Experimental research on the effect of air bubble properties on aluminum cavitation erosion

Qing-Feng Wang,Wang-Ru Wei

doi:10.1063/5.0077860

Abstract

Cavitation has been proven to cause damage to hydraulic structures. In recent times, aeration has been receiving increasing attention as a suitable method for preventing or reducing the erosion effects of cavitation. In this study, an orifice with a micrometer-sized diameter was designed for introducing air bubbles in water to examine the reduction in erosion caused by cavitation in ultrasonic environments. The experimental results showed that cavitation erosion is significantly reduced by low air concentration, which also reduces structural damage due to cavitation. At a certain air concentration level, the erosion reduction effects of the material do not change when the conditions of the air are altered, and the wall surfaces are protected by aeration and corrosion reduction; the air bubble frequency also influences cavitation erosion, with a high air bubble frequency resulting in a more conducive environment for minimizing cavitation damage. The influence of cavitation damage under the same aeration concentration and different air bubble sizes was also analyzed. The analysis results indicated that the combination of air concentration that satisfies the corrosion reduction requirements and smaller bubble size is highly advantageous for achieving the aeration and corrosion reduction effect at a smaller aeration concentration. Therefore, the aeration and corrosion reduction effect can be effectively achieved through the size of the bubble, and, in water conservancy projects, it can be beneficial for designing and analyzing methods to reduce corrosion and aeration.

Highlights

Dam discharge structures are protected from cavitation damage via aeration, which is used as an erosion control and protection method
Air entrainment had a considerable effect on cavitation erosion in the first set of experiments, while the second set showed that at 3.5% air concentration, there was a noticeable reduction in cavitation erosion; cavitation erosion could be eliminated entirely when it decreased to ∼7%
The results show that the effect of the erosion reduction of different sizes of the air bubbles is associated with no significant differences in air concentration, but a smaller air bubble size is a more conducive setup for reducing the occurrence of cavitation damage

Summary

Introduction

130 years ago, the performance of early marine propellers declined. Decades later, research conducted by Ross and Kuperman identified the cause of the damage as cavitation. Dam discharge structures are protected from cavitation damage via aeration, which is used as an erosion control and protection method. Aeration concentration is an important engineering index for aeration and corrosion reduction to protect dam discharge structures from cavitation damage. According to Peterka, two sets of experiments were carried out to determine whether air entrainment reduces cavitation erosion. Air entrainment had a considerable effect on cavitation erosion in the first set of experiments, while the second set showed that at 3.5% air concentration, there was a noticeable reduction in cavitation erosion; cavitation erosion could be eliminated entirely when it decreased to ∼7%. The two experiments conducted by Rasmussen showed that cavitation erosion is preventable when the air concentration is ∼1%. Once the cavitation damage phenomenon is eliminated, it is expected to cease Researchers differ in their views regarding the minimal aeration concentration required to avoid cavitation damage. The basic principles of aeration and erosion have been studied in depth, considering cavitation bubble dynamics, air bubbles, cavitation bubbles, and the interaction of cavitation and other relevant issues. The basic cavitation theory has been explored.

Objectives

Results

Conclusion