The effect of impurities on jet-cavitation

Cavitation is a common and usually undesirable phenomenon in fluid power systems. Understanding the basics of cavitation phenomenon is important in order to prevent cavitation in fluid power systems. In the birth process of cavitation, nuclei of all kinds play an important role. Impurities of fluid (liquid, gas, or solid) can act as cavitation nuclei. The growth of a cavitation void starts typically from a "weak spot", which tends to reduce the tensile strength of fluid. This kind of weak spot can be for example a microscopic undissolved gas bubble or a solid contamination particle. When reducing pressure, aeration and vaporisation of fluid takes place more easily, at the solid-liquid interface and the effect of particle count becomes evident, In this paper, various air bubble concentrations of hydraulic oil are used in order to study their effect on inception and development of jet-cavitation. Different concentrations are acquired by altering the size of oil reservoir. When the reservoir is relatively small, deacration of oil does not have enough time to take place. The effect of solid particle count on cavitation is studied as well. Test dust is fed gradually into the test system and the cavitation behaviour of orifice flow is studied. In this paper, the importance of air and particle concentration on inception and development of cavitation is discussed. The test procedures are described and test results are presented. The curves of turbulent flow are presented with various air and particle concentrations. The starting point of cavitation is determined with various methods and they are presented in the paper.