Improved cleaning performance through jet instability in single- and multi-Helmholtz nozzle spray systems

The increasing demand for energy conservation has driven the development of efficient and eco-friendly cleaning technologies. In this study, an unstable water jet utilizing a Helmholtz nozzle was investigated to enhance the cleaning efficiency while operating at low pressure. Helmholtz nozzles with varying chamber aspect ratios were designed and fabricated using high-resolution three-dimensional printing, and their jet breakup dynamics, pressure oscillations, and impact forces were analyzed. The results demonstrated that a higher chamber aspect ratio induces stronger jet fluctuations, leading to shorter breakup lengths and enhanced splash generation. The Helmholtz nozzles exhibited increased pressure oscillations, with the root mean square values increasing as the chamber aspect ratio increased, highlighting the role of vortex structures in amplifying jet fluctuations. Cleaning experiments with various pollutants (oatmeal and oil) revealed that Helmholtz-induced jet breakup improves the indirect cleaning efficiency owing to increased water splashes. Furthermore, a multi-nozzle spray system integrating Helmholtz nozzles demonstrated superior cleaning performance in a dishwasher testbed under dynamic conditions, particularly in the indirect cleaning regions, where water splashes play a dominant role. These findings indicate that Helmholtz nozzles are a viable solution for energy-efficient and high-performance cleaning applications, making them suitable for household and industrial cleaning systems.