Rotordynamics and Air Lubrication

Aerodynamic foil bearings allow oil-free bearing of high-speed rotors and are designed for operation at high or low temperatures. The elastic foil structure in foil bearings ensures that thermal and mechanical deformations (e.g. expansion due to centrifugal forces) during operation and manufacturing inaccuracies can be compensated for, so that lubrication in the bearing is ensured without breakage despite higher eccentricity of the rotor. The effective structural damping mechanism in foils increases energy dissipation throughout the bearing, and with optimal design, self-excited vibration can be avoided over the entire speed range. The highly precise design and dimensioning of air bearings despite numerous advantages for different operating conditions is a challenging task due to complicated physics behind air as lubrication. SADAP is happy to support you with its expertise, software and hardware competences on the way to a successful design of new concepts or the application of oil-free bearing.

Our services in the field of rotor bearing systems as PDF

Design with digital calculation tools

We design it for you …

SADAP supports its customers on the way to a successful development of air and foil bearings for their applications. Using high-precision digital design tools, we develop the air-lubricated bearings for your machine (e.g. compressors in fuel cells) in such a way that the bearing meets all your requirements and has optimized properties against the effects that occur during operation. We pay particular attention to ensuring that the lift-off process (build-up of aerodynamic pressure in the lubricant film) is as fast as possible and that the bearing has sufficient load capacity over the entire operating range. Minimizing energy losses due to frictional torques is another objective in the development of air and foil bearings. In addition, the self-excited (so-called subsynchronous) vibrations must be avoided as far as possible by an optimized design and stable operation must be realized over the targeted operating range. In this context, the bearing should be designed against both external excitation and self-excited vibrations with sufficient stiffness and damping. In applications where eccentric operation of the shaft is not a major problem (e.g. in the automotive industry), foil bearings are recommended, where the additional damping mechanism in the foil structure (due to frictional effects) provides stability and simplifies the manufacture of the bearing in terms of manufacturing tolerances. Air bearings without a compliant foil structure, on the other hand, are recommended for applications where there is little room for shaft motions (e.g., in medical technology or precision machining). We can answer these and other application-specific questions with our expertise based on the current state of the art, thus significantly optimizing the performance and efficiency of your machine!

Experimental Studies

We measure it for you …

In addition to the design of air and foil bearings, SADAP offers experimental investigations as the next step in a cooperation with the TU Braunschweig. Here, the bearing designed in the first step (as a prototype) is tested and validated in and out of operation.

Experimental studies (out of operation):

The foil bearing consists primarily of compliant foil structures connected in series with the lubrication film to provide stiffness and damping. This additional viscoelastic property keeps the bearing more robust to harmonic and subharmonic shocks and protects the minimum lubrication film thickness from failure.

Based on this consideration, the dynamic properties of the foil structure as a function of the excitation frequency play an essential role. In this respect, SADAP offers a careful investigation of the dynamic behavior of the foil bearings with a focus on film structure and out of service. This type of investigation is called measurement of the mechanical impedance of the foil structure.

The bearing assumed for investigation is harmonically excited in two directions perpendicular to each other (up to 9000 Hz) and the deflection in the respective directions is measured. Post-processing of the measured data determines how the stiffness and damping coefficients of the foil structure react to different frequencies that may occur during operation.

Training offers

We train your team …

Benefit from high-quality knowledge in the direction of optimizing your company’s performance.

  • Are you looking for a high-performance training partner?
  • Want to train your team at a specific location?
  • Or are you planning to have development staff on your team trained in specific areas of expertise?

We offer training services for industrial workers with unique knowledge potential in all areas covered by SADAP. These are mainly training services in the field of rotor dynamics calculation, bearing testing and evaluation of data from experimental investigations and simulation products. But that is not all we would like to offer you. You are welcome to send us your individual request as a corporate customer in the following areas:

  • Structural Health Monitoring area
  • System identification under mechanical aspects
  • Adaptive electromechanical solutions for vibration and noise reduction