Experimental study on the influence of geometrical parameters on the cavitation erosion characteristics of high speed submerged jets

Abstract

The influence of the geometrical working parameters on the cavitation erosion process was experimentally investigated by exposing the surfaces of copper samples (as a kind of Face Centred Cubic material (FCC)) to a high speed submerged cavitating jet for various time periods using a cavitating jet generator. The resulting erosion rate and eroded area is discussed in detail. Influences of the nondimensional standoff distance, the non-dimensional aspect ratio and the angle of attack is experimentally determined. The results show that the erosion rate and weight loss are strongly depending on these separately investigated parameters. With this test rig facility and applied hydrodynamic parameters the maximum erosion was found to take place with a non-dimensional standoff distance varying between 42-48 (depending on the nozzle diameter), with a non-dimensional aspect ratio of 11 and with 105° angle of attack. A model to explain the influence of the angle of attack on the erosion rate based on the cavity bubble and target surface interaction is presented. In addition, the obtained results demonstrate that the used small-diameter (0.4 -0.6 mm) water cutting nozzles could be applied for metal machining by cavitation and cavitation cutting with low power consumption and high cutting efficiency.

Study and analysis of the cavitating and non-cavitating jets - Part two: Parameters controlling the jet action and a new formula for cavitation number calculation

“…At high ambient pressure, Pa or P2, it means that minimum pressure, Pmin, will be greater than the saturation pressure for a given working temperature. This relation gives an explanation why there is a low erosion in terms of erosion area, small cavity length and width at high downstream pressure in the test chamber, more explanation is given in our previous publications [9,12,13].…”

“…The relation between the average cloud length and the tested parameters are of a power function relationship form. This power function relationship was also presented in the literature, but they were presented only for the cavitation number and cloud length [9,13,15]. In this work, we tested the other parameterdynamic power of the jet.…”

“…The cavitation number calculation was done using a classical formula based on the average exit jet velocity (assumed single-phase flow). Because of the pressure fluctuation, as well as the velocity decrease and the compressibility change along the jet trajectory co-ordinates (R, x), the cavitation number varies with the coordinates (R, x) [9,12,13]. In addition, the cavitation number calculated using ASTM formula (If = P2/P1) was examined against the dynamic power and against the static power.…”

“…[1,2,[5][6][7]. However, the structure of the cavitating jet and the behavior of the unsteady cavitation bubbles are still in question, mostly due to the difficulty to observe the interior of cavitating flows [9][10][11][12][13]. With the purpose of performance prediction and efficient design of many engineering devices such as turbomachinery, turbo-pumps in rocket propulsion systems, hydrofoils, fuel injectors, marine propellers, nozzles, and cavitating jet generators, etc., recently attention has also been focused on the numerical simulation of cavitating flows beside the experimental work [14].…”

BME VIK Annual Research Report on Electrical Engineering and Computer Science 2016

“…The relation between the behavior of the cavitation erosion process and the geometrical parameters of the generator (e.g. nozzle diameter and sample standoff distance) was also studied in detail in order to maximize its efficiency [54,55]. In connection to the nano-level surface investigation with atomic force microscopy (AFM), another paper was published which demonstrated and discussed the possible application of a novel parameter called localization factor (introduced by A. Bonyár in 2012) for the characterization of the shape of surface structures [56].…”