Downdraft Double Barrel Wood Furnace
- 8 years ago
PROJECT REQUIREMENTS
The project was to build a D.I.Y. wood furnace which would be able to burn efficiently big pieces of wood (up to 1.5 [m]) with an autonomy of 24 hours.
The furnace would also be capable to replace the burner of oil or gaz furnaces and thus, by plugin itself to a industrial water boiler be the first element of the central heating system of a house.
Finally the project would have to be feasible with easy to find material and basic tools.
DESIGN
To fit these requirements, the downdraft design was the best suited. In downdraft combustion systems (also known as reversed combustion or wood gasification systems), the so called primary air enters above the fire but below the main load of wood. It is then drawn down through the glowing bed of coals in the primary combustion chamber, pulling volatile gases with it. Secondary preheated air is introduced under the coals where it can oxidize these superheated flammable gases, resulting in their combustion in the secondary combustion chamber.
In this project I use an electric draft inducer fan, to be able to control the combustion more accurately. Down draft is also possible without draft inducer, but require then an excellent « natural » draft.
ADVANTAGES OF THE DOWNDRAFT DESIGN
This way of burning wood, used by almost all industrial wood and pellet furnaces, has a lot of advantages :
-Complete combustion of wood. By burning the flammable gaz that are normally exhausted in traditional stoves, we can extract up to 40 % more energy from wood. It results also in less pollution, and less clogging of the chimney, as the exhaust gases contain mainly water steam and CO2. It's not a dense smoke full of hydrocarbons anymore. Produces also less ashes !
-This draft pattern prevents heat of fire from rising up through fresh wood load, isolating it from fire until the preheated wood has dropped down into proper burning position. That makes possible to pile up enough wood in the first combustion chamber to gradually feed the fire by gravity for more than 24 hours.
-This draft pattern by preheating and gradually delivering the fresh wood load, prevents it to cool the fire below. Furthermore it allows wood of poor quality to dry up slowly, resulting in a better combustion.
-With this draft pattern, volatile gases from the new fuelwood are also released more slowly for more efficient burning.
WHERE TO FIND THE FILES
https://downdraftdoublebarrelfurnace.wordpress.com/
The project was to build a D.I.Y. wood furnace which would be able to burn efficiently big pieces of wood (up to 1.5 [m]) with an autonomy of 24 hours.
The furnace would also be capable to replace the burner of oil or gaz furnaces and thus, by plugin itself to a industrial water boiler be the first element of the central heating system of a house.
Finally the project would have to be feasible with easy to find material and basic tools.
DESIGN
To fit these requirements, the downdraft design was the best suited. In downdraft combustion systems (also known as reversed combustion or wood gasification systems), the so called primary air enters above the fire but below the main load of wood. It is then drawn down through the glowing bed of coals in the primary combustion chamber, pulling volatile gases with it. Secondary preheated air is introduced under the coals where it can oxidize these superheated flammable gases, resulting in their combustion in the secondary combustion chamber.
In this project I use an electric draft inducer fan, to be able to control the combustion more accurately. Down draft is also possible without draft inducer, but require then an excellent « natural » draft.
ADVANTAGES OF THE DOWNDRAFT DESIGN
This way of burning wood, used by almost all industrial wood and pellet furnaces, has a lot of advantages :
-Complete combustion of wood. By burning the flammable gaz that are normally exhausted in traditional stoves, we can extract up to 40 % more energy from wood. It results also in less pollution, and less clogging of the chimney, as the exhaust gases contain mainly water steam and CO2. It's not a dense smoke full of hydrocarbons anymore. Produces also less ashes !
-This draft pattern prevents heat of fire from rising up through fresh wood load, isolating it from fire until the preheated wood has dropped down into proper burning position. That makes possible to pile up enough wood in the first combustion chamber to gradually feed the fire by gravity for more than 24 hours.
-This draft pattern by preheating and gradually delivering the fresh wood load, prevents it to cool the fire below. Furthermore it allows wood of poor quality to dry up slowly, resulting in a better combustion.
-With this draft pattern, volatile gases from the new fuelwood are also released more slowly for more efficient burning.
WHERE TO FIND THE FILES
https://downdraftdoublebarrelfurnace.wordpress.com/