Possibilities of using producer gas with different types of engines
Spark ignition engines, normally used with petrol-or kerosene, can be run on producer gas alone. Diesel engines can be converted to full producer gas operation by lowering the compression ratio and the installation of a spark ignition system. Another possibility is to run a normal unconverted diesel engine in a "dual fuel" mode, whereby the engine draws anything between 0 and 90 per cent of its power output from producer gas (17), the remaining diesel oil being necessary for ignition of the combustible gas/air mixture. The advantage of the latter system lies in its flexibility: in case of malfunctioning of the gasifier or lack of biomass fuel, an immediate change to full diesel operation is generally possible.
However, not all types of diesel engines can be converted to the above mode of operation. Compression ratios of ante-chamber and turbulence chamber diesel engines are too high for satisfactory dual fuel operation and use of producer gas in those engines leads to knocking caused by too high pressures combined with delayed ignition (20). Direct injection diesel engines have lower compression ratios and can generally be successfully converted.