Pressure Profile Measurements within The Gas Film of Journal Foil Bearings Using An Instrumented Rotor with Telemetry

Foil bearings are strong candidates to support oil-free turbomachinery. Although foil bearings are a widely used technology, models describing their behavior are not validated using the film pressure, which is the fundamental variable of any fluid film bearing. This paper presents pressure profiles measured within the gas film of a journal foil bearing. The pressure is measured using an instrumented rotor with embedded pressure probes and wireless telemetry. The measurements yield the simultaneous circumferential pressure profiles at two axial positions inside the bearing. Proximity probes on the bearing allowed the measurement of the corresponding rotor orbits. The bearing under investigation is a bump type compliant journal bearing, with a nominal diameter of 40mm, an L/D = 1, and was tested up to 37.5 krpm. Load-displacement and break-away tests were performed on the test bearing in order to identify bearing parameters necessary for reproducibility. The pressure profiles are compared to a frequency domain foil bearing model. This paper is a step towards further fundamental understanding of the foil bearing behavior, and the validation of the rich modelling literature.

Pressure Profile Measurements Within The Gas Film Of Journal Foil Bearings Using An Instrumented Rotor With Telemetry

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Foil bearings are strong candidates to support oil -free turbomachinery. Although foil bearings are a widely used technology, models describing their behavior are not validated using the film pressure, which is the fundamental variable of any fluid film bearing. This paper presents pressure profiles measured within the gas film of a journal foil bearing. The pressure is measured using an instrumented rotor with embedded pressure probes and wireless telemetry. The measurements yield the simultaneous circumferential pressure profiles at two axial positions inside the bearing. Proximity probes on the bearing allowed the measurement of the corresponding rotor orbits. The bearing under investigation is a bump type compliant journal bearing, with a nominal diameter of 40mm, an L/D = 1, and was tested up to 37.5 krpm. Load-displacement and break-away tests were performed on the test bearing in order to identify bearing parameters necessary for reproducibility. The pressure profiles are compared to a frequency domain foil bearing model. This paper is a step towards further fundamental understanding of the foil bearing behavior, and the validation of the rich modelling literature.

Amer Soc Mechanical Engineers2019

An Instrumented High-Speed Rotor With Embedded Telemetry For The Continuous Spatial Pressure Profile Measurement In Gas Lubricated Bearings: A Proof Of Concept

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Gas lubricated bearings are capable of supporting high speed rotors with satisfactory load capacities. Pressure is one of the constitutional quantities governing the flow field in gas lubricated bearings. Knowledge of the pressure is of principal importance in the fundamental understanding of such bearings and for the calibration of reduced order models. These measurements can be done from the bearing side using pressure taps in the bushings, however, the measurement points will yield a spatially sampled profile consisting of discrete points relative to the bearing bushing. This measurement technique is simple, yet, several details cannot be captured. In order to acquire a continuous scan of the pressure field inside the bearing, it is necessary to measure from the rotor side. Such onboard measurement technique is challenging due to constraints in volume, G-force, and data and power transmission through the rotor. This paper presents an instrumented measurement rotor with embedded pressure probes and a wireless telemetry, which is capable of the continuous pressure field measurement inside a high-speed externally pressurized gas journal bearing. The bearing under investigation has a diameter of 40mm, L/D = 1, and was tested up to 37.5 krpm. The bearing is of the annular type, with 2x18 00.1mm restrictor orifices. Measurements at discrete points using pressure taps inside the test bearing were also performed for the sake of comparison. The measurements from both sides (bushing and rotor) were in good agreement at quasi-static conditions. At higher operational speeds, it was necessary to perform an in -situ system identification and calibration for the embedded pressure probes using the bearing side measurements as a reference. The in-situ system identification technique was successful to reconstruct the attenuated pressure signals for a wide range of supply pressures and rotor speeds. The instrumented rotor was proven qualified to perform time-resolved pressure measurements within the gas film ofjournal bearings up to 37.5 krpm.

Amer Soc Mechanical Engineers2019

An Instrumented High-Speed Rotor With Embedded Telemetry For The Continuous Spatial Pressure Profile Measurement In Gas Lubricated Bearings: A Proof Of Concept

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Amer Soc Mechanical Engineers2019