Thermal and Non-Newtonian Effects on the Steady State and Dynamic Characteristics of Hydrodynamic Journal Bearings—Theory and Experiments
TL;DR: In this paper, the steady state and dynamic characteristics of a plain journal bearing with non-Newtonian lubricants were investigated using a thermohydrodynamic analysis of a bearing lubricated by a nonlinear fluid model.
Abstract: Theoretical investigations are carried out for a plain journal bearing considering the influence of thermal effects on non-Newtonian lubrication. With reasonable assumptions, the steady state and dynamic characteristics are presented using a thermohydrodynamic analysis of a bearing lubricated by a nonlinear, i.e., cubic, fluid model. Experiments are conducted on a rig to study the steady state and dynamic performance of a full journal bearing with different types of non-Newtonian lubricants. Experiments include the measurements of eccentricity ratio, critical speed, and stability limit. The theoretical investigation reveals that the interaction of the non-Newtonian effect and the thermohydrodynamic effect is strong for friction, and the interaction effect is negligible in the case of eccentricity ratio, attitude angle, and lubricant flow rate. Further, for relatively high values of non-Newtonian parameter, αn , the effect due to the non-Newtonian parameter is not negligible. Presented at the 46th Annual M...
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TL;DR: In this paper, the authors analyzed the problems of tilting-pad thrust bearing static instability and lubrication performance under static bistability, and a calculation method was proposed to obtain bearing lube performance under the bistabilities.
Abstract: Purpose – The purpose of this paper is to analyze the problems of tilting-pad thrust bearing static instability and lubrication performance under static bistability. Design/methodology/approach – The static equilibrium state of tilting-pad thrust bearing is analyzed, and key parameters are extracted from the general lubrication model. Then, a distribution area of bearing static equilibrium points is achieved by solving the model. The area is divided into three sub-areas which represent monostabillity, bistability and instability, and an unstable boundary of the area is discovered. By these findings, a reversible lubrication failure phenomenon is explained. A calculation method is proposed to obtain bearing lubrication performance under the bistability. Findings – The variation of working conditions can lead to migration of unstable boundary and static instability. After resuming the working conditions, unstable boundary will resume in situ, and the bearing will operate steadily again. Moreover, there is a...
5 citations
01 Sep 1994
TL;DR: In this paper, a rotary shear viscometer was used to measure the effect of test parameters on the performance of a journal bearing lubricated with different types of non-Newtonian fluids.
Abstract: Viscosity index improvers cause the lubricants to exhibit non-Newtonian flow behaviour and display shear thinning and normal stress differences. Shear thinning behaviour is studied by using a rotary shear viscometer. Owing to the non-availability of a rheogoniometer (for the measurement of normal stress differences), the first normal stress difference is calculated from the viscometric data using the Carreau viscosity function. The influence of the first normal stress difference on the hydrodynamic lubrication is analysed and shows that most of the commercial oils are inelasticoviscous in nature. Regression analysis shows that a large number of commercial lubricants follow the inelasticoviscous cubic law fluid model. Hence the cubic law fluid model is considered for the theoretical analysis.An experimental programme is developed to measure the effect of test parameters on the performance of a journal bearing lubricated with different types of non-Newtonian fluids. The experiments mainly include the measur...
4 citations
TL;DR: In this paper, an experimental investigation with surface textures and a non-Newtonian polymer solution (polyisobutylene in oil) was conducted to determine synergistic effects on laminar hydrodynamic friction reduction.
Abstract: We present an experimental investigation with surface textures and a Non-Newtonian polymer solution (polyisobutylene in oil) to determine synergistic effects on laminar hydrodynamic friction reduction. Gap controlled experiments were performed on a custom parallel disk tribo-rheometer to systematically vary the Reynolds number (0.1–16), Weissenberg number (0.1–30), and Deborah number (0.005–0.5) in bi-directional sliding motion with five different texture geometries: cylindrical holes with varying asymmetric angle β. Cavitation effects are not present, thus normal force is produced solely by the textures and the lubricant rheology. Contrary to Newtonian fluids without cavitation, the normal force is positive, independent of the direction of motion when shear normal forces dominate purely viscous effects. We observe that the normal thrust can be larger than a simple superposition of forces due to viscous hydrodynamics and shear normal stresses. This synergistic coupling between the asymmetric textures and the polymer solution (at high Wi) produces an optimal angle of texture asymmetry β for dramatically decreasing the effective coefficient of friction compared to the Newtonian oil without polymer.
3 citations
TL;DR: In this paper, the behavior of a rotating system after its power supply is cut off is called the coastdown phenomenon, and an experimental investigation was carried out on a rotor rig with a single rotor.
Abstract: The behavior of a rotating system after its power supply is cut off is called the coastdown phenomenon. An experimental investigation of the coastdown characteristics was carried out on a rotor rig...
3 citations
15 Feb 2021
TL;DR: In this article, a numerical investigation is used to predict the dynamic performance of finite bearing considering the combined influence of turbulence regime and non-Newtonian flow. But the current numerical analysis is limited to finite bearing.
Abstract: The current numerical investigation is used to predict the dynamic performance of finite bearing considering the combined influence of turbulence regime and non-Newtonian flow. With appropriate ass...
2 citations
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TL;DR: In this article, a relatively simple journal bearing rig was used to test the elasticity of viscoelastic lubricants and showed that the extra benefit of elasticity is much greater than that predicted by existing theory.
Abstract: Experiments have been carried out on a relatively simple journal bearing rig to test the theory that extra load-carrying capacity is generated the elasticity of viscoelastic lubricants. Model lubricants were used. The viscoelastic lubricants were solutions of high-molecular-weight polyisobutene in low-molecular-weight polyisobutene while the inelastic lubricant was low-molecular-weight polyisobutene. The extra load-carrying capacity has been established. An analysis of the detailed results strongly indicates that the extra benefit of elasticity is much greater than that predicted by existing theory. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in San Diego, California, October 22–24, 1984
28 citations
TL;DR: In this paper, a modified form of Reynolds' equation (nonlinear) is derived under conventional hydrodynamic lubrication approximations under correlation effect for pseudoplastic (shear thinning) lubricants.
Abstract: Starting from the general shear stress-shear strain relation of the odd cubic polynomial type considering correlation effect for pseudoplastic (shear thinning) lubricant, a modified form of Reynolds’ equation (nonlinear) is derived under conventional hydrodynamic lubrication approximations. The finite difference technique with successive over relaxation is used adopting the solution of the associated linear equation as a first approximation to obtain the pressure distribution of a finite cylindrical journal bearing incorporating Reynolds’ boundary conditions. Steady state performance characteristics such as load capacity, attitude, friction and flow rate are obtained for various values of nonlinear parameter and bearing slenderness ratio. The results presented in nondimensional form are compared with established results for Newtonian lubricants. The investigation shows a significant effect of correlation on the bearing load capacity and flow rate.
15 citations
TL;DR: In this article, the simultaneous effects of non-Newtonian lubricant behavior and thermal dissipation during hydrodynamic lubrication of a journal bearing were investigated, and the results showed that thermal effect is an important factor not to be neglected in any theoretical analysis of hydrodynamical lubrication.
Abstract: An experimental investigation was conducted to study the simultaneous effects of Non-newtonian lubricant behavior and thermal dissipation during hydrodynamic lubrication of a journal bearing. The results show that thermal effect is an important factor not to be neglected in any theoretical analysis of hydrodynamic lubrication. When we compare a non-Newtonian oil (2.25 percent PIB L80 in Vitrea 32) and a Newtonian oil of the same zero shear rate viscosity (Vitrea 320), they show the same load capacity (or Sommerfeld number) up to a relative eccentricity e = 0.5. Beyond this point, the Newtonian oil exhibits a higher Sommerfeld number. Due to viscous dissipation, the normal stresses exhibited by the non-Newtonian oil cannot compensate for the loss of viscosity by shear thinning.
14 citations
TL;DR: The ASME/ASLE Tribology Conference in Pittsburgh, Pennsylvania, October 20-22, 1986 as discussed by the authors presented an American Society of Lubrication Engineers paper on the subject.
Abstract: Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Tribology Conference in Pittsburgh, Pennsylvania, October 20–22, 1986
4 citations