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Post by sierramog on Mar 5, 2013 1:06:28 GMT -8
Donkey, thanks for the excellent 'Adventures with a horizontal feed' thread. This forum ought to be attracting the attention of fluid dynamics students. I am fascinated with the 'double ram's horn' movies by Peterberg in Page 5 Reply #65, Satamax in P13#83 & Jham in P14#200. I imported Jham's file into iMovie to see frame by frame how the sound pattern matches the horn movements from side to side. As a casual student of physics it looks to me like a Karman vortex street inside the tube instead of in a free stream as is normally seen on Utube. If so, it should be that the vortex action shown is inherently unstable so we get pulse mode at higher Reynolds numbers. It follows that other vortex generation methods would be far less effective. Peter, can you confirm this? A borosilicate (pyrex) sight glass installed in the top of a barrel to allow a camera view down the riser would probably survive the heat as long as it was not shocked with cold. It would make show & tell more fun! One of these days I will learn enough to start building. You guys are keeping me up nights studying!  |
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Post by peterberg on Mar 5, 2013 2:22:01 GMT -8
As a casual student of physics it looks to me like a Karman vortex street inside the tube instead of in a free stream as is normally seen on Utube. If so, it should be that the vortex action shown is inherently unstable so we get pulse mode. It follows that other vortex generation methods would be far less effective. Peter, can you confirm this? To date, this method proved to be very reliable. Even the square or rectangle riser doesn't produce the same vortexes again and again. You could be right, though, the Karman vortex street is a repeating phenomenon like the double ram's horn pattern. It's a quite violent vortex generator as well, maybe this is why the air/combustible gas mixing is still excellent during a huge overload of those combustibles. And yes, I've tried to attract the attention of several under graduate physicists before. All to no avail, I'm no scientist myself so I think I should have world media coverage to get in the picture. The latest attempt is to contact a plasma physicist via a nephew student, but that guy didn't react to my emails. |
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Post by pinhead on Mar 5, 2013 7:19:32 GMT -8
I made a short recording of the flame pattern in my stove as well. It seems that the pattern is pretty consistent, from a small flame when the fire is just starting all the way up to full-out roar.
I didn't hang out up there for too long, though; I didn't want to melt my camera. The idea of a Pyrex "sight glass" is intriguing; there's something mesmerizing about the organized chaos demonstrated within the heat riser.
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Post by matthewwalker on Mar 5, 2013 8:54:18 GMT -8
I could make you guys a video. My barrel has a 4" hole right over the riser already since I use it for cooking. I have plenty of ceramic glass around. I can lay a piece on there and shoot some video no problem.
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Post by Donkey on Mar 5, 2013 8:58:06 GMT -8
Ooh! how fun!
Yes, please.
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Post by peterberg on Mar 6, 2013 9:19:52 GMT -8
Today, I've tried to shoot a video clip through the bung hole of the uppermost drum. I've burned my hands slightly and the clip do last for 11 seconds only.
The temperature sensor directly above the riser end registered 1690 F. Mind you, the riser is 3' long and is 3'8" away from the bung hole. It felt like looking down into a volcano...
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Post by grizbach on Mar 6, 2013 12:13:10 GMT -8
I don't know if most people think of a ram's horn as 2 dimensional. I know I do. I like to think of the pattern as opposing corkscrews.
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Post by pinhead on Mar 7, 2013 6:57:47 GMT -8
Here's my short video. It would have been longer but I didn't want to melt my camera.
The heart-shaped heat riser was caused by thermal expansion in the metal pipe. The clay hardened before this video, though, and I've since pulled the pipe out which made it a normal round riser.
I like the idea of a heart-shaped riser, though... Reminds me of a modern combustion chamber, guiding combustion gasses into a pattern which promotes excellent mixing.
It would also eliminate any "dead spots" that don't see a whole lot of gas movement. This is all just conjecture at the moment, though.
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Post by sierramog on Mar 8, 2013 1:57:14 GMT -8
Today, I've tried to shoot a video clip through the bung hole of the uppermost drum. I've burned my hands slightly and the clip do last for 11 seconds only. The temperature sensor directly above the riser end registered 1690 F. Mind you, the riser is 3' long and is 3'8" away from the bung hole. It felt like looking down into a volcano... I can see the safety problem!  Would a swing arm peekaboo camera heat shield help? I spent the day gathering junk parts to make the simple contraption shown in the photobucket link.  Still a work in progress but it is very easy to make if you have the parts. My old camera has a field of view of about 7.5° when zoomed in which is more than enough to view a 6" pattern 8' away. The barrels have to be tilted a couple degrees to get a clear view of the double ram's horn through a quarter inch hole I drilled on the edge of the big bung. Otherwise another hole needs to be made near the center of the shield for the camera to peek through.  My camera fits snugly in a hole in the insulation. The entire shield with camera is easily lifted off by grabbing the small pipe or it can be swung 180 degrees. s1149.beta.photobucket.com/user/sierramog/media/swingarmcamerashield.jpg.html?sort=3&o=0Any suggestions/comments are appreciated. I have not tested this. Attachments:
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Post by satamax on Mar 8, 2013 9:59:14 GMT -8
Hey guys, photographing the ram horns is easy, use a miror like in a periscope half |
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Post by sierramog on Mar 9, 2013 0:44:17 GMT -8
Hey guys, photographing the ram horns is easy, use a miror like in a periscope half Hi Satamax. Excellent thought!  1. Much easier to use camera viewfinder and controls from the side rather than looking down. 2. Reduces convection heat. 3. Hanging a 'down mirror' support tube on an external object such as ladder rungs should reduce vibration when photographing in pulse mode. 4. Camera mount could be made much lighter.  3. Would a heat resistant tube angled up with a mirror fastened at an appropriate angle to view down the barrel be what you have in mind? I envision the mirror blocks one end with a small hole underneath. An insulation shield at the viewing end would protect the camera. What would be a good side distance from barrel? Can shoot time be long without damaging camera? Thanks for commenting. Attachments:
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Post by satamax on Mar 9, 2013 10:36:35 GMT -8
Sieramog, you're making things too complicated! ;D
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Post by sierramog on Mar 9, 2013 20:12:03 GMT -8
Sieramog, you're making things too complicated! ;D Sorry Satamax, can't help myself, it's a lifelong disorder Are you using a metal mirror? What temperature does the your barrel get to in pulse mode like in Peter's experiments? |
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Post by satamax on Mar 9, 2013 22:57:53 GMT -8
Hi Sieramog.
I've used a glass mirror. that was just for the core testing. No barrel. Thought since, i've fited it inside a water heater tank. The top goes up enough to heat powdercoat so i can scrape it easily. No other measurements were made.
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Post by pinhead on Mar 14, 2013 9:08:45 GMT -8
In case anyone also wanted to see/hear the innards of a burning Peterberg batch-fed rocket stove. Notice that my stove doesn't draft nearly as much as Peterberg's prototype does -- the flames in front go "up" in mine, while all of the flame and smoke go "back" in his.
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Would a swing arm peekaboo camera heat shield help?
Still a work in progress but it is very easy to make if you have the parts. 
My camera fits snugly in a hole in the insulation. 
