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Experiments have been conducted on a gas fueled spark ignition engine using natural gas and two hydrogen containing fuels. The hydrogen containing fuels are Reformulated Natural Gas (RNG) and a mixture of 50% (Vol.) natural gas and 50% (Vol.) producer gas. The producer gas is a synthetic gas with the same composition as a gas produced by gasification of biomass. The hydrocarbon emission, measured as the percentage of hydrocarbons in the fuel, which passes unburned through the engine, was for the mixture of natural gas and producer gas up to 50% lower than the UHC emissions using natural gas as fuel. The UHC emission from the experiments using reformulated natural gas was 15% lower at lean conditions. Furthermore, both hydrogen-containing fuels have a leaner lean burn limit than natural gas. The combustion processes from the experiments have been analyzed using a three-zone heat release model, which is taking the effect of crevices into account.

Engine experiments with a 0.964 l. DI diesel engine have been carried out applying mixtures of diesel and bitumen as fuel. These investigations showed that there is an increase in emissions of CO, NOx, PM1 and SOF2 as the share of bitumen in the fuel increases. Sampled PM from the exhaust gas from a 0.296 ltr. DI diesel engine was analysed for its contents of 16 specific PAH-compounds. The results showed that the emission of PAH in the exhaust gas was significantly lower for mixtures of bitumen/diesel than for mixtures of heavy-fuel-oil/diesel. Seven different components where detected. Analysis of soot deposits from the combustion chamber and of the crank case lubricant concerning magnesium, vanadium and nickel have been carried out. The results showed that 2-5% of the amount of metals in the injected fuel could be found in the engine lubricant. Only a small amount of magnesium and vanadium was detected in the soot.