NEW UNITED THEORETICAL AND EXPERIMENTAL APPROACH TO THE CALCULATION OF THE DISTRIBUTION OF TOXIC GASES IN CASE OF FIRE IN THE ROOM

Abstract

There are considered two typical schemes of the thermodynamic picture of the fire when burning solid and liquid combustible substances and materials: the combustion process with the use of exhaust ventilation to remove combustion products from small-scale chamber and fire in a full-scale room with a small square of holes or at the initial stage of fire, when through the openings occurs only a displacement of the gaseous environment of the room to the outside. It is presented the analytical dependence for the calculation of the average volume density of toxic gas in the case of the above mentioned schemes of fire development. It is shown that the density does not depend on the properties of the combustible material, the size of the room and exposed surface area of combustible material. Three-zone mathematical model of initial stage of fire in the room is described. Small-scale pilot plant is created for realizing the combustion process with the use of exhaust ventilation to remove products of combustion. The results of calculations of the carbon monoxide density, obtained for full-scale fire using analytical solution of the integral model and zonal mathematical model, are compared with the experimental data. It is shown that the calculations of densities of toxic gases in full-scale room can be performed taking into account only the experimental dependencies of the above mentioned densities from the temperature without using specific coefficients for the release of toxic gases. The accuracy of such calculations is sufficient to solve practical problems. On the basis of obtained results it is suggested a new approach to the calculation of the spread of toxic combustion products during a fire in a full-scale room, which, unlike traditional, is the following: • it is conducted experimental research of combustible material in the proposed small-scale pilot plant with the aim of obtaining dependencies between average volume densities of toxic gases and temperature (up to 70 °C); • dependencies volumetric average temperature (integral model) or volumetric average temperature of under ceiling layer (zonal model) on the time the fire started are calculated, as well as the value of the coefficient of heat losses; • the corresponding average volumetric densities of toxic gases are defined by the corresponding obtained experimental curves using the calculated average volume temperature or average volume temperature of under ceiling layer for each point in time of fire.