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
