Operating Engines on Woodgas

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.

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.

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.