Wednesday, February 28, 2007

Injector Version 2 flow tests


Based on my previous testing and some advice I received on Arocket I built a new injector.
Its got a smaller pintile and a tapered out area behind the annular gap. the annular gap is only 0.050 deep. the new pintile is only 0.400" across. I flow tested it tonight and the Fuel came out perfectly within 1.5 % of where I wanted. Well within my experimental error! The oxidizer is about 10% low (Meaning I'll need to run my pressure 20% high) Its good enough to test as is. The visual quality of the combined spray cone is very good. I took a fast flash picture of the result its on the left.

I also took a picture of just the fuel orfice

















I also tried to take a picture of just the lox spray and got everything in the entire shop wet. Sorry for the bad quality, but after wiping the water off of my Lathe and Mill I was not about to try to take the picture again.

Thursday or Friday I'll try to braze the igniter mount on the the assembly and I'll have a new motor by the end of the week end!

5 comments:

Carl Tedesco said...

Paul,

The cone angle of the mixed streams looks large... I'd say about 120 to 130 degrees. Is this normal for a pintle (i.e. are there any rules of thumb to cone angle)? The only issue I can think about with such a high cone angle is hot spots on the chamber wall, as I understand you're not doing any boundary layer cooling.
--- Carl

Paul Breed said...

I could not find much info on Pintiles. Also since the fuel and O2 flows are fixed equal volumes I don't know how I would change the cone angle. I could change the feed pressures, but that has other issues.
From what I've read about the spacex pintile development pintiles seem to be really hard on the top end of the chamber, but also allow smaller chambers overall.

Timothy Massey said...

I had the same thought regarding cone angle. This is quite a departure from, say, Armadillo's injector: theirs seems to have a well under 90 degree cone angle...

Carl Tedesco said...

With such a large cone angle it appears the LOX streams have more momentum than the fuel annular stream. Could you not reduce the momentum through a single LOX orifice by making it smaller and adding more LOX orifices to maintain the same overall flowrate? Just somethink to think about if you have issues and have to do another revision. The fastest way to debunk speculation is get out there and hot fire test it!

Anonymous said...

Drill the holes to the pintle at 45 degree angle downwards? Then the cone should be roughly 22 degree half angle...
Now the inner flow (lox?) is sticking right out of the pintle.

-mz