Among the elastic, or flexible elements of damper supports are “squirrel cage” springs and elastic rings (often “Alison rings”). One of the main differences is related to the possibility to transmit axial force from the rotor.
Squirrel cage spring
The elastic part of the squirrel cage may be calculated by a DYNAMICS R4 function.
Advantages:
- Constant stiffness throughout the operating ranges.
- Possibility to transfer large axial forces.
- Operational reliability.
- Effective damping tuning due to SFD usage.
- Availability of mathematical models for the dynamic characteristics calculation.
- The rotor is centered at zero rotation speed.
In order to stay in linear zone sqeeze film damper with centering spring must have the hydrodynamic film stiffness smaller than the elastic spring at all engine operation modes. So support stiffness characteristic will be practically constant.
For more complex configurations, the engineer can calculate the stiffness characteristics using the FEM program.
DYNAMICS R4 has special element for Squirrell cage properties.
Elastic rings
Advantages:
- Small dimensions and mass.
- Linear stiffness characteristic (may be nonlinear due to design flaws).
- The rotor is centered against the engine axis.
- High damping performance.
- Availability of industry standard for elastic rings.
- Methods for calculation of the ring flexibility and strength.
DYNAMICS R4 has special element for the ring elastic properties calculation.
