OWB Smoke

[Stihl310]

Well, I've been tossing around ideas on designing something that I could retrofit to my OWB to try and decrease smoke... Mine is a homebrew, so I'm continually tweaking things and trying different things out... Aside from installing a secondary burn chamber, which isn't out of the question, does anyone have any ideas of anything to try???

I've contemplated fabricating some sort of adjustable baffle/damper/chamber that would slow down the flow slightly to try and burn some more of the smoke up.

I'm burning dry wood, and I just threw some hickory in that has probably been sitting for 3-4 years in our barn, and it is chugging like a choo choo out there... the main reason for wanting to do something is I have a neighbor about 200' foot from me, I doubt he would ever complain as he burns wood as well, and chugg's on cancer sticks all the time... but I'd like to be able to decrease the smoke and increase overall efficiencies if I could...

I do notice that when I open the door after the blower has just fired, that the chimney has a ton of draft, it will litereally almost suck the flame right out of the burner... I'm thinking if I could somehow baffle/damper this that I would be more likely to burn up a little more smoke...

Correct me if I'm wrong on my thinking, and throw out any ideas you have,I'm up for anyhting...

By the way, I'm getting a design ready for a potential gasifier unit that I'm going to build here in a few years... I'll post some 3D models when I get something decent together, I've found myself continually scrapping design after design, trying to get the best of everything...

 

[barnumb]

Would love to see pics of your stove.

 

[Circle B MN]

I do believe that deep baffle design of my CB5036 does a lot to reduce the amount of smoke that escapes the unit. That and the dry seasoned wood, that you said you are burning yourself..

 

[applefarmer]

The design of my hawkin has a round firebox with 3 or 4 large 4" tubes running cross ways near the top. Then above that it has a wide channel that is only open near the front (it butts up to the back). The idea is it traps and forces the heat throughout the firebox, up across the tubes, (which increases firebox surface area) to the front of the channel which forces hot gasses across the top of the firebox before it goes out the stack. I really like the design and I really don't have any smoke after the first 5 minutes after I load the stove. Like you I also only burn seasoned wood.

 

[jgoodhart]

I added a 2nd blower and add air in above the fire. The only time I get much smoke is right after I load it with wood. The bottom blower damper is about 1" open and the top blower is set at 1/4" open.

 

[Stihl310]

I added a 2nd blower and add air in above the fire. The only time I get much smoke is right after I load it with wood. The bottom blower damper is about 1" open and the top blower is set at 1/4" open.

That's interesting, I have another blower, (smaller CFM) sitting in my car right now, maybe I should try to tie it in somehow. I did just order the sheet metal i need to fab up a piece that will fit onto my existing chimney pipe inside the burner, that will basically create a secondary chamber to try and slow the process down...

I may try to see if I can't get that second blower mounted though this weekend yet and see what difference it makes.

I will say that once the fire gets going there is little to no smoke, it's just somedays it really get's to chugging out there and I'd like to try and elimninate that as much as possible

 

[teamhog]

Adding more air could really help especially if you're starving the fire at full load. That's something that you'll have to watch for though as it's the dampening of the fire that helps control the burn cycle and therefore the recovery and how often you'll need to add more fuel.

If you can add more air with another fan AND increase the velocity you may be able to decrease the smoke...

Have you searched (googled) ways to decrease the smoke? If so, what did you find?

 

[STLfirewood]

You could try a blower o the smoke stack. Kind of the same principal as this.

http://www.youtube.com/watch?v=mo4K1dM2GH4


Scott

 

[Stihl310]

Adding more air could really help especially if you're starving the fire at full load. That's something that you'll have to watch for though as it's the dampening of the fire that helps control the burn cycle and therefore the recovery and how often you'll need to add more fuel.

If you can add more air with another fan AND increase the velocity you may be able to decrease the smoke...

Have you searched (googled) ways to decrease the smoke? If so, what did you find?

It almost seems to me that I don’t have enough restriction, (too big of chimney 8”) and that I’m getting a good fire, but the smoke is escaping long before it even has a chance to burn. Does that make any sense?? I’m sort of questioning now what to do, more air??? Or less???

Suppose I can crack my door and let it run, that should tell me as the blower should just naturally induce a draft around the door and let more air in.

 

[Iska3]

I do believe that deep baffle design of my CB5036 does a lot to reduce the amount of smoke that escapes the unit. That and the dry seasoned wood, that you said you are burning yourself..

I had some old oak that sat in our barn for 4 or 5 years. It seems like that stuff soaked up a lot of water during the last rains and smoked some when I first used it. Like MNGuns, I think the long baffle in the rear of my CB helps a lot. I also found if I lay a short log across the back and block off a little more of the open space, I get a longer burn time but not has fast heating between cycles.

Be sure to post some of your pictures. Thanks!

 

[Stihl310]

Here's the only pics I have right now on my computer of it... during build and initial install... Going on it's second year right now...

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[Stihl310]

Here are a few more...
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View attachment 163051

 

[Stihl310]

Is there any way you could extend the chimney down into the firebox near floor level so exhausted gasses would have to pass close to hot coals before going up the chimney?

Also if a opening could be put on this extended chimney near the top of the firebox that could be opened when the wood stove door is opened it would cut back on smoke escaping when fueling.

As of right now the chimney sticks down inside the firebox about 5 inches... that's on a 28" diameter fire chamber, so I've got some distance to work with. I had an initial design that I was going to build, and just picked up hte material. Basically it extended the chimney down like you suggested, but then had another chamber that turned 180 degrees back up to the top of the firebox, and then extended towards the door approx 16"... I'm thinking I'm just going to fab up the initial piece that lowers the chimeny down an give that a try first.. If it doesn't prove out I'll move onto my original concept.

Thanks for everyone's input.

 

[WVwoodsman]

I too am curious about decreasing the smoke output from my OWB. In searching the net, I came across this: http://www.clearstak.com
I have sent an e-mail to the company and I am waiting to hear back. There is also a video on youtube of one in action. I was impressed!

 

[H-Ranch]

Here's my baffle design in a similar round firebox. First picture is installing it through the door opening before the top fin was welded on and the second picture is during operation. The top fin extends to the rear of the firebox with a 6" gap at the front. The exhaust has to enter the tube low and to the rear in the fire, go up and forward around the fin on the top of the baffle, then rearward and up out of the 7' stack. It seems to cut down on smoke a bit, but it really cuts down on the sparks. I can fit a small rod in each side to scrape some of the ashes out with the door open as needed.

Unfortunately my overhead welding skills are a bit lacking and it fell down this week. I temporarily extended the stack low into the firebox and could tell right away that it was not nearly as good (at least on the sparks.) Looks like you won't have the same problem with welding judging by your pictures.

Hope that helps.

 

[goosegunner]

Smaller fires helped my Taylor. Also, When mine would chug it was getting too much air. When it was cold the air is dense so I would have to close damper plate on the fan to reduce air.

gg

 

[CTYank]

I'm gonna guess that you've got a box with essentially a water-jacketed wood furnace. And suggest that the overall design makes it difficult for you.

To burn completely (cleanly) you need temps in the firebox above 1000 deg F, per research done in the '70s. Hard to do that with cooling water right there.

Like the old "Hill boiler" or current Varmebaronen, you'll get best results with separating combustion from heat transfer. And storage is a real plus- think 500 to 1000 gal storage.

Search on Prof. Richard Hill, Mechanical Engineering, Univ Maine Orono for some of the interesting systems he designed.

 

[donthraen]

have you tried getting a good hot flame and then restricting the airflow---I use good hot burning wood (hedge)and don't have any smoke except wen I throw a fresh cut oak or something like that on it and it only lasts fore a minute or so

 

[Windwalker7]

I too am curious about decreasing the smoke output from my OWB. In searching the net, I came across this: http://www.clearstak.com
I have sent an e-mail to the company and I am waiting to hear back. There is also a video on youtube of one in action. I was impressed!

Here is a video!


Check out the UFO at the end, LOL!

http://www.youtube.com/watch?v=dInj-0-B2BA

 

[smus]

I have often wondered if the gases (smoke) could be recirculated as it is in some of the newer trucks and cars, by drawing air from the stack and directing it back into the hottest part of the firebox, using a blower similar to what is used on most boilers anyway. It looks like it should work in my "minds eye".