摘要:

A parametric study of the effects of oil inlet temperature and pressure in half-circumferential grooved journal bearings under aligned and misaligned conditions has been carried out by solving numerically the coupled Reynolds and energy equations system. Five different sets of boundary conditions for the energy equation have been used which include mixing between recirculating oil and inlet oil and a contraction ratio for the cavitation region. The effects of changes of the wall temperature and of the LID ratio have also been examined. For the ranges of parameters found in internal combustion engines, the wall temperature and heat transfer rate have been found to be of secondary importance to the mixing effectiveness at the groove and the resulting final mixture temperature. Realistic inlet pressure increases also have been found in capable of affecting significantly the bearing performance. The variability of the temperature, though, has been shown to smooth out the peaks of both pressure and friction during misaligned conditions. Distributions of friction and pressure in the oil are also examined which may be useful in attempts to reduce friction without reducing load. Results for an axial grooved bearing are also presented for comparison purposes.Presented at the 44th Annual Meeting in Atlanta, Georgia May 1–4, 1989

ISSN:1040-2004    

DOI:10.1080/10402009208982111

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This study explores the design of a low-friction cam/tappet system. An elastohydrodynamic contact analysis is conducted to predict lubricant film-thickness and Hertzian pressures at the cam/tappet contact. In addition, a mixed-friction model that can predict the changes in the cam/tappet interface friction due to changing operating conditions is adopted and integrated into the analysis. Also included in the study is a model of tappet spin allowing for slip at the cam/tappet interface. Modeling tappet spin makes it possible to see the effects of the tappet crown radius and cam-taper angle on the interface frictional loss.

ISSN:1040-2004    

DOI:10.1080/10402009208982112

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A model for the loss of oxidative stability of engine oil is presented in which the oil in an operating engine is assumed to be in one of three categories: oil which is lost from the system, oil in which the oxidative stability is reduced or lost as a consequence of exposure to harsh conditions, and the bulk of the oil which is neither lost nor reacted. Graphical examples are presented to show how various events or conditions in an engine, for example, oil consumption, oil additions, residual oil from the previous oil change period, and the presence of contaminants in the oil, affect the oil's oxidative stability.Presented at the 46th Annual Meeting in Montreal, Quebec, Canada April 29–May 2, 1991

ISSN:1040-2004    

DOI:10.1080/10402009208982113

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Energy efficient hydrodynamic, tilting pad thrust bearings find wide use in industry for high speed applications. This paper presents results of comparative experiments between the two main design philosophies currently available for these bearings. It is concluded that given identical operating conditions, one of the approaches, the “low loss” or “directed” design, is the more efficient by a significant amount. The robustness of the low loss design is confirmed in a series of further experiments which test its tolerance to various adverse circumstances.Presented at the 46th Annual Meeting in Montreal, Quebec, Canada April 29–May 2, 1991

ISSN:1040-2004    

DOI:10.1080/10402009208982114

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Since the thermoelastohydrodynamic and elastohydrodynamic lubrication (TEHL and EHL) problems are predominantly heat transfer (HT) and/or fluid mechanics (FM) problems, it is proposed that the pertinent dimensionless quantities defined, in some instances tabulated, and commonly used in these branches of engineering science (HT and FM) should be used consistently and uniformly throughout for TEHL and EHL studies.

ISSN:1040-2004    

DOI:10.1080/10402009208982115

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

To predict the performance of the energy-efficient finger follower system with a roller follower requires an adequate understanding of the kinematics and forces in the roller cam contact. This paper analyzes the kinematics, lubricant film thickness and normal/friction tractions in the finger follower and the roller itself The analysis includes the EHD tractions, hydrodynamic rolling friction and bearing torque to determine the cam-roller slippage and tractions for various positions of a cam cycle. For a roller finger follower and a sliding finger follower of similar design, a comparison is given for the calculated EHD film thickness and power losses in various parts of the tappet.Presented at the 45th Annual Meeting in Denver, Colorado May 7–10, 1990

ISSN:1040-2004    

DOI:10.1080/10402009208982116

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Analytical formulations for the computation of lubricant film thickness and traction in a high-speed rolling-sliding contact are presented with the objective of investigating the viscoelastic response of the MIL-L-7808-type lubricant Two types of relations are used to model the viscous shear strain rate. In the Type I model, a hyperbolic sine relation is used to model the viscous effect which becomes significant when the shear stress reaches a critical value. The Type II model employs a limiting shear stress, which the lubricant can withstand, and an inverse hyperbolic tangent function is considered to model the viscous behavior. Both models are based on three fundamental properties: lubricant viscosity, shear modulus and a critical shear stress. While the viscosity relations may be obtained by direct measurements, estimates of shear modulus and critical shear stress may be derived by curve-fitting the model predictions to experimental traction data.Presented at the 45th Annual Meeting in Denver, Colorado May 7–10, 1990

ISSN:1040-2004    

DOI:10.1080/10402009208982117

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Viscoelastic behavior of the MIL-L-7808-type lubricant is modeled by correlating experimental traction data to rheological models based on lubricant viscosity, shear modulus and a critical or limiting shear stress. The two types of traction models used respectively employ a hyperbolic sine and inverse hyperbolic tangent function between the viscous shear strain rate and shear stress in the lubricant. While the viscosity-pressure-temperature relation is determined from viscosity measurements on a high-pressure viscometer, estimates of shear modulus and critical or limiting shear stress are derived by curve-fitting the model predictions to actual traction data obtained from a rolling-disk traction machine.Presented at the 45th Annual Meeting in Denver, Colorado May 7–10, 1990

ISSN:1040-2004    

DOI:10.1080/10402009208982118

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper reports on the development of a thermal model that can be used to analyze transient elastohydrodynamic lubrication (EHL) of rough surfaces. The thermal domain is composed of three sub-domains, including the film region and the two bounding solids with the thermal boundaries placed inside the solids at which the temperature variation is insignificant. The irregular and time-varying sub-domains, primarily due to the presence and motion of rough surfaces, are mapped onto rectangular and time-invariant sub-domains so that numerical methods can be easily applied. A control-volume approach is taken to formulate the interfacial conditions between the lubricant film and the bounding solids. Finally, a computational algorithm is developed to calculate the temperature field in high-Peclet-number EHl contacts. The calculation yields results that are shown to be meaningful and consistent through extensive evaluations. A substantial amount of numerical results will be presented in a companion paper.Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in St. Louis, Missouri, October 14–16, 1991

ISSN:1040-2004    

DOI:10.1080/10402009208982119

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this study, the authors investigated the synergistic effects of liquid and solid lubrication on the tribological behavior of yttriastabilized zirconia (ZrO2) ceramics. Thin silver films 1 to 2 μm thick were produced on ZrO2flats by ion-beam-assisted deposition (IB AD) and used as the solid lubricant. A fully formulated synthetic oil (polyolester-based) served as the liquid lubricant. Wear tests were performed on an oscillating-slider wear test machine at temperatures up to 250°C. For the specific test conditions explored, it was found that: (a) without any type of lubrication, the friction coefficients of ZrO2/Z*rO2test pairs were on the order of 0.6, and the average wear rates of pins were in the range of 5 × 10−5to 10−4mm3· N−1·m−1, depending on the test temperature; (b) the use of solid-lubricant silver films alone reduced the friction coefficients of sliding pairs by factors of two to four, and the wear rates of pins by three orders of magnitude; (c) the use of liquid lubricants reduced the friction coefficients of ZrO2/ZrO2test pairs by a factor of about five and the wear rates of pins by one to two orders of magnitude; and (d) the concurrent use of silver films and lubricant oil resulted in the virtual elimination of the wear of both the pins and the flats, and in a significant reduction of the friction coefficients at room temperature and at 250°C.Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in St. Louis, Missouri, October 14–16, 1991

ISSN:1040-2004    

DOI:10.1080/10402009208982120

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor