Last time I worked on a similar project, we hung the LOx tank from a load cell
to measure capacity.
This was connected to the chamber with a flexible braided stainless line. The
injector was sealed with a PVC cap with a small weep hole.
This weep hole allowed gaseous oxygen to fill the ignition system: a wad of
steel wool, energized with 24 vdc of truck batteries and an aviation starter
solenoid. Everything worked quite for a one ton thrust hybrid and I expect it
will scale for your application.
In hindsight, I can't recommend bouncing the LOx off the forward closure to
improve atomization. This seemed to produce spectacular failures as it burned
the heavy steel chambers. Seemed to make since at the time though... Every
static test is a potential learning experience.
--------------------------------------------
On Sat, 8/25/18, miguel charette <miguel.charette@xxxxxxxxx> wrote:
Subject: [AR] Re: Cryo-Valves (and other related questions)
To: arocket@xxxxxxxxxxxxx
Date: Saturday, August 25, 2018, 2:14 PM
Hi
Brett,
From my
experience with LOx, using thermocouples along the height of
the tank is the easiest, surest way to go. I've tried
differential pressure sensors probing at the top and bottom
of the tank, but first they seem very prone to failure
during pressure spikes and second they tend to end up giving
very noisy signal as LOx in the bottom pressure tap will
boil off. The way tou can fix the latter is to inject some
of your pressurant gas in the bottom tap to create a buffer,
but since you're going with the piston approach this
might not work. I've heard of people using ultrasonic
sensor I believe at the top of the tank but again, with the
piston, it might not be possible.
Has anyone ever tried to use the
paramagnetic properties of LOx as a sensing
mechanism?
Cheers,
Miguel
On Aug 26, 2018 7:52 AM,
"Brett Coles" <brettcoles@xxxxxxxxx>
wrote:
I love how posts on this list can randomly
reappear later.
Lars,
Thanks for the advice about the
piston. I have been a little nervous about whether or not we
will be able to get it to seal. Sutton does have piston
expulsion listed as an option (Though it is pressure driven
rather than mechanically driven). Perhaps some small-scale
tests are in order with LN2.
Also, I think we are just going to
buy purpose-made Cryo ball valves and actuate them using
servos like Bob has done. We thought about using the check
valve as a main ox valve, but I wanted to make sure we could
shut the motor off if something happened to the piston
actuator.
Henry,
Thanks for the emphasis on not using
carbon steel. I have no interest in having our test setup
fail like a dropped glass bottle. We are currently planning
on using 6161 and Stainless 304.
Also, is there a
way we can measure the fill level in the LOX tank? The best
idea I have so far is just to put a whole bunch of
Thermocouples on the side and watch the cold climb up the
tank as it chills in.
On Sat, Aug
25, 2018 at 12:43 PM Lars Osborne <lars.osborne@xxxxxxxxx>
wrote:
Henry,
Thank you
for pointing that out. I had forgotten to mention the caveat
that the materials themselves must be cryo compatible!
Thanks,Lars Osborne
On Sat, Aug
25, 2018 at 11:01 AM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Sat,
25 Aug 2018, Lars Osborne wrote:
I'm surprised no one else has pointed this out, butany valve can be a
cryo valve if you have enough torque...