Hybrid Journal Bearing System Research Articles

Study on Thermal Properties of Hybrid Journal Bearing for Super High Speed Grinding Machine

As the high speed bearings, hybrid journal bearings are usually used in high and super high speed grinding machine spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of bearing is a key factor to lower the accuracy of the spindle system and limit the bearings working speed, so restrict the bearing applications. In this paper, the model of hybrid journal bearing is established to analyze the heat mechanism. In addition, the temperature field distribution for the certain hybrid journal bearing at high speed is studied by ANSYS considering the heat transfer characters between fluid and solid. The experiment of temperature for hybrid journal bearing system in super high speed grinding machine is also performed. The thermal properties and the measure for controlling temperature rise of such bearings are analyzed.

Performance of slot-entry hybrid journal bearings considering combined influences of thermal effects and non-Newtonian behavior of lubricant

This paper presents theoretical investigations of the thermal and rheological effects of lubricant on the performance of symmetric and asymmetric slot-entry hybrid journal bearing system. FEM has been used to solve the Reynolds equation governing flow of lubricant in bearing clearance space along with restrictor flow equation, energy equation and conduction equation using suitable iterative technique. The thermohydrostatic (THS) rheological performance of slot-entry hybrid journal bearings are studied for small temperature variation of the lubricant. The computed results reveal that variation of viscosity due to temperature rise and non-Newtonian behavior of lubricant affects the bearing performance quite significantly.

A study of misaligned electrorheological fluid lubricated hole-entry hybrid journal bearing

The present work describes a theoretical study to demonstrate the effect of the journal misalignment on the performance of an orifice compensated hole-entry hybrid journal bearing system lubricated with ER fluid. The journal misalignment has been accounted for by defining a pair of misalignment parameters sigma and delta. Continuous Bingham Model has been used to describe the behavior of ER fluid. The bearing static and dynamic characteristic parameters presented in the study indicate that the effect of journal misalignment is in general to cause a reduction in bearing dynamic characteristic parameters whereas the electric field in the ER fluid is to partially compensate this loss.

Analysis of thermal effects in capillary compensated hole-entry hybrid journal bearings lubricated with a non-Newtonian lubricant

The present work describes the performance characteristics of the capillary compensated symmetric and asymmetric hole-entry hybrid journal bearing systems considering the combined influence of the temperature rise and the non-Newtonian behaviour of the lubricant. The required governing equations have been solved using the finite-element method and a suitable iterative technique. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The thermohydrostatic rheological performance of symmetric and asymmetric hole-entry hybrid journal bearing configurations is studied. The computed results show that the variation of viscosity due to the temperature rise and the non-Newtonian behaviour of the lubricant affects the performance of the hole-entry hybrid journal bearing system quite significantly.

A study of misaligned roughened two‐lobe hole‐entry hybrid journal bearing

PurposeThe non‐recessed hybrid journal bearings of cylindrical type, when operating at higher rotational speeds can suffer self‐exited vibrations(oil‐whirl Instability), which can cause excessive rotor motion causing bearing and sometimes total machine failure. The multi‐lobe journal bearing exhibits better stability as well as a superior capability to suppress oil‐whirl. The paper aims to present a theoretical study pertaining to a two‐lobe hole‐entry hybrid journal bearing by considering the combined influence of surface roughness and journal misalignment on the performance of the bearing.Design/methodology/approachThe average Reynolds equation governing the flow of lubricant in the clearance space between the rough bearing surfaces together with the equation of flow through a capillary restrictor has been solved using FEM. The bearing performance characteristics have been simulated for a two‐lobe hole‐entry hybrid journal bearing for the various values of offset factor, restrictor design parameter, surface roughness parameter, surface pattern parameter and journal misalignment parameters.FindingsThe two‐lobe hole‐entry hybrid journal bearing system with an offset factor greater than one indicates significant improvement of the order of 15‐25 percent in the values of direct stiffness and direct damping coefficients compared to a circular hole‐entry hybrid journal bearing system. Also the lubricant flow of a two‐lobe hole‐entry hybrid journal bearing is reduced by 25 percent vis‐à‐vis circular bearing.Originality/valueThe present work is original of its kind, in case of two‐lobe hole‐entry hybrid journal bearing. The results are quite useful for the bearing designer.

Thermohydrostatic analysis of capillary compensated symmetric hole‐entry hybrid journal bearing operating with non‐Newtonian lubricant

PurposeEvery high speed machine, demanding high level of perfection, can operate successfully through a precise design of bearings. Such a design can be formulated after carefully studying both static and dynamic characteristics of the journal bearing. The present paper aims to describe the study of static and dynamic performance of a hole‐entry hybrid journal bearing system compensated with capillary restrictor by considering the combined influence of thermal effects and non‐Newtonian behavior of the lubricant.Design/methodology/approachThe variation of the viscosity due to the non‐Newtonian behavior of the lubricant and temperature rise is considered in the study. The numerical solution of the generalized Reynold's, equation governing the flow of the lubricant having variable viscosity along with the energy and heat conduction equations is obtained using finite element method. The non‐Newtonian lubricant has been assumed to follow the cubic shear stress law. The study includes performance of a double row symmetric hole entry hybrid journal bearing configuration containing 12 holes per row.FindingsThe results indicate that change in viscosity of lubricant affects the bearing design parameters.Originality/valueThe paper shows that accurate theoretical modeling of the bearing is an effective tool for the selection of design parameter such as bearing land width ratio (ab), restrictor design parameter (Cs2), and non‐linearity factor (K).

Performance of an Orifice Compensated Two‐Lobe Hole‐Entry Hybrid Journal Bearing

The work presented in this paper aims to study the performance of a two‐lobe hole‐entry hybrid journal bearing system compensated by orifice restrictors. The Reynolds equation governing the flow of lubricant in the clearance space between the journal and bearing together with the equation of flow through an orifice restrictor has been solved using FEM and Galerkin′s method. The bearing performance characteristics results have been simulated for an orifice compensated nonrecessed two‐lobe hole‐entry hybrid journal bearing symmetric configuration for the various values of offset factor (δ), restrictor design parameter , and the value of external load . Further, a comparative study of the performance of a two‐lobe hole‐entry hybrid journal bearing system with a circular hole‐entry symmetric hybrid journal bearing system has also been carried out so that a designer has a better flexibility in choosing a suitable bearing configuration. The simulated numerical results indicate that for the two‐lobe symmetric hole‐entry hybrid journal bearing system with an offset factor (δ) greater than one provides 30 to 50 percent larger values of direct stiffness and direct damping coefficients as compared to a circular symmetric hole‐entry hybrid journal bearing system.

Non‐Newtonian and thermal effects in constant flow valve compensated symmetric hole‐entry hybrid journal bearing

AbstractEvery high speed machine, demanding high level of perfection, can operate successfully through a precise design of bearings. Such a design can be formulated after carefully studying both static and dynamic characteristics of the journal bearing. The present paper described the study of static and dynamic performance of a hole‐entry hybrid journal bearing system compensated with constant flow valve restrictor by considering the combined influence of thermal effects and non‐Newtonian behaviour of the lubricant. The variation of the viscosity due to the non‐Newtonian behaviour of the lubricant and temperature rise has been considered in the study. The numerical solution of the generalized Reynolds equation governing the flow of the lubricant, having variable viscosity along with the energy and heat conduction equations, was obtained using finite element method. The non‐Newtonian lubricant has been assumed to follow the cubic shear stress law. The study included the performance of a double row symmetric hole‐entry hybrid journal bearing configuration containing 12 holes per row. The results presented in this paper indicate that change in viscosity of lubricant affects the performance of the hole‐entry hybrid journal bearing system quite significantly. Copyright © 2007 John Wiley & Sons, Ltd.

Effect of Wear on the Performance of Non-Recessed Orifice Compensated Hybrid Journal Bearing

A bearing subjected to frequent start/stop operations is worn progressively due to rubbing. As a consequence, the geometry of the bearing changes and the performance is affected. This paper presents a theoretical study of the performance of an orifice compensated worn non-recessed hole-entry hybrid journal bearing system. The finite element method has been used to solve the Reynolds equation, governing the flow of the lubricant in the clearance space between the journal and the bearing, along with a restrictor flow equation. The global system equation with the orifice restrictor is nonlinear, which is solved by an iterative technique using the Newton-Raphson method. Two types of journal bearing configurations, having symmetrical and asymmetrical distribution of supply holes around the circumferential direction, have been investigated in the present study. The effect of the wear depth on the journal bearing performance characteristics have been presented for a wide range of restrictor design parameters and external loads. The study demonstrates that the wear affects the bearing performance parameters and the degree of variation is affected by the operating condition, the bearing configuration, and the type of restrictor used. The influence of wear can be reduced by a proper selection of the bearing configuration (symmetrical/asymmetrical), the restrictor, and its design parameter.

Influence of Surface Roughness on Non-Newtonian Thermohydrostatic Performance of a Hole-Entry Hybrid Journal Bearing

A general solution scheme to account the surface roughness and the cross-film viscosity variation of lubricant due to its non-Newtonian behavior and rise in fluid-film temperature for the analysis of fluid-film bearings is presented. The combined influence of surface roughness, non-Newtonian behavior of lubricant, and thermal effects on the performance of a hole-entry hybrid journal bearing system has been investigated. The surface roughness, especially stationary roughness (i.e., rough bearing and smooth journal) with a transverse pattern was found to partially compensate for the loss in load-carrying capacity due to the thermal and/or non-Newtonian behavior of lubricant effects. It limits 18.86% loss in load-carrying capacity due to the thermal effect to only 1.6% and 33.99% loss due to the combined influence of non-Newtonian lubricant and thermal effect to 16.76%.

Performance of worn non-recessed hole-entry hybrid journal bearings

Non-recessed journal bearings have been successfully used in various engineering applications because of their good performance over a wide range of speed and load, besides their relative simplicity in manufacturing. Due to many starts and stops in its lifespan, the bearing bush wears progressively on account of rubbing, which affects bearing performance. The present work is an attempt to analytically study the performance of a worn non-recessed (hole-entry) capillary-compensated hybrid journal-bearing system. FEM has been used to solve the Reynolds equation, governing the flow of lubricant in the bearing clearance space along with the restrictor flow equation using suitable iterative technique. A study is conducted for two configurations, i.e., symmetrical and asymmetrical hole-entry journal-bearing system. The simulated results of bearing characteristics parameters in terms of maximum fluid-film pressure, minimum fluid-film thickness, flow rate, frictional torque, rotor dynamic coefficients, stability threshold speed and whirl frequency ratio, etc. have been presented for the wide range of various values of load and speed. The results indicate that the wear affects the bearing performance considerably; therefore, a due consideration of wear defect should be given for an accurate prediction of the bearing performance over a number of cycles. The computed results further indicate that the influence of wear defect on journal bearing performance may be minimized if a designer selects a suitable bearing configuration.

Study of orifice compensated hole-entry hybrid journal bearing considering surface roughness and flexibility effects

The present work describes a theoretical study to demonstrate the combined influence of surface roughness and bearing flexibility on the performance of an orifice compensated hole-entry hybrid journal bearing system. The average Reynold equation governing the flow of lubricant in the clearance space between rough journal and bearing surfaces and 3-dimensional elasticity equation governing the displacement field in the bearing shell have been solved simultaneously using finite element method. The influence of transverse, isotropic and longitudinal roughness patterns on the performance of orifice compensated hole-entry journal bearing configuration have been studied for the various values of surface roughness parameter ( Λ), surface pattern parameter ( γ) and bearing shell deformation coefficient ( D ¯ c ) . The study indicate that the reduction in the bearing characteristic parameters such as load carrying capacity, fluid-film stiffness and damping coefficients due to the bearing shell flexibility effect can be partially compensated in roughened hole-entry flexible journal bearing system by making a proper selection of roughness patterns. The results presented in the study demonstrates that for an accurate prediction of bearing characteristic data, the consideration of combined influence of surface roughness and bearing flexibility effects in the analysis may be more appropriate to use.

On the restrictor design parameter of hybrid journal bearing for optimum rotordynamic coefficients

The precise design of bearings can be formulated after carefully studying both static and dynamic characteristics of journal bearing. The present paper deals with the investigation of restrictor design parameter of a capillary compensated hole–entry hybrid journal bearing system for optimum stiffness and dynamic coefficients of the bearing. The bearing flexibility and variation of viscosity due to temperature rise of the lubrication has been considered in the study. The numerical solution of governing equations, i.e. Reynold's, energy, heat conduction, and elasticity equations has been obtained using finite element method. The study includes performance of a double row symmetric hole–entry hybrid journal bearing configuration containing 12 holes per row. The results presented herein indicate that change in viscosity of lubricant and bearing flexibility affects the bearing design parameter, so the stability of rigid rotor also gets affected. The results show that theoretical modeling of the bearing presented in this work will certainly prove to be effective tool for the selection of restrictor design parameter, C ¯ s 2 for optimum stability parameters.

The Stability Margin of a Roughened Hole-Entry Hybrid Journal Bearing System

The present work describes a theoretical investigation into the effect of surface roughness on the stability margin of an orifice-compensated, hole-entry hybrid journal bearing system. A modified form of the average Reynolds equation is used for the solution of a lubricant flow field in the clearance space of a rough journal bearing system. The effects of surface roughness parameter (Λ), variance ratio (V̄rj), and the surface orientations (γ) on the bearing flow, load-carrying capacity, and stability threshold speed margin are studied. The study indicates that the bearing configurations having surface roughness on one of the opposing surfaces (stationary or moving roughness) show an opposite trend between stability threshold speed margin and load-carrying capacity. However, the bearing configurations having transverse- and isotropic-type roughness patterns on both bearing and journal surfaces provide an improved value of both stability threshold speed margin and load-carrying capacity only when the surface roughness has a variance ratio value between 0.49 and 0.59 for the transverse roughness pattern and between 0.59 and 0.84 for the isotropic roughness pattern.

Performance of an Orifice Compensated Hole-Entry Hybrid Journal Bearing System Considering Surface Roughness and Thermal Effects

The present study describes the static and dynamic performance of an orifice-compensated hole-entry hybrid journal bearing system considering the combined influence of surface roughness and thermal effects. The Dowson generalized Reynolds equation governing the flow of variable viscosity lubricant in the clearance space of a smooth journal bearing is modified using the flow factors developed by Patir and Cheng. The effects of surface roughness parameter Λ, variance ratio V̄rj, and the surface orientations vis-á-vis transverse, isotropic, and longitudinal roughness patterns on the performance characteristics of bearings are studied. The rough bearing and smooth journal combination (V̄rj = 0.0) with a transverse roughness pattern (γ = 1/6) is observed to show the largest predicted load-carrying capacity of the bearing. The smooth bearing and rough journal combination (V̄rj = 1.0) with a transverse roughness pattern shows the highest stability threshold speed margin.

Stability Margin of Hybrid Journal Bearing: Influence of Thermal and Elastic Effects

This paper deals with the stability margin of a constant flow valve compensated hole-entry hybrid journal bearing system considering bearing flexibility and variation of viscosity due to temperature rise of the lubricant. The journal temperature is computed on the basis of average fluid-film temperature and axisymmetric isothermal element is assumed. The coupled solution of Reynold’s, energy, conduction, and elasticity equations is obtained using finite element method. The performance of a symmetric and asymmetric hole-entry hybrid journal bearing configurations is studied. The results presented in the study indicate that the bearing flexibility and temperature rise of the lubricant fluid-film affects the performance of the hole-entry hybrid journal bearing system quite significantly and proper selection of restrictor design parameter is quite useful in maintaining the fluid film thickness and threshold speed of the journal.

Study of hole-entry hybrid journal bearing system considering combined influence of thermal and elastic effects

A theoretical model is developed to study the performance of a hole-entry hybrid journal bearing system by considering variation of viscosity due to temperature rise of the lubricant in the analysis. The deformation of bush due to fluid-film pressure and temperature has been considered to establish the modified fluid-film profile. The journal temperature is computed on the basis of the fluid-film temperature. The relevant governing equations have been solved using the finite element method and a suitable iterative technique. The thermoelastohydrostatic performance of an orifice compensated symmetric and asymmetric hole-entry hybrid journal bearing configurations has been studied for the chosen bearing operating and geometric parameters. The results presented in the study indicate that the variation of viscosity due to temperature rise of the lubricant fluid-film have a quite appreciable influence on the static and dynamic performance of a hole-entry hybrid journal bearing system.

Performance of Externally Pressurized Non-Recessed Roughened Journal Bearing System Operating with Non-Newtonian Lubricant

The present work describes the static and dynamic performance of an orifice compensated hole-entry hybrid journal bearing system considering the combined influence of surface roughness and non-Newtonian behavior of the lubricant. The modified form of average Reynolds equation has been used for the solution of the lubricant flow field in the clearance space of a rough journal bearing system. The non-Newtonian lubricant has been assumed to obey the power law model. The effects of surface roughness parameter (Λ), variance ratio (V̄ rj) and the surface orientations such as transverse, isotropic and longitudinal surface orientations on the performance characteristics of the bearing have been studied for various values of power law index (n). Scheduled for Presentation at the 58th Annual Meeting in New York City April 28–May 1, 2003

On The Stability Margin of Hole-Entry Hybrid Journal Bearings Considering Viscosity-Temperature Variation

The present study describes the theoretical investigation into the stability margin of a constant flow valve compensated hole-entry hybrid journal bearing system considering the variation of viscosity due to temperature rise of the lubricant. The journal temperature is computed on the basis of average fluid-film temperature. The relevant governing equations are solved using a finite element method and a suitable iterative technique. The thermohydrostatic performance of symmetric and asymmetric hole-entry hybrid journal bearing configurations are studies. The results presented in the study indicate that the variation of viscosity due to temperature rise of the lubricant fluid-film affects the performance of hole-entry hybrid journal bearing system quite significantly.

Influence of surface roughness effects on the performance of non-recessed hybrid journal bearings

The effect of journal and bearing surface roughness on the performance of a capillary compensated hole-entry hybrid journal bearing system has been theoretically studied. The analysis considers the average Reynold’s equation for the solution of lubricant flow field in the clearance space of a rough surface journal bearing system. The finite element method and Galarkin’s technique has been used to derive the system equation for the lubricant flow field. The non-dimensional parameters Λ (surface roughness parameter) and γ (surface pattern parameter) have been defined to represent the magnitude of height distribution of surface irregularities and their orientation, respectively. The influence of surface roughness on the bearing performance has been studied for the transverse, isotropic and longitudinal surface patterns. The bearing performance characteristics have been computed for both symmetric and asymmetric capillary compensated hole-entry journal bearing configurations for the various values of surface roughness parameter (Λ), surface pattern parameter ( γ) and restrictor design parameter ( C ̄ S2 ). The computed results indicate that the inclusion of surface roughness effects in the analysis affects the performance of a bearing quite significantly vis-à-vis smooth surface bearing. The study indicates that for generation of accurate bearing characteristic data, the inclusion of surface roughness effects in the analysis is essential.