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

Abstract

In view of irregular abnormal cavitation noise in main bearing of engine under the dynamic load from engine spindle, this paper is devoted to finding effective factors that can reduce this cavitation noise. The experiments are carried out in the oscillatory parallelplate squeeze film test apparatus which can simultaneously collect five kinds of signals including vibration, displacement, sound pressure, force and images of cavitation. The influence of lubricant viscosity and three different solid additives (carbon black, molybdenum disulfide, hexagonal boron nitride) on the cavitation noise were investigated experimentally. The experimental results show that as the viscosity of the lubricants increases, the cavitation area increases significantly, and the cavitation noise is more likely to occur. For eliminating the irregular cavitation noise, three different solid additives were added to the experimental lubricant base oil separately. The results show that after adding molybdenum disulfide, the occurrence of cavitation noise become intense dramatically. And hexagonal boron nitride does not have obviously effect on cavitation noise reduction. However, the cavitation noise reduces prominently after the carbon black is added, and this suppression effect enhances as the carbon black concentration increases. The noise reduction mechanism of carbon black is that the carbon black increases the cavitation nucleus in the lubricant and disperse cavitation, which reduce the chances of connecting with the atmosphere in the process of cavitation collapse and realize the effect of noise suppression.

Keywords

• main bearings
• engine
• irregular noise
• cavitation
• fluid lubrication
• lubricant viscosity
• additives