## stack flow or flu effect ramjet

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makulit
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### stack flow or flu effect ramjet

Ive seen a lot of discussion on how to make ramjets work at slower speeds but haven't seen this yet. The stack or flu effect could get air moving at 50 mph prior to a nozzle that could easily double the speed. To do so the engine would have to inlet 5 meters lower than the outlet nozzle and heat the air by 1500°C. Water injection and inlet cooling would greatly increase efficiency. I picture a long sloped tube with a bend and a nozzle at the top. The long run should allow efficient use of flame.

Viv
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### Re: stack flow or flu effect ramjet

Drag, turbulence, thermodynamics, these are just some of the things that get in the way of what you want to do, consider for a moment that a Ram jet is an energy exchange device, you are swapping the speed of your incoming flow for pressure then adding heat to it, and then expanding it out through a nozzle for an overall momentum increase in that flow.

Consider the energy in the incoming flow of a typical high subsonic Ramjet (about 500 mph) compare it to the energy available in your proposed system, is there going to be enough to make it work?

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

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Monsieur le commentaire

makulit
Posts: 17
Joined: Sun Jul 31, 2011 11:04 pm
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### Re: stack flow or flu effect ramjet

Drag, turbulence, thermodynamics. It works because of thermodynamics. Drag is minimal at low speeds and since I've not provided a layout yet, it can't really be commented on, ditto turbulence. Your analysis of ramjet operation is not applicable to the subsonic case. Speed is not converted to pressure because at subsonic velocities, air flow is incompressible. The flow area expands, slowing the velocity.The application of heat expands the air volume. With a properly designed body, the energy of the entrance velocity will be maintained and all the heat energy adds to the momentum. The expanded Gas Volume will be moving at something like the entrance speed at the end of the Combustion area. This alone would provide some thrust. However much more thrust is available using the nozzle. Because the area is smaller than the combustion area, the velocity is increased. Lastly, this case has nothing to do with the 500 mph case. Its related to the static ramjet and 50 mph ramjet discussions.

I recommend NACA tm 1106 by E. Sanger and I Bredt 10 Dec 1947

Viv
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### Re: stack flow or flu effect ramjet

Ok, good luck then,

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire