On the Numerical and Experimental Analysis of Internal Pressure in Air Bearings

Dynamics of a rotor supported by air bearings is strongly depends on the pressure distribution between the rotor and the bearing. In this study, internal pressure in air bearings is numerical and experimental analyzed for different radial clearances. Firstly the pressure distribution between rotor and bearing is modeled using Reynold's equation and this model is solved numerically. The rotor-bearing system is also modeled in four degree of freedom and it is simulated for different radial clearances. Then, in order to validate numerical results, a test rig is designed and the rotor bearing system is run under the same operational conditions. Pressure signals of left and right bearings are recorded. Internal pressure variations are compared for numerical and experimental results for different radial clearances.

Authors:

• Abdurrahim Dal
• Tuncay Karaçay

Keywords:

• Air bearing
• internal pressure
• Reynold’s equation
• rotor.

References:

[1] J., Wang, “Design of gas bearing systems for precision application,”
PhD Thesis, Technische Universiteit, Eindhoven, 1993, pp. 1-35
[2] M., Uneeb, “Theoretical investigation of whirl instability in externally
pressurized gas journal bearing,” PhD Thesis, Imperial College of
Science, Technology and Medicine, London, 1992, pp. 29-92.
[3] J. H., Laub, “Externally Pressurized Gas Bearings,” ASME Journal of
Lubrication Technology.,vol.4 (1), pp. 261, 1961.
[4] J. W. Powell, “Gas behavior and load capacity of hydrodynamic gas
journal bearing,” Transactions American Society Lubrication Engineers,
vol. 6, pp. 11, 1963.
[5] E. H. Dudgeon and I., R., G., Lowe, “A theoretical analysis of
hydrostatic gas journal bearings,” Mechanical Engineering Report 54,
Canada, 1965, pp. 15-50.
[6] J. S. Ausman, “The fluid dynamic theory of gas lubricated bearing,”
Trans. Amer. Soc. Lub. Engrs., vol. 79, pp. 1218-1224, 1957
[7] W. J. Lund, “A theoretical analysis of whirl instability and pneumatic
hammer for a rigid rotor in pressurized gas journal bearing,” Journal of
Lubrication Technology, vol. 89 pp. 154-165, 1967.
[8] D. Fleming, P. Cunningham, and W, J. Anderson, “Stability analysis for
unloaded externally pressurized gas lubricated bearings with journal
rotation,” Technical Report TN D-4934, NASA Levis Research Centre,
United States, 1968.
[9] N. Wang and C. Chang, “An application of Newton’s method to the
lubrication analysis of ari lubricated bearings,” Tribology Transactions,
vol. 42, pp. 419-424, 1998.
[10] K. Czolczynski, “Mathematical model of a gas journal bearing,”
Rotordynamics of Gas-Lubricated Journal Bearing System, Springer,
New York, pp. 1-48, 1999.
[11] C. Wang, M. J. Jang, and Y. L. Yeh, “Bifurcation and nonlinear
dynamic analysis of a flexible rotor supported by relative short gas
journal bearings,” Chaos, Solitons& Fractals, vol. 32, pp. 566-582,
2007.
[12] J. Park and K. Kim, “Stability analysis and experiments of spindle using
new type of slot restricted gas journal bearings,” Tribology
International, vol. 37, pp. 451-462, 2004.
[13] Y. S. Chen, C. C. Chiu, and Y. D. Cheng, “Influences of operational
conditions and geometric parameters on the stiffness of aerostatic
journal bearings,” Precision Engineering, vol. 34, pp. 722-734, 2010.
[14] G. Belforte, T. Raparelli, V.Viktorov, and A. Trivella, “Discharge
coefficients of orifice-type restrictor for aerostatic bearings,” Tribology
International, vol. 40, pp. 512-521 2007.
[15] A. Dal, and T. Karaçay, "Dynamics of Externally Pressurized Air
Bearing with High Values of Clearance," in ASME 2014 12th Biennial
Conference on Engineering Systems Design and Analysis. Copenhagen,
2014.
[16] T. Karaçay, "Theoretical and experimental investigation of dynamics of
rotor supported by externally pressurized air bearings", The Scientific
and Technology Research Council of Turkey, Ankara, Technical Report,
ARDEB-1001-112M847-2, Oct. 15, 2014 (In Turkish).
[17] MATLAB version 7.0.1, 2004, computer software, The MathWorks Inc.,
Natick, Massachusetts.