Tuesday, July 29, 2008

Very Strange...

I posted this graph a few weeks ago:


June14_data


The very strange thing is that the chamber pressure is 500+ PSI where the feed pressure is 250 or so. I believed I had a data collection anomoly. I do not. I just finished testing the pressure transducer and checking out the wireing and it is all correct. The calibration of the ggraph is also correct.


The mechanical schematic of my motor is:


ChamberResonant


So the only possible conclusion is that I have a resonant pulse jet with the check valves. I’m going to run it again with a lot higher pressure and higher time resolution pressure transducer in place.


 


 


 


 


 


 

4 Comments:

Blogger Carl Tedesco said...

Paul,
I'm skeptical that it was pulse jetting. I recall the sound was more like a machine gun... at 7-15 Hz. Your transducer data is not as uniform and the frequency isn't as consistent as what I heard that day. I would try to dampen your transducer better from pressure & temperature transients. Is Krytox compatible with peroxide?
--- Carl

10:20 PM  
Blogger Carl Tedesco said...

I've also wondered if the sharp entrance to the nozzle throat is problematic.
--- Carl

10:44 PM  
Anonymous Rob Goldsmith said...

Paul here are some comments i found on the Space Sellowship

Could be very high frequency combustion instability, if your pressure transducer is sampling too slowly I'd imagine you'd see some strange data like in that graph. How is your injector set up? Do you have unlike impingement? I think I read recently that in US hypergolic motors it is more common to use like impinging injector patterns, I believe because unlike impinging streams with reacting propellants can 'blow apart' and cause instability if the reaction is strong and fast enough.

link
http://spacefellowship.com/Forum/viewtopic.php?t=7054

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