摘要:

This paper presents an improved dynamic analysis for liquid annular seals with arbitrary profile based on a method first proposed by Nelson and Nguyen. An improved first-order solution that incorporates a continuous interpolation of perturbed quantities in the circumferential direction is presented. The original method uses an approximation scheme for circumferential gradients of zeroth order solution based on Fast Fourier Transforms (FFT). A simpler scheme based on cubic splines is found to be computationally more efficient, with better convergence at higher eccentricities. Arbitrarily varying seal profiles in both axial and circumferential directions are considered. A procedure for computing dynamic coefficients based on external specific load is discussed. An example case of an elliptical seal with varying degrees of axial curvature is analyzed. A case study based on actual operating clearances (6 axial planes with 68 clearances/plane) of an interstage seal of the Space Shuttle Main Engine High Pressure Oxygen Turbopump (SSME-ATD-HPOTP) is presented.Presented in the 48th Annual Meeting in Calgary, Alberta, Canada May 17-20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983346

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A comprehensive thermohydrodynamic (THD) analysis of steadily loaded journal bearings has been developed that includes mass conserving cavitation, full solution of the 3-D energy equation in the oil film, heat conduction in the bushing and journal, mixing of hot circulating oil with fresh supply oil and solution of the inverse problem (given the load, find the film thickness). The temperature distribution in the oil film and bushing is found using a coupled approach where the same 3-D energy equation is solved in both the oil film and bushing. With this approach the steady-state problem can be solved without iterations between the thermal solutions in the oil film and the bushing, thereby allowing ready analysis of multilayer bushings. Predictions of the analysis compared very well with measurements reported by Dowson et al. (1). A thermohydro-dynamic study of bearing performance as a function of clearance for a typical automotive bearing revealed that there is an optimum clearance that gives the largest minimum-film thickness. In contrast, isothermal analyses did not show any optimum.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17-20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983347

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A new disk-type viscous pump utilizing multi-radial pumping grooves on its stator has been designed, analyzed and subsequently fabricated and tested. Analyses show that this new design pump exhibits higher flow rate characteristics than the recently reported multi-lobe design for the same pump size and rotor-stator clearances. Test results at rotor speeds of 600, 900, 1200 and 1500 rpm for a nominal rotor-stator clearance of 135 μm show the linear relationship between flow rate and discharge pressure for each speed, even though gradual increase in the working fluid temperature occurred during each test. This temperature increase can be the main practical problem in operating such a pump, along with maintaining very small rotor-stator clearances at high rotor speeds. Comparisons between the test results and the analytical predictions show good qualitative and quantitative agreements, especially for pump speeds of 600, 900 and 1200 rpm. For the present set-up, only low flow rate readings were obtained at a higher pump speed of 1500 rpm, since air entrainment occurred for higher flow rates at this speed. However, the experiment has shown that his new type of viscous pump is practically feasible.

ISSN:1040-2004    

DOI:10.1080/10402009408983348

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A partially porous mechanical face seal is analyzed. The Reynolds equation is solved analytically and the pressure distribution, leakage, and dynamic coefficients are presented in closed form analytical expressions. It is shown that a partially porous seal has an axial stiffness even in cases of flat parallel faces when solid face seals have no such stiffness at all. A comparison is made between optimally designed partially porous and coned face seals. It is shown that the former give substantial improvement.Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in New Orleans, Louisiana, October 24-27, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983349

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this paper, film thickness and pressure distribution of EHL in line contacts for four kinds of greases and one type of oil are calculated under a series of rolling velocities by using an inverse solution method. The Herschel-Bulkley model is used for the rheological characteristics of the grease. Based on the theoretical analysis and numerical calculation, the following influences on film thickness and pressure distribution in EHL of grease are analyzed: the effects of starvation, yield stress, presheared grease and fresh grease, and approach and separation between two cylinders. The effect of different rheological characteristics of grease on film thickness is also investigated.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Diego, California, October 19-21, 1992

ISSN:1040-2004    

DOI:10.1080/10402009408983350

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The use of multigrade oil in engine lubrication is being advocated to consumers to minimize viscosity-temperature effect. However, its effect on piston ring-liner contact has not been fully ascertained. In this work, an attempt has been made to evaluate the friction behavior of multigrade oil in piston ring lubrication. The theoretical model developed by the authors predicts thinner oil films as a result of introduction of multigrade oil in the hydrodynamic zone and a larger piston travel distance near the TDC region in the compression-power stroke cycle without any appreciable film thickness. The multigrade oils are known to offer elasticity, and this is also considered in the analysis to evaluate film thickness.

ISSN:1040-2004    

DOI:10.1080/10402009408983351

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An attempt is made to formulate a thermohydrodynamic model of fluid-film lubrication that is valid in turbulent flow regimes. The model considers the flow to be a small perturbation of turbulent Couette flow. The modified Reynolds equation is obtained for the turbulent flow and the integro-differential energy equation makes the turbulence analysis easier by replacing the conductive terms in terms of the convective boundary conditions at two solid surfaces. Sample results applying the perturbation method agree well with available experimental data and theoretical methods.

ISSN:1040-2004    

DOI:10.1080/10402009408983352

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The wear behavior of SiC particle-reinforced aluminum alloy matrix composites as journal bearing materials in conformal contact against case hardened AISI 1016 steel under mixed lubrication conditions using SAE 10W30 oil was investigated. The bearings exhibited weight gain, followed by weight loss and subsequent weight gain as the sliding distance increased. Iron transfer and tribo-chemical reaction product formation were responsible for the observed weight gain. The surfaces of the composites contained transferred iron, layers rich in Fe, S, P and Zn, and hard tribo-deposits of high phosphorus concentration. The hard tribo-deposits were thought to be an important factor in lubrication breakdown and contact failure.Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in New Orleans, Louisiana, October 24-27, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983353

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A previously validated finite difference computer model for seal leakage was used in developing an advanced seal with reduced leakage. A new design feature is an annular groove judiciously located in the stator housing. A detailed assessment of this preliminary groove configuration was conducted, both experimentally and computationally. It was found that the presence of the particular groove considered here contributes an approximately 20 percent decrease in leakage, while introducing no shaft speed effects. To enhance physical insight, detailed computed distributions of streamlines are included. Further, the interesting measured effect of the relative axial position of the rotor/stator sealing surfaces on leakage rate and stator wall axial pressure distribution is examined.

ISSN:1040-2004    

DOI:10.1080/10402009408983354

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Kinetic friction force varies with time in many sliding systems. In some poorly-lubricated tribosystems, or unlubricated systems in which significant interfacial adhesion occurs, this variation can be as large as the nominal value of the friction force itself. Time-varying friction arises from changing combinations of interfacial processes. The changing contribution of frictional processes in complex sliding interfaces can be represented using graphical constructions called friction process diagrams (FPDs). Using FPDs, the frictional changes within a tribosystem are analyzed on the process level, without the need to know exactly how detailed mechanisms, such as deformation, fracture, diffusion, defect generation, and tribochemcial reactions, interact within each process. Binary and ternary forms of FPDs are used to explain the causes of frictional behavior observed in studies of metallic and ceramic sliding. Extensions of FPDs to more complex cases, for example involving elevated temperatures, are also discussed.Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in New Orleans, Louisiana, October 24-27, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983355

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor