Numerical and experimental investigation of pressure-swirl nozzles produced by additive manufacturing
Patrick Lüscher  1, *@  , Janine Bochsler  1@  , Daniel A. Weiss  1@  , Marc Huber  2@  , Kaspar Löffel  2@  , René Van Nieulande  3@  , Tom Duda  4@  
1 : Institute of Thermal and Fluid Engineering, FHNW
Windisch -  Switzerland
2 : Institute of Product and Production Engineering, FHNW
Windisch -  Switzerland
3 : Emerson Automation Solutions
Breda -  Netherlands
4 : Emerson Automation Solutions
Baar -  Switzerland
* : Corresponding author

Conventionally produced pressure-swirl nozzles suffer from the disadvantage that the geometry is restricted by the manufacturing technique. Modern technologies like metal 3D printing by selective laser melting (SLM) allow for more complex geometries with reduced flow resistance, which can improve overall efficiency. In this paper three nozzles for steam temperature control are investigated, two conventional ones and one designed for additive manufacturing. The goal is to optimize the nozzle to as small droplets as possible at an identical flow rate to achieve a fast evaporation. The different nozzles were investigated using ANSYS CFX based on a VOF (Volume of Fluid) approach combined with a RANS turbulence model. As validation, the droplet distributions generated by the three nozzles were measured at a test stand using laser diffraction analysis together with the mass flow rate and the spray angle. The droplet size cannot be determined from the simulations, but mass flow rate and spray angle showed good agreement. Both the simulation as well as the experiments were carried out with water sprayed into ambient air with a pressure difference of 0.61 MPa. For a proper comparison between nozzles with a different throughput, a new way was introduced to estimate the drop size if the nozzle were geometrically scaled to the desired mass flow. To investigate the influence of a higher surface roughness, the conventional nozzles were also produced by SLM and various quantities were compared. As expected, the nozzles with a high surface roughness produce larger droplets, but they also have a higher throughput.

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