The relation between the high speed submerged cavitating jet behaviour and the cavitation erosion process

Abstract

In order to accurately and reliably evaluate the cavitation erosion resistance of materials using a cavitating jet generator, the effects of the hydrodynamic parameters and the nozzle geometry on the erosion process were investigated. Since the behaviour of a high speed submerged cavitating jet is also depending on the working conditions; their influence is also discussed based on the evaluation of cavitation erosion process. The erosion rate was used as an indicator for cavitating jet behaviour. Specimens of commercial-purity copper were subjected to high speed submerged cavitating jets under different initial conditions, for certain time periods. The force generated by jet cavitation is employed to initiate the erosion in surface. The tested specimens were investigated with a digital optical microscope and a profilometer. It was found that erosion becomes more pronounced with decreasing cavitation numbers, as well as with increasing exit jet velocities. The nozzle configuration and hydrodynamic parameters have strong influences on the erosion rate, eroded area and depth of erosion. A comparison between the obtained results explains some of the mechanisms involved in cavitation and erosion processes and their relation to the tested parameters. Mathematical expressions which combine these parameters with the erosion rate are obtained. These parameters are very important in order to control the cavitation as a phenomenon and also to control the performance of the cavitating jet generator.

Optimized Erosion Prediction with MAGA Algorithm Based on BP Neural Network for Submerged Low-Pressure Water Jet

“…y i is the output of the j neuron. Activation function is Equation (11). The activation function of the hidden layer uses the tan-sigmoid function with Equation (12).…”

“…The erosion effect of the nozzle is often reflected by the damage parameter of the impacted target in the water jet erosion test. The existing experimental researches [10][11][12][13][14] mostly studied the impact and cavitation effect of submerged water jets on the surfaces of pure copper, copper alloys, aluminum alloys, ti alloys and other metal materials at the jet pressure in the range of 100-200 MPa, which belongs to high-pressure conditions. However, the jet pressure in our project is lower than 10 MPa, which is under low-pressure conditions.…”

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].…”

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

“…[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].…”

“…If the relationship between the cavitation intensity and the cavitation damage of materials would be investigated precisely, the key parameter for the prediction of the cavitation damage stages (plastic, crackers, erosion, etc.) may be clarified [5,7,12]. The flow through a nozzle can be controlled by the operating conditions, orifice geometry, and flow properties.…”