mixed fuel - CO2/propane

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mixed fuel - CO2/propane

Post by zee » Sat Sep 27, 2008 11:33 am

I read that non pulsing pressure jets which use superheated propane to compress air in an ejector are limited because they cannot entrain enough air to work efficiently. Would it be possible to mix, say (off the top of my head), 3 parts CO2 to 1 part propane in the same cylinder and use this to fuel a non - pulsing pressure jet?

The advantages I see this bringing are; a) the tank pressure of this mixture would be far higher so the velocity of the compressing stream might be higher, b) the flow rate would be ?quadrupled c) the temperature would be less hellish, and d) the co2 might become an oxidizer at these temperatures and improve combustion.

I wonder if the co2 would react with the propane while it passes through the coil in the combustion chamber and whether this reaction would be helpful, or harmful.

3co2 + c3h8 (4 moles) --> 6co + 4h2 (10 moles)??

IF? the above reaction occurred then would the volume of the resulting inducting stream be 10 times that of a conventional pressure jet that is fueled on propane?

Obviously the fuel economy would be bad because the energy density is so low and the jet might have limited application.

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Re: mixed fuel - CO2/propane

Post by Viv » Mon Sep 29, 2008 2:19 am

Hi Zee

Interesting thread but the "none pulsing pressure jet" is a problem as they are just valveless pulse jets with an ejector intake system, however you slice your maths you only have vapor pressure of the propane (unless you boost it) as your starting energy level, so what ever 100 psi expanded through your nozzle orifice will give you for a resultant velocity and entrainment of air is all you have to play with, the super heating is just to get round the energy exchange problem of pressure for velocity in the nozzle.

I love the idea of reacting the Co2 but I think the energy level available in the heat exchanger coil would be to low to crack the Co2 and if you did get it up high enough the coil metal will want to precipitate its own carbon in an interesting but ultimately destructive way ;-) Bad things happen to good coils when contaminated fuel is run through them.

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Re: mixed fuel - CO2/propane

Post by zono » Wed Mar 25, 2009 9:03 pm

Hi Zee,

you have quite a similar idea than me. some years ago I and a good friend had trials with propane running a pulsing pressure jets which use superheated propane to compress air in an ejector .

and-- poor results ! much heat (yellow heat) but low thrust, because bad ratio of steam impulse to caloric fuel value.

better choice are fuels with lower caloric fuel value and more impulse, like superheated methanol vapor (or your mixture)

please look at this post:
zono - the thruster buster

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