HCCI combustion: Effect of NO in EGR
Résumé
Experiments were performed for the oxidation of mixtures of n-heptane and iso-octane and of n-heptane and toluene in a jet-stirred reactor (JSR) under dilute conditions, at 10 atm. The effect of the addition of variable initial NO concentration was also studied. A detailed kinetic model was performed to rationalize the results. Experiments were also performed using a homogeneous charge compression ignition (HCCI) engine to characterize the effect of exhaust gas recirculation (EGR) rates (from 0% to 50%) with NO addition (from 0 to 500 ppmv) on ignition delays at low and high temperatures for an equivalence ratio of 0.3 and a constant intake temperature of 350 K. Two surrogate automotive fuels (n-heptane/iso-octane, n-heptane/toluene) were used and compared to the pure n-heptane case. Zero-dimensional single zone modeling was also performed using the detailed kinetic scheme and compared to the experimental results in terms of cool and principal flames ignition delays, phasing time and also the importance of the cool flame combustion heat release in comparison to the main one.