Analysis of the Erosivity of High-Pressure Pulsating Water Jets Produced in the Self-Excited Drill Head

Abstract

The dynamic impact of a water jet with a periodically changing structure can be used in various industries. The paper presents a design solution for a self-excited pulse head. This head can be used in mining for drilling holes and breaking rocks. The design of the head was developed based on computer simulations, which made it possible to learn the mechanism of impulse shaping inside the head. Tests of the water jet produced in the self-excited pulsation head showed the occurrence of periodic changes in its internal structure and pulsation frequency. A significant increase in the dynamic stream pressures was demonstrated for the head working in the water environment compared to the head working in the air environment For example, for nominal medium and highest pressures, this increase is up to 82%, while for the lowest pressures (10 MPa), the pressure force values increase by 46%. It was found that an increase in the nominal water pressure causes a decrease in the frequency of hydrodynamic pulses in the head operating in both the water and air environment.

Assessment of the effectiveness of high-pressure water jet machining generated using self-excited pulsating heads

“…Based on the obtained results, it was found that for the head model with two side holes, the inlet of medium occurred when the diameter of the inlet nozzle was smaller than the diameter of the outlet nozzle (d1< d3) [31]. The greatest value of inlet mass velocity through the side holes was obtained for d3=1.2 mm and d1=0.6 mm.…”

“…The solution was examined in terms of the influence of the number of holes on the surface cleaning process. The principle concerning the location of the side holes perpendicular to the chamber was used in all such heads, regardless of their application [30,31,32]. The simulation tests were carried out for the same range of diameter variation (0.6 ÷ 1.2 mm) of both types of nozzles: inlet d1 and outlet d3 at a constant pressure of 15 MPa and maintaining the unchanged values of the other dimensional parameters of the self-excited pulse head.…”

“…There was no heat exchange with the environment, which was also assumed in [30]. The process was stopped automatically after achieving convergence criterion, which required at least 500 iterations [31]. Roughness of the side walls was not considered.…”

Evaluation of the Surface Topography of Microfinishing Abrasive Films in Relation to Their Machining Capability of Nimonic 80A Superalloy

“…The presence of loose abrasive particles in the cutting zone, where substantial forces are present, can lead to various issues. This phenomenon finds application in water jet machining, where loose abrasive particles are propelled into the medium at high pressure, or occasionally, the medium's pressure alone is adequate to induce erosive effects on the surface [49,50]. Partially liberated abrasive grain parts from the bond can also be observed, with fragmented grain residues remaining attached to the carrier (Figure 17h).…”

A Short Note about the Impact Action of a Water Jet Stabilized by a Coaxial Air Stream in the Air and Underwater

“…Another way of pulsing jet generation, applying self-excited oscillations in the nozzle, has attracted waterjet researchers for years [ 4 , 5 , 6 , 7 ] but it still remains in the experimental phase although it should be more energy-saving and environmentally friendly. Quite recently, a brand new promising study introducing a self-excited pulse waterjet head applicable in mining for drilling holes and breaking rock was published [ 8 ]. The presented research is focused on the waterjet stability improvement in the near field and support of jet pulsation in the far-field which represents the operation zone of the device.…”