Selective laser melting-assisted venturi-type nozzle in a pressurized dissolution microbubble generator

A selective laser melting (SLM) process was adopted to construct SLM structures for a venturi-type nozzle in a pressurized dissolution microbubble generator. The SLM structures with stainless steel 316L were built on the distribution plate of a venturi-type nozzle with different geometries to investigate the effects of the sidewall angle of the SLM structure and empty space at the center of the distribution plate. The microbubble generation test was conducted for 30 s using a pressurized dissolution microbubble generator, and venturi-type nozzles with and without the SLM structures were installed in the water tank. The generated microbubble size ranged from 1 to 110 μm. A greater number of microbubbles was generated for the SLM structure-assisted nozzles. The largest number of generated microbubbles was 70,490 with a microbubble size of 31.82 μm. Computational fluid dynamics simulation revealed that the SLM structures induced turbulent vortexes by impeding the water flow along the radial direction. Consequently, a low-pressure region developed in the water flow, and the liquid phase of water changed to the vapor phase. Eventually, microbubbles were generated by the SLM structures via vortex-induced cavitation.