Considering the actual roughness dimensions as well as the typical dimensions of a hydrodynamically lubricating film, the Stokes equations are used to analyze the roughness effects. The surface profile is modeled by an ergodic, stationary random process. It is revealed that the roughness effects can be determined by three parameters; viz., the rms roughness, the correlation length, and the correlation wavelength. The present results are significantly different from those in the literature, where the Reynolds equation is used for analysis.
The steady state operational performance of gas-lubricated porous journal bearings is analyzed by using a numerical iterative method. Results are obtained, and presented in charts and tables, for the length-to-diameter ratio values of 1, 2, and 3; the eccentricity ratio values of 0.2, 0.4, 0.6, and 0.8; the compressibility number from 0 to 10; and several values of the feeding parameter and the supply-to-ambient pressure ratio commonly found in applications.
A ~louel test appamtzrs zuus built to mecuure the i.~ltelface friction betrueen n single cam-lifier p(l,ir i.rola/ed from otlter frictional con!-po7tettLs in the uolue train. Detr~iled i?~uestigatio?zs were n~nde,for botlt co~~uenti.o~t(~l lifter (111d a roller lifter. Measured res~i1t.s shoroed an 80 percent reductioil in fj-iction with tile use of the mller 1 f k r and tlte trend of dec.rec~i,~tg frictio?~ zuitlt e~tgine speed for botlr. types of 1ifier.s. The obserued lack of friction reductior~ over any part of the cotttact cycle (i11d llle large coefj/;cient'off,-iclion in tire true of tile corl~ue~~tio~tal lifier ruled out the possibility rf elastolty(.ydro(ly~lamic lubricatio~t at the contrrct.
A linear theory of hybrid instability, due to a combination of both whirl and pneumatic hammer, in gas-lubricated porous journal bearings is presented. An approximate solution to the stability problem is obtained by the use of a Galerkin expansion. Results are presented in terms of the variation of stability parameters, such as the threshold mass, the whirl frequency ratio, etc., with the compressibility number and eccentricity ratio. In addition, the effects of permeability, supply pressure, and bearing length are investigated.
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