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The addition of hydrogen to the gasoline-air mixture may contribute significantly towards accelerating the combustion process, with the beneficial effects on engine performance and emissions. The present contribution describes the results of an experimental research where gasoline-air mixture was enriched with a Hydrogen Rich Gas (HRG) produced by the electrical dissociation of water. The HRG analysis shows the presence of hydrogen and oxygen together with some additional species. Experiments were carried out at engine light and partial load. Detailed results of the measurements are shown, namely engine torque and efficiency, exhaust emissions, cyclic variability, heat release rates and combustion duration. The possibilities of improving engine performance and emissions in correlation with the amount of HRG, the equivalence ratio and the engine operating condition are thus outlined.

A LPG fuelled, spark ignition engine for heavy duty vehicles has been developed from a Diesel DI engine which is currently in production. The development concept was based on the targets of obtaining output performances by LPG fuelling comparable with those of the original Diesel engine under full load conditions to be achieved with relatively simple technologies. A conventional mixer system with closed-loop control was consequently used for the LPG fuel supply system, operating at λ = 1.0. A systematic optimization was applied in the areas of the compression ratio, combustion chamber configuration, intake swirl ratio and plenum configuration, spark timing, in view of reaching high output performances and knock phenomena control. The results of optimization were higher torque and equal fuel conversion efficiency (at full load) in comparison with the original Diesel version of the engine.

The strategy of using hydrogen as an additive fuel for the diesel engine to improve exhaust emissions and combustion efficiency has been explored by many researchers in the last decade. The effects of pure hydrogen or the hydrogen-oxygen mixture generated by water electrolysis fueling car or heavy-duty diesel engines were studied, with notably different results. In the present work the supplementary fuel used was the gas produced by the water electrolysis process in a reactor with a special electrode design. Hydrogen-oxygen mixture or pure hydrogen was inducted with air in the engine intake manifold. Performance and emissions characteristics of a 3.6 liters tractor engine, naturally aspirated, were investigated for different operating conditions with gas substitution of diesel fuel up to 12% on energy basis.