Stoichiometric model of forced ignition of flammable liquids and their binary mixtures

Controlling the characteristics of stable combustion and emissions during the combustion of alternative liquid fuels, reducing the carbon index is achieved through the use of oxygen- containing alcohols and hydrogen-containing substances (hydrogen, ammonia, water) as admixtures. The critical temperatures of forced ignition and spontaneous ignition of liquid fuels are important characteristics of stable flame combustion, which depend on the composition of the liquid and the oxygen-nitrogen gas mixture. This paper addresses the urgent issues of finding the temperature of spontaneous ignition of combustible liquids and their mixtures in an oxygen-nitrogen gas environment with a temperature lower than the temperature of liquids as a result of short-term exposure of the liquid surface to a pilot flame (thermal ignition source). After the ignition source is removed from the droplet surface, the droplet continues to burn steadily. The model is based on the assumption that at liquid temperatures lower than the ignition temperature, the oxygen content in the saturated layer is much higher and the combustible vapours are less than the stoichiometric composition according to the chemical reaction equation. At the same time, the necessary condition for ignition is fulfilled − the self-acceleration of the exothermic reaction rate. As a result of heating and evaporation in a saturated gas layer at the ignition temperature, the concentrations of the components reach equivalent values, and the initial increase in the temperature of the gas layer leads to a stable burning of the droplet with its own diffusion flame Little attention is paid to the ignition temperature of liquids. There are very few experimental values. However, there is a Jones model, which is the basis for most of the works. We have obtained analytical dependences of the ignition temperature for individual liquids, their aqueous solutions, and binary solutions of two flammable substances. These dependences are in satisfactory agreement with the available experimental data.