A few (7) short months ago I was
working on a turbo pump to use compressed air to supply fuel and air to a rocket. Now the original plan for this video
was to go back and optimize the film cooling method from another
video which used a thin film of fuel to protect a 2 liter whoosh
rocket from the heat of combustion The idea being that if I optimized how
I made that film I could eventually use the turbo along with it and
have a more self-contained, easier to set up rocket for longer
running tests, except for when I tried it… Yeah that wasn’t a very long test. So
I’m going to switch gears a little bit to something hopefully less likely
to blow up and scare my neighbors, and try to optimize the turbo,
specifically the turbine The first and most practical problem
with testing the turbo in the last video was that it was pumping around water, which
meant that every time it failed or I needed to make an adjustment, I would usually
have to clean up a lot of water as well But this time, since I’m focusing on the
turbine, I don’t need the impeller or the water, or the complexities that come along with
them. Instead I can just use a propeller attached directly to the turbine and
measure how much thrust is generated The second problem I encountered in the last
video is that I couldn’t find any formulas or equations on how to optimize a turbine, and
after almost 30 seconds of googling this time, I still couldn’t find anything. So
instead I’m going to make multiple different variations on the turbine
and see which ones perform the best The setup is really simple. The turbine
is hooked up directly to the propeller, and the entire thing is mounted to a load cell so
I can measure the thrust. The housing around the turbine is essentially the same as it was for the
turbopump, where pressurized air comes in through an inlet, passes over the turbine spinning
it up, and then leaves through the exhaust. The only difference is, is that now I care
which direction that exhaust is pointing. The load cell measures force along one axis, but
not perpendicular to that axis. So I want to make sure the thrust is along that measurement,
but the exhaust is perpendicular to it. This way I don’t mess up the thrust measurements
with any kind of additional thrust from the exhaust. Other than that, I made one more
change, which was to print threads directly into the turbine shaft, and into the housing
which made mounting everything a lot easier. Now, on to the turbines. I came up with 6
different turbines to test. The first and probably the worst is one with just straight
blades. Maybe a slight improvement from there would be offsetting those straight blades
from the center. Next there’s one with a very simple one dimensional curve along the
blades, and then those same simply curved blades except for they’re also offset
from the center. And then we have the original turbine which I “Optimized” by
making it just look like a turbine. And then we have that same turbine but with extra
blades where there seemed to be large gaps. I would guess that the “Optimized” turbine with
the extra blades would probably be the best, and the straight bladed one would probably
be the worst. but honestly I would say your guess is as good as mine, so pick your
favorite and let me know in the comments, along with any other turbine designs
you think might be fun to try. Now I just need to set it all
up and give each turbine a test. Alright, first up we will test each turbine being
supplied pressurized air at about 4 Bars or 60 psi Well it looks like winging it works well enough
since the turbine that I “optimized” seems to have worked the best. That being said, the
turbine with the simple curved blades was so close behind it that I would say it’s well
within the margin of error for this setup. I was also very surprised at the straight
bladed turbine working as well as it did, and the offset ones did pretty poorly compared to
the rest. My guess is that the gap produced by the offset was just a space for the air to go through
the turbine without imparting any energy to it. Next we’ll test each turbine again, but this time the air being supplied
will be at about 7 bar or 100 psi This time both versions of the
“optimized” turbine performed the best, and once again the turbine with the
simple curved blades was not far behind, followed by the straight
blades and both the offsets So in the end the turbines that I just kind
of eyeballed were the best but the turbine with the simply curved blades was not far
behind, especially in the low pressure tests. These turbines were really fun to design
and I like how they ended up turning out, so I made a cross sectional version of both
this test setup and the original turbopump, and they’ll be available with the
other files linked in the description Thanks for watching
