Modeling lubricant flow between thrust-bearing pads

Inlet temperature is one of the main inputs in all models for the analysis of fluid film bearing performance. At the same time, inlet temperature distribution and also oil velocity distribution at the inlet are the result of flow phenomena in the gap between the bearing pads. These phenomena are complex and in many cases further affected by any special arrangements of forced oil supply to the gap between pads. The reason for such arrangements is the more efficient introduction of externally cooled lubricant. Not many details are known about any flow phenomena in the gap between the pads and even less if the bearing is fitted with any kind of directed lubrication system. Contemporary tools of computational fluid dynamics (CFD) enable one to study the flow between bearing pads and even to build models of a whole hydrodynamic bearing. Preliminary results of modeling lubricant flow in the gap, in a bearing with a direct oil supply system will be presented in this paper. The effects of modified inlet oil temperature on some aspects of bearing performance are also presented.     

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.     

Rolling Contact Testing of Vapor Phase Lubricants—Part II: System Performance Evaluation

The relative effects of several vapor lubrication parameters on bearing performance were examined using a ball-on-rod tester. Lubricants included in the evaluation were a tertiary-butylphenyl phosphate (TBPP), a 2 cSt polyalphaolefin blended with 15 percent TBPP (PAO+), the TBPP blended with 33 percent tributyl phosphate (TBPP+), a cyclophosphazine (X-1P), a polyphenylether (5P4E), and a perfluoroalkylether (Z). Parameters included in the study were bearing temperature, vapor concentration, and vapor temperature. Additionally, a solid lubricant coating was included to improve the bearing performance under cold-start conditions. The lubricants containing phosphorus demonstrated the best high temperature performance. The TBPP lubricant failed shortly after test at 650°C., while the X-1P lubricant performed satisfactorily over an eight-hour period at 650°C. The TBPP+ lubricant demonstrated the widest temperature range capability, with 600°C operation and a projected pump-ability point of–-45°C. Lubricant concentration was the most significant system parameter affecting bearing friction and wear.     

压缩机可倾瓦轴承先进模型预测与测试数据的对比

The paper details fundamental progress on the analysis of tilting pad journal bearings that includes both pivot flexibility and pad surface deformation due to pressure and pad crowning due to thermal effects.The work introduces a novel model for the mixing of flow and thermal energy at a lubricant feed port that sets the temperature of the lubricant entering a pad leading edge. Precise estimation of this temperature, the inlet oil viscosity, and the flow rate entering a pad largely determines the temperature rise along the pad lubricated surface as well as the drag power loss, and ultimately the bearing load capacity. The model predictions are validated against bearing test data applicable to a compressor. The paper delivers recommendations for a novel feed port efficiency parameter that represents various types of oil supply configurations. Importantly enough, and as is done in actual practice, the model allows the specification of the delivery flow date into the bearing rather than a supply pressure.     

Influence of Particles on the Loading Capacity and the Temperature Rise of Water Film in Ultra-high Speed Hybrid Bearing

Ultra-high speed machining technology enables high efficiency, high precision and high integrity of machined surface. Previous researches of hybrid bearing rarely consider influences of solid particles...     

水润滑动静压滑动轴承的临界温度研究

建立水润滑动静压滑动轴承的弹流润滑几何模型,采用考虑热效应的Reynolds方程,对水润滑动静压滑动轴承进行弹流理论分析,计算一定供水压力下当润滑剂局部最高温度达到临界值时不同的速度、载荷极限值;分析润滑介质、轴瓦材料以及供水压力变化对速度、载荷达到极限值时的临界温度曲线的影响,得到润滑剂局部最高温度达到临界温度时的轴承速度和载荷极限值的临界温度曲线,并通过拟合得到曲线的函数表达式。研究结果显示:海水润滑下的临界温度曲线高于纯水润滑,塑料轴瓦的临界温度曲线高于陶瓷轴瓦;供水压力对不同轴瓦材料的临界温度曲线变化趋势影响不同,对不同润滑介质的临界温度曲线的变化范围影响不同。     

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.     

Non-Newtonian Temperature and Pressure Effects of a Lubricant Slurry in a Rotating Hydrostatic Step Bearing

The purpose of this research was to investigate the pressure and temperature effects of graphite powder lubricant when added to a Newtonian carrier fluid and applied in a rotating hydrostatic step bearing. Temperature and pressure profiles were determined both analytically and experimentally. The rheological behavior of the non-Newtonian lubricant was modeled using a power law model previously shown to approximate experimental data for this fluid. Ethylene glycol was used as the Newtonian lubricant, providing a check on the test apparatus and a base line for comparison with the non-Newtonian graphite slurry.

Data revealed a temperature increase with bearing rotational speed for both fluids and compared favorably with the mathematical predictions. A significantly higher temperature rise was seen in the non-Newtonian lubricant due to the higher shear rates. The pressure profile was not directly dependent on bearing rotational speed in the mathematical model, but experimental data demonstrated a reduction in pressure at higher rotation speeds. This loss was greater for the non-Newtonian lubricant and attributed to temperature dependence of power law constants. It was concluded that the effects of operating speed and temperature on a non-Newtonian lubricant should be considered as well as their greater load-carrying capacity.     

球磨机滑履轴承油温升高的处理

根据球磨机滑履轴承的结构,从滑动轴承动压润滑的润滑机制,分析了球磨机正常工作时,滑履轴承油温居高不下的原因。根据分析结果,找到油温升高的主要原因是由于带油不畅和供油量不足引起,提出刮瓦和改造低压供油装置的措施。改造后效果良好,解决了球磨机滑履轴承油温升高的问题。     

薄膜润滑时分层粘度模型的速度场分析

流体的流动将直接影响其润滑特性，特别是润滑剂粘度的分布，速度变化除产生温升外，还将可能使润滑剂产生剪切稀化，在薄膜润滑中，润滑剂量的相对运动速度大，其特性变化将更为突出。本以分层粘模型来研究在此时润滑剂的速度特性，为研究流体温度场和剪切稀化问题提供数据，对揭示薄膜润滑状态下轴承的性能和变化规律具有重要的意义。     

Thermal analysis of microtextured journal bearing using non-Newtonian rheology of lubricant and JFO boundary conditions

This paper presents investigations related to the combined influences of viscous heat dissipation and non-Newtonian rheology of lubricant on the performance parameters of micro-textured journal bearing. The model proposed herein is solved using finite difference technique by incorporating mass conservation algorithm (JFO boundary conditions) and oil mixing temperature concepts. Some results have been also presented with Reynolds boundary conditions (RBC) for comparison point of view. Based on the present numerical investigations, it is found that JFO boundary conditions yield realistic results in comparison to RBC. Moreover, JFO boundary condition provides numerical stability in getting the converged results with micro-textured surfaces of journal bearing. Reductions in average temperature of the lubricant have been noticed in presence of surface texturing in comparison to smooth surface of the bearing.     

The role of lubricant feeding conditions on the performance improvement and friction reduction of journal bearings

Most conventional hydrodynamic journal bearing performance tools cannot suitably assess the effect of lubricant feeding conditions on bearing performance, even though these conditions are known to affect important performance parameters such as eccentricity and power loss.A thermohydrodynamic analysis suitable to deal with realistic feeding conditions has been proposed. Special attention was given to the treatment of phenomena taking place within grooves and their vicinity, as well as to the ruptured film region.The effect of lubricant feeding pressure and temperature, groove length ratio, width ratio and number (single/twin) on bearing performance has been analyzed for a broad range of conditions. It was found that a careful tuning of the feeding conditions may indeed improve bearing performance.     

Study of Flow Characteristics of Lubricant in Spiral-Groove Bearings by the Fluorescent Method

Abstract

The hard disk drive spindle is one of the critical mechanical components in hard disk drives (HDDs). It has great influence on overall performance, including track density, data-transfer rate, energy consumption, noise, and so forth. Nowadays, HDDs with higher density and speed, larger capacity, and smaller size are under active development. This requires that HDD spindles have fast rotating speed, excellent accuracy, and small size. However, ball-bearing spindles, which are widely used in current HDDs, cannot meet these requirements. HDD spindles supported by oil-lubricated spiral-groove bearings are considered to be a candidate to replace ball-bearing spindles. There is no oil-supply device in the bearing, and the flow characteristics of the lubricant in the bearing have a great effect on the performance of the spindle.

In this article, the fluorescent method is used to study the flow characteristics of the lubricant in a spiral-groove bearing. The establishment and recovery of the lubricant film during start/stop of the spindle are observed. The effects of working conditions on the thickness and distribution of the lubricant film are investigated. The influence of oil supply on the performance of the bearing is also studied.     

The design of fuel efficient automotive hypoid gear lubricants

Synthesised lubricant base stocks and the performance additives used in hypoid gear lubricants can both be chemically designed to give improved hypoid gear efficiency and, therefore, better vehicle fuel economy than provided by conventional lubricants In this paper, the authors review, relative to a widely used SAE 90 grade mineral oil-based lubricant, the changes in gear efficiency which have been documented using certain classes of synthesised lubricants. These advantages are described in terms of (a) EPA City and Highway Cycle efficiencies, (b) absolute data over a wide temperature range under four selected speed/torque combinations, and (c) absolute changes in inefficiency compared to the mineral oil product. Newtonian and non-Newtonian fluids have been studied. The bulk oil temperature at which a specific lubricant gives maximum efficiency is dependent on both gear operating conditions and on the chemical composition of the lubricant.     

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

Every 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.     

Orifice compensated multirecess hydrostatic/hybrid journal bearing system of various geometric shapes of recess operating with micropolar lubricant

The objective of the present paper is to study analytically the performance of four-pocket orifice compensated hydrostatic/hybrid journal bearing system of various geometric shapes of recess operating with micropolar lubricant. The modified Reynolds equation for micropolar lubricant is solved using FEM and the Newton-Raphson method along with appropriate boundary conditions. The results suggest that the influence of micropolar effect of lubricant on bearing performance is predominantly affected by the geometric shape of recess and restrictor design parameter. Therefore, the bearing designer must judiciously choose an appropriate geometric shape of recess in order to get an overall enhanced bearing performance.     

Static and dynamic analysis of elastohydrodynamic elliptical journal bearing with micropolar lubricant

In this paper the effect of deformation of the bearing liner on the static and dynamic performance characteristics of an elliptical (two-lobe) journal bearing operating with micropolar lubricant is presented. Lubricating oil containing additives and contaminants is modeled as micropolar fluid. A generalized form of Reynold's equation is derived from the fluid flow and diffusion equations. Finite element technique is used to solve the modified Reynold's equation governing the flow of micropolar lubricant in the clearance space of the journal bearing and the three-dimensional elasticity equations governing the displacement field in the bearing shell. The static and dynamic characteristics of the bearing are computed for a wide range of deformation coefficient which takes into accountant the flexibility of bearing liner by treating operating lubricant as (i) Newtonian and (ii) micropolar. The computed results show that the increasing volume concentration of additives and mass transfer of additives produce significant changes on the performance characteristics.     

Performance of flexible shell journal bearings with variable viscosity lubricants

In heavily loaded rotating machines, both the deformation of the elastic bearing shell and the dependence of lubricant viscosity on pressure become significant and may result in an appreciable change in the performance of the journal bearing system. In this paper, stable solutions for bearing deformation and the lubricant flow field are obtained which combine the effects of the elastic deformation of the bearing shell with the pressure-viscosity dependence of the lubricant. Two elastic models were tried for deformation calculations in the bearing. One which was computationally economical and consistent in accuracy was adopted for the detailed computation. The effects of bearing deformation on the performance characteristics of the journal bearing system are reported for both isoviscous and variable viscosity lubricants.     

An Analysis of the Effect of Lubricant Supply Rate on the Performance of the 360° Journal Bearing

A theoretical study was made to determine the influence of lubricant supply rate on the performance of the 360° journal bearing for L/D = 1. The results are presented in chart form to facilitate their application to analysis and design.     

考虑温度因素时等效粘度模型及轴承特性的研究

同时考虑温度和流体内能及壁面对润滑剂的强作用对润滑剂粘度的影响，在等效粘度模型的基础上，融入温度对润滑剂特性的影响，建立了粘温修正的等效粘度分析计算模型，运用该模型进行了薄膜润滑条件下的轴承特性分析计算，确立了参数与轴承性能的变化之间的关系。