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The Ice abrasive water jet technology uses cryogenically cooled ice particles instead of the mineral abrasive used in the Abrasive water jet technology. The aim is to avoid contamination of workpieces with mineral abrasives and to reduce the environmental impact of this technology. The ice particles are sucked into a high-speed water jet with speeds of up to 600 m∙s$^{−1}$ using the Venturi effect. Direct observation of the process is very difficult due to the extreme operating conditions. We have clearly shown that at least some of the ice particles, which have cryogenic temperatures when entering the high-speed water jet, neither completely melt nor are completely crushed in contact with the jet. Further on, the erosion capability of ice particles was evaluated by blasting the aluminium and glass surfaces at two impinging angles and compared to garnet mineral abrasive, showing that ice particles have the potential to generate similar damage in the workpiece material as garnet. These findings pave the way for exploring the potential of abrasive waterjet technology in a wide range of new applications, such as food processing, medical implant and turbine blade manufacturing, and post-processing of parts manufactured with additive manufacturing technologies. more...

This paper deals with visualization and velocity analysis of a self-excited water jet generated by a designed prototype of hydrodynamic nozzle. The high-speed camera in combination with four high-energy pulsed LED lights and the particle image velocimetry method were tested. The influence of water pressure on the jet shape, velocity field and frequency of the self-excited jet was studied. The designed diagnostic water line consisting of pressure sensors and a turbine flowmeter was used for flow monitoring during experimental flow visualization. It was observed that the used optical equipment is suitable for velocity-frequency investigation up to 40 MPa with the maximal jet velocity 247 m/sec, 4.5 kHz oscillation frequency. The overall speed dependence of velocity on the distance downstream from the nozzle outlet (0–100 mm) decreases by 13–15% for tested pressure levels. Oscillation of self-excited jet in the 10–40 MPa pressure range is changing in range 2.5–4.5 kHz. more...

This paper deals with performance analysis of disintegration of polymethylmethacrylate using pulsating liquids jet with different density with frequency 20 kHz using condition monitoring. The influence of the liquid on the cutting depth was studied by using contactless measurement device MicroProf, FRT. The cutting depths were compared to studies that used a continuous water jet to assess the volume flow reduction. On-line condition measurement was used for controlling the disintegration process without compromising the structural integrity of neighbouring materials. With a flow rate of 0.54 l/min, a maximum disintegration depth of 1.3 mm and material removal of 0.4 mm3 was obtained using physiological saline and 1.1 mm and 0.2 mm3 for water. Continuous jets required approximately 1.0 l/min to reach similar cutting depths. Hence, a pulsating liquid jet enhances the cutting capacity with reduced flow rate. Signal strength for individual pressures 7–10 MPa is not significant, but signal increases during significant bone cement removal. The results open new avenues for research a minimally invasive and non-thermal technique for on-line controlled processes for medical purposes. more...

The paper is dealing with the effects of flat high-speed water jet on concretes affected by high temperature. Research should help to correct use of water jet technology in repair works on concrete structures especially after wildfires in tunnels, underground garages, etc., which are exposed to enormous thermal stress. Four concrete mixtures were prepared for tests of interaction of water jet with concrete. The samples were exposed to 200 °C and 600 °C and for comparison one third of samples were left unaffected. It was found, that both lower traversing velocity (cutting speed) and higher water pressure led to removal of higher amount of concrete. Higher temperature loading caused decrease of concrete strength and thus easier removal of surface layers by water jet. Concrete mixtures with basalt aggregate demonstrate higher resistance against water jet penetration regardless thermal loading compared to mixture with standard granodiorite aggregate. Presence of polypropylene fibres has substantial influence on concrete strength properties, however only marginal impact on resistance against water jet penetration. more...