Abstract
In the literature, there exists no consensus on a best practice for
modelling the compliant foil structure of Gas Foil Bearings (GFBs). This
paper focuses on the top foil modelling and its original contribution
to the modelling problem is a comparison of steady state analysis
efficiency, and transient and steady state accuracy between four top
foil models with and without gas injection. The bump foil is modelled
using the Simple Elastic Foundation Model (SEFM), and the four top foil
models are (a) neglecting the top foil, i.e. the foil structure is
modelled as a basic SEFM, (b) Euler–Bernoulli (EB) beam elements, (c)
non-curved shell elements, and (d) curved shell elements. The
theoretical analysis is carried out using a multi-domain numerical model
and exemplified using a rigid rotor supported by three-pad GFBs.
Comparing steady state journal eccentricities, low discrepancies are
seen between almost all investigated models. However, the basic SEFM is
found to be insufficient for cases with injection. Using the curved
model as a benchmark, it is found that the predictions of steady state
journal eccentricities, transient response, and eigenvalues made by the
model with non-curved shell elements are less accurate than those of the
model with EB beam elements. Thus, despite a higher degree of
simplification, the model with EB beam elements is found to be both more
computationally efficient as well as more accurate for steady state
analysis when compared to the model with non-curved shell elements.
While the radial foil deformation for the curved model exhibits
dependency on the axial coordinate, this dependency is significantly
overestimated by the model using non-curved shell elements. This is most
pronounced for the case without injection, and it could explain the
inferiority of the model using non-curved shell elements for estimating
steady state journal eccentricities. A stress analysis indicates that
this is caused by the non-curved shell element model not accounting for
the membrane stresses in the top foil.
Original language | English |
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Article number | 117513 |
Journal | Journal of Sound and Vibration |
Volume | 547 |
Number of pages | 26 |
ISSN | 0022-460X |
DOIs | |
Publication status | Published - 2023 |
Keywords
- Compliant foil structure
- Computational complexity
- Gas foil bearings
- Membrane stresses
- Numerical modelling
- Radial gas injection
- Steady state analysis