Investigation of the flow phenomena in high-pressure water jet nozzles

Abstract

High-pressure water jets are often used as a tool for cleaning, cutting or for modification of the surface morphology. The nozzle design has a considerable influence on cavitation and wear effects as well as on the nature of the exiting jets. Different applications are affected by different flow regimes, such as cavitation or hydraulic-flip, which depend on the radius of the nozzle edge.In this work, the turbulent two-phase flow within two different nozzle types is analyzed using Computational Fluid Dynamics. The focus was to establish a relationship between the geometry of these nozzles and the flow phenomena as well as between wall shear stress and the wear, which leads to the change of the water jet shape and reduces the lifetime of high-pressure nozzles. The performed variation of the nozzle edge from sharp to round showed a significant influence on the maximum wall shear stress and cavitation. Additionally, the inner surface of used nozzles was investigated with Scanning Electron Microscope. Numerous marks of erosion were found at the nozzle edge. For the validation, the volumetric flow rate through the nozzles was measured at different inlet pressures and compared with the simulation results, which showed a good agreement.