FLOODED JET OF SELF-FOAMING GAS-AEROSOL FOAM WHEN EXTINGUISHING PETROLEUM PRODUCT FIRES IN TANKS BY SUB-LAYER METHOD

Abstract

Тушение пожаров нефтепродуктов в резервуарах с использованием технологии получения самовспенивающейся газоаэрозоленаполненной пены и подачей ее в слой горючего является наиболее перспективным направлением. В статье проанализированы методы расчета осевой скорости турбулентной затопленной струи в жидкости. Эти методы базируются на решении уравнений Навье-Стокса с привлечением экспериментальных данных. Выполнен расчет осевой скорости струи по разным формулам и для различных уровней взлива нефтепродуктов. Получена хорошая сходимость результатов расчетов и экспериментальных данных. Under-layer extinguishing of petroleum product fires in tanks is widely used in practice, but has a number of significant drawbacks – dissolution of foam in alcohol-containing fuels, failure to penetrate the water cushion and strongly heated layer of fuel. A new extinguishing technology using the technology of self-foaming gas-aerosol foam (SGF) allows to overcome the noted disadvantages of the classical method of under-layer extinguishing. According to this technology, the foam is supplied in the form of a flooded turbulent jet, flowing from a pipe in the base of the tank. The maximum height of the tank, according to modern standards, is 18 meters. The question arises as to what parameters a turbulent flood jet will penetrate the oil product layer and spread over the surface of the tank mirror. The motion of a flooded turbulent jet in a liquid is described by a system of Navier-Stokes equations. This system can be solved analytically with some assumptions or numerically. When solving this problem, some coefficients appear, which, as a rule, are determined experimentally. In this article, various approaches to solving the Navier-Stokes equations for determining the axial velocity of a turbulent flooded jet are considered in the axisymmetric formulation. Calculation formulas and values of empirical constants are determined. The calculation of velocity values on the axis of turbulent flooded jet has been carried out for values of its initial velocity U0 = 35 m ∙ s–1 and pipe diameter D0 = 0,159 m, through which the stream flows out. The values of these parameters are realized in practice in the installation “Uragan”, which implements the technology of obtaining SGF. The calculation results were compared with the data obtained in natural experiments, their good agreement was obtained. As a result, it has been experimentally and computationally proved that the new technology of sub-layer fire extinguishing of SGF is effective.