Mongkolwongrojn, Mongkol

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Mongkolwongrojn, Mongkol
Alternative Name
Mongkolwongrojn, M.
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Email
mongkol.mo@kmitl.ac.th

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    Static Characteristics of High-Speed Slider Bearings Lubricated with Non-Newtonian Fluids (In the Case of Infinitely Long Bearings)
    (1995-01-01)
    Hashimoto, Hiromu
    ;
    Mongkolwongrojn, Mongkol
    In this paper, the static characteristics of infinitely long slider bearings lubricated with non-Newtonian fluids are examined theoretically by considering the fluid inertia effects. In the derivation of the modified Reynolds equation, the fluid inertia terms in the momentum equation for the lubricant film are averaged over the film thickness, and the Rabinowitsch empirical model is used as a constitutive equation of non-Newtonian fluids. Applying the modified Reynolds equation to the infinitely long slider bearings, the film pressure, load carrying capacity, friction force and inlet flow rate are obtained under various values of the dimensionless nonlinear factor and film thickness ratio, and the effects of fluid inertia on these static characteristics are discussed. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.
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    Adiabatic Approximate Solution for Static and Dynamic Characteristics of Turbulent Partial Journal Bearings With Surface Roughness
    (1994-01-01)
    Hashimoto, H.
    ;
    Mongkolwongrojn, M.
    Hydrodynamic bearings are generally used for a long term, so the bearing surfaces may be roughened for many reasons such as wear, impulsive damage, foreign particles, cavitation erosion, rust, and so on. Under the turbulent operating conditions of high speed bearings, the surface roughness may result in considerable increase in both film pressure and temperature. This paper describes an adiabatic approximate solution for the static and dynamic characteristics of 180 deg partial journal bearings with homogeneous surface roughness. Applying the modified lubrication equation and energy equation, considering the combined effects of turbulence and surface roughness, to the finite width 180 deg partial journal bearings, the static and dynamic characteristics such as pressure and temperature distributions, Sommerfeld number, attitude angle, spring and damping coefficients and whirl onset velocity are obtained numerically. In the numerical analysis of the temperature distribution, adiabatic boundary conditions are assumed and then the heat transfer effect to the journal and bearing-bush surfaces is omitted. The numerical results are indicated in graphic form for various relative roughness under the mean Reynolds number of Re = 5000 and 10,000. Moreover, some numerical results of static characteristics are compared with the experimental results. © 1994 by ASME.
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    Theoretical Prediction of Journal Center Motion Trajectory in Two-Lobe Hydrodynamic Journal Bearings23
    (1995-01-01)
    Mongkolwongrojn, Mongkol
    ;
    Prabkaew, Chamlong
    ;
    Hashimoto, Hiromu
    In this study, the theoretical prediction of a journal center motion trajectory for high-speed rotors supported by two-lobe hydrodynamic oil film journal bearings is presented for three different values of the noncircular ratios, 7 = 0, 0.5 and 1.0. In order to obtain values for the oil film forces used in the equations of motion for rotor-bearing systems, the Reynolds equation governing the oil film pressure generated in the bearing gap was solved using the semianalytical finite-element method for each time step. Furthermore, for each time step, the nonlinear equations of motion for a rigid rotor supported by two identical aligned bearings were solved using the improved Euler integration method. From the numerical results, the relations between the journal center motion trajectory and the corresponding pressure distribution were examined theoretically, and the effect of the noncircular ratio on the stability of rotor bearing systems was clarified for the cases of both balanced and unbalanced rotors. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.