On the future of controllable fluid film bearings

Abstract

Keywords: fluid film bearings, vibration control, friction reduction, temperature effect, stability. Mots clés : paliers de film fluide, contrôle des vibrations, réduction de friction, effet de température, stabilité.This work gives an overview of the theoretical and experimental achievements of mechatronics applied to fluid film bearings. Compressible and uncompressible fluids are addressed. Rigid and elastic (deformable) bearing profiles are investigated. Hydraulic, pneumatic, magnetic and piezoelectric actuators are used. The ideas of combining control techniques, informatics with hydrodynamic, thermo-hydrodynamic, elastohydrodynamic and thermo-elasto-hydrodynamic lubrication techniques are carefully explored in this paper, considering theoretical as well as experimental aspects. The main goal of using controllable fluid film bearings is to improve the overall machine performance by: controlling the lateral vibration of rigid and flexible rotating shafts; modifying bearing dynamic characteristics, such as stiffness and damping properties; increasing the rotational speed ranges by enhancing damping and eliminating instability problems, for example, by compensating cross-coupling destabilizing effects; reducing start-up torque and energy dissipation in bearings; compensating thermal effects. It is shown that such controllable fluid film bearings can act as "smart" machine components and be applied to rotating and reciprocating machines with the goal of avoiding unexpected stops of plants, performing rotordynamic tests and identifying model parameters "on site". Emphasis is given to the controllable lubrication (hybrid and active) applied to different types of oil film bearings under different lubrication regimes, i.e., as tilting-pad journal bearings, multirecess journal bearings and plain journal bearings. After a comprehensive overview of the theoretical and experimental technological advancements achieved in university laboratories, the feasibility of industrial applications are highlighted, trying to foresee the future trends of such mechatronic devices.

New Designs of Centrifugal Magnetic Fluid Seals for Rotating Shafts in Marine Technology

“…blood, lymph, etc., as another promising application for the shaft seal. Magnetic fluid seals were developed in the 1960s in devices controlling the rocket fuel flow, and their use has been extended to various other applications [28,[49][50][51][52][53][54]. These seals work without rubbing contact of the rotating shaft surface, and hence, there is no wear.…”

“…However, the effect of contact with body liquids upon the performance of the magnetic fluid seals was not investigated. Further investigations of the seal performance during acceleration tests [47][48][49][50][51][52] have proved that the radial clearance between the pole piece and the shaft can be up to 400 µm, i.e. is much larger than the conventional setting (50 µm).…”

Controllable Sliding Bearings and Controllable Lubrication Principles—An Overview

“…Fluid film bearing technology is nowadays witnessing an explosive expansion of active magnetic bearing technology, a typical so-called smart product. Some of the limitations and drawbacks associated to fluid film bearing technology could be overcome by combining fluid film bearings with sensing, control and signal processing techniques, lending them "smartness", "multi-functionality" and "higher reliability" [9]. In such a framework, it is important to evaluate the state-of-the-art of controllable fluid film bearings, which fit perfectly within Industry 4.0 and have been investigated over the last two decades but have not yet found their space in industrial applications, despite several promising theoretical and experimental achievements.…”

Improving stability and operation of turbine rotors using adjustable journal bearings

“…The theoretical proposals are numerous, however, only some would meet a practical application in industrial turbines mainly due to reasons of cost, simplicity, and reliability. A quite complete overview of the experimental and theoretical achievements on mechatronics applied to controllable journal bearings can be found in [5]. Many concepts for bearing adjustability/control utilize active oil injection [6][7][8] while other proposed concepts incorporating movable bearing pads, among others the very recent [9][10][11][12], the application of external forces in the bearing shell or the journal, for example magnetic [13][14][15][16], or piezo-mechanical [17][18][19] without changing the bearing's clearance geometry.…”