FLAME PROPAGATION IN LIQUID FUEL DROPLETS SPRAY

Abstract

Taking into account the significant volumes of liquid fuels consumption in the world fuel balance, one of the most urgent tasks of our time is to reduce the anthropogenic impact on the biosphere by completely or partially replacing mineral fuels with their renewable plant origin analogues. In this paper we present the experimental studies results of the flame propagation process in a one-dimensional set of ethanol droplets with water addition up to 50% by volume. In contrast to studies of processes accompanying the combustion of a single liquid fuel droplet, the combustion of their aggregate, in the form of a jet, has been studied to a lesser extent. The proposed scheme of a jet generator with a vibrating needle makes it possible to obtain a chain of monodisperse fuel droplets with a diameter d=490±5 μm, which is sufficiently stable over time (within 10 min), with the possibility of varying the inter-drop distance. As control parameters for changing this distance, the vibration frequency of the membrane and the value of constant pressure on the reservoir with liquid were used. Using the developed experimental procedure, dependences of the relative distance between the droplets, on the value of constant pressure on the reservoir with liquid fuel, at different monodisperse aerosol generator needle oscillation frequencies were obtained.The whole process of the flame front propagation along the monodisperse aerosol chain was recorded with a frequency of 300 fps. The video capturing results analysis of the flame propagation process made it possible to determine the dependence of flame propagation velocity on the distance between the droplets. A qualitative picture process analysis showed the flame propagation velocity decrease along the inter-droplet distance increase. The critical distance between droplets that is an order of magnitude greater than the droplet size under experimental conditions, at which the flame propagation stopped, was determined experimentally. The obtained results are explained with a sufficient degree of reliability within the framework of the proposed relay flame propagation mechanism within a one-dimensional monodisperse aerosol system.