Analysis of a spray diffusion flame and its extinction in a shear layer

Abstract

A new semi-analytical solution for a laminar spray diffusion flame in the shear layer between fuel and oxidant streams is developed. The Stokes number is identified as a small spray droplet-related parameter to be used in a perturbation analysis of the liquid phase governing equations. Appropriate specification of an additional parameter ensures that similarity is achieved so that the concentration field of the liquid in the spray can be readily found. The coupled gas-phase equations are treated using the usual inverse of the large Zeldovitch number for the asymptotic analysis. Numerical results demonstrate how the distribution of the liquid phase in the developing shear layer between two unidirectional gas streams flowing over one another with (the possibility of) dissimilar velocities in their respective free-streams influences the flame shape, location, fuel vapour and temperature fields. An extinction analysis enables a parametric mapping of conditions for extinguishment of the spray diffusion flames to be drawn.

Keywords:

• shear layer
• diffusion flame
• spray

Acknowledgements

JBG acknowledges the support of the Lady Davis Chair in Aerospace Engineering, the Technion Fund for the Promotion of Research and the US–Israel Binational Science Foundation. Thanks are also due to Rony Hachmon and Yonit Mindelis for their dedicated technical assistance.