Convergent divergent nozzles

[GRIM]

Eric posted a comment in the lady astor thread regarding convergent divergent nozzles , this set me thinking

in the last photo there is a vise grip with two drill bit shanks welded in the front of the jaws , they look oval but there not its just the weld

these work very well to pinch the tube , with the cantilever and positive stop that these tools have, it is very easy to produce multiple injectors with the same opening

The middle photo shows the crimped style of nozzle

The first photo shows nozzles that were rolled using something similar to a rotary pipe cutter but instead of a sharp edged wheel i turned up a wheel to swedge the throat shape , then hammered in the front a spike to finish off the divergent cone

This style of nozzle is intended to be used with very high velocity gas (at least supersonic)

I dont think that with propane supersonic speed could be achieved , correct me if im wrong

However the point is that when you blow through them , (with your mouth )they make the typical rocket nozzle type type sound and small strips of paper taped to the end get pulled tight against the outer cone , leading me to believe that air is being entrained even at very low velocity

im not sure if these will be of any benefit , testing will define this , however its interesting just the same , well i think it is anyway !

what do you guys that know about these things think?

[Irvine.J]

Oh man that freaking sick, Just a blunt wheel on a big ass pipe cutter eh? Is that right? Thats a great looking nozzle, I'll have to make on of those

Fantastic stuff GRIM, rossco was playing with steam a while back he's gonna love that.

[Mike Everman]

Very, very good. Poor man's metal spinning 101. Great work, Grim.
Oh, and yeah, you can go supersonic.
When pressure is high enough to get the throat sonic, then the divergent part of the nozzle actually speeds up the gas, contrary to subsonic behavior.