[Gasification] water gas and IC Engine exhaust gas temperatures

[Ken Boak]

Dan, Jeff, Jonathan & List,

Diesel engines burn a variable amount of fuel oil, within a fixed volume of
atmospheric air.

At low power, with little fuel injected, there is signifcant excess air,
contained in the exhaust, and even at full power the fuel/air ratio is about
50% of stoiciometric.

Running at low speed (325rpm)  the engine draws in  14m3 of air per hour,
and consumes 0.46kg of vegetable oil fuel.
Taking the density of air (sea level , 20 C) to be 1.2 kg/m3 the air to fuel
ratio is  36.5:1

In another full load test (650rpm) the fuel consumption was 1.2kg,  with
28m3 of air being inducted.  The air fuel ratio is lowered to   28:1, and
with a notable rise in the exhaust gas temperature.

Some texts suggest that the stoichiometric air fuel ratio for complete
combustion of this type of oil is around 14:1, so even at full load,  half
of the air drawn into the engine is not being used in the combustion of the
fuel, which makes it available for providing the oxygen required for the
exothermic charcoal bed in the gasifier.
If  half of the oxygen content has been consumed in the engine, and
converted to CO and CO2, then does this imply that the exhaust gases still
contain around 10% O2 ?

The next tests to perform are whether the exhaust of the diesel engine will
not only torrefy but support exothermic combustion of woodchips.

My investigations have been based on the single cylinder, slow speed Lister
6hp engine, still being volume manufactured in India.

The goal is to effectively couple this engine to a wood chip gasifier, for
reliable, domestic scaled combined heat and power.  About 3kW of electrical
power and 6kWh of heat are the expected outputs of the system.


Ken