Check out my thermojet dimensions, a few questions

[nalexandrov]

OK so I used the design principles posted on the forum. Could you guys look at my dimensions in the attached photos? I am interested in making a valveless pulsejet for an RC plane. Can anyone estmate thrust/propane usage of this engine from the stats? For those that dont want to open the attachment here is the stats:

1.5" ID tailpipe/28" long
3" ID chamber/6" long
2x inputs, ID .92"/4" long

I want to use a 16oz propane tank with a needle valve for the fuel system. I understand these tanks freeze so I will wrap the copper fuel line around the pulsejet body and then wrap the copper with insulation around the bottle before it connects to the needle valve. As the thing heats up the copper will keep the bottle hot. What is SOP for using these bottles? Would the orfice be too small for this use? If so I plan on punching out the valve, filling with water and then drilling out the valve to a larger hole (1/4" ID). I will then use a 1"-20 adapter to connect the bottle to a needle valve, this is how I will refill it also.

What is the thinnest wall of tubing I could use for this project in your opinions?

Will I lose signifigant performance not using a flare in the intake end of the chamber?

I really would like to be able to autostart with this guy and followed basic design rules to allow for that (intake is an odd multiple of exhaust, etc)

[ganuganu]

Regarding your design i would suggest you to add choke in between CC and exhaust. Tailpipe looks too long you can reduce it to 15" and make the intake length to 4.2inches.

Flares are very important in valveless pulsejets because at higher throttle it helps the engine to breath easily. 1mm wall thickness is recommended to use.

[John Hasler]

The tank won't freeze if you arrange for the propane to flow out of it as liquid.

[nalexandrov]

ganuganu: Your reccomendations seem to violate all the design rules on this board. What is your logic behind shortening the tailpipe? Also the intake is supposed to be an odd multiple of the tail for easy starting.

Thanks for the advice.

[nalexandrov]

ganuganu: pyrojoes method requires that the inner diameter of the exhaust is multiplied by 20 for the length. With in ID of 1.5 for the exhaust that makes the length 30". With your suggestion we are only using a 10x multiple. I am totally on board if this does not cost performance but it just seems to be such a large deviation. Can anyone else speculate if I can get away with a 15" exhast at 1.5" ID?