摘要:

This paper introduces a simple “Rule of Thumb” (ROT) method to estimate the load capacity of foil air journal bearings, which are self-acting compliant-surface hydrodynamic bearings being considered for Oil-Free turbomachinery applications such as gas turbine engines. The ROT is based on first principles and data available in the literature and it relates bearing load capacity to the bearing size and speed through an empirically based load capacity coefficient, D. It is shown that load capacity is a linear function of bearing surface velocity and bearing projected area. Furthermore, it was found that the load capacity coefficient, D, is related to the design features of the bearing compliant members and operating conditions (speed and ambient temperature). Early bearing designs with basic or “first generation” compliant support elements have relatively low load capacity. More advanced bearings, in which the compliance of the support structure is tailored, have load capacities up to five times those of simpler designs. The ROT enables simplified load capacity estimation for foil air journal bearings and can guide development of new Oil-Free turbomachinery systems.Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000

ISSN:1040-2004    

DOI:10.1080/10402000008982410

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Chemical modification technique with X-ray photoelectron spectroscopy has been used for a quantitative analysis of surface functional groups of the carbon overcoats. As the nitrogen content in the carbon overcoat layer increases, the total abundance of functional groups on the carbon overcoat surface increases. The increase of the functional groups leads to an increase of a physisorbed lubricant layer ratio.

ISSN:1040-2004    

DOI:10.1080/10402000008982411

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The tribological properties of highly disordered graphitic carbon layers formed on silicon carbide (SiC) substrates by reaction with chlorine and chlorine-hydrogen gas mixtures at 1000 °C were studied. Si was selectively removed from the near surface of SiC by chlorine gas, leaving behind a layer of carbon having high structural density and strong bonding characteristics. Tribological tests showed that the carbon films were highly adherent and able to reduce friction coefficients of the base SiC by factors of up to seven. There was little or no change in the factional behavior of carbon layers when sliding velocity and load were increased. Low friction coefficients (∼0.1) could be obtained under wet, dry, polished, and rough conditions. The initially rough carbon surface underwent plastic flow producing a smooth, self-adjusting carbon layer. Structural morphology and the amount of disorder in the carbon layers were correlated with the friction and wear performance of the resultant films.Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000

ISSN:1040-2004    

DOI:10.1080/10402000008982412

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The electrical conductivity and friction force of a compliant curved beam loaded by a rigid flat surface which simulate electrical connectors in high-tech applications is analyzed. Both the elastic deformation of the curved beam and elastic-plastic deformation of the asperities are considered. The effects of the applied load, the surface hardness and roughness as well as the beam geometry on the electrical conductivity and friction are investigated. It is found that the electrical conductivity is insensitive to changes in the beamís geometry like its angular span and slender ratio. Surface roughness and hardness affect both electrical conductivity and friction.Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000

ISSN:1040-2004    

DOI:10.1080/10402000008982413

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The authors report here the results of a study undertaken to determine how aircraft engine oil degrades to form coke in static films on engine components and the impacts of additives and surface materials upon the coke production processes. The research is presented in two parts. This first paper deals with the initial research to develop a simple laboratory oil-coking test capable of monitoring antioxidant depletion, oil degradation, and coke formation of stressed aircraft turbine engine oils. Details of the analytical chemistry experiments performed on the stressed samples to quantitate the percentage of oil, polymer dissolved in the oil, and insoluble coke are also presented. The second paper (Part 2) (I) deals with more quantitative measurements of the degradation of thin layers of oil on heated surfaces. Effects of different oils and surfaces are explored.

ISSN:1040-2004    

DOI:10.1080/10402000008982414

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper describes a model which can be used to analyze the friction losses in the guide shoe of the cross head bearing of a large two stroke diesel engine. It describes further methods by which the friction losses in this component can be significantly reduced.

ISSN:1040-2004    

DOI:10.1080/10402000008982415

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A shape optimization of magnetic head for magnetic recording device with rotating drum was studied. An optimization algorithm was developed based on genetic algorithms in conjunction with finite element method which analyzed interface phenomena between a magnetic tape and a magnetic head. The head shape was defined by a second order spline function. Three reference points and first order derivatives at a origin point were coded by the genetic algorithm. As a result, an applicability of genetic algorithms to the given optimization problem was verified.Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000

ISSN:1040-2004    

DOI:10.1080/10402000008982416

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The authors propose a new design concept for controlling the deflection of a micro-membrane with the aid of its thickness distribution for realizing a prescribed design in the MEMS. As an example, the authors treat a micro air pump that comprises a micro-membrane. The membrane is actuated by an electrostatic force. The membrane deflects and thus the deflection is influenced by the air pressure and the electrostatic field. This is a highly complicated system. To find out a proper thickness distribution, the authors use the genetic algorithm that is appropriate to reduce the searching space of solution.Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000

ISSN:1040-2004    

DOI:10.1080/10402000008982417

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The cross head guide shoe plate of a large diesel engine operates under a large normal force which presses it against the rails between which it executes both axial and transverse motion. In order to ensure the safe operation of an unconventional bearing such as the guide shoe system of the cross head engine, an algorithm that can be used to predict accurately the oil film thickness that can be achieved for all the engine's operating regimes, is invaluable. A solution of the three dimensional form of Reynolds differential equation can provide the requisite oil film thickness. However, with even the availability of very fast computers and large computer storage capacity this solution for a large axial bearing such as the guide shoe becomes impractical in terms of computation time and computer core requirements. This paper describes alternative simplified algorithm for accurate prediction of the oil film thickness developed in the guide shoe bearing at different operating regimes of the engine.

ISSN:1040-2004    

DOI:10.1080/10402000008982418

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor