Context. One of the ways to determine the contribution of the dark halo to the gravitational potential of a galaxy is the study of noncircular (streaming) motions and the associated gas shocks in the bar region. These motions, determined by the potential in the inner parts, can break the disk-halo degeneracy. Here, two main fluid dynamical approaches have been chosen to model the non-circular m...

A 2005 TRC report presents imbalance response measurements of a hollow test rotor supported on bump-type gas foil bearings. The top speed of the tests is 25 krpm, the limit of the drive router motor. The 2005 measurements show the gas foil bearings are prone to subsynchronous whirl with amplitudes of motion exacerbated by the imbalance condition of the rotor, i.e. a forced nonlinearity. Present...

An in situ measurement of micro-friction torque in MEMS gas bearings, which has been a challenging research topic for years, is realized by a system designed in this paper. In the system, a high accuracy micro-force sensor and an electronically-driven table are designed, fabricated and utilized. With appropriate installation of the sensor and bearings on the table, the engine rotor can be drive...

A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low A region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important ...

nowadays, due to the increasing power of diesel engines, especially heavy duty diesel engines, and increasing gas pressure inside the combustion chamber, the forces acting on the engine bearings have dramatically raised. on the other hand, becaus eof the competition in the market, it is necessary to increase the engine bearing life and reduce its failure as much as possible. the engine bearings...

Oil-free microturbomachinery (MTM) are inevitably subjected to base or foundation excitations: passenger and commercial transportation vehicles experiencing intermittent excitation from road conditions, and (multiple) periodic load excitations from internal combustion (IC) engines in turbochargers, for example. Too large base excitations can produce severe damage, even failure, due to hard coll...

Foil gas bearings are in widespread commercial use in air cycle machines, turbocompressors and microturbine generators and are emerging in more challenging applications such as turbochargers, auxiliary power units and propulsion gas turbines. Though not well known, foil bearing technology is well over fifty years old. Recent technological developments indicate that their full potential has yet ...

1. Asymmetric Volume Coils Asymmetric, noncircular volume coils are required in situations where the available access bore is noncircular in cross section, such as for table-top applications [1] or where the gradient bore is noncircular [2]. They consist of ladder network resonators such as the birdcage [3] or TEM [4] coil that have been modified by placing their rungs on a cylindrical surface ...