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One scenario for reducing engine out NOx in a spark ignition engine is to introduce small amounts of supplemental hydrogen to the combustion process. The supplemental hydrogen enables a gasoline engine to run lean where NOx emissions are significantly reduced and engine efficiency is increased relative to stoichiometric operation. This paper reports on a mass and energy balance model that has been developed to evaluate the overall system efficiencies of a thermal reformer-heat exchanger system capable of delivering hydrogen to the air intake of a gasoline engine. The mass and energy balance model is utilized to evaluate the conditions where energy losses associated with fuel reformation may be offset by increases in engine efficiencies.

Compact plasmatron devices can provide important new possibilities for reducing engine pollution, making use of alternative fuels and increasing the engine efficiency. These improvements involve the use of the plasmatron as a compact, rugged, rapid response and highly flexible means of converting a wide range of hydrocarbon fuels into hydrogen rich gas onboard a vehicle. Opportunities for engine operation with a greater variety of fuels and fuel combinations could be significantly increased by use of plasmatron devices. In addition to the capability of using alternative fuels, large reductions in pollutant emissions from SI engines are possible. Very lean operation, by hydrogen addition to the main fuel, can reduce NOx production by large factor relative to stoichiometric combustion without a catalytic converter, and provide a reduction of more than a factor of ten relative to operation with a three way catalytic converter at stoichiometric air to fuel ratios.