Methods for Detemerination of the Gap Height in water-lubricated contacts


A paper on “Methods for Determination oft he Gap Height in water-lubricated Contacts” was published at the 16th Scandinavian International Conference on Fluid Power in Tampere.

  Pressure distributions in the contact of slipper and swashplate Copyright: ifas Pressure distribution due to different effects

Applications, which require the pressure fluid to be environmentally safe, often use water hydraulics as motion technology. If the tribological contacts of the components are chosen to be lubricated with water as well, the gap height is reduced compared to oil lubrication due to the lower viscosity of water. Because of occurring wear and increased leakage the pressure load of the components is limited. This limitation is investigated for the purpose of the piston slipper / swash plate contact of an axial piston pump. This research is based upon simulation using a model containing the Reynolds-Equation and a solid contact model. Furthermore deformation of the slipper surface is considered.

  Results Copyright: ifas Results for deformed surfaces

The investigation of the slipper / swashplate with water lubrication has been conducted using a simulation model containing the Reynolds-Equation including with the Greenwood-Tripp and Patir-Cheng models. Furthermore the model has been combined with a simulation of the surface deformation for a plastic slipper pad, carried out in ANSYS Workbench. The results show that the typical gap height of the water-lubricated slipper contact is in the range of about 2 to 4 µm, which is also given by literature references. The deformation of the surface increases the gap height as well. The increase in leakage shows the limitation for pressure in water-lubricated contacts using plastic materials. The investigation is only theoretical and needs yet to be validated using experiments with the given geometry and materials. A disadvantage of this way of modelling are not known input parameters and the loss of accuracy due to the use of simplification. The benefit of this research is a statement of the limits of water lubrication in the piston slipper / swashplate contact according to the pressure range and the used materials, e.g., plastic materials.