The Influence of Inlet Geometry and Back Pressure on Cavitation and Noise Reduction in High Pressure Nozzles

Cavitation is a phenomenon in fluid flow that can have devastating consequences on component life. The understanding of this occurrence and the compressibility effects in liquid flow are of utmost importance to the operation of fluid equipment. Reducing or eliminating cavitation is one of the most elusive and difficult tasks in ultra high-pressure technology, especially when nozzles are examined. There are several papers that have described cavitation, why and how it occurs, and a plethora of ideas or examples showing how it can be reduced. However, in waterjet applications (40–60 ksi), the application of backpressure (to reduce noise and cavitation), and the cavitation phenomenon itself, can reduce the cutting nozzle’s performance significantly. When studying cavitation, one must not only take into account the magnitude of the turbulence, but also the structure of the turbulence. Four different types of nozzle inlet geometry are investigated, as well as the influence of several levels of backpressure in “water only” waterjet applications. The experimental data will also be compared to a CFD simulation.