Analytical characterization of the divided-chamber combustion process

Abstract

Theoretical analysis of the divided-chamber, two-stage combustion process has demonstrated the effect of several design and operating variables on engine-exhaust emissions. The divided combustion-chamber design, which has been described in several recent publications, produces a timed staging of the combustion process. The basis for pollutant reduction is division of the combustion space into two regions, a primary chamber to which a fuel—air mixture is supplied and a secondary chamber containing only air. Combustion products issuing from the primary chamber into the secondary chamber are quenched by the low-temperature secondary air with consequent suppression of nitric oxide formation reactions. The present work has involved digital computer analysis of the divided-chamber-combustionprocess. The analysis has been based on a two-system thermodynamic model in which the primary and secondary chambers are represented as separate thermodynamic systems coupled by mutual mass flow. Stepwise solution of the time-dependent mass- and energy-conservation equations together with associated gasdynamic and chemical rate equations yields the histories of primary and secondary chamber thermodynamic properties and chemical compositions. The results demonstrate major effects of relative primary chamber volume and of dividing orifice area on exhaust emission of nitric oxide.