I have gone a little further down the road to producing a swirl prototype by machining some swirl inducers.
A two start metric trapezoidal thread was generated on a section of round brass bar. The metric trapezoidal thread form is similar to acme, though with a thread angle of 30 degrees as opposed to 29 degrees.
The photograph shows a swirl inducer that has just been machined. The insert tool can also be seen. The thread is of 2mm pitch, meaning that the Harrison was set up to cut a 4mm pitch for the first start, and then the compound was advanced by 2mm to put the second start in between the first.
The liquid will be swirled through the annulus, thereby creating a thin film which will be atomised very completely by the high speed gas flow through the core. High swirl and high momentum flux ratio are the keys to this system.