Proposed Design Idea for Small Jet

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larry cottrill
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Proposed Design Idea for Small Jet

Post by larry cottrill » Wed Oct 05, 2005 7:45 pm

The recent discussion in the Rockets Forum that mentioned the little N2O cylinders (I had completely forgotten about those!) brought this to mind: Why not rig one of these cylinders so when it gets pierced the high velocity stream is channeled through a short straightening tube into the center of a small intake bell, forming a little ejector system. In other words, the N2O would flow down the center and outside air would be pulled in. The neck of the ejector (maybe 3-5 mm ID) would break sharply out into a much larger combustion chamber (perhaps a used CO2 cylinder) for expansion. Gasoline or other liquid fuel would be pulled in at the throat by the venturi suction of the ejector. Alternately, it might work better to have the downstream side of the ejector set up as a long diffuser with an "asterisk" style flameholder in front of the chamber, as in Steve's TLAR ramjet. The exhaust nozzle would be as short as possible to limit any pulsing tendency.

The idea, of course, would be to have a constant-burn air-breathing jet in very small size, with the N2O to provide the "static ram" momentum as well as augmenting oxidation. The amount of fuel that would correspond properly to a cylinder of N2O, as well as the correct N2O vapor flow rate, would need to be determined by experimentation. Of course, I have no idea how ambient temperature or the cooling of the cylinder might affect running.

Any ideas on why something like this wouldn't be worth trying?

L Cottrill

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re: Proposed Design Idea for Small Jet

Post by El-Kablooey » Wed Oct 05, 2005 8:00 pm

Why not use high pressure compressed air, like from a scuba tank for instance. Oh.. I guess it would not be a small jet, if it was big enough to push a scuba tank. Those little micro-hybrid rocket engines only burn for approximately 1 second before they run out of NO2 though.. :(
On an endless quest in search of a better way.

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