Importance of Over Fire Air & Blue Flames

Re: Importance of Over Fire Air & Blue Flames

PostBy: nortcan On: Sat Aug 10, 2013 10:36 am

Me too :)
Attachments
DSC04223.JPG
(91.05 KiB) Viewed 24 times
View: New PagePopup • Select:BBCode
[nepathumb]43066[/nepathumb]
nortcan
 
Stove/Furnace Make: Stuart,Peterson/ Grander
Stove/Furnace Model: Sunnyside/ Golden Bride

Re: Importance of Over Fire Air & Blue Flames

PostBy: franco b On: Sat Aug 10, 2013 10:59 am

It might help to realize that there are two types of blue flame. Those caused by the release of gas when the coal is first heated and those created as a product of incomplete combustion in the form of carbon monoxide. The most efficient fire is the one burning briskly enough to burn both gasses. That would mean some blue flame all the time since air supplied will never be supplied evenly throughout the burning bed and some carbon monoxide generation is inevitable.

Because we want to operate the stove with varying heat output, in order to accomplish that the stove has to run at other than its most efficient burn setting at times. By fussing more and loading in layers with a batch loading stove and paying more attention as Rwalker does, overall efficiency will be better.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Importance of Over Fire Air & Blue Flames

PostBy: dcrane On: Sun Aug 11, 2013 5:41 am

very good observation my friend!!! Yes... a lil' over bed air is necessary on a good coal burner (most stoves call this "secondary air") which is better to come from below (around firebed to above rather than through the top door or in the case of some stoves a lil' flapper above the coal bed). but either way... you should have some secondary air allowed to reach the gases over the coal bed to burn them!
dcrane
 
Hand Fed Coal Stove: Crane 404

Visit Hitzer Stoves

Re: Importance of Over Fire Air & Blue Flames

PostBy: dcrane On: Sun Aug 11, 2013 5:48 am

fastcat wrote:I have no over fire air but I have found as Fred said with the blue flames dancing there is more heat coming from the stove, so I have found that if I turn down the stat on the rear of the stove down some I can have the blue flames and still maintain my 72*. So I would also agree with Lightning that if you are not burning the gasses you are wasting good heat up the chimney, my lower vent is always open some and I always have blue flame after the fire settles out after loading and they continue throughout the 12 hour cycle.


Be careful because many handfired coal stoves have secondary air that you may not be aware of... these would be air channels or holes of some sort that allow some small percentage of air to get from ash area to above the coal bed (without flowing through the coal bed itself). Sometime this secondary air is simply vertical groves made in the firebrick itself! (but its achieving the same function and purpose). If a handfired coal stove does not take this into account in some fashion It not as truly efficient coal burner as it could otherwise be..

Can you find "Waldo" in this Picture of a Crane 404 ;)
P1010004.JPG
(111.38 KiB) Viewed 26 times
View: New PagePopup • Select:BBCode
[nepathumb]43096[/nepathumb]


Can you find "Waldo" in this picture of a Chubby ;)
chubby.jpg
(147.86 KiB) Viewed 22 times
View: New PagePopup • Select:BBCode
[nepathumb]43097[/nepathumb]


Fine print regarding Alaska
"Our secondary air is preheated for greater efficiency. Our secondary air system remains clean and operable because of proper protection and location. Our secondary air is properly distributed so you have the most control of burning with this amazing top load/gravity fed coal stove - Kodiak by Alaska Company"

In the case VC I will use their words and logic but I'll never agree it functioned for coal as they wished it to...

"when a fuel is heated and burns, the volatile combustible gases naturally locked in it are driven off. In an updraft combustion stove these volatiles may be left unburned for two reasons. first, by the time the gases have left the fuel, they are too cool to ignite. second, the oxygen that enters the stove is usually consumed by the glowing coals at the base of the coal bed, so the gases rise through an atmosphere too deficient in oxygen to allow combustion to take place. The loss of volatile gases is serious for it represents approx. half the total heat value of the fuel."
This may be exaggerated slightly by VC and god knows their secondary system of air sucked for coal burning BUT the premise of this statement is very valid and very true! (something William here realizes which is why he burns a Glenwood).
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: Importance of Over Fire Air & Blue Flames

PostBy: Rob R. On: Sun Aug 11, 2013 8:21 am

Just my opinion, but in a mature coal fire, the absence of blue flames above the coal seems to indicate incomplete combustion. With that said, a home heating appliance is hardly "laboratory conditions" and some compromises must be made. It is a delicate balance to admit enough air over the fire to properly burn off the volatiles and CO, while not sending excessive amounts of heat up the chimney...I think we can agree that it is preferable to run the stove at less than ideal combustion conditions and not overheat the living area than the other way around.

A similar discussion often comes up in the stoker section of the forum. Some people mistakenly think they must use enough combustion air to eliminate all traces of unburned coal from the ashes. In doing so more heat is sent up the chimney compared to what would be lost from unburned coal in the ash.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Coal Size/Type: Rice/buck
Other Heating: Dad's 1953 EFM Highboy

Re: Importance of Over Fire Air & Blue Flames

PostBy: franco b On: Sun Aug 11, 2013 10:13 am

Rob R. wrote:A similar discussion often comes up in the stoker section of the forum. Some people mistakenly think they must use enough combustion air to eliminate all traces of unburned coal from the ashes. In doing so more heat is sent up the chimney compared to what would be lost from unburned coal in the ash.

Both excess air and unburned fuel are wasteful and the need for either indicates a deficiency in design. More or more efficient heat exchange can compensate for excess air, and better more uniform air introduction will lessen the need for excess air.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Importance of Over Fire Air & Blue Flames

PostBy: Lightning On: Wed Nov 13, 2013 8:16 pm

My new load door window is coming in handy! :D I tried some pictures thru it today in an attempt to demonstrate different reactions to the fire with secondary air. SO, with that lets start the show lol..

My secondary air comes in thru a port on the back of the furnace about 6 inches over the top of the coal bed. Being cooler than the air in the fire box, it sinks and flows across the top of the coal bed.


1.... This is after loading and immediately after I've closed the ash pan door and load door (for volatile bake off) about 45 minutes after loading.. Secondary air is open.. (8 second exposure)
IMG_0921.JPG
(32.78 KiB) Viewed 10 times
View: New PagePopup • Select:BBCode
[nepathumb]45573[/nepathumb]



2.... Same conditions as above, except now secondary is closed..
The blues seem to be starving and following the camera exposure, the blues were lost.
As soon as the blues were lost, I opened the secondary again to let them reignite.
IMG_0922.JPG
(24.54 KiB) Viewed 9 times
View: New PagePopup • Select:BBCode
[nepathumb]45574[/nepathumb]



3.... About an hour later, I checked the fire again and there were still some blues over the fire bed. Then, I closed the secondary, the blues went away and this is what I saw. It looks like a cold smoldering coal fire doesn't it??
IMG_0927.JPG
(22.33 KiB) Viewed 9 times
View: New PagePopup • Select:BBCode
[nepathumb]45575[/nepathumb]


4.... Heres the really neat part.. I shut the lights off in the basement. Its pitch dark down there. Within several minutes my eyes adjust to the darkness and I notice a soft blue hue in the fire box.. I set the exposure on the camera for the shutter to be open for 15 seconds (Its on a tripod for longer exposure times)..
This is the same fire as the one above.. Can you believe it??!!
IMG_0929.JPG
(182.14 KiB) Viewed 22 times
View: New PagePopup • Select:BBCode
[nepathumb]45576[/nepathumb]




5.... Now, lets do that again with the secondary open.
IMG_0931.JPG
(169.46 KiB) Viewed 15 times
View: New PagePopup • Select:BBCode
[nepathumb]45577[/nepathumb]



SO what does this all mean? I don't know :lol: But seems like a little secondary air is helpful for completing combustion a little better.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut Size / White Ash

Re: Importance of Over Fire Air & Blue Flames

PostBy: wsherrick On: Wed Nov 13, 2013 8:33 pm

Very nice pictures. You can see flames visible throughout the entire burn cycle in the big Glenwood. After several hours you can see a yellow to almost white flame around the holes in the secondary air ring. They are quite faint, but; plainly visible. I don't think they could be photographed very easily without some expensive photography stuff.
But for those who haven't seen it, here is the cast iron ring around the fire pot that supplies pre heated secondary air directly over the top the fire. I am convinced that this option increases the combustion efficiency of the stove by quite a margin.

You can see the ring with the little exit holes just under the exhaust manifold. In the second picture showing the loading door, you can see a tiny row of little holes under it. These are the intake holes for the secondary air. The air then flows into a manifold just under the loading door on the inside, then is distributed to the iron ring around the top of the fire pot. You also have the extra choice of adding more secondary air with the adjustable damper in the loading door.
Attachments
178.JPG
(135.77 KiB) Viewed 6 times
View: New PagePopup • Select:BBCode
Glenwood 6 interior. Secondary air supply ring.
[nepathumb]45578[/nepathumb]
027.JPG
(149.02 KiB) Viewed 4 times
View: New PagePopup • Select:BBCode
Intake for secondary air under the loading door.
[nepathumb]45579[/nepathumb]
wsherrick
 
Stoker Coal Boiler: None
Hand Fed Coal Boiler: None
Hot Air Coal Stoker Furnace: None
Hot Air Coal Stoker Stove: None
Hand Fed Coal Stove: Glenwood Base Heater, Crawford Base Heater
Hand Fed Coal Furnace: None
Baseburners & Antiques: Crawford Base Heater, Glenwood, Stanley Argand
Coal Size/Type: Chestnut, Stove Size

Re: Importance of Over Fire Air & Blue Flames

PostBy: wsherrick On: Wed Nov 13, 2013 8:44 pm

It might be possible to make something for other stoves that is similar to that in the Glenwood. I wonder if a heavy duty steel pipe, bent to go around the top of the fire pot with holes drilled in it might be fairly easy to adapt. One would need the proper calculations about what is the proper amount of air to be admitted would be. I wouldn't even know how to begin to discover that. It has to be a proper proportion for the best results.
wsherrick
 
Stoker Coal Boiler: None
Hand Fed Coal Boiler: None
Hot Air Coal Stoker Furnace: None
Hot Air Coal Stoker Stove: None
Hand Fed Coal Stove: Glenwood Base Heater, Crawford Base Heater
Hand Fed Coal Furnace: None
Baseburners & Antiques: Crawford Base Heater, Glenwood, Stanley Argand
Coal Size/Type: Chestnut, Stove Size

Re: Importance of Over Fire Air & Blue Flames

PostBy: Lightning On: Wed Nov 13, 2013 8:57 pm

I've considered constructing a secondary air distribution system like you described with piping and drilled holes, running the perimeter of the fire box lol.

Must be brilliant minds think alike :ugeek: :lol:
Last edited by Lightning on Thu Nov 14, 2013 3:40 am, edited 2 times in total.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut Size / White Ash

Re: Importance of Over Fire Air & Blue Flames

PostBy: McGiever On: Wed Nov 13, 2013 9:02 pm

If you stay tuned long enough to this video you will see some results from just such a undertaking. :)

Watch a old woodburner get modified...and the Secondary Burn
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Importance of Over Fire Air & Blue Flames

PostBy: dcrane On: Wed Nov 13, 2013 9:38 pm

McGiever wrote:If you stay tuned long enough to this video you will see some results from just such a undertaking. :)

Watch a old woodburner get modified...and the Secondary Burn


that's a great rebuilt for a piece 0 chit for sure... but in all fairness, unless you have serious quips, pro welder, and lots of money (nobodys doing that)... to replicate what that dude did in manufacturing would price that stove out of possibility (3/4" plate :wtf: )

anyways... William is right that the proportion of secondary air has major effects, I can remember dad lining up 404 stoves (all with various size secondary air holes around the collar that holds the cast firepot up)... I know for dad their was no formula used (it was trial and error and trying best to determine what HE believed to be the best burn). This is the resulting air holes can be seen on coal vets post here I have my base burner (BB)
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: Importance of Over Fire Air & Blue Flames

PostBy: franco b On: Wed Nov 13, 2013 9:47 pm

Enjoyed it the second time around just as much. thank you.

Notice the degree of secondary burn going on even when the wood has reached the charcoal stage which is analogous to our coal fires.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Importance of Over Fire Air & Blue Flames

PostBy: dcrane On: Wed Nov 13, 2013 9:56 pm

dcrane
 
Hand Fed Coal Stove: Crane 404

Re: Importance of Over Fire Air & Blue Flames

PostBy: franco b On: Wed Nov 13, 2013 10:00 pm

franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Visit Hitzer Stoves