Spray flamelet structures in a tubular counterflow configuration

TL;DR

This study investigates how curvature affects spray flamelet structures in a tubular counterflow setup, revealing significant impacts on evaporation, extinction limits, and extinction mechanisms compared to gas flamelets.

Contribution

It introduces a theoretical extension of the tubular counterflow configuration with droplet injection, analyzing curvature effects on spray flamelet structures and extinction behavior.

Findings

Increasing curvature alters flamelet structures due to evaporation profile changes.

Higher curvature reduces the stretch-induced extinction limit.

Extinction mechanisms in spray flames differ from those in gas flamelets.

Abstract

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.