Fire Safety Science Digital Archive

Theoretical and experimental investigations of explosion parameters of aerosol-vapour mixtures, appearing due to evaporation of pools of heated combustible liquids with high boiling points (diphyl and some other oils) were executed. Experiments were performed in chambers, which had volumes 8 and 42 m³ (measuring of the rate of liquid pool evaporation and sizes of explosion zones) and 10 m³ (aerosol-vapour explosions). Semi-empirical formulas were derived, which described the dependence of rate of evaporation Wev and vertical size of explosion zone Zexp from time and physico-chemical properties of combustible liquids. These formulas are in a good agreement with the experimental results and may be written in the following form: Wev a- Pe •exp b•t>,1,5 1 .!:5me Pe F Tin - To n Zexp C'--- . ( 1 ) -, ( ) 1/2 2 M Pf 11a. To where a, b, c, n - constants; Pe - pressure of the liquid vapour at the initial temperature of the liquid Tin , kPa; t time from the beginning of liquid pool evaporation, s ; me - mass of liquid in the pool, kg; M - molar mass of liquid, g mole -1; Pf - pressure of the liquid vapour at a flash point, kPa; F - area of the pool, m²; ti initial temperature of liquid in the pool, K; ~ the ambient air temperature , K; v2 kinematic viscosity of the air at the temperature of To , m² * s-1 Some series of experiments of aerosol; vapour mixtures explosions in the closed chamber of volume 10 m were executed. The rate of pressure rise during the explosion was low in respect with gaseous mixtures explosions for such substances as methane and propane . The explosion pressure depends on pool area, initial temperature of liquid and time delay of combustion initiation . The effective mass coefficient of vapour participation in explosion which characterizes the mass fraction of aerosol-vapour mixture between lower and upper flammability limits, was close to unity.