Design and Manufacturing of nano-micro nozzles

problems and solutions posted by ioos systems

A small nozzle orifice size results in small droplet sizes.” This assumption is often not true, in particular for multiple-fluid or twin-fluid nozzles due to high demanding tolerance and surface finish requirements. Seemingly small manufacturing errors have a big impact on the spray performance of nozzles with a small orifice. Poorly designed and manufactured micro nozzles may therefore perform worse than larger scale nozzles. The presumption for a successful miniaturization and small droplet sizes is consequently the nozzle design and fabrication technique employed. Micro-nozzles should be designed and precision machined to prevent manufacturing errors and improper assembly. For example, the liquid nozzle and the inner contour of the gas cap should be shaped using a special micro-machining procedure to maximize the concentricity and surface finish of the atomizing end. It is important that the concentricity of the gas and liquid orifice is ensured by tight tolerances and the use of centering sections.
It is assumed that “an equal width of the annular gap between liquid and gas orifice results in a homogenous gas velocity distribution.” However, a poor nozzle performance in terms of droplet size and distribution is often not caused by an unequal width of the annular gap. The presumption for a good spray performance is the homogeneity of the gas velocity distribution within the tip, which is ensured by its shape and quality. This translates, for instance in a spray with homogenous spray density distribution.

CAD-CAM and Micromanufacturing
CAD-CAM and Micromanufacturing

Spray Quality

defining spray quality posted by ioos systems

The keys to spray quality are:
+ Uniform spray pattern
+ Small droplets or particlea size
+ Tight droplet size distribution
+ Atomization consistency over time

Spray quality measured using Spray Error Patternator
Reference pattern (left), spray pattern (right)

Spray Quality Control

problems and solutions posted by ioos systems

Reproducible operation of one micro nozzle to the next should be ensured by controlling the quality of each spray nozzle during incoming quality control and depending on the particular application during the entire spraying process. The Spray density distribution is preferably measured with a SED Spray Error Patternation system (optical patternator). More on spray quality control.