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Armadillo Aerospace News: Engine improvements, Mixture ratios

Published by spacecowboy on Sat Oct 25, 2003 1:48 am
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chabot imageOn Tuesday, we did several things to test improvements to our highly successful combination of last week.
We used the short (2”) chamber extension, and packed it with one 1” thick foil monolith catalyst and covered that with 110 grams of catalyst bale. This extension is 6” ID, and the monoliths are only 5.5” OD, so we packed the bale catalyst around the sides as much as possible. It turns out that the Champion diesel glow plugs we are using have the same thread diameter and pitch as 1/8” NPT, but with a straight thread. This allows us to weld a 1/8 F-F pipe union on the outside of the chamber, and thread the glow plug into it. With some anti-seize on it and a bit of torque, it seems to seal even though the taper is only on the female threads. The glow plug tip does protrude slightly past the end of the union into the chamber, but we didn’t expect quenching to be a problem.
I made new three-pass catalyst plates. Because the upper catalyst doesn’t get much over 250F, the monolith has plenty of structural strength to support itself without the cross bars, so I removed those for better flow. The upper plate is also 0.050” thicker to give a bit more turn-around volume. Russ welded on some spacers at the top of this plate to guarantee that it wouldn’t bow up and close off any of the top flow. Instead of standing the perforated flame holder away from the bottom of the lower plate, we welded it directly to the plate, which gives a 0.25” gap between the bottom of the catalyst and the perforated plate. Read More

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