A bibliography /with abstracts/ on gas-lubricated bearings Interim report

Gas lubricated bearings - annotated bibliograph

Research and development of high-performance axial-flow turbomachinery. Volume 3 - Design of backup gas bearings

Gas lubricated bearing system for turbine compresso

Development of compressor end seals stator interstage seals, and stator pivot seals in advanced air breathing propulsion systems. Part 1: Screening studies and analysis

Design and characteristics of 28-inch diameter seals for air breathing propulsion systems - Part

Turbomachinery Clearance Control

Controlling interface clearances is the most cost effective method of enhancing turbomachinery performance. Seals control turbomachinery leakages, coolant flows and contribute to overall system rotordynamic stability. In many instances, sealing interfaces and coatings are sacrificial, like lubricants, giving up their integrity for the benefit of the component. They are subjected to abrasion, erosion, oxidation, incursive rubs, foreign object damage (FOD) and deposits as well as extremes in thermal, mechanical, aerodynamic and impact loadings. Tribological pairing of materials control how well and how long these interfaces will be effective in controlling flow. A variety of seal types and materials are required to satisfy turbomachinery sealing demands. These seals must be properly designed to maintain the interface clearances. In some cases, this will mean machining adjacent surfaces, yet in many other applications, coatings are employed for optimum performance. Many seals are coating composites fabricated on superstructures or substrates that are coated with sacrificial materials which can be refurbished either in situ or by removal, stripping, recoating and replacing until substrate life is exceeded. For blade and knife tip sealing an important class of materials known as abradables permit blade or knife rubbing without significant damage or wear to the rotating element while maintaining an effective sealing interface. Most such tip interfaces are passive, yet some, as for the high-pressure turbine (HPT) case or shroud, are actively controlled. This work presents an overview of turbomachinery sealing. Areas covered include: characteristics of gas and steam turbine sealing applications and environments, benefits of sealing, types of standard static and dynamics seals, advanced seal designs, as well as life and limitations issues

Oil film bearings applied to heavy duty rolling mill drive couplings.

The present work describes an investigation related to rolling mill drive-lines in the Steel Industry with special reference to Hookes joint couplings. This coupling transmits the torque and the rotational motion, required for the rolling process, and contains four hearings which are under oscillating motion. Together with the impact loads often found in rolling mills this provides a severe operating environment which has been simulated to permit an experimental investigation of the suitability of oil film bearings for such applications. In the rig, displacements of the shaft centre, i.e. locus path or eccentricity, have been recorded versus load levels and frequencies of oscillation or rotational speeds for constant oil inlet pressure. Three different types of oil lubricant bearings have been tested under the adverse conditions of dynamic load and oscillating motion, but less severe tests for conditions of continuous motion and static load were also carried out to give reference of the behaviour of such bearings. Comparisons have been obtained between hydrodynamic bearings with axial and circumferential grooving and slot entry hybrid bearings, showing the latter to be suited to the particular application considered. Results have been compared with existing design procedures suitably modified to take account of the adverse operating conditions

Performance of hydrodynamic journal bearing under the combined influence of textured surface and journal misalignment: A numerical survey

A wisely chosen geometry of micro textures with the favorable relative motion of lubricated surfaces in contacts can enhance tribological characteristics. In this paper, a computational investigation related to the combined influence of bearing surface texturing and journal misalignment on the performances of hydrodynamic journal bearings is reported. To this end, a numerical analysis is performed to test three texture shapes: square “SQ”, cylindrical “CY”, and triangular “TR”, and shaft misalignment variation in angle and degree. The Reynolds equation of a thin viscous film is solved using a finite differences scheme and a mass conservation algorithm (JFO boundary conditions), taking into account the presence of textures on both full film and cavitation regions. Preliminary results are compared with benchmark data and are consistent with a positive enhancement in misaligned bearing performances (load carrying capacity and friction). The results suggest that the micro-step bearing mechanism is a key parameter, where the micro-pressure recovery action present in dimples located at the second angular part of the bearing (from 180° to 360°) can compensate for the loss on performances caused by shaft misalignment, while the micro-pressure drop effect at the full film region causes poor performances. Considering the right arrangement of textures on the contact surface, their contours geometries can have a significant impact on the performance of misaligned journal bearings, particularly at high eccentricity ratios, high misalignment degrees and when the misalignment angle α approaches to 0° or 180 °