Исследование динамики выравнивания воздушного давления в замкнутой системе отсеков для оценки параметров развития пожара

Abstract

Introduction. The compartments of a ship or submarine are a closed system in which the development of fire parameters can be assessed and predicted by monitoring the gas pressure and the rate of its change. However, the question of the effect on the accuracy of such estimates of the process of gas flowing from the emergency compartment to adjacent ones in the presence of hole between them, that is, in conditions of incomplete sealing of the emergency compartment, remains unclear. Aims and purposes. The goal of the study is to develop a model of the process of air flowing through a hole in a closed system of two compartments with a certain initial pressure drop, as well as computational methods for estimating the pressure equalization time and the minimum (critical) area of the hole between the compartments, at which the equalization process occurs almost instantly. Methods. To estimate the rate of gas flow between compartments, it has been proposed to use the equation of the adiabatic outflow of gas from a large volume with some initial overpressure through the hole, obtained on the basis of the transformation of the Bernoulli equation. The equation has been transformed taking into account the fact that the density of the flowing gas is approximately the same at all sections of the outflow process. This assumption is justified by the fact that during a fire in a closed volume, an increase in excess pressure occurs not due to an increase in the density of the medium, but as a result of an increase in its temperature. Results and discussion. As a result, a new differential equation has been obtained, the integration of which made it possible to obtain an analytical expression for calculating the pressure equalization time depending on the initial pressure drop, the area of the hole and the volumes of the compartments. All other things being equal, the dependence of the alignment time on the ratio between the volumes of the compartments is parabolic, reaching a maximum when these volumes are equal to each other. The gas flow model and the resulting equations have been verified and confirmed experimentally. The relative error does not exceed 20 %. Conclusions. The developed model and the equations obtained at the same time allowed us to propose a methodology and calculation formulas for estimating the critical value of the opening area between compartments, at which the equalization time is negligible, and there is no need to control the air pressure in each of the adjacent compartments, for example, to diagnose the parameters of fire development. Keywords: closed system of adjacent compartments, gas flow through the hole, pressure equalization time, critical area of the overflow hole.