Woodgas, how does it work?

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Karl2353

Member
Jan 8, 2011
21
0
Cumbria
Hi all,
I made a woodgas stove today from a bean tin and a small WD40 can. It seems to do what its supposed to do.

Can anyone tell me how it works?
 

JonathanD

Ophiological Genius
Sep 3, 2004
12,809
1,479
Stourton,UK
Wood_gas_stove_Principle_of_operation.png
 

Teepee

Bushcrafter (boy, I've got a lot to say!)
Jan 15, 2010
4,115
5
Northamptonshire

This diagram would be great if it was correct :)

If you want to find out how they work, ignore this diagram. Its led to much confusion around the world by people trying to get a handle on whats happening. There are many different types of 'Woodgas' stoves. Without seeing your stove I can't be certain, but its possible that you have made a hobo stove and more likely that you have made a Tlud (Top Lit Updraught ) stove.
Have a look at Bioenergy lists and the article called "The Tlud Handbook". Its in depth in places, but the diagrams are correct.
http://www.bioenergylists.org/files/TLUD%20Handbook%202010-02-21.pdf
 

slammer187

Nomad
Jul 11, 2009
411
0
Ireland
Do you have any pics of your stove Karl? The BushBuddy/Cooker is a TLUD stove, It is lit at the top and the gas travels straight out the top of the combustion chamber and never enters the innerwall, the only reason of the 2 can design is to achieve the Venturi effect and force air into the combustion chamber to be mixed with the gas, the only time that this changes is with a stove that has a complete flame cap, this kind of stove is sometimes known as a TLOD and air never enters the combustion chamber, it only feeds the flame cap but don't try and take in too much information and get confused....JonathanD's diagram is of a TLOD but the size of the bottom holes within the combustion chamber known as the Venturies is incorrect also no flame cap is shown and the fuel is shown to be burning, only the gasses are burned in a TLOD, if you search for "WorldStove" on youtube, Nat has some great demonstrations of a TLOD stove....But for Bushcraft uses stick with a TLUD :) With TLUD stove you can achieve a very clean burn, Tepee has a great video of a forced air TLUD if you ever want to check that out.
 

Karl2353

Member
Jan 8, 2011
21
0
Cumbria
Here is a picture of my home-made woodgas stove, I'm not sure if the design is correct because I only heard of woodgas the other day and saw a picture of another stove and tried to make something similar. I'll probably make another couple more before I get it perfect although this one works OK. Thanks to slammer for advice and links, I'm sure I'll get my head round it after I've seen a few more vids. Ideas on improving my own design very welcome. Thanks, Karl2353.
th_Pic_0115_014.jpg
 

JonathanD

Ophiological Genius
Sep 3, 2004
12,809
1,479
Stourton,UK
Arnt all wood burning stoves "woodgas"? :rolleyes:

No. Woodgas stoves re-ignite the gas produced by burning wood by means of a double skinned cooker circulating it back into the centre flames. They burn much hotter and more efficiently without smoke. On normal hobo type wood burning stoves, this gas would just waft into the air without re-igniting and there is obviously smoke.
 
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lou1661

Full Member
Jul 18, 2004
2,177
194
Hampshire
So the word woodgas is used to describe a stove that produces a premix flame rather than a standard diffuse flame?
 

Teepee

Bushcrafter (boy, I've got a lot to say!)
Jan 15, 2010
4,115
5
Northamptonshire
All fires obviously produce woodgas. The distinction between a woodgas stove and a hobo type stove (normal fire, complete combustion) is that the produced gas is burnt remotely from where it is produced. This seperation can be very small in terms of time and distance, but must be present. Its this seperation that distinguishes a 'Woodgas' stove from other types. Woodgas is full of very volatile subtances including the magic Hydrogen, which offers much greater flame speed than burning char and thus greater heating power and efficiency. An efficient Tlud can be incredibly clean burning.
When wood is burnt in an oxygen controlled environment, char is produced (think charcoal making), releasing flamable volatiles(smoke). When the smoke is burnt remotely, it leaves some char (up to 50% of the original fuel)) which can then be burnt aswell. In effect, this is burning the wood twice. Whether the flame is pre-mixed or diffuse has no effect on the terminology.
 

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