The vibration amplitude can be reduced by various means, reduction of the rotor center of mass eccentricity (balancing), or the critical speed reduction which are the unbalanced force reduction. Another method is the rotor system vibration energy dissipation (damping).
The last two functions are performed by damper supports, which are often also called elastic damper bearings.
More detailed information can be found in subsections HYDRODYNAMIC SUPPORTS, ELASTIC ELEMENTS and DAMPER R3.1.
The damper support structures are very different but their main functions are the following:
- Reduction of the rotor support stiffness which changes the engine elastic dynamic system. At the same time, the natural oscillation frequencies of the system are reduced, and resonances at operating speeds may be eliminated.
- They absorb the energy of vibrations of the dynamic system of the engine, turning it into heat, which does not allow the development of large amplitudes of oscillations, dynamic loads and stresses in all parts of the engine.
Basic requirements for damper supports
- The support must have a certain radial stiffness, which is determined from the engine dynamic system analysis. The purpose of this calculation is to eliminate resonant frequencies from the engine operating range.
- The stiffness of the support, that transfer loads from the sqeeze film damper with centering spring case, should be several times higher than the hydrodynamic damper with an flexible element one.
- The support must have a definite damping capacity to prevent high engine vibrations at various operating conditions, including extreme ones.
- The support must allow sufficient radial elastic deformations. Radial displacement limiters in the support prevent large radial deformations, overstress of flexible elements and their failure. The limiters come into operation only under extreme off-design operating conditions.
- To ensure the central position of the rotor relative to the housing, the axis of the elastic sleeve is shifted by the amount of static deformation of the support.
- The damper support elements should have the capability that allows the adjustment and optimization of its damping during the experimental development.
- To ensure the support dynamic characteristics stability and certainty is required high precision in the flexible elements, seating surfaces, gaps, and calibration holes manufacturing.