pad Bearing Using Fluid Structure Interaction

2021 ◽  
Author(s):  
Harishkumar Kamat ◽  
Chandrakant R. Kini ◽  
Satish B. Shenoy
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Fluid Film ◽  
Structural Deformation ◽  
Radial Clearance ◽  
Solution Technique ◽  
Eccentricity Ratio ◽  
Positive Direction ◽  
Film Pressure ◽  
Marine Propulsion

Abstract High-speed turbomachinery like turbine generators and marine propulsion systems uses special fluid film bearing called externally adjustable pad bearing due to their great advantages. The principal feature of this bearing is to alter the radial clearance and film thickness along the circumferential direction to improve the bearing performance parameters. In the present study, the effect of radial and tilt adjustment of 120° pad both in upward (or negative) and downward (or positive) direction on the bearing performance is predicted for various eccentricity ratios using the CFD technique. Later the influence of fluid film pressure on the bearing pad is examined using the FSI technique. Furthermore, the effect of eccentricity ratio on the bearing performance and also on pad structure is also analyzed using CFD coupled FSI analysis. The solution technique of the present numerical analysis is validated with the already published literature and the results are in good agreement. The numerical results suggest that for bearing with negative radial and negative tilt adjustment, bearing performance is superior compared to the other adjustments. However, the structural deformation is also significant for the negative radial and negative tilt adjustment. It is also observed that pad deformation increases with the increase in eccentricity ratio as there has been a rise in fluid film pressure.

scholarly journals Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Eliott Guenat ◽  
Jürg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Load Capacity ◽  
Saturation Pressure ◽  
Operating Conditions ◽  
Fluid Film ◽  
Small Scale ◽  
Vapor Compression ◽  
Density Profiles ◽  
Film Pressure

Abstract High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might locally reach the saturation pressure with potentially hazardous effects on the performance of the gas bearing. The present work introduces a model based on the Reynolds equation and the development of cavitation modeling in liquid-lubricated bearings for condensing gas bearings. The effect of condensation on load capacity and pressure and density profiles is investigated for two one-dimensional bearing geometries (parabolic and Rayleigh step) and varying operating conditions. The results suggest that the load capacity is generally negatively affected if condensation occurs. An experimental setup consisting of a Rayleigh-step gas journal bearing with pressure taps to measure the local fluid film pressure is presented and operated in R245fa in near-saturated conditions. The comparison between the evolution of the fluid film pressure under perfect gas and near saturation conditions clearly suggests the occurrence of condensation in the fluid film. These results are corroborated by the very good agreement with the model prediction.

Nonlinear Effects in a Plain Journal Bearing: Part 1—Analytical Study

1991 ◽  
Vol 113 (3) ◽  
pp. 555-561 ◽  
Author(s):  
F. K. Choy ◽  
M. J. Braun ◽  
Y. Hu
Keyword(s):  
Equilibrium Position ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Fluid Film ◽  
Liquid Oxygen ◽  
Solution Technique ◽  
Space Applications ◽  
Linear Solution ◽  
Film Pressure ◽  
Linear And Nonlinear

Hydrodynamic/hydrostatic journal bearings have been widely used in various types of high speed rotating machinery. For space applications, the issue of using cryogenic fluids as working lubricants has steadily gained in significance. The primary goal of this paper is to model the nonlinearities that occur in a hydrodynamic journal bearing with both cryogenic and oil lubricants. Results will be examined through bearing fluid film pressure distribution and bearing linear and nonlinear stiffness characteristics. The numerical model that couples a variable property Reynolds equation with the dynamics of the rotor is solved by means of a finite difference solution technique. The procedure for the fluid film pressure solution involves an iterative scheme that solves the Reynolds equation coupled with the equations of state for liquid oxygen (LO2). The pressure curve is then integrated to calculate bearing supporting forces. A two-dimensional Newton-Raphson iteration method is used to locate the journal equilibrium position from which both linear and nonlinear bearing stiffness are evaluated by means of the small perturbation technique. The effects of load on the linear/nonlinear plain journal bearing characteristics are analyzed and presented in a parametric form. The relationship between the accuracy of the linear solution and the various orders (3rd, 5th, and 7th power for ΔX) of the nonlinear approximation are also discussed. The validity of both linear and nonlinear solutions at various distances from the journal equilibrium position is also examined. A complete parametric study on the effects of load, temperature, operating speed, and shaft misalignment will be given in Part 2 of this paper.

Static Performance Analysis of Foil Thrust Bearing Based on Thin Plate Theory

2014 ◽  
Vol 621 ◽  
pp. 437-442
Author(s):  
Jian Jun Zhu ◽  
Jian Jun Du ◽  
Bing Li ◽  
Chang Lin Li ◽  
Dun Liu
Keyword(s):  
Thin Plate ◽  
Rotational Speed ◽  
High Speed ◽  
Plate Theory ◽  
Load Capacity ◽  
Structural Parameters ◽  
Structural Deformation ◽  
Foil Thickness ◽  
Frictional Torque ◽  
Eccentricity Ratio

The thrust foil bearing, as one of the key parts in high-speed rotating machineries, is used to sustain the axial force, and its load performance has a crucial relationship with the structural parameters and working condition. In this paper the top foil is modeled as a thin plate supported by the bumps underneath. The finite element method (FEM) is used to calculate the structural deformation coupled with the pressure distribution obtained through the solution of Reynolds equation by the finite difference method (FDM). The effects of structural and operating parameters, such as rotational speed, eccentricity ratio, top foil thickness and bump foil thickness on the load capacity and frictional torque are discussed in detail. The results show that the increase of rotational speed, eccentricity ratio and bump foil thickness is beneficial to increase the load capacity and frictional torque. The effect of variation of top foil thickness on load capacity is not obvious, which implies that the top foil plays a role in building the lubricant surface rather than providing supporting stiffness.

Jumping Phenomenon in Journal Bearing

1991 ◽  
Author(s):  
Krystof Kryniski
Keyword(s):  
High Speed ◽  
Standard Procedure ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Theory And Practice ◽  
Fluid Film ◽  
Design Parameters ◽  
Radial Clearance ◽  
Rotor Systems ◽  
Rotating Machine

Abstract Due to their reliability and low maintenance costs over an extended service time, the journal bearings, also known as fluid-film bearings, are commonly incorporated in the super-critical rotor systems. Together with proven balancing methods, they allow rotating machine to pass smoothly through the various of critical speeds, both during start-ups and shut-downs. However, journal bearings need to be designed very carefully, as at some operating conditions (speed and load), they may introduce the undesired effects, such as unstable operations or sub-harmonic resonances. The standard procedure leading to the optimum fluid-film bearing design is based on the bearing capacity, defined by the Sommerfield number [1][2]. When Sommerfield number is determined, all design parameters, such as viscosity, radial clearance, diameter and rotation speed, etc. are matched to satisfy the engineering requirements specified. The procedure is considered to be completely reliable and is commonly used in turbo-machinery and high-speed compressor design. However, the significant divergences between theory and practice were observed with the increase of a bearing radial clearance [3].

Modeling Non-Newtonian Piston Skirts EHL in the Initial Engine Start Up

2010 ◽  
Author(s):  
Syed Adnan Qasim ◽  
Usman F. Chaudhri ◽  
M. Afzaal Malik ◽  
Riaz A. Mufti
Keyword(s):  
High Speed ◽  
Relaxation Times ◽  
Radial Clearance ◽  
Solution Technique ◽  
Engine Operation ◽  
Low Speed ◽  
Start Up ◽  
Piston Skirts ◽  
Engine Start ◽  
Speed Engine

In the normal high speed engine operation at small piston-to-bore radial clearance, elastohydrodynamic lubrication (EHL) of skirts and non-Newtonian lubricant behavior prevent adhesive wear, but in the initial engine start up, the large clearance, low speed and absence of EHL, cause start up wear. This study models 2-D upper convected Maxwell viscoelastic EHL of piston skirts at small radial clearance in a few initial low speed engine start up cycles by solving the Reynolds equation and using the inverse solution technique. The numerical analysis incorporate characteristic lubricant relaxation times and a perturbation method to predict and compare hydrodynamic and EHL pressures and film profiles. The effects of viscoelasticity on the lubricant characteristics, transverse eccentricities of piston, film thickness, and pressure fields in the hydrodynamic and EHL regimes are investigated. This study suggests that EHL film is formed at very small piston-to-bore radial clearance at low start up speed under assumed conditions to prevent start up wear as viscoelasticity produces a beneficial effect on piston skirts lubrication in the initial engine start up.

Floating Ring Balance Analysis of Journal Floating Ring Hybrid Bearing in Turbulent Regime

2014 ◽  
Vol 672-674 ◽  
pp. 1637-1641
Author(s):  
Hong Guo ◽  
Shao Lin Zhang
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Flow Equation ◽  
Radial Clearance ◽  
Speed Ratio ◽  
Turbulent Regime ◽  
Shaft Speed ◽  
Eccentricity Ratio ◽  
Pressure Boundary Condition ◽  
Balance Analysis

An externally pressurized deep/shallow pockets hybrid journal floating ring bearing compensated by flat capillary restrictor which can meet the need of high speed rotating machinery is presented in this paper. Bases on turbulent flow theory, the equations governing the flow of inner and outer fluid film in the journal floating ring bearing are established. The control equations together with the pressure boundary condition and the restrictor flow equation are solved by using the Finite Element Method. The balance of floating ring is achieved by adjusting ring-to-shaft speed ratio, inner film radial clearance and inner film eccentricity ratio. It can be seen from simulation results that the ring-to-shaft speed ratio and inner film clearance vary slightly and the floating ring can keep balance under different speed and eccentricity ratio. The variation of static and dynamic performance with eccentricity and rotational speed are calculated and analyzed based on floating ring balance.

scholarly journals Numerical study and parameter optimization of partial journal bearing using MOPSO algorithm

2019 ◽  
Vol 234 (1) ◽  
pp. 145-158
Author(s):  
SZ Mikaeeli ◽  
C Aghanajafi ◽  
P Akbarzadeh
Keyword(s):  
Particle Swarm Optimization ◽  
Numerical Study ◽  
Particle Swarm ◽  
Journal Bearings ◽  
Fluid Film ◽  
Radial Clearance ◽  
Objective Functions ◽  
Governing Equations ◽  
Swarm Optimization ◽  
Multi Objective

In this paper, multi-objective particle swarm optimization method is developed for optimizing thermo-hydrodynamic journal bearings. This paper focuses on the use of multi-objective particle swarm optimization algorithm with a combination of the thermal hydrodynamic governing equations of the fluid film (i.e. momentum and energy equations) to optimize hydrodynamic partial pad journal bearings and compare with other articles. The governing equations are solved by the central difference method with a successive over-relaxation scheme and the backward difference with an iterative technique. In the paper, the lubricant viscosity changes with the temperature variation in whole fluid film. In this optimization, the bearing power loss, the minimum oil film thickness, and the maximum oil temperature are considered as objective functions and the radial clearance and length to diameter ratio are selected as design variables. The results of the objective functions are compared to other articles. Also, this study discusses the entropy and availability of two concentric cylinders with low curvature and constant wall temperature. Calculations showed that by increasing the Eckert number, the availability increases.

A Numerical Model for Elastohydrodynamic Analysis of Plunger and Barrel Clearances in Fuel Injection Equipment

1994 ◽  
Vol 116 (3) ◽  
pp. 597-605 ◽  
Author(s):  
D. H. Gibson ◽  
P. J. Dionne ◽  
A. K. Singhal
Keyword(s):  
Numerical Model ◽  
Pressure Distribution ◽  
Fuel Injection ◽  
Fluid Film ◽  
Structural Deformation ◽  
Squeeze Film ◽  
Poisson Effect ◽  
Full Account ◽  
Film Pressure ◽  
Strongly Coupled

This paper describes a numerical model developed to predict the elastohydrodynamic (coupled solid-fluid) response of unit injector fuel systems. These systems consist of a concentric barrel and plunger with a small annular clearance. During operating (axial movement of the plunger), highly nonuniform pressure and clearance fields are developed which are strongly coupled with each other. The model simultaneously solves for the transient response of the fluid film pressure distribution and three different structural deformation components in a two-dimensional (axial-circumferential) domain. These structural components are the transverse bending of the plunger, radial expansion of the barrel, and radial growth of the plunger from a Poisson effect. The fluid film pressure distribution is governed by the transient Reynolds equation (i.e., lubrication theory) and the structural deformation components governed by linear elastic theory. Full account is taken of these hydrostatic, hydrodynamic, and squeeze-film forces generated in the fluid. The model has been applied to several injector designs. Results have been compared with known performance characteristics and have been found to be qualitatively accurate, in that locations of plunger/barrel contact, and potential for failure, have been accurately predicted.

On the Computation of Inertial Coefficients in Squeeze-Film Bearings

1987 ◽  
Vol 201 (2) ◽  
pp. 125-131
Author(s):  
M D Ramli ◽  
J Ellis ◽  
J B Roberts
Keyword(s):  
Differential Equation ◽  
Diameter Ratio ◽  
Fluid Film ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Film Pressure ◽  
Static Eccentricity ◽  
Computational Simplicity ◽  
Analytical Expressions ◽  
Good Agreement

Inertial coefficients for full squeeze-film bearings are evaluated theoretically using Smith's differential equation relating fluid-film pressure to journal acceleration (1). The variations of the non-dimensionalized inertial coefficients with static eccentricity ratio in the radial and transverse directions are compared with some corresponding values obtained from Reinhardt and Lund (2) and Szeri et al. (3). The results from these three methods show good agreement, especially for short bearings (that is bearings with low values of length–diameter ratio). However, Smith's approach has the advantage of computational simplicity and leads to fairly simple, asymptotic, analytical expressions for very short, and very long, bearings.

scholarly journals Improvement of Tilting-Pad Journal Bearing Operating Characteristics by Application of Eddy Grooves

Lubricants ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 18
Author(s):  
Eckhard Schüler ◽  
Olaf Berner
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Load Capacity ◽  
Fluid Film ◽  
Operating Characteristics ◽  
Fluid Film Bearings ◽  
Tilting Pad ◽  
Bearing Load ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

In high speed, high load fluid-film bearings, the laminar-turbulent flow transition can lead to a considerable reduction of the maximum bearing temperatures, due to a homogenization of the fluid-film temperature in radial direction. Since this phenomenon only occurs significantly in large bearings or at very high sliding speeds, means to achieve the effect at lower speeds have been investigated in the past. This paper shows an experimental investigation of this effect and how it can be used for smaller bearings by optimized eddy grooves, machined into the bearing surface. The investigations were carried out on a Miba journal bearing test rig with Ø120 mm shaft diameter at speeds between 50 m/s–110 m/s and at specific bearing loads up to 4.0 MPa. To investigate the potential of this technology, additional temperature probes were installed at the crucial position directly in the sliding surface of an up-to-date tilting pad journal bearing. The results show that the achieved surface temperature reduction with the optimized eddy grooves is significant and represents a considerable enhancement of bearing load capacity. This increase in performance opens new options for the design of bearings and related turbomachinery applications.

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