EXPERIMENTAL STUDIES OF THE RELATIONSHIP BETWEEN THE BOILING TEMPERATURE AND THE FLASH TEMPERATURE OF MIXED HYDROCARBON FUELS

В работе экспериментально показано, что по мере испарения смесевой горючей жидкости при одновременном повышении плотности и снижении упругости пара в многокомпонентных взаиморастворимых композициях температура кипения повышается. В этом случае и температура вспышки смесевой горючей жидкости также будет повышаться. Так, при проливах горючих жидкостей происходит довольно быстрое обеднение легкими фракциями, упругость пара при заданной температуре существенно снижается, а температуры кипения и вспышки, соответственно, повышаются. Полученные в работе зависимости температур кипения и вспышки испытанных смесевых горючих жидкостей характерны и для других различных многокомпонентных жидких композиций. Эти зависимости могут учитываться при разработке планов предотвращения и ликвидации аварий в случае их проливов. Based on the experiments it is shown that as the flammable liquid mixtures evaporate, while increasing density and decreasing vapor tension in multicomponent compositions-soluble, the boiling temperature increases. In this case, the flash point of the mixed combustible liquid will also increase. Thus, in the case of spills of flammable liquids there is a fairly rapid depletion of light fractions, the vapor tension at a given temperature reduces significantly, and the boiling and flash temperatures increase accordingly. The dependences of the boiling and flash temperatures of the tested mixed combustible liquids obtained in this work are also typical for other various multicomponent liquid compositions. These dependencies can be taken into account when developing plans for the prevention and elimination of emergencies caused by their spills.

Reducing the intensity of thermal radiation at the sublayer extinguishing of alcohols by ecologically acceptable aerosols

This paper has theoretically substantiated and experimentally established the intensity of thermal radiation at burning and sublayer extinguishing of alcohols with environmentally acceptable aerosols. An installation has been improved that determines the effectiveness of sublayer extinguishing with fire-extinguishing aerosols; a procedure that has been devised for determining the intensity of thermal radiation implies equipping it with an additional heat flow meter HFM–01 at a distance of 30 and 60 mm. The task to establish the intensity of thermal radiation when burning alcohols and its impact on the process of sublayer extinguishing of alcohols with aerosols has been solved. The dependence of sublayer extinguishing efficiency on thermal radiation implies that the fire extinguishing aerosol completely shields the surface of the combustible liquid against its action. The result of this study has established that the intensity of thermal radiation at a distance of 60 and 30 mm from the surface of an alcohol flame with an area of 234 cm2 ranges from 0.8 to 4.7 kW/m2; the intensity of burning and, accordingly, radiation, maximizes on seconds 30‒40 of burning. It has been found that the intensity of thermal radiation for ethanol decreases with the addition of an aerosol with an intensity of up to 0.2 g/s, and decreases even more at the intensity of supply from 1.2 g/s. With a further increase in the intensity of aerosol supply, the radiation intensity begins to decrease, probably due to a decrease in the rate of combustion. In this case, the flame first decreases in size up to 2 times, and then, after 2‒3 seconds, it goes out. The use of fire-extinguishing aerosol for the sublayer extinguishing of alcohols ensures the effect of several factors that synergize and reduce the intensity of evaporation, burning, and, accordingly, thermal radiation

Determination of efficiency parameters of foaming agents for layer-by-layer extinguishing of gasoline containing water-soluble flammable liquids

In case of fires in tanks with a fixed roof (except for tanks with oils and fuel oils), it is allowed to use layer-bylayer extinguishing with low expansion foam. This method of fire extinguishing is well studied in relation to flammable liquids that do not contain water-soluble (polar) components. Foam based on fluorine-containing foaming agents is used, which creates a film on the surface of the flammable liquid, which prevents the evaporation of flammable vapors and promotes spreading of the foam. However, the introduction of watersoluble (polar) components into a combustible liquid (they are contained, for example, in motor gasoline) can lead to a decrease in film formation and an intensification of foam destruction. As part of the research work, experimental studies have been accomplished to determine the possibility of layered extinguishing of gasoline in tanks using fluorosynthetic film-forming foaming agents of the AFFF type. A series of tests have confirmed the possibility of layered extinguishing of an alcohol-containing combustible liquid in a tank at a standard rate of supply of a foaming agent solution with a specially modified formulation during the course of the study. A list and values have been established, and methods have been formulated for determining the parameters affecting the fire extinguishing efficiency of foaming agents intended for layered extinguishing of oil and petroleum products (including gasoline) in tanks.

PROSPECTS AEROSOL SUBLAYER QUENCHING OF ALCOHOLS

The study addresses the problems of gas alcohols and describes the factors that make the fire extinguishing efficiency of aerosol refractory gas alcohol. To date, alcohol storage facilities are not sufficiently protected, as evidenced by the fires that occur on them. The actuality of the work is emphasized by the fact that the fires at the objects for the storage and processing of alcohols and their mixtures are characterized by a high velocity of flame propagation up to 10 m / s, and the achievement of high values of temperatures inside the volume in the first minutes, the possibility of explosions of both gas and air mixtures and pressure vessels subjected to heat. The article theoretically describes the quenching process and shows that such quenching must be effective at the expense of synergies between the factors of influence. The paper presents the analysis and theoretical generalizations of the process of extinguishing alcohols and alcohol-containing liquids. The disadvantages of quenching alcohols and alcohol-containing liquids by foam agents are indicated. The process of quenching by inert gas is considered and the method of sublayer quenching of alcohols by extinguishing aerosol is proposed. It is established that sublayer quenching by aerosol occurs in 3 stages. At the first stage - at the exit of the aerosol there will be mixing of the liquid, reducing the surface temperature of the combustible liquid and equalizing the temperature on its height the column of the liquid. At the second stage - after the aerosol exits the fluid layer and enters the surface, the concentrations of the components of the combustion mixture are reduced, the radiation shielded from the combustion zone and its influence on the surface of the combustible liquid and the sides of the tank are reduced. At the third stage, when the aerosol enters the combustion zone, the following extinguishing factors are realized: inhibition, phlegmatization, cooling, and partially change of physical parameters, such as increase in pressure and volume. The combination of these factors at the same time provides a significant reduction in the time of quenching of alcohol compared to conventional methods of quenching. By the result of the analysis of the process of extinguishing alcohol and alcohol-containing mixtures by different extinguishing agents it has been theoretically substantiated and experimentally confirmed the high efficiency of sublayer quenching by gas-aerosol mixtures of alcohols and their mixtures. The advantages of this type of extinguishing are the low cost of the fire extinguishing system, the considerable period of operation, the high extinguishing efficiency and ease of maintenance and use.

Numerical Simulation of Two-Phase System of “Combustible Liquid – Solid Fuel” Combustion in a Fixed Bed

Investigation of combustion of complex heterogeneous systems and particularly of twophase “combustible liquid – solid fuel” systems is topical because of the need to improve combustion of multicomponent and non-standard fuels as well as for resolution of specific ecological problems. The qualitative and quantitative peculiarities of combustion of two model combustible systems, notionally corresponding to the “sawdust – oil” and “wood chips – oil” mixtures are investigated numerically. The main peculiarity of the systems is volatility of the fluid component, being gaseous-flow driven inside porous media. A one-dimensional plain problem of combustion of compact layer with the ignition from the bottom and from the upper side is considered. It is demonstrated that due to low gas permeability of the fine-dispersed solid matrix (sawdust), air flow velocity is relatively low which results in slow formation of the combustion front (the characteristic time is tens of minutes). In case of coarse solid phase (wood chips), airflow rate is higher and corresponding time of temperature fronts formation is smaller (a few minutes). Both for the cases of fine-dispersed and coarse particles solid matrix phase, when set on fire from below, the fluid component is evacuated from the hot zone before the combustion front is formed. Since that, the main characteristics of the temperature front dynamics correspond to “dry” fuel system. In case of upper side ignition the combustion wave is formed at the time of the order of 100 s (when the used magnitudes of parameters are being used again), then it spreads downstream of the layer, accompanied by incomplete oxidation of solid fuel and complete combustion of oxygen. The effect of incomplete solid fuel combustion was noted earlier in the investigations of combustion of lean coal layer and some other systems. The velocity of the combustion wave propagation does not differ much for the cases of upper side and bottom side ignition. But the time of establishing the quasi-stationary velocity of the front to the steady-state value at the initial stage is much less in case of bottom side ignition. The results obtained by the authors can be utilized for optimization of multi-phase fuels combustion in compact layer, the regime parameters of in-situ combustion method of oil recovery increase as well as for improvement of some specific chemical processes.