Abstract
In order to study the cavitation characteristics of water jet nozzles, a realizable model was selected to simulate the flow field inside the nozzle at the inlet pressure of 15 MPa. The pressure at the starting point of the nozzle throat section dropped to the minimum, and the liquid velocity reached the maximum. From the vapor volume distribution map of the nozzle, it can be seen that the vapor fraction is the largest on the wall of the expansion section, and a local reflux is formed in the expansion section, which results in the gradual diffusion of the vapor fraction distribution along the wall of the expansion section. In addition, the influence of nozzle inlet pressure on the vapor fraction and vapor fraction distribution region in the expansion section is analyzed. The results show that the larger vapor fraction and vapor fraction distribution region can be produced under the 25 MPa inlet pressure. At the pressure inlet of 25 MPa, six groups of numerical simulations were carried out with different the length to diameter ratio of the nozzle throat section (L4/d0). The results show that when L4/d0 is 2, it is more conducive to the formation of cavitation and the quality of cavitation is better.
Highlights
The nozzle is the actuator of the high pressure water jet generating device, which plays a dominant role in the quality of the resulting water jet and limits the other components of the system
Cavitation bubbles occur near the wall of the nozzle throat section, and the maximum vapor fraction occurs at the beginning of the expansion section
We quantitatively study the distribution of the vapor fraction distribution curve of nozzle expansion section wall under different length to diameter ratio
Summary
The nozzle is the actuator of the high pressure water jet generating device, which plays a dominant role in the quality of the resulting water jet and limits the other components of the system. The rate of temperature change is as high as 107 K/s, accompanied by strong shock wave and micro-jet with a velocity of up to 400 km/h Under such extreme conditions, free radical reactions, chemical bond breaking or high temperature cracking reactions occur in the organic matter in the fouling, so as to achieve the purpose of cavitation cleaning [12,13]. Through six groups of numerical simulation of different the length to diameter ratios, the cavitation quality of nozzles with different the length to diameter ratio of the nozzle throat section was obtained at a specific pressure inlet. It provides a theoretical basis for the design of nozzle structure
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