Half a croissant, on a plate, with a sign in front of it saying '50c'
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pulse ramjet

ramjet that functions as a pulsejet at low speeds
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im sure that there would be tremendous problems with this type of engine, and im not an engineer. i know that you'd have to use natural gas as fuel, or maybe propane. how you'd get the shutter to stay open at high speeds is also a mystery. but im sure that a smart person, smarter than i could figure it out...

historically, pulsejets were run off of low octane gasoline, and started with propane. you need a low octane fuel because it uses the shockwave going back up the exhaust toward the intake to slam the valves shut and "diesel" the fuel air mixture. so it basically knocks. hot gases travelling backwards also have something to do with ignition. hydrogen knocks like crazy in a piston engine. you have storage problems, though.

hydraulics could be used to hold the intake valves open. indeed, in order to work, the intake valves might have to be forced open and shut anyway. then solenoids would be used, like how solenoid valves are used on some 2 stroke diesels...

bobenhotep, May 23 2005

Pulse Jet vs. Ram Jet http://www.aardvark...nz/pjet/ramjets.htm
[Klaatu, May 24 2005]


       Well... it's not a tremendously farfetched idea. I'll bun it.
5th Earth, May 24 2005

       Are you suggesting a pulse jet to get to the 400MPH required to operate a ramjet, then opening the valves to make it into a ramjet?   

       I've linked to a site that explains both engine types.
Klaatu, May 24 2005

       I like how the one thing you do know about this idea: "that you'd have to use natural gas as fuel", is immediately padded with "or maybe propane."
I would like more information on which areas of the design require you to restrict yourself so harshly on fuel choices.
baconbrain, May 24 2005

       As a low-speed pulsejet, you don't need anything to operate the valves, the shockwave does that for you. I imagine that with good engineering and careful study of the resonance profiles, you could get the valves to just "stick" open at the transition stage and allow the air in unimpeded, yielding a no-control-required conversion.   

       Good luck throttling this thing.
elhigh, Aug 01 2005

       // Are you suggesting a pulse jet to get to the 400MPH required to operate a ramjet[…]? //   

       The Low-Cost Cruise Missile project on that same site you linked to planned to use a pulsejet to fly at 600 MPH, IIRC.
notexactly, Jan 14 2016


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