<p>The purpose of the project is to replicate conditions found
inside the reaction chamber of a nuclear thermal propulsion (NTP) rocket
engine, thereby evaluating robust materials and construction techniques for
future NTPs. The need to test materials exposed to hydrogen under combined high
temperatures and pressures is crucial to determine their resistance to hydrogen
attack.</p>
<p>The proposed test article is a SiC resistive heating element
which would heat the hydrogen gas flowing at 5.6 g/s from 300 to 2400 K at
nominal pressure of 1000 psia then cool it to below its auto-ignition
temperature before it is vented to the ambient air. The experimental evaluation
of the test article should validate the reliability of materials used in the
construction of the pressure vessel. The pressure vessel houses a resistive
heating element made from open-cell refractory carbide foam which pairs well
with hot hydrogen gas due to its resistance to thermal shock. The enclosure to
encapsulate the heating element is lined with an oxide coated rhenium tube
capable of sustaining high thermal and structural loads, and the outer shell is
made from Inconel 718. Rhenium is a robust material with excellent ductility,
is non-reactive with hydrogen, and is creep-resistant at high temperatures.
Inconel 718 has a high yield strength capable of handling high temperature
applications. </p>
<p>Cooling the hydrogen gas requires designing a water-cooled
nozzle to transport the gas to a heat exchanger. The design of the nozzle and
its mechanical components involved analyzing the heat transfer through
materials, predicting their structural integrity, and examining potential
failure points. The 1-D steady-state heat transfer analysis is conducted to
predict the inner and outer surface temperatures, heat flux, and fluid heat
transfer coefficients. These parameters are considered in selecting the best
candidate materials, copper and Inconel 718, to make the nozzle. To prevent gas
leakage between interfaces of multiple components and joints, a careful
selection of sealing techniques are implemented, including the use of
bimetallic weldments and pressure-energized metal seals. </p>
<p>Although the proposed test article was never tested due to
schedule and budget limitations, the documentation of its design and analysis
is complete and the system is ready for manufacturing and testing. The long
lead times to manufacture, to inspect, and to validate the vessel were
underestimated in the project scheduling. The rental cost of the electrical
equipment required to run the test under initial design conditions exceeded
budget. As a solution to satisfy the temperature and budget requirements,
halving the flow rate and decreasing the delivered electrical power by 48% are
proposed. </p>
<p> The success of
testing the pressure vessel at operating conditions would provide a physical
and quantitative study on potential materials used on future NTP ground tests.
The test would run for 5 minutes during which the strength of the materials
weaken as a result of the diffusion of free carbon from their surfaces. Upon
completion of the test, the performance of these materials would be evaluated
for signs of macroscopic and microscopic surface effects on the test article. </p>
<p> </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/8041094 |
| Date | 10 June 2019 |
| Creators | Juhee Hyun (5930675) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Design_of_a_Pressure-fed_Gas_System_Operating_at_Supercritical_Temperatures_and_Pressures/8041094 |
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