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Saturday, August 02, 2003
Armadillo Aerospace News: Engine work, big vehicle work
We are seeing reduced catalytic activity in our test motor, which is worrisome. There are several possibilities:
It may be poisoning from the stabilizers in food grade peroxide. If true, it should be possible to clean.
It may be soot deposits from the propane preheating. That should also be cleanable, and possibly avoidable with lean preheat or hydrogen.
It may be a degrading of the mechanical structure, allowing more channeling around the outside. Welding in the anti-channel rings should help.
Worst case, it is an actual stripping of the platinum from the support base. We may have aggravated this with some preheats that got out of temperature range, but if it is stripping due to fluid flow, all we can do is make sure we even out the flow as much as possible.
We welded two stainless AN fittings to the top of the engine to allow us to plumb in the propane or hydrogen and forced air without going through any pipe taped connections. This turned out to be a bad idea, because the air and fuel did not mix well before flowing through the spreading plate, resulting in a very rich mixture on the side by the fuel, a very lean mixture on the side by the air, and a very hot stoichemetric mixture near the middle, which melted some screens. We capped the fittings and went back to mixing the air and fuel together above the engine. Read More
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