A Model Description of the Effects of Variable Fuel-Air Mixture Composition on Turbulent Flame Propagation

摘要: Stratified direct-injection spark-ignition engines feature a fuel-air mixing field characterized by large spatio-temporal variations of the mean mixture composition, \( \tilde{Z}({{x}_{i}},t) \), as well regions with significant statistical fluctuations around \tilde{Z} \). Modifications to Coherent Flame Model (CFM) are proposed in present study account for effects variable strength on primary premixed flame, downstream formation secondary non-premixed reaction zone. Compared previous work, domain validity modifications is extended case combustion occurences flame extinction. The modeling strategy based results from direct numerical simulations theoretical analysis simplified problem due Kolmogorov, Petrovskii and Piskunov (KPP). KPP corresponds one-dimensional, turbulent propagating steadily into frozen turbulence distribution, provides convenient framework test modified CFM model. In this but somewhat generic configuration, following trends predicted: small strength, i.e. absence extinction, partial premixing has net negative (positive) impact speed, s T , mixtures close stoichiometry (close flammability limits); presence increased levels burning.