Providing a cavitation-free regime when flushing ship pipelines with a two-phase mixture

Abstract

It is noted that during the flushing of ship systems and their elements, the mixed flow of water and air has proven itself well as a flushing medium. It has been experimentally established that there is a significant acceleration of the washing process and an increase in the number of flushed-out dirt particles. At the same time, the two-phase flushing method currently has a number of unsolved theoretical and practical problems. One of such tasks is to ensure a cavitation-free flushing regime. The issue of ensuring a cavitation-free regime when flushing ship pipelines with a twophase mixture during the passage of narrownesses stream is considered in the paper. It is known that the cavitation occurrence depends on a number of factors. The degree of each factor influence on the probability of cavitation occurrence is investigated. In this paper, an attempt to theoretically assess the development of cavitation in narrow technological jumpers is made. The main theoretical dependence of the maximum permissible diameter of the jumper on the main parameters of the mixed flow, as well as on the initial pressure of the flushing flow is determined. The main parameters of the mixed flow are the mass flow rate of the flushing water, the densities of the mixture phases, the mass content of air in the flow, the initial diameter of the pipeline and the compression ratio of the jet in a narrow section. A homogeneous mixture model is used in the theoretical study of cavitation phenomena in a two-phase flow. The main design dependencies for determining the maximum allowable diameter of the jumper depending on the main factors of the two-phase flow are defined in the paper. The influence of various factors on the development of cavitation phenomena is evaluated. Particular attention is paid to the choice of the flow diameter of the technological jumper depending on the mass flow rate of the flushing stream, the air content and the initial pressure.