Aslan Core Melts Down on First Firing Feb 18, 2021 12:19:59 GMT -8
Post by Solomon on Feb 18, 2021 12:19:59 GMT -8
Hey all, I've been farting around here for a few months talking about stuff of which I know not (like most newbies do) but now I have been deflowered.
I built and tested my first CFB core yesterday and it it went straight from awesome to scary.
Here it is, 2300 degree ceramic fiber board, based on Matt Walker's 6" core but scaled up, and using a 2" thick 4 foot CF riser sleeve as a heat riser. I placed a 1300C (2372F) thermocouple six inches up from the riser/core interface and sticking about 4" into the gas stream.
Yesterday, I cut it all out, put it together and fired it up. No hiccups, everything worked perfectly. I also placed a copper wire about 56" down the riser to check temperature through melting.
Everything was going great, burning out the binder in the board, and the temps continued to rise. Then it approached and passed 2300 degrees and that's when I started getting concerned because my materials are all rated at right around that. This was burning dry but not particularly well cured small split wood and some dry 2x4s and 2x6s. At the end of the burn it was hitting 2300 degrees burning ONLY TWO 2X6s!
Here is the peak I measured. This is a screen cap from the video. 2446.7 was the last number the thermocouple read before going all -----. On the video, the temperature is still rising at a rate of 2-3 degrees every half second. So, though I don't have numbers, I would say it approached 2500 degrees before backing off.
Later during cool down, the riser made loud cracking noises. Disassembly showed cracks in the lower riser section. Cracks appear to propagate about half the thickness of the riser.
Copper melted up to just below the edge of the top of the burn tunnel. Copper melts at 1984F. A small nodule of copper dripped down and made a pile (though not a puddle).
Now the major problem, every piece of the internal layer of CFB warped and cupped. You can see in the picture down the riser above that the back of the burn tunnel piece curved into the flow path. This does not seem to have affected the draw or output of the core at all. The feed tube is still likely the most constricted point in the system.
The outer layer of the CFB seems to have had little issue. After burning for several hours, there was maybe half a cup total of ash. Firebricks were unaffected, and were still at 200 degrees four hours later when I took them out and hauled everything inside to avoid rain. Even though the thermocouple went well outside specifications, it seems to have survived unscathed.
I named this core the Aslan Core. Points to the first person who figures out why.