Technology · Gas foil bearings
Gas foil bearings for oil-free high-speed turbomachinery
MITIS designs, manufactures and tests its own compliant gas foil bearings. They carry the rotor of our M10 micro gas turbine above 100,000 rpm with no oil, no lubrication circuit and minimal maintenance. We put the same in-house capability at the service of OEMs developing turbines, compressors and cryogenic machines.
How a gas foil bearing works
At nominal speed, the rotating shaft drags gas into a thin hydrodynamic film that lifts it off the foil: there is no contact and no wear during operation. Behind the smooth top foil, an engineered spring-foil structure gives the bearing its stiffness and damping.
- Excellent suitability for very high rotational speeds
- No lubrication circuit, reducing maintenance and system complexity
- High-temperature compatibility
- Compliant structure that accommodates thermal expansion and rotor misalignment
Radial bearing: three-lobe design
Our radial bearing uses three independently compliant sectors for enhanced rotor stability. Each sector has its own spring-foil structure, engineered to provide radial compliance and damping where the rotor needs it.
Thrust bearing: segmented compliant pads
The thrust bearing supports axial loads on segmented compliant foil pads with integrated structural damping. It delivers a high axial load capacity in a compact architecture, for stable high-speed operation.
From specification to a tested bearing
Every bearing is designed for the machine it supports, not picked from a catalogue. Starting from your loads, speed range, temperature and working gas, our engineers combine in-house design methods, simulation of the foil structure and rotordynamic analysis of the complete rotor–bearing system, before any hardware is built.
Manufactured and tested in our own lab
We manufacture prototype bearings and validate them on our instrumented high-speed test rigs, then feed the measurements back into the design. In bearing design, details at the micron scale matter, and only testing proves them.
Design examples
Bearing designs in our portfolio
| Bearing | Size | Design values |
|---|---|---|
| Radial foil bearing | 56 mm diameter | 3.3 million DN · load capacity 222 N |
| Radial foil bearing | 28 mm diameter | For compact high-speed rotors |
| Thrust foil bearing | 110 mm diameter | Load capacity about 1.5 kN |
Indicative design values. Each bearing is sized for the customer's machine.
Applications
Where our foil bearings make the difference
Micro gas turbines
Oil-free turbogenerators such as the MITIS M10.
Cryogenic turbo-Brayton
Silent, contamination-free coolers and companders running on nitrogen.
Compressors & e-compressors
Fuel-cell air compressors, heat-pump compressors and air-cycle machines.
Turbo-expanders
Compressed-air turbines and energy-recovery expanders.
Hydrogen systems
Machines where oil contamination of the process gas is not acceptable.
Your machine
Bearing studies, prototypes or full machine development: tell us your specification.
FAQ
Gas foil bearings: frequently asked questions
What is a gas foil bearing?
A gas foil bearing is a self-acting, oil-free bearing. At operating speed the rotor drags gas into a thin film between the shaft and a compliant foil, so the shaft floats without contact. A spring-foil structure behind the top foil provides stiffness and damping.
Which machines can use gas foil bearings?
Gas foil bearings suit small, very high-speed machines: micro gas turbines, turbo-compressors and e-compressors, turbo-expanders, cryogenic turbo-Brayton coolers, heat-pump compressors and compressed-air turbines. They work in air, nitrogen and other process gases.
Can MITIS design foil bearings for our machine?
Yes. MITIS designs radial and thrust foil bearings to your load, speed, temperature and gas specification, checks them with rotordynamic analysis, manufactures prototypes and tests them on its own test rigs in Liège, Belgium.
How fast can a gas foil bearing run?
Foil bearings have no inherent speed limit like rolling bearings and suit very high DN values. MITIS rotors run above 100,000 rpm on its own foil bearings.
Do foil bearings work at high temperature?
Yes. Because there is no oil, foil bearings tolerate temperatures that would degrade a lubricant, and the compliant structure accommodates thermal expansion and rotor misalignment.
Developing an oil-free high-speed machine?
From a first feasibility study to tested prototype bearings, our engineers can support your team.