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Post by satamax on Jul 16, 2015 4:38:28 GMT -8
Peter, you just sound like Allen, in more understandable way  Well, just pulling your leg! |
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Post by josephcrawley on Jul 16, 2015 5:33:54 GMT -8
Peter I would like to build a cookstove that is not enormous that has an oven and that isn't possible using the existing design.
I started with your existing design and quickly realized that there is no way to fit a riser in a cookstove and the side draft design makes the stove way to wide. So I went with a shortened riser. This focused the heat so that I had only one good burner and made the depth of the stove untenable. Your design is excellent for mass heater but a cookstove is a different kind of wheel.
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Post by peterberg on Jul 16, 2015 6:05:04 GMT -8
OK then, I'd think Satamax has to chime in. He's been quite succesful with a cookstove as I understand it.
Max, come in please, this is something you could shine your light on.
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Post by satamax on Jul 16, 2015 14:45:09 GMT -8
Peter, ye'r joking? I understand fuck all at what is going on here. And i don't know if you've noticed, but i don't feel comfy at all with riserless builds. I have zilions of things to understand first.
And this one isn't triggering my interest. Since i am not that good a reader of english, i preffer sketchup views. They make things clearer for me! I know how i would do a kitchen accumulating rocket. As i suggested before. Cooking plate as the ceilling of the firebox. gases going up a normal riser, and into a high oven. Not that easy to use, but workable. Then gases going back under another part of the cast iron cooking top, which serves as the top of a brick bell with pillars, for accumulating heat. And may be a last brick bell, depending on how hot the exhaust gases are. Your "burner" works for me. I'm no expert. The only thing i can do, is seeing the wood for the trees. And i can click, connecting shapes, or concepts together. I'm just an assembler, rather than a researcher.
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Post by josephcrawley on Jul 16, 2015 15:10:25 GMT -8
After looking at diagrams of several commercial cookstoves I've decided to add a burn grate ash pan and the like. I will apply my meager sketch up skills when I'm bored at work and post something here. Thanks gor taking the time.
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Post by Daryl on Jul 17, 2015 2:27:35 GMT -8
Joseph, Why are you trying to invent the wheel? I've spent 6 months of work in 2012 to optimize the batch box so what a good configuration is should be well known. But you are changing the firebox, riser, primary air, secundary air and probably more as far as I can see. So you are doing development all over again with a design which happens to be very tight to begin with. For example, the horizontal part of the p-channel inside firebox won't work as well. The reason could be that the air need to be go down in the vertical part of it. So the hotter the air, the more it will resist to go down. Hot air wants to rise after all... May I suggest you check out the tried and tested setup first and work your way from there?
I was under the impression that the rocket wouldn't fit so Joseph was trying to build something closer to a standard stove where the gases exit the top of the burn chamber.
I am looking forward to the sketchup drawing.
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Post by josephcrawley on Jul 17, 2015 18:40:52 GMT -8
well here it is my crude sketchup drawing. It gets really tough for me when layering an excess of objects so I left the skin of the thing to your imagination. Thanks a lot for looking at this. you guys rule oh and it's 2014 format if that works Attachments:newcookstove2014.skp (56.72 KB)
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Post by peterberg on Jul 19, 2015 0:56:56 GMT -8
OK, I think I get the concept now of what you are trying to do. Quite a number of people, myself included, tried to have the riser on top of the firebox. For some reason, each and all of those didn't cut the cake. Your setup is new to me with the horizontal port lying flat, one aspect of the firebox strikes me as probably troublesome. That's the primary air inlet through the grate. More often than not, this intake is the cause of a too quick pyrolysis process and the reason of over fuelling. When that happens the thing starts belching smoke. Best to have the primary inlet as small as possible I would say.
The one thing what makes the batch box tick is the double vortex in the riser. How to achieve such a state of affairs, that problem is hard to crack. Even Larry Winiarski has seen this happen now and then and for a very limited duration of time but didn't realize this could be a key to clean combustion. Of course, it's not the only way to woodfire heaven nor is the batch box itself. But it means a lot of work to get there.
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Post by josephcrawley on Jul 19, 2015 6:31:54 GMT -8
Do you think the grate is bad even if the air intake stays small? My current cookstove uses this design it has a cast iron grate the length of the firebox with an air intake below. Do you think it would be beneficial to narrow the gap between the secondary air channels to act like your p channel? Thanks again for the advice. I will probably get this thing rebuilt this week and give you guys an updat
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Post by peterberg on Jul 19, 2015 7:07:17 GMT -8
A grate is useful for coal, even charcoal, and bad for wood fuels. Your range is built as a coal stove, that's for sure. So it will off gassing the wood at an alarming rate, causing a fuel overload. Around 1987 I tried to optimize a DIY Finnish contraflow heater with a refractory floor with some slits in it, acting as a grid. The only measure that helped was minimizing the air inlet under the floor by 95%. Making the slits smaller didn't help, only the inlet itself so that the cold air rushing in under the floor slowed down to a crawl.
I would view the gap between the secundary air channels as a port. So in theory this csa need to be somewhat smaller than the chimney size in order to speed up gas velocity. In order to be able to induce the double vortex just behind the port the space need to get back to system size with the main cooking plate on top. When there's an opening at the back to the other plates this might work. But your chances are slim I would say, sorry.
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Post by josephcrawley on Jul 19, 2015 10:29:42 GMT -8
My existing stove burns cleanly or st least the chimney produces no visible smoke once it gets going. The modern stoves I have looked at all include a burn grate la nordica in Italy and the stoves sopka inc imports from Serbia.
Maybe I should ditch the grate but in my testing so far I'm left with a large amount of coals in the average cooking time and to keep the fire running hot I have to add more wood. So it seems like I'm getting to much pyrolysis. Maybe this will change as the design evolves.
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Post by josephcrawley on Jul 19, 2015 16:11:54 GMT -8
Looking at the magnum stove that sopkainc.com imports it has a firebox dimenison of 12 15 11 h d w and the primary damper appears to be no more than 3 in sq. Not sure if this is as small as you needed to make the primary air in the grate stove you modified. Looking at the batch box dimensions this stove is the same firebox volume as a six inch system with about half as much primary air. Maybe the concepts are not relateable like that. Thanks again for your generosity with your time.
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Post by satamax on Jul 19, 2015 23:39:47 GMT -8
Well, i still don't understand much, even with the ketchup. Tho, i have questions. How much space is there between your secondary air channels on top, and the cooking plate above? I would view the gap between the secundary air channels as a port. So in theory this csa need to be somewhat smaller than the chimney size in order to speed up gas velocity. In order to be able to induce the double vortex just behind the port the space need to get back to system size with the main cooking plate on top. When there's an opening at the back to the other plates this might work. But your chances are slim I would say, sorry. I'm no expert, remember! The double vortex Peter is talking about can form behind any type of venturi. But it has to have space and time to develop. In this case i'm with Peter, too wide a port between the two legs of the secondary air channel. My gut feeling tells me to get a good reburn after that, you need the narrowest slot possible between the two. which for a 6 incher, with 16 inches long slot, would be 1, 3/4 inch wide for equal CSA. To get a good depression behind that, i'd say use 50% csa or 7/8th". May be less if you have a real strong draft. Again, no backup for this, but i would make the slots in the secondary air channels 1/3rd of that 50% CSA; on each side. To get real fancy, you could use round tube for your channels, and make the slots at the begining of the trailing edge oposite the firebox. That would give you a nice suction. To counteract the "jet" going too much to the right side (oven side) and killing the swirls, you could orientate your secondary air slots differently. Then to me, you should realy leave three times the port size between the top of that port and the underneath of the cooking plate. Even then, i'm not too keen on the direct cooling effect of the gases. So i would raise that cooktop a bit more, and put a refractory brick slab under the cooktop directly above the firebox. I realy preffer Vortex's stove in that sense that there's a brick insulated chamber behind his firebox. If not a proper heat riser. Visualisation of flow after a venturi. Here you can realy see the jet Actualy peter, re visioning this video make me think that for best turbulence, the backside of the port in the heat riser has to be flat. May be add a vertical brick behind the port in the heat riser? for even more shaking? What's happening behind matt's pre port round tube? Well, 'nough for the moment! |
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Post by peterberg on Jul 20, 2015 0:59:22 GMT -8
Actualy peter, re visioning this video make me think that for best turbulence, the backside of the port in the heat riser has to be flat. I don't agree with that. Inducing a double vortex in a round or octagon shape is easier as compared to a square one. On top of that, the octagon riser delivered consequently better results. I've tried a riser with the back wall shape of the vortex already in it, yielding meager results. Those vortexes are doing the mixing and it appears that leading it too much in the desired shape influenced the mingling of the gases in a negative way. Maybe this has something to do with drag loss through friction. Just guessing, I am in the dark as well as you most of the time, only some speck of light now and then... |
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Post by satamax on Jul 20, 2015 3:28:23 GMT -8
Peter, you might not have understood me. May be! I like the round riser, it makes perfect sense to make the riser round on the "receiving end" of the ram horns. Since it facilitates the occuring of thoses. But i think the back of the port has to be flat on 3 or 5 cm each side. To actualy start the swirls by means of friction, since on the two flat sides, it's a complete stall of the gases. Remember how i did the port of the range retrofit? Exactly like that. I'm still trying to find a way to round the leading edge of the port, and adapt the P channel with the rounded edges. One day, i'll find the right video |
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