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AbstractCarbon monoxide is suitable fuel for gasoline engines. The output power is about 50%
of that generated with gasoline fuel.
Carbon monoxide can also be used in direct injection diesel engines. However a small
amount of diesel oil is needed to ignite the mixture. The output power is about 75% of
that generated with diesel fuel. Important facts to be noted when selecting the engine are
the following:
Carbon monoxide is not suitable fuel for diesel engines with precombustion chamber;
only direct injection diesel engines and gasoline engines qualify.
When driving a vehicle equipped with a wood gas system the changes in required power
output must be noted in advance: start of driving must be done slowly and hills must be
climbed using a low gear. The idling speed is high, often more than 1400 r/min. Gas
production is not even all the time and the speed of the engine can vary up to 20%. The
system works best when the engine speed stays the same all the time. The driver must
control the mixture and move the hearth every now and then to make the generator work
properly.
The equipment is very hot and it must not be touched. Typical temperatures in the system
are the following:
The quality of the gas generated depends on the type of fuel used. Chopped firewood and
large sized wood chips provide a reliable process but the power output is less than that
with small sized wood chips. Small sized wood chips generate great amounts of gas with
good quality but malfunctions can occur easily and special arrangements are needed to
prevent the hearth from clogging and arch forming in combustion chamber. Other fuels,
for example pellets made of sod or straw, can possibly generate gas with very good
quality but a lot of ash is produced and it melts in relatively low temperature which can
cause problems.
The fuel consumption depends on the required power output, size of the wood particles,
moisture content of the fuel and dimensions of the generator.
The drier the fuel is the better it suits the gas generating process. Totally dry wood is not
possible to use in practice and therefore the equipment is designed to use wood with a
moisture content of 10 - 20%. Even fuel with a moisture content of 30% burns but the
power output is decreased and risk of arch formation is high. Temperature in the
combustion chamber is lower and the gas contains tar which makes the inlet valves of
the engine to stick. A gas generator that uses wood chips as the fuel needs a movable
hearth. This can be constructed using for example a windshield wiper motor. The
smaller the size of the wood chips, the more ash and charcoal dust is produced. The
hearth must move vertically to keep the charcoal layer loose, suction resistance low and
impurity content in the gas low.
The gas generating equipment is simple and can be easily manufactured using common
tools and materials. The only special material is the woven glass fabric used in the gas
filter. When steel with good quality is used the lifetime of the parts is longer.
The given dimensions must be used when building the generator. The most critical
dimensions are:
The other dimensions are not critical.
When installing the equipment on a vehicle the generator should be installed as close to the engine as possible to keep the suction resistance as low as possible. The generator and other equipment must be installed so that the visibility is reasonable.
Translated by Olli.
