In this work, spray flamelet structures subject to curvature are systematically studied, emphasizing the ways in which this quantity modifies the budgets of the corresponding flamelet equations and their stretch-induced extinction limit. More specifically, a theoretical extension of the tubular counterflow configuration is first proposed, which allows the injection of droplets from the inner cylinder. After appropriate mathematical descriptions for this new configuration in physical and composition space are introduced, several ethanol/air tubular counterflow flames are studied. It is found that increasing curvature leads to major modifications of the resulting flamelet structures, which is attributable to its influence on the evaporation profiles. Further, it is found that increasing curvature considerably reduces the stretch-induced extinction limit, which can be directly related to a corresponding reduction of the maximum mixture fraction within the flamelet. Finally, it is concluded that extinction in tubular counterflow spray flames occurs through a mechanism significantly different from what has been previously observed for gas flamelets. Novelty and Significance Statement A theoretical extension of the classical gas tubular counterflow configuration is proposed, which allowed systematically studying curvature effects on spray flamelet structures for the first time. Mathematical models currently available in the literature, both in physical and mixture fraction space, are extended accordingly and used to analyze different flamelet structures. It was found that spray flamelet structures are considerably more sensitive to curvature than their gaseous counterpart, which can be attributed to the explicit effect of this quantity on the evaporation profiles. Additionally, a new extinction mechanism is identified, which considerably differs from what has been previously observed for gas flamelets.
Rivadeneira et al. (Tue,) studied this question.