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Analysis of Axial Stratification on SI Engine Performance and Emissions
Published April 28, 1998 by Institution of Mechanical Engineers in United Kingdom
Emissions legislation has renewed interest in the stratified charge SI engine. Much recent work into different ways of configuring charge stratification has been carried out. This paper examines the effect of a specific form of stratification upon NO emissions and performance. The stratification is orientated towards offering part load operation with reduced throttling losses. Towards this aim, a stratification system of two distinct zones is considered. These comprise of a homogeneous, stoichiometric mixture zone and a dilution zone. A phenomenological engine model was used to perform the analysis. Significant insight was thus gained with respect to the differences between the stratified charge engine and the equivalent throttled engine.
The use of EGR as a diluent is considered because of current catalytic limitations. However, the analysis has general relevance, particularly with respect to DI gasoline engines.