Abstract
The quantitative impact of pivot position, pivot support stiffness, and deformation on frequency dependency of a stiffness (K) and damping (C) KC matrix model for tilting-pad journal bearings is investigated. A theoretical model for prediction of frequency influences is introduced neglecting inertia effects. Predictions based on this model are validated with test data taken from literature. The results achieve good agreement with experimental data. A sensitivity analysis is performed providing the following key results: (i) all three investigated parameters possibly exhibit non negligible frequency influences, (ii) significant misinterpretations are possible if single influencing parameters on the operation conditions are disregarded or only roughly estimated, (iii) a frequency independent KCM model is suitable for off-center pivot position and sub-synchronous frequency ratios, (iv) a state-space model separating rotor and pad movement is necessary to model all theoretical possible effects by a linear model with frequency independent coefficients for a certain rotor speed.
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Abbreviations
- a * F :
-
Pad-pivot offset
- C R :
-
Bearing radial clearance
- D :
-
Bearing diameter
- D :
-
Pad thickness
- F :
-
Bearing force
- H :
-
Film thickness
- K x , K z :
-
Turbulence factors
- L :
-
Axial bearing length
- n :
-
Rotational speed
- p :
-
Pressure
- p q :
-
Specific bearing load
- Q :
-
Lubricant flow rate
- R p :
-
Pad radius
- r :
-
Journal radius
- T :
-
Temperature
- T 0 :
-
Lower reference temperature
- x, y, z :
-
Cartesian coordinates
- η :
-
Lubricant dynamic viscosity
- Π:
-
Nondimensional pressure, \(\Pi = p\,\psi^{2} /(\eta_{0} \omega )\)
- ɛ :
-
Relative eccentricity
- γ :
-
Attitude angle
- ρ :
-
Lubricant density
- φ, ϕ:
-
Angular coordinate in circumferential direction
- ψ :
-
Relative bearing clearance
- ω :
-
Shaft rotational angular velocity
- ω s :
-
Angular vibrational frequency
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Hagemann, T., Schwarze, H. (2015). A Theoretical Study on Frequency Effects on Tilting-Pad Journal Bearing Dynamic Coefficients. In: Pennacchi, P. (eds) Proceedings of the 9th IFToMM International Conference on Rotor Dynamics. Mechanisms and Machine Science, vol 21. Springer, Cham. https://doi.org/10.1007/978-3-319-06590-8_87
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DOI: https://doi.org/10.1007/978-3-319-06590-8_87
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