You heard wrong about the venturi which works great as a passive flow
meter they're even sometimes called "venturi flowmeters" the only caveat
is you need to accurately measure LOx inlet temp and pressure which is easy
with modern instrumentation systems OTS. Calibrate your type T
thermocouple,best for cryo,
with a small wide mouth dewar of LOx. That gives you a good data point at ~
-300F or whatever the elevation of your test site is which determines baro
pressure and thus boiling point of LOx. Our test site was 6000' MSL. LOx
bolis at -297 @ SL.
Once you do these things you'll have good real time mass flow data, works
for fue;l too and nitrous but 2 phase flow can complicate matters.
If $ wasn't a concern, Micromotion mass flow meters are the gold standard,
I used them to measure GOx to a biprop engine with <0..25% accuracy.
Good luck,
Ken
On Sat, Jan 30, 2021 at 11:01 AM Brett Coles <brettcoles@xxxxxxxxx> wrote:
Hi all,
I know I ask a lot of questions, but you're the best resource I have.
For our hybrid project, we were going to measure the mass flow rate of the
LOX by constantly weighing the propellant tank with a load cell. I thought
we would be able to account for the variation caused by the pressurization
of the stainless tubing, but I have heard that it will be extremely
difficult or impossible. Will we be able to measure the mass flow rate that
way, or will we need to choose a different method?
If we need to choose a different method, what options do we have? I would
like to use a venturi, but I have heard that they don't work well for LOX.
We can't really afford a turbine flow meter either.
Alternatively, we are taking pressure measurements on both sides of our
injector. If we characterize the injector well, could we use that
differential pressure to determine the mass flow rate?
Thanks,
Brett