Thermohydrodynamic Characteristics and Stability Analysis for a Journal Hybrid Floating Ring Bearing Within Laminar and Turbulent Mixed Flow Regime

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Yang Shuai ◽  
Guo Hong ◽  
Zhang Shao-Lin ◽  
Xia Bo-Qian
Keyword(s):  
Turbulent Flow ◽  
Thermal Effect ◽  
Flow Regime ◽  
High Speed ◽  
Load Capacity ◽  
Kinematic Model ◽  
Fluid Film ◽  
Mixed Flow ◽  
Fluid Films ◽  
Friction Moment

Abstract There exist laminar and turbulent flow in the inner and outer fluid film of the hybrid floating ring bearing at high speed. The finite element method (FEM) and finite difference method (FDM) are used to solve the thermohydrodynamic (THD) lubrication model within the laminar and turbulent mixed flow regime which governs the pressure, temperature, viscosity, and Reynolds number of the two-layer fluid films together for a type of the journal hybrid floating ring bearing with deep/shallow pockets. The static and dynamic characteristics are analyzed including the load capacity, the friction moment, the volume flowrate, the stiffness, and damping coefficients with consideration of the mixed flow and thermal effect based on the floating ring balance. The unitized kinematic model of the shaft and floating ring is proposed to deduce the instability criteria and calculate the threshold rotational speed of a rigid Jeffcott rotor system supported on two hybrid floating ring bearings by the Routh–Hurwitz method. The results present that there are non-uniform pressure and temperature profile within the fluid film field, and the laminar flow and turbulent flow appear at certain positions of film through theory and experiment, separately. The mixed flow effect promotes the bearing load capacity and the friction moment at high speed and eccentricity, and the system threshold speed drops within the mixed flow regime. Therefore, the thermal effect and mixed flow existing in the fluid film should be considered into the lubrication analysis for the floating ring bearing.

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.

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.

Performance Analysis of High Speed Floating Ring Hybrid Bearing in the Laminar and Turbulent Regimes

2011 ◽  
Vol 197-198 ◽  
pp. 1776-1780 ◽  
Author(s):  
Hong Guo ◽  
Bo Qian Xia ◽  
Shao Qi Cen
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Load Capacity ◽  
Flow Equation ◽  
The Finite Element Method ◽  
Static And Dynamic Characteristics ◽  
Hybrid Bearing

This paper presents a theoretical study concerning the static and dynamic characteristics of high speed journal floating ring hybrid bearing compensated by interior restrictor under laminar flow and turbulent flow respectively. The turbulent flow fluid film control equations and the pressure boundary conditions of this floating ring bearing together with the restrictor flow equation are solved by using the Finite Element Method. The variation regularity of static and dynamic characteristics such as load capacity, friction power loss, stiffness, damping etc. is analyzed. By comparing the laminar flow results and turbulent flow results, it is found that the characteristics coefficients are adjacent under small Reynolds number (laminar flow is dominant). But the characteristics coefficients are discrepant under big Reynolds number (turbulent flow is dominant). So turbulence lubrication theory is more accurate to high speed floating ring bearing.

BLENDING CHARACTERISTICS OF HIGH-SPEED ROTARY IMPELLERS

2013 ◽  
Vol 34 (4) ◽  
pp. 427-434 ◽  
Author(s):  
Ivan Fořt ◽  
Pavel Seichter ◽  
Luboš Pešl ◽  
František Rieger ◽  
Tomáš Jirout
Keyword(s):  
Turbulent Flow ◽  
Flow Regime ◽  
High Speed ◽  
Large Scale ◽  
Energy Savings ◽  
Axial Flow ◽  
Power Input ◽  
Maximum Energy ◽  
Cylindrical Vessel ◽  
Turbulent Flow Regime

Abstract This paper presents a comparison of the blending efficiency of eight high-speed rotary impellers in a fully baffled cylindrical vessel under the turbulent flow regime of agitated charge. Results of carried out experiments (blending time and impeller power input) confirm that the down pumping axial flow impellers exhibit better blending efficiency than the high-speed rotary impellers with prevailing radial discharge flow. It follows from presented results that, especially for large scale industrial realisations, the axial flow impellers with profiled blades bring maximum energy savings in comparison with the standard impellers with inclined flat blades (pitched blade impellers).

A Thermoelastohydrodynamic Analysis for the Static Performance of High-Speed Heavy Load Tilting-Pad Journal Bearing Operating in the Turbulent Flow Regime and Comparisons to Test Data

2018 ◽  
Author(s):  
Hirotoshi Arihara ◽  
Yuki Kameyama ◽  
Yoshitaka Baba ◽  
Luis San Andrés
Keyword(s):  
Turbulent Flow ◽  
Flow Regime ◽  
Flow Rate ◽  
Power Loss ◽  
High Speed ◽  
Hydrodynamic Pressure ◽  
Thermally Induced ◽  
Turbulent Flow Regime ◽  
Tilting Pad ◽  
Static Performance

Tilting-pad journal bearings (TPJBs) ensure rotordynamic stability that could otherwise produce dangerously large amplitude rotor oil-whirl/whip motions in high speed rotating machinery. Currently, highly efficient turbo compressors demand an ever increasing rotor surface speed and specific load on its support bearings. The accurate prediction of bearing performance is vital to guarantee reliable products, specifically with regard to reducing maximum bearing pad temperature and drag power losses, and operating with the least flow rate while still maximizing load capacity. The hydrodynamic pressure and heat generation in an oil film acting on a bearing pad produce significant mechanical and thermal deformations that change the oil film geometry (clearance and preload) to largely affect the bearing performance, static and dynamic. In addition, a high surface speed bearing often operates in the turbulent flow regime that produces a notable increase in power loss and a drop in maximum pad temperature. This paper details a thermoelastohydrodynamic (TEHD) analysis model applied to TPJBs, presents predictions for their steady-load performance, and discusses comparisons with experimental results to validate the model. The test bearing has four pads with a load between pads configuration; its length L = 76.2 mm and shaft diameter D = 101.6 mm (L/D = 0.75). The rotor top speed is 22.6 krpm, i.e. 120 m/s surface speed, and the maximum specific load is 2.94 MPa for an applied load of 23 kN. The test procedure records shaft speed and applied load, oil supply pressure/temperature and flow rate, and also measures the pads’ temperature and shaft temperature, as well as the discharge oil (sump) temperature. The TEHD model couples a generalized Reynolds equation for the hydrodynamic pressure generation with a three-dimensional energy transport equation for the film temperature. The pad mechanical deformation due to pressure utilizes the finite elemental method, whereas an analytical model estimates thermally induced pad crowning deformations. For operation beyond the laminar flow regime, the analysis incorporates the eddy viscosity concept for fully developed turbulent flow operation. Current predictions demonstrate the influence of pressure and temperature fields on the pads mechanical and thermally induced deformation fields, and also show static performance characteristics such as bearing power loss, flow rate, and pad temperatures. The comparisons of test results and analysis results reveal that turbulent flow effects significantly reduce the pads’ maximum temperature while increasing the bearing power loss. Turbulent flow mixing increases the diffusion of thermal energy and makes more uniform the temperature profile across the film.

Research on Static Characteristics of Deep/Shallow Pockets Hybrid Bearing under Laminar and Turbulent Mixed Regimes

2011 ◽  
Vol 291-294 ◽  
pp. 1516-1520
Author(s):  
Hong Guo ◽  
Shao Lin Zhang ◽  
Shao Qi Cen
Keyword(s):  
Laminar Flow ◽  
Turbulent Flow ◽  
High Speed ◽  
Flow Equation ◽  
Static Characteristics ◽  
Mixed Flow ◽  
Flow Models ◽  
Load Carrying ◽  
Flow Part ◽  
Hybrid Bearing

For high speed hybrid journal bearing with deep/shallow pockets, film thickness and film Reynolds number vary considerably in different position. Laminar flow and turbulent flow exist simultaneously in the bearing film. This paper establishes the laminar and turbulent mixed film control equations and the pressure boundary conditions together with the restrictor flow equation for a deep/shallow pockets journal hybrid bearing compensated by interior restrictor. The static characteristics such as attitude angle, load carrying capacity, friction power loss and flow volume rate are given by solving the equations with Finite Element Method. By comparing the laminar, turbulent and mixed flow results, it can be seen that the coefficients are proximity under journal speed 5000 rpm (only part of deep pockets is turbulent flow). But the characteristics coefficients of three flow models contrast evidently under journal speed 50000 rpm (deep and shallow pockets are turbulent flow, part of bearing land is laminar flow). Laminar and turbulence mixed flow lubrication theory is more accurate to high speed hybrid bearing with deep/shallow pockets.

A Thermoelastohydrodynamic Analysis for the Static Performance of High-Speed—Heavy Load Tilting-Pad Journal Bearing Operating in the Turbulent Flow Regime and Comparisons to Test Data

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Hirotoshi Arihara ◽  
Yuki Kameyama ◽  
Yoshitaka Baba ◽  
Luis San Andrés
Keyword(s):  
Turbulent Flow ◽  
Flow Regime ◽  
Flow Rate ◽  
Power Loss ◽  
High Speed ◽  
Hydrodynamic Pressure ◽  
Thermally Induced ◽  
Turbulent Flow Regime ◽  
Tilting Pad ◽  
Static Performance

Tilting-pad journal bearings (TPJBs) ensure rotordynamic stability that could otherwise produce dangerously large amplitude rotor oil-whirl/whip motions in high-speed rotating machinery. Currently, highly efficient turbo compressors demand an ever increasing rotor surface speed and specific load on its support bearings. The accurate prediction of bearing performance is vital to guarantee reliable products, specifically with regard to reducing maximum bearing pad temperature and drag power losses, and operating with the least flow rate while still maximizing load capacity. The hydrodynamic pressure and heat generation in an oil film acting on a bearing pad produce significant mechanical and thermal deformations that change the oil film geometry (clearance and preload) to largely affect the bearing performance, static, and dynamic. In addition, a high surface speed bearing often operates in the turbulent flow regime that produces a notable increase in power loss and a drop in maximum pad temperature. This paper details a thermoelastohydrodynamic (TEHD) analysis model applied to TPJBs, presents predictions for their steady-load performance, and discusses comparisons with experimental results to validate the model. The test bearing has four pads with a load between pads configuration; its length L = 76.2 mm and shaft diameter D = 101.6 mm (L/D = 0.75). The rotor top speed is 22.6 krpm, i.e., 120 m/s surface speed, and the maximum specific load is 2.94 MPa for an applied load of 23 kN. The test procedure records shaft speed and applied load, oil supply pressure/temperature and flow rate, and also measures the pads' temperature and shaft temperature, as well as the discharge oil (sump) temperature. The TEHD model couples a generalized Reynolds equation for the hydrodynamic pressure generation with a three-dimensional energy transport equation for the film temperature. The pad mechanical deformation due to pressure utilizes the finite elemental method, whereas an analytical model estimates thermally induced pad crowning deformations. For operation beyond the laminar flow regime, the analysis incorporates the eddy viscosity concept for fully developed turbulent flow operation. Current predictions demonstrate the influence of pressure and temperature fields on the pads mechanical and thermally induced deformation fields and also show static performance characteristics such as bearing power loss, flow rate, and pad temperatures. The comparisons of test results and analysis results reveal that turbulent flow effects significantly reduce the pads' maximum temperature while increasing the bearing power loss. Turbulent flow mixing increases the diffusion of thermal energy and makes more uniform the temperature profile across the film.

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