The prediction of liquid film journal bearing performance with a consideration of lubricant film reformation: part 2: experimental resuIts

Analyses and design data for plainjournal bearings rarely take into account the phenomenon of film reformation. The consideration of the re-establishment of the lubricantfilm after the cavitation region is difficult in a number of ways. The importance of allowingfor reformation is, however, being increasingly recognized. Tht.J is particularly true as regards the satisfactory predlction of lubricant ftowrate...and the thermal operating characteristics of a bearing. The authors have previously implemented a cavitation algorithm to enable the cavitation region in a plain journal bearing to be Iocated automatically and efficiently in a computer analysis. In Part I of the present paper theoretical results have been presentedfor the case of a plain bearing with a square-ended, axial groove located at the position of maximumfilm thickness. The second part of the paper gives detai/s of an experimental investigation designed to establish the validity of the analysis

Observations of Film Thickness Profile and Cavitation Around a Journal Bearing Circumference

The film formation in a journal bearing and the extent of the cavitated region is an important contribution to load carrying capacity. In the present work, an ultrasonic method has been used to measure the film thickness profile around the circumference of an operating journal bearing. The reflection of an ultrasonic pulse at an oil layer can be used to determine the film thickness. A transducer was mounted inside a hollow shaft and the signal passed through slip rings. The journal bearing was run at a series of loads and rotational speeds. The transducer continuously pulsed and received as it swept around the bush circumference. This enabled the full film thickness profile to be established. In the converging region the predicted film shape agrees well with predictions from classical lubrication theory. When cavitation occurs, the presence of oil-air and aluminum-air interfaces disrupts the ultrasonic signal. Evidence of cavitation appearance is very clear from the measurement results. The minimum film thickness, the attitude angle, and the onset of cavitation are compared with theoretical solutions