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Objective:
- ZBOT research will aid the design of long-term
storage systems for
cryogenic fluids. Simulated by Perfluoro-normal-Pentane (P-n-P).
- Obtain 1-g and microgravity two-phase flow data
for pressure control
through mixing and active cooling.
- Verify and validate a Computational Fluid Dynamics
(CFD) model for
cryogenic storage in 1g and microgravity.
- Use data and CFD model to assess and optimize
cryogenic liquid storage
design concepts.
Relevance/Impact
- Reduces launch mass and decreases risks through
enabling design
concepts for long-term storage of cryogenic fluids.
- Cost effective and reliable cryogenic storage
for both life support and
propulsion systems satisfying the requirements for long term mission
scenarios from Moon to Mars and beyond.
Development Approach
- Ground phase: develop ground-based experiment
and obtain 1-g data for
tank pressurization and pressure control.
- Flight phase: develop ISS experiment and obtain
microgravity data for tank
pressurization and pressure control.
- Develop a state-of-the art two-phase CFD model
for tank pressurization and
pressure control.
- Validate and Verify (V&V) the CFD model with
microgravity and 1g data.
- Use the validated CFD model and empirical correlations
derived from the 1g
and microgravity data for scale-up tank design.
Flight Operations Summary
The following general steps are taken to prepare the tank before each
test run in order to ensure that the tests are all started from a
common initial state:
- Set the jet temperature to the desired initial
fluid temperature.
- Set jet flow rate so that fluid will be well
mixed.
- Continue to run the jet until:
- All thermal gradients have sufficiently decayed
(i.e. until all thermistor temperatures are within +/- 0.25 oC of
each other).
- All thermistors are within +/- 0.25oC of the
desired starting temperature.
- Turn on the heater power supply and set desired
heat input.
- Configure the data acquisition system to record
desired.
Brief descriptions of the microgravity
test categories
- Self-Pressurization Tests: Isolate test cell from
mixing/cooling loop by valving off the jet inlet and the tank outlet.
At time = 0, turn on the heater and record measurements. After a
prescribed pressurization time, turn off the heaters and go back
to step #1 to prep the tank for the next run.
- Mixing Tests: Set desired jet speed. At time =
0, turn on the heaters allowing the tank to pressurize for a specified
time period. After the pressurization time has elapsed, turn on
the jet and continue to run until either the maximum allowable mixing
time has elapsed or the tank pressure has returned to the initial
pressure for this particular experimental run. Turn off the heaters
and jet and go back to step #1 to prep the tank for the next run.
- Subcooled Jet Cooling/Mixing Tests: Specify heater
power, jet inlet temperature and jet speed. Specify whether jet
will be active during the entire run or whether an initial pressurization
will occur. For mixing throughout, at time = 0, turn on the jet
and heaters. After a specified elapsed time, turn off the jet and
the heaters and return to step #1. For an initial pressurization,
at time = 0, turn on the heaters allowing the system to pressurize.
After the pressurization time as elapsed turn on the jet. Continue
until either the maximum allowable mixing time has elapsed or the
tank pressure has decayed to the initial pressure. Turn off jet
and heaters and return to step #1.
Data to be taken during the
course of experiment operations
- Tank Pressure
- Heat Powers
- Temperature at all locations (inside and outside)
- Ullage position
- Inlet Jet Temperature
- Tank Outlet Temperature
- Jet Flow Rate
- Gravitational Acceleration Data
- Velocity Field Visualization-PIV
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