2015 stl emeeting at dallas (1)
TRANSCRIPT
THERMOELASTIC DISTORSION AND ITS CONTROL IN THIN FILM HYDRODYNAMIC LUBRICATION THRUST BEARINGS
Presented byFarooq Ahmad Najar
Under track Fluid Film Bearings2015 STLE Annual Meeting & Exhibition,17-21 May 2015
Venue: Trinity 1, Omni Hotel Dallas, Texas USA
Time: 2030 hours
Dated: 21 May 2015
Session Chair: Michael Fillon
THERMOELASTIC DISTORSION AND ITS CONTROL IN THIN FILM HYDRODYNAMIC LUBRICATION THRUST BEARINGS
By Farooq Ahmad Najar
Research Scholar Under the Supervision of
Prof. G A Harmain
Department of Mechanical Engineering National Institute of Technology
Srinagar-190006, (J&K), India
Contents Outline
Objectives of present work
Motivation
Methodology
Numerical work & Solutions
Reynolds Equation
Energy Equation
Heat Conduction Equation
Biharmonic equation
Results and Discussions
Conclusion
Overview Conventional cooling of thrust bearings
Thermo elastic deformation
Piezoelastic deformation
Material Failure of pads due to overheating.
Innovative method of cooling pads.
Increased Efficiency and availability of serviceability
Thrust bearing pads and their characteristic dimensions.
Deformations and damage of Thrust Segments
Less due to Pressure & More due to Temperature
Handmade Pad Set Model for Thrust Bearing Presenting the new Cooling arrangement
Problem Description The present problem addresses the control of thermal
effects on a sector shaped pad extensively used in thrust bearings which supports the heavy axial loads.
Large hydro-generator thrust bearings are susceptible to thermo-elastic deformation when oil film thickness is subjected to high pressure and temperature which can even lead to the bearing failure.
The present study is an effort towards reducing the oil film temperature by incorporating a suitable cooling arrangement in the proximity of heat source.
The cooling circuit, in this study, essentially follows a path of hot spots observed by solving energy equation and generalized conduction equation.
The numerical scheme followed during investigation is finite difference method (FDM).
Objectives
To compute the pressure distribution in the oil film between pad surface and runner by solving generalized Reynolds’s Equation after introducing a cooling circuit.
To compute the temperature distribution in the oil film by solving Energy Equation with and without viscosity variation in conventional pad and non conventional one.
To compute the heat transfer between pad and water circuit by solving 3D heat conduction equation.
To study the pressure induced deformation and temperature induced deformation of pad by solving 4th order bi-harmonic equation.
Motivation Control of thermal effects. Temperature-viscosity variations lead to hot-spots ----
thin Babbitt lining gets damaged to a great extent. The conventional cooling --outside of thrust bearing
pads. An alternative way of cooling --Close proximity of
cooling arrangement to the actual location of heat production.
Governing Equations Generalized Reynolds Equation
Equation of Film Geometry
Energy Equation
Three Dimensional Heat Conduction Equation
4th Order Bi-harmonic Equation.
Reynolds Equation
where h is the film thickness, µ is the viscosity of oil and ω is the angular speed of the runner.
Equation of Film Geometry
where h is the film thickness, h0 is the minimum film thickness, hs is the taper, θ and θt are the general angular extent and total angular extent of the pad respectively.
Energy Equation
where, ρ is the density of oil and cv is the specific heat of the oil
Three dimensional heat conduction equation
Kr, Kθ and Kz represent thermal conductivity of the pad in radial, circumferential and (thickness) directions respectively, and r,θ and z are the cylindrical coordinates.
Biharmonic Equation
Where Load = Hydrodynamic Pressure or Thermal stress
The numerical strategy followed for pressure distribution
Continued
Continued
Pressure Generation
Different possible cooling arrangements in a thrust pad
Flow chart for computation
Continued
Temperature Profile
Maximum nodal Temperature (oC) Values along with the depth of Pad.
Pad DepthIn terms of Z’s
Flow Velocity(V=0.5m/s) Flow Velocity(V=1.0m/s) Flow Velocity(V=1.5m/s) Flow Velocity(V=2.0m/s)
Z=2 57.30 56.14 55.11 54.18
Z=3 52.05 50.48 49.05 47.70
Z=4 49.85 48.11 46.50 44.77
Z=5 48.93 47.11 45.43 43.09
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