Principle Experiments Research of Noise in Engine Main Bearing

Abstract

A squeeze film test apparatus was used to study the mechanism and characteristics of the irregular typewriter noise in engine main bearings oil films. To simulate the dynamic load of the bearing, the transparent moving plate in the test apparatus was moved upward and downward rapidly. The high-speed camera system was used for photographing oil film of the test area. The test apparatus could collect five kinds of signals, sound, displacement, vibration acceleration, force, and pictures of squeeze oil simultaneously during the test running. The irregular noise appeared in the test and the maximum value of irregular noise's sound pressure reached 3 Pa. And the clear pictures of cavitation when irregular noise occurred were taken simultaneously and consecutively via high-speed camera system. The results show that noise occurs under the condition where the collapsed cavitation reached the atmosphere in the falling process of the moving plate. The parameters such as vibration exciting signals, lubricating oil quantity, and oscillation frequency were tested in experiments. There are negative correlations between lubricating oil quantity and the intensity and occurrence rate of the noise. The noise is most prone to occur under square wave excitation and at the oscillation frequency of 12 Hz.

Experiment Study on the Influence of Lubricant Viscosity and Solid Additives on Irregular Cavitation Noise in the Oscillatory Squeeze Film

“…2 Schematic of the test apparatus and its photograph The squeeze oil film was between two flat horizontal plates, the lower thrust plate (8) made of steel and the upper plate (11) made of transparent K9 optical glass, approximately 25 mm in thickness and 50 mm in diameter. The vibration sensor (9) was mounted on the lower thrust plate which was fixed on the base plate (6). During the experiment, the lower thrust plate was submerged in an oil pool confined by the wall of oil pool (10).…”

“…However, these conclusions are obtained through simulation and calculation, so further experiments are needed to verify them. In 2018, our team [6] study the relationship between this irregular noise with cavitation by experiments and reduce this noise by changing experimental conditions. But it is not practical for the engine.…”