I have found a very useful slide show on wood gasification. There are 100 slides covering all aspects of wood gas theory, history and operation. No stone left unturned, a recommended read.
Slideshare - Operating Engines on Woodgas
Constructing a blower - continued
The blower has been completed.
First, the end of the drum holding the fans was trimmed and tabbed so that it could accept the other end of the blower enclosure.
A hole was drilled in the drum end so that the wires from the fan could be fed to the outside. The wires are visible just below the bolts holding the fan in place.
The bottom off another 20-litre drum was cut off. This end of the enclosure was measured to provide just enough clearance above the fan.
Two holes were drilled into this part of the enclouse. These holes take tank connectors and act as the gas inlet and outlet.
The two ends of the enclosure were pressed together and the blower tested. The aperture for the gas inlet is a little small. It will enlarged when the rest of the gasifier is built.
Constructing the blower has given rise to some ideas for its integration into the gasifier so they will now be investigated.
First, the end of the drum holding the fans was trimmed and tabbed so that it could accept the other end of the blower enclosure.
A hole was drilled in the drum end so that the wires from the fan could be fed to the outside. The wires are visible just below the bolts holding the fan in place.
The bottom off another 20-litre drum was cut off. This end of the enclosure was measured to provide just enough clearance above the fan.
Two holes were drilled into this part of the enclouse. These holes take tank connectors and act as the gas inlet and outlet.The two ends of the enclosure were pressed together and the blower tested. The aperture for the gas inlet is a little small. It will enlarged when the rest of the gasifier is built.
Constructing the blower has given rise to some ideas for its integration into the gasifier so they will now be investigated.
Constructing a blower
This is a work in progress and will be appended to the No-Weld Gasifier instructions in due course.
A blower is important in gasifier manufacturer, either for blowing air in or drawing wood gas out.
In the case of a downdraught gasifier, the blower is used in place of an engine to draw wood gas out of the gasifier until the gas is of sufficient quality for the engine to be started.
As part of the no-weld ethos, a blower has been constructed from scrap. In this case a car air-conditioner fan and vegetable oil drums were used.
In the first photograph we see a typical car fan.
The intention is to build a metal casing around the fan. Gas can then be drawn via an inlet pipe and forced out by the fan through an outlet pipe to a flare. At the flare the gas can be bunt to determine its quality. To facilitate the construction of the blower the two halves of the fan casing were prized apart so that the fan could be bolted into the blower housing.
The "squirrel cage" of the fan can clearly be seen. At the rear is the motor and other end of the rotor shaft. This shaft would rub off the intended metal casing so the assembly had to be held clear.
In the next photo you can just about make out a sandwich of plywood which holds the fan proud of the metal drum. The fan was bolted to the drum through the plywood sandwich.
Exact details for attaching the fan to the drum will not be given as every car fan is different. It will be necessary for the builder to discover the best way for themselves.
The next stage of construction is to fit the other half of the drum and then attach the inlet and outlet pipes. The blower can then be tested to determine its suitability.
A blower is important in gasifier manufacturer, either for blowing air in or drawing wood gas out.
In the case of a downdraught gasifier, the blower is used in place of an engine to draw wood gas out of the gasifier until the gas is of sufficient quality for the engine to be started.
As part of the no-weld ethos, a blower has been constructed from scrap. In this case a car air-conditioner fan and vegetable oil drums were used.
In the first photograph we see a typical car fan.
The intention is to build a metal casing around the fan. Gas can then be drawn via an inlet pipe and forced out by the fan through an outlet pipe to a flare. At the flare the gas can be bunt to determine its quality. To facilitate the construction of the blower the two halves of the fan casing were prized apart so that the fan could be bolted into the blower housing.
The "squirrel cage" of the fan can clearly be seen. At the rear is the motor and other end of the rotor shaft. This shaft would rub off the intended metal casing so the assembly had to be held clear.In the next photo you can just about make out a sandwich of plywood which holds the fan proud of the metal drum. The fan was bolted to the drum through the plywood sandwich.
Exact details for attaching the fan to the drum will not be given as every car fan is different. It will be necessary for the builder to discover the best way for themselves.
The next stage of construction is to fit the other half of the drum and then attach the inlet and outlet pipes. The blower can then be tested to determine its suitability.
MIDGE stove update
This article details changes we made to the original MIDGE stove. When building a wood gasifier, care must always be taken to prevent air from entering from where it should. If air is permitted to enter from anywhere other than where it should then the gasifier will not operate properly and can even explode under certain circumstances.
When first built, the combustion chamber rested precariously on four bolts attached to the outer chamber.
The weight of the combustion chamber pushed down on the bolts and allowed a sizeable air gap to appear between the top of the combustion chamber and the top lid. This gap allowed cold air to get to the secondary air holes from the top rather than entering through the primary air holes at the bottom.
To remedy this problem the hole on cowling lid was widened by cutting small tabs around the circumference of the hole so that the hole the combustion chamber could just pass through. The tabs were then folded back onto combustion chamber to lock it in place.
The area around the tabs was then sealed with fire cement to ensure there were no air gaps, as can be seen in the following photo.
Not only did this reduce the air gap but also meant that the supporting bolts could be removed from under the combustion chamber as the cowling lid now supported the combustion chamber.
Another test firing was performed. The air throughput was much enhanced resulting in much higher temperatures being read.
In the following photo we see a burn with a stove pipe on top of the stove, which increases the air throughput.
The draught was such that red hot particles of ash were ejected from the combustion chamber. A draught control that changes the size of the primary air intake may be needed. The very bright colour of the combustion shows great heat being generated. Small jets of gas can be seen emanating at the perimeter where the secondary air holes meet the wood gas.
When first built, the combustion chamber rested precariously on four bolts attached to the outer chamber.
The weight of the combustion chamber pushed down on the bolts and allowed a sizeable air gap to appear between the top of the combustion chamber and the top lid. This gap allowed cold air to get to the secondary air holes from the top rather than entering through the primary air holes at the bottom.
To remedy this problem the hole on cowling lid was widened by cutting small tabs around the circumference of the hole so that the hole the combustion chamber could just pass through. The tabs were then folded back onto combustion chamber to lock it in place.
The area around the tabs was then sealed with fire cement to ensure there were no air gaps, as can be seen in the following photo.
Not only did this reduce the air gap but also meant that the supporting bolts could be removed from under the combustion chamber as the cowling lid now supported the combustion chamber.Another test firing was performed. The air throughput was much enhanced resulting in much higher temperatures being read.
In the following photo we see a burn with a stove pipe on top of the stove, which increases the air throughput.
The draught was such that red hot particles of ash were ejected from the combustion chamber. A draught control that changes the size of the primary air intake may be needed. The very bright colour of the combustion shows great heat being generated. Small jets of gas can be seen emanating at the perimeter where the secondary air holes meet the wood gas.
Commercial MIDGE stoves are a waste of money
Not only are commercial MIDGE stoves a waste of money but they also go against the spirit of wood gasification. Self-reliance is the key to wood gasification, the ability to provide for yourself and for others in times of hardship.
If there was an energy crisis then popping down to the shop for a MIDGE stove is not an option. There won't be any. Nor will there be an Internet for you to purchase one on either.
Another reason for not buying a commercial MIDGE stove is that for some reason they come with an integral battery operated fan to produce a stronger draught. The battery operated fan also goes against the spirit of wood gasification. Where are you going to get batteries from in an emergency?
A well-built gasifier simply doesn't need a forced draught. I have boiled water and cooked meals on my MIDGE stove. That is all they are meant to do and a handmade one does the job perfectly.
Read the plans. Find some cans. Make gas!
MIDGE stove plans - The Complete MIDGE (pdf)
If there was an energy crisis then popping down to the shop for a MIDGE stove is not an option. There won't be any. Nor will there be an Internet for you to purchase one on either.
Another reason for not buying a commercial MIDGE stove is that for some reason they come with an integral battery operated fan to produce a stronger draught. The battery operated fan also goes against the spirit of wood gasification. Where are you going to get batteries from in an emergency?
A well-built gasifier simply doesn't need a forced draught. I have boiled water and cooked meals on my MIDGE stove. That is all they are meant to do and a handmade one does the job perfectly.
Read the plans. Find some cans. Make gas!
MIDGE stove plans - The Complete MIDGE (pdf)
No-weld downdraught gasifier #3
In this section we complete the combustion tube inside the combustion chamber. Then we marry the combustion chamber to its shroud.
You will remember that we had introduced the combustion tube into the hole at the bottom of combustion chamber. Tabs were cut to hold the tube in place.
After checking that the tube has an idea fit we remove it. Four holes are drilled into the side walls of the combustion tube. These holes will take a bolt each so that they take the weight of the tube.
Next, a restraining band is made from a thin strip of steel (such as was leftover when cutting the 20-litre drum. Four holes are drilled into this band so that it can be held in place by the four bolts on the side wall of the combustion tube.
Holes are drilled into the bottom, closed end, of the combustion tube. This allows ash to fall out of the tube.
A disk of metal sheet is cut and entered into the combustion tube. It rests upon the bolt heads and acts as a throat inside the combustion tube. A hole (or holes) will be cut into this to allow char to fall into the combustion tube.
The combustion tube is placed back into the combustion chamber such that the tabs holding the tube in place are caught between the tube and the restraining band. This band holds the combustion tube firmly in place.
The combustion chamber was turned upside-down and the gap between the combustion tube and chamber sealed to prevent air from bypassing the char.
Here we can see the combustion tube sitting on top of the shroud we made in section #1. On top of the combustion chamber sits a hopper. Details of the hopper will be given in section #4.
No-weld gasifier sections:
#1 - Introduction - materials and tools, building the combustion chamber shroud
#2 - Building the combustion chamber
#3 - Completing the combustion tube
You will remember that we had introduced the combustion tube into the hole at the bottom of combustion chamber. Tabs were cut to hold the tube in place.
After checking that the tube has an idea fit we remove it. Four holes are drilled into the side walls of the combustion tube. These holes will take a bolt each so that they take the weight of the tube.
Next, a restraining band is made from a thin strip of steel (such as was leftover when cutting the 20-litre drum. Four holes are drilled into this band so that it can be held in place by the four bolts on the side wall of the combustion tube.
Holes are drilled into the bottom, closed end, of the combustion tube. This allows ash to fall out of the tube.
A disk of metal sheet is cut and entered into the combustion tube. It rests upon the bolt heads and acts as a throat inside the combustion tube. A hole (or holes) will be cut into this to allow char to fall into the combustion tube.
The combustion tube is placed back into the combustion chamber such that the tabs holding the tube in place are caught between the tube and the restraining band. This band holds the combustion tube firmly in place.
The combustion chamber was turned upside-down and the gap between the combustion tube and chamber sealed to prevent air from bypassing the char.
Here we can see the combustion tube sitting on top of the shroud we made in section #1. On top of the combustion chamber sits a hopper. Details of the hopper will be given in section #4.
No-weld gasifier sections:
#1 - Introduction - materials and tools, building the combustion chamber shroud
#2 - Building the combustion chamber
#3 - Completing the combustion tube
No-weld downdraught gasifier #2
In this section we detail the construction of the combustion chamber. This is where air from the outside meets hot char to form wood gas.
The combustion chamber is made from two ends of a 20-litre vegetable oil drum. A whole drum is too big so we just cut off what is needed from either end and then join the two ends together.
In the following photo we can see an old drum being cut with tin snips. Drill a hole (using a low setting on your drill) in the side of the drum so that the tin snips can be inserted into the drum wall. I won't give dimensions here. It is up to you to decide what sizes you need depending on what tins and drums you have available. Read the whole of this article before starting work.
Here we can see the two ends of the drum. Keep the strip of metal between the two ends as that will come in useful later.
The bottom end of the drum has tabs cut into its wall section. This allows the top end of the drum to be pushed over the tabs and locked in place.
Now, a hole is cut into the bottom of the drum. The hole has a diameter about 2 centimetres smaller than your chosen combustion tube.
Here we see the completed hole. The hole doesn't have to be accurate, just smaller than the combustion tube. You then cut tabs so that they can be bent up and cling to the combustion tube. This will help hold the tube in place.
Here we see the tabs bent up and clasping the inserted combustion tube. The tube is a tin of about 15 cm diameter with one end open and the other closed.
In the next section we will complete the combustion tube and show the combustion chamber and shroud joined together.
No-weld gasifier sections:
#1 - Introduction - materials and tools, building the combustion chamber shroud
#2 - Building the combustion chamber
The combustion chamber is made from two ends of a 20-litre vegetable oil drum. A whole drum is too big so we just cut off what is needed from either end and then join the two ends together.
In the following photo we can see an old drum being cut with tin snips. Drill a hole (using a low setting on your drill) in the side of the drum so that the tin snips can be inserted into the drum wall. I won't give dimensions here. It is up to you to decide what sizes you need depending on what tins and drums you have available. Read the whole of this article before starting work.
Here we can see the two ends of the drum. Keep the strip of metal between the two ends as that will come in useful later.
The bottom end of the drum has tabs cut into its wall section. This allows the top end of the drum to be pushed over the tabs and locked in place.
Now, a hole is cut into the bottom of the drum. The hole has a diameter about 2 centimetres smaller than your chosen combustion tube.
Here we see the completed hole. The hole doesn't have to be accurate, just smaller than the combustion tube. You then cut tabs so that they can be bent up and cling to the combustion tube. This will help hold the tube in place.
Here we see the tabs bent up and clasping the inserted combustion tube. The tube is a tin of about 15 cm diameter with one end open and the other closed.
In the next section we will complete the combustion tube and show the combustion chamber and shroud joined together.No-weld gasifier sections:
#1 - Introduction - materials and tools, building the combustion chamber shroud
#2 - Building the combustion chamber
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