Regarding 0.008” annular LOX clearance on the pintle…
As mentioned that needs to be controlled via tight tolerancing. I think you
would need to post machine some alignment features. Even a precision
cylindrical boss into a precision reamed hole will have some tolerances
(+/-.0005 ???). I wonder if a tapered boss and tapered hole would be better for
alignment. Thoughts?
Carl Tedesco
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Kristin Travis
Sent: Saturday, April 30, 2016 8:35 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Portland State Aerospace Liquid Fuel Rocket Engine
Hello All,
My senior mechanical engineering capstone team is designing a 250 lb thrust
liquid fuel engine for the Portland State Aerospace Society. This is our first
time posting on arocket. We are working with Kyle Meeuwsen who has posted about
designing the test stand.
Our plan is to 3D print the engine in metal so we can print regenerative
cooling channels in the nozzle and chamber walls. We are planning on using a
pintle injector and ethanol/liquid oxygen propellants. We have been told we can
print to a resolution of 0.03 for steels and 0.015 for aluminum.
Here is the link to our engine design document:
https://github.com/psas/liquid-engine-capstone-2015/blob/master/PSAS_Design_Review1.pdf
1. This design assumes we are printing in inconel, which results in very thin
chamber walls due to heat transfer properties of the metal. We are wondering
what people think about printing it in aluminum in order to have thicker walls
and larger cooling channels.
2. For the pintle injector we have been getting some mixed feedback on whether
we should have a fuel centered (fuel inside the pintle) or LOX centered design.
The plumbing gets much simpler with a LOX centered design, but most of our
research on small engines indicated fuel centered designs are better because
they spray the chamber walls with fuel instead of oxidizer.
3. We are also looking for recommendations for connectors to the test stand
plumbing (not shown in our drawing). We can 3D print bosses and cut threads or
we can 3D print some type of male connectors.
4. We are thinking of machining the pintle injector out of stainless steel and
using EDM (electric discharge machining) to create the holes. We are wondering
about material compatibility issues (such as thermal expansion) between the 3D
print metal and a stainless steel pintle.
We are documenting our design calculations in Jupyter notebooks. They are still
a work in progress, but they can be viewed here:
https://github.com/psas/liquid-engine-capstone-2015/blob/master/Pintle%20Injector.ipynb
https://github.com/psas/liquid-engine-capstone-2015/blob/master/Nozzle_Construction/LFRE.ipynb
Any feedback would be greatly appreciated.
Thank you,
Kristin Travis
