SAMPE Journal - March/April 2024 - 22

FEATURE / SUPERSONIC NOZZLES
Figure 11. Evolution of the stagnation point sample with Titanium liner during the test campaign.
worth noting that samples with a graphite liner did
not experience the same demise behavior as the
graphite liner remained intact. (Figure 12)
4.2 Semi-elliptical Nozzle, Flat Plate Material
Tests
A flat plate experimental campaign was conducted
using the semi-elliptical nozzle and the setup
presented in Figure 6. A schematic of the flat plate
and the Plasmatron running is shown in Figure 13.
The test matrix was chosen based on the available
flow regimes in the supersonic flat plate test
configuration. Those are mostly dictated by the
mass flow (between 6 and 12 g/s) and the angle of
attack of the plate (AoA, between 0 and 20 degrees).
Various materials were tested: Haynes, steel, CFRP,
quartz, and titanium. An overview summary of the
test parameters is presented in Table 6. The results
in this section will only cover some of the titanium
testing.
The titanium samples, both pre-and post-test,
are depicted in Figure 14(a). The variation in the
yellow hue of the sample arises from the uneven
lighting conditions within the chamber during
different tests. The post-test images reveal the
presence of an oxide layer composed of titanium
dioxide on the surface, along with visible damages
and/or melted regions. It became evident that a
higher angle of attack and an increased flow rate
had a more pronounced impact on the material
surface, leading to the propagation of the oxidation
region further into the specimen.
Figure 14(b) illustrates the temperature
recorded by the thermocouples and the optics over
time for all three titanium tests.
Following injection, an oxidation layer begins
to develop from the leading edge (the edge closer
to the nozzle exit), succeeded by the formation of
a thin crust on the surface Figure 15. The picture
taken after the test illustrates the various oxide
scales on the surface ranging from a white crust,
to more brownish, and blueish decoloration.
We assume that those are caused by different
thicknesses, porosities, and microstructures of the
oxides (such as several layers, filament structures,
compacted flakes, and grains).
Figure 12. A top view picture of the stagnation point of tested samples, the picture
on the left has a graphite liner while the picture on the right has a titanium liner. Both
samples were tested in stagnation configuration.
Figure 13. 2D test bed along with the schematic of the flat plate and a picture of the
Plasmatron running.
(a)
(b)
Figure 14. (a) Pictures of Ti (grade-2) flat plate samples before testing(left) and posttesting
(right) (b) Monitored temperature using various instrumentation. Top to bottom:
angle of attack 0°, 10°, and 10° and mass flow rate 6 g/s, 6 g/s, 12 g/s.
22 | SAMPE JOURNAL | MARCH APRIL 2024
www. sampe.org

http://www.sampe.org

SAMPE Journal - March/April 2024

Table of Contents for the Digital Edition of SAMPE Journal - March/April 2024