hydrostatic lubrication

Hydrostatics

We study hydrostatic lubrication, which works on the principle of external supply of lubricant to the contact area under increased pressure. This creates a continuous lubricating film separating the friction surfaces, which is able to transfer very large loads while maintaining high precision. This type of lubrication is suitable both for small and very precise bearings and for ensuring the rotational movement of large structures exceeding tens of meters, such as telescopes, radars and theatre turntables. This is a multi-disciplinary issue of the mechanics of fluids and solid mechanics, the knowledge of which leads to a reduction in energy requirements and ensuring the long-term and stable operation of machines with hydrostatic bearings.

Reasearch characteristics

Hydrostatic (HS) lubrication occurs in the conformal contact of two rigid bodies, which are completely separated by a continuous layer of lubricant. A necessary condition for ensuring HS lubrication is a continuous supply of pressure oil through the hydraulic circuit to the contact area. Thanks to this, the separation of the sliding surfaces can be ensured even without relative movement of the contact bodies. Since these are conformal surfaces, the oil pressure between the sliding surfaces is evenly distributed in the area of the inlet groove (so-called recess), and it usually ranges in units of MPa and already drops to atmospheric pressure at the outlet from the bearing. The shape of the recess significantly affects the behaviour and the resulting arrangement parameters. We make numerical solution of computational fluid dynamics (CFD) and fluid-solid interaction (FSI). However, most of the research is focused experimentally on our own test bearings, which we have developed for this purpose. In addition to parameter control, we deal with geometric accuracy and pad placement for the most stable operation. An integral part of HS bearings is the hydraulic circuit that supplies the pads with pressure lubricant. We cooperate with industrial partner Bosch Rexroth in the field of hydraulics and control of HS bearing parameters.

Laboratory equipment

  • two-pad reciprocal hydrostatic bearing (2-PAD) with complete condition diagnostics (max. load: 40 kN, max. flow: 20 l/min, max. pressure: 100 bar)
  • three-pad hydrostatic bearing (3-PAD) with feedback control of the lubrication layer (max. load: 30 kN, max. flow: 10 l/min, max. pressure: 100 bar)
  • four-pad rotary hydrostatic bearing (4-PAD) with a diameter of 2 m with complete condition diagnostics and feedback control of the lubrication layer (max. load: 400 kN, max. flow: 40 l/min, max. pressure: 100 bar)
  • Rtec universal tribometer with rotary module and pin-on-disk configuration for evaluation of modifications of sliding surfaces of HS bearings
  • Bruker Contour GT X8 optical profilometer