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Post by dpottier on Aug 28, 2014 3:40:01 GMT -8
David, I think something is definitely wrong as the drawing you showed in your post is far off a real life setup. Modified to this and tested. How does it look?  Images: Drag CoefficientSurface PressureCan easily remove spheres and change brick to 5mm tripwire. best regards David |
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Post by DCish on Aug 28, 2014 11:06:56 GMT -8
Tripwire belongs on the roof of the burn tunnel where the bulk of the volatiles rise to, I believe.
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Post by ericvw on Aug 28, 2014 14:18:02 GMT -8
Hi dpottier, DCish is def right, perhaps a slight graphics "typo?" I'd like to know about the sizing of the p channel- looks a bit large in the X direction... Maybe you could look at the Dragon burner for feed and p channel size and relation? Hope all is well with you, Eric VW donkey32.proboards.com/thread/803/evaluating-6-dragon-burner |
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Post by dpottier on Aug 28, 2014 14:48:37 GMT -8
Tripwire belongs on the roof of the burn tunnel where the bulk of the volatiles rise to, I believe. Yes, I posted the incorrect image. Now corrected. Thanks for catching that one. :-) |
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Post by dpottier on Aug 28, 2014 15:22:40 GMT -8
I'd like to know about the sizing of the p channel- looks a bit large in the X direction. Hi Eric Both the feed tube and the P-Channel are "off the shelf" box and rectangular steel tubes. Feed Tube is 4"x4"x1/4"; the P-Channel is 4"x1"x1/4". I can model 4"x1/2" but haven't seen it commercially in 1/4" stock. Four pieces of 1/4" flat bar and about 4' of weld but an expense for DIY. I could/can change to round iron pipe of the same intake area. I think a 4"x1/2" square = 2" diameter pipe. Additionally, I want to tilt the Feedtube 20 degrees to "soften" the 90 degree angle on the deck of the Burn Chamber. David |
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Post by dpottier on Aug 28, 2014 16:03:37 GMT -8
A thought on creating the curve before the Bell Chamber if casting a Burn Chamber like Peters. Cedar or Redwood gutters are common in North America but I am not sure if available in Europe. Any gutter shop will have lots of small scrap pieces laying about that I am sure they would be only to happy to give away.  Cutting concept once you find the right gutter profile. The mold would be reusable and both cedar and redwood are easy to sand and shape.  |
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Post by satamax on Aug 28, 2014 22:21:19 GMT -8
David, btw, metal is doomed!  |
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Post by peterberg on Aug 29, 2014 0:51:13 GMT -8
David,
Apart from the location of the trip wire and the size of the p-channel there's the fact that the p-channel has got a slight overhang. Your drawing is correct at that point bar one detail. The side facing the feed has got the overhang, the side facing the burn tunnel hasn't. That side is flush with the ceiling of the burn tunnel. This seemingly small detail makes a lot of difference according to the Testo analizer.
The csa of the p-channel is 5% to 7% of the feed's total csa, by the way.
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Post by dpottier on Aug 30, 2014 7:58:26 GMT -8
David, Apart from the location of the trip wire and the size of the p-channel there's the fact that the p-channel has got a slight overhang. Your drawing is correct at that point bar one detail. Peter I shall make the corrections and based on the 5% - 7% ration on a 4"x4" feedtube the P-Channel opening should be about 1/4". I am not sure how well this will test as a wind tunnel only blows air but will try it. I can place the wind start point so will try it deeper in the burn chamber instead of at the entrance to the feedtube and hope it will create the draft effect needed. David |
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Post by dpottier on Aug 30, 2014 8:28:10 GMT -8
David, btw, metal is doomed! In another life I was a Master Cabinetmaker and Luthier. Real wood rocks. |
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Post by satamax on Aug 30, 2014 12:49:54 GMT -8
David, btw, metal is doomed! In another life I was a Master Cabinetmaker and Luthier. Real wood rocks. Guitarmaker? Violinmaker? Mimf member? I was not saying this because i preffer wood. Metal in a properly working rocket, in areas where it's in contact with flames is bound to fail sooner more than later. Talk about 50 hours burning time for 3mm steel! Tho, I have a city and guilds of guitarmaking, from a previous life! Now, i'm more into roofing and timberframing. |
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Post by dpottier on Aug 30, 2014 17:35:41 GMT -8
Guitarmaker? Violinmaker? Mimf member? Tho, I have a city and guilds of guitarmaking, from a previous life! Now, i'm more into roofing and timberframing. A builder of harps, aeolian harps, hammer dulcimers, zithers, bodrahns and instruments from China like their violins and Cheng. I learned balloon construction methods from shipbuilders. It was how they built houses. I like the old Guild system. You are lucky to have them and those craftsmen in your city. Here is an idea I don't think has been tried before - a glass burn chamber. In this there are two options: Borosilicate glass, AKA Pyrex - Softening point: 820 °C - Maximum Use Temperature 515 °F (268.3 °C). Fused Silica Glass or Fused quartzware - Softening point: c. 1665 °C - Maximum Use Temperature 1100 °C - Thermal conductivity: 1.3 W/(m·K) Fused silica glass is a very low thermal expansion material and is extremely thermal shock resistant. Use the fused silica for the burn chamber and the pyrex for the very hot part of the flume. The joints can be sealed with a good gasket sealer like Deacon 8875 sealant. |
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Post by dpottier on Aug 30, 2014 21:32:26 GMT -8
The csa of the p-channel is 5% to 7% of the feed's total csa, by the way. After the mods to the P-Channel  That being done and based on information from the Fluid Mechanics Research Laboratory, University of Waterloo in Canada, I made a change in the sphere to a stepped diameter sphere.  Normal Sphere Results (looking towards Burn Chamber):  Looking towards Feedtube - 10mm Tripwire  Stepped Diameter Spheres looking down Burn Chamber  Drag and Surface Pressures looking towards Feedtube. Note the higher Drag Force and Lower Drag Coefficient  A 10 point drop in the Drag Coefficient from introduction of the stepped spheres Out of curiosity and based on the above results, a 20mm X 10mm blade was added to stop vortex oscillations in hopes of getting an even lower Drag Coefficient  Instead of a lower Drag Coefficient the test showed an elevated DC which was about the same as the single Sphere setup.  It looks like the oscillations caused by the stepped Spheres are sweeping the surface and disturbing more of the laminar layer than just a single 20mm sphere. best regards David |
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