Linear stability analysis of laminar premixed water-in-fuel emulsion spray flames

This paper considers the stability of a laminar water-in-fuel spray premixed flame. The droplets of the spray are comprised of two immiscible components viz. water and fuel, with the water being contained within an outer liquid shell of fuel. The fuel and water evaporate sequentially. Due to its relatively large latent heat of vaporization the water vapor acts to cool the flame that is sustained by prior release of fuel vapor. To simplify the inherent complexity that characterizes the analytic solution of multi-phase combustion processes, the analysis is restricted to fuel-rich laminar premixed water-in-fuel flames, and assumes a single-step global chemical reaction mechanism. Steady-state solutions are obtained and the sensitivity of the flame temperature and the flame propagating velocity to the initial water content of the emulsion droplets is established. The linear stability analysis revealed an increased proneness to cellular instability induced by the presence of increased water content of the emulsion droplets. A similar effect was noted for the neutral pulsating stability boundaries.