The Effect of Air–Water Mixture on the Dynamic Response of a Hydrodynamic Journal Bearing With Inclined Grooves

Abstract

Water lubricated hydrodynamic journal bearings with deep inclined grooves are often used to support radial loads and dampen pump vibrations in nuclear power plants. The inclined grooves increase the pumping effect of the lubricant thus reducing wear and friction during rotor start-up and coast-down. The deep grooves also facilitate the removal of debris without damaging the bearing. The load capacity and the stability of this type of bearing is studied in the present work. A sensitivity study of the impact of the number of grooves on bearing performance underlined the superiority of the journal bearing with two inclined grooves. Moreover, these journal bearings may operate with a mixture of water and air. This compressible two-phase lubricant will modify the load capacity and the stability of the journal bearing. The impact of the ingested volume fraction of air is therefore investigated. A physical model of the homogeneous air-water mixture linking the local air volume fraction with the pressure was used in conjunction with the numerical solution of the compressible Reynolds equation on an unstructured grid. It was found that the air ingestion in the 2-inclined grooves journal bearing decreases the load capacity but improves the stability for mild and low loads.