Of the many ideas being considered to attempt to meet the strict standards dictated by protocols to reduce harmful NOx and PM emissions to the atmosphere is the use of water-in-fuel emulsions (WIFE). The current research addresses the combustion of a spray of droplets that are comprised of two immiscible fluids components viz. water and fuel, with the water being contained within an outer liquid shell of fuel. The fuel and water evaporate sequentially. By strategically placing the fluid with higher volatility and latent heat of vaporization at the core a phenomenon called micro-explosion may be induced (under appropriate operating conditions), in which smaller fuel droplets are produced. Two main benefits accrue to the process of combustion by using WIFE sprays: (a) a reduction in the combustion temperature, thereby reducing harmful emissions, and (b) an increase in fuel efficiency, by creating a second mechanism of atomization.
A model is presented for a one-dimensional laminar premixed flame, propagating into a rich, off-stoichiometric, fresh homogenous mixture of water-in-fuel emulsion spray, with air and inert gas. The two main purposes of this thesis is to investigate the effect of initial water content and total liquid droplet loading on the (a) steady-state velocity of the propagating flame and burnt temperature, and (b) the cellular and pulsating stability limits of such flames. The influence of the micro-explosion of the spray’s droplets on the flame’s characteristics will be highlighted for the first time.