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It is well known that hydrogen addition to spark-ignited (SI) engines can reduce exhaust emissions and increase efficiency. Micro plasmatron fuel converters can be used for onboard generation of hydrogen-rich gas by partial oxidation of a wide range of fuels. These plasma-boosted microreformers are compact, rugged, and provide rapid response. With hydrogen supplement to the main fuel, SI engines can run very lean resulting in a large reduction in nitrogen oxides (NOx) emissions relative to stoichiometric combustion without a catalytic converter. This paper presents experimental results from a microplasmatron fuel converter operating under variable oxygen to carbon ratios. Tests have also been carried out to evaluate the effect of the addition of a microplasmatron fuel converter generated gas in a 1995 2.3-L four-cylinder SI production engine. The tests were performed with and without hydrogen-rich gas produced by the plasma boosted fuel converter with gasoline.

A study is carried out here to examine the probable causes for the seemingly contradictory results found in the present-day literature on low-heat-rejection (LHR) engines, provide plausible explanations, and indicate possible directions for future research. Almost all numerical studies predict improved thermal efficiency, increased availability in the exhaust, and reduced in-cylinder heat rejection in the case of LHR engines. The degree of improvement varies considerably from a few percentage points to several, depending on the extent of insulation and whether or not turbocompounding and Rankine bottoming cycle are included. In these simulations, care is taken not to allow the volumetric efficiency to decrease due to higher cylinder temperatures in LHR engines. In addition, air-fuel ratio and, in many instances, peak conditions are maintained constant in both the LHR and conventionally-cooled engines.