Experimental study of the influence of bubbly oil on cavitation erosion of engine journal bearing materials

In reciprocating internal combustion engines, air can become entrapped in the lubricant circulating around the engine such that it cannot be taken into solution under the prevailing operating conditions, producing a two-phase flow system referred to as bubbly oil. This paper describes the development and application of a laboratory simulator to investigate the influence of such bubbly oil on the cavitation erosion of typical engine bearing shell materials. Cavitation erosion is instigated using an ultrasonic vibrator with a flat horn tip in close proximity to a flat sample of engine bearing material. Bubbly oil clearly reduces the wear due to cavitation erosion under the test conditions of the laboratory simulator and also suppresses the increase in cavitation erosion with increasing temperature observed with unaerated oil.