small ramjet

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Zippiot
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small ramjet

Post by Zippiot » Tue Jan 17, 2006 6:25 am

i made a small ramjet that runs off of a shop vac and liquid gasoline, but it is very inefficient. for a ramjet that will be 5 inches long and 1 inch wide (width and length are not set in stone) can someone help me design the intake and nozzle?

im having trouble getting it to sustain, i get a whole lotta big bangs and then it goes out...
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larry cottrill
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re: small ramjet

Post by larry cottrill » Tue Jan 17, 2006 1:31 pm

When it "goes out", does that seem to be from the flame blowing out through the tail end? If so, your problem is that you are not slowing down the air enough at the front of the combustion zone. You would either need a better diffuser, a better flameholder, or both.

You MUST get the local velocity down to the combustion speed of the air/fuel mixture - usually just a few metres/second. This is even more difficult as entering airspeed is increased, naturally. The diffuser is also what gives you the operating pressure you'll achieve in the chamber!

L Cottrill

Zippiot
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re: small ramjet

Post by Zippiot » Wed Jan 18, 2006 6:40 am

now that i took it apart i see that my flameholder...wasnt quite made of steel!!!

thats y it ran for like 5 seconds before it started blowing out
Sailing Student- How do I know if my life jacket is tight enough?
Me- Can you breathe?
Sailing Student- Yes
Me- Then its too loose!

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