Combustion Characteristics of Small Spark Ignition Engines Using Hydrogen Supplemented Fuel Mixtures

Small industrial type spark ignition engines are generally designed to operate on rich fuel-air mixtures. Although improvement in fuel economy can be expected with lean mixtures problems associated with such mixture operation prohibit the use of too lean mixtures in these engines. However, it is possible to achieve satisfactory engine performance when small amount of fuel having very lean flammability limit is added to lean gasoline-air mixture. Since hydrogen has wide flammability limits, an experimental study was conducted to study engine performance and combustion characteristics of hydrogen supplemented mixtures in a small spark ignition engine.

The results of the study showed: 1) flame speeds with hydrogen supplemented mixture were higher particularly in lean mixture region, 2) the engine could be run on lean air-fuel ratios where operation without hydrogen supplementation was not possible. There was overall increase in engine efficiency and reduction in cyclic pressure variations.