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Cup burner tests: extinguishing concentration of CO 2 as a function of loading of fire suppressants.
Source publication
Inhibition and suppression effectiveness of recently prepared volatile organophosphorus compounds (OPC) was studied. For this purpose the influence of OPC on concentration limits of combustion of cup-burner flame and on inhibition of premixed propane/air flame using Mache- Hebra burner was studied. The most promising compounds were tested with the...
Contexts in source publication
Context 1
... number of novel synthesized OPC were tested using the cup-burner technique. Figure 3 shows the extinguishing concentration of CO 2 as a function OPC loading to a n-heptane/air flame. The measured extinguishing concentrations for the tested compounds are tabulated below. ...
Context 2
... solution H3PO4 solution For some compounds a secondary flame in upper part of the chimney was observed because of combustion of their vapors in heated airflow. For these OPC a distinctive dependence of CO 2 extinguishing concentration on OPC loading is observed (see Fig. 3). For example, when OPC loading increases a higher concentration of CO 2 is necessary for flame extinguishing. This effect as it was reported by us earlier [3] is connected with 2 competitive processes: (1) the flame inhibition by OPC and temperature decrease due to an increase of heat capacity of the combustion products; (2) an ...
Context 3
... a different effectiveness of various OPC can be explained by influence of several reasons: the heat of formation of OPC, heat capacity of their vapors, their destruction rate and destruction products in a flame. The results presented in Table 3 and Figure 3 indicate that under the same conditions the effectiveness of some OPC is higher than that of CF 3 Br in 1.8 -2.5 times. In this case the relative effectiveness is the ratio of minimal extinguishing concentrations. ...
Context 4
... data presented in Fig. 3 indicate the organophosphorus fire suppressant to be more effective than Halon 1301. The temperature dependence of extinguishing concentration is presented in Fig. 4. and Fig. 5. The results for the halon obtained using both techniques are quite close, whereas the data for (CF 3 CH 2 O) 3 P are appreciably different. The extinguishing ...
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Citations
... At the same time, there is some disagreement between calculation and the experiment, which may be attributed to the fact that the reactions of radicals with other active products of salt decomposition (for example, with iron and its oxides) were not taken into account, as well as the heterogeneous reactions of the loss of active centers on the surface of the salt particles and condensed products of its decomposition, and possible incorrectness of the rate constants of the reactions. Earlier authors demonstrated that the suppression effectiveness of K 4 [Fe(CN) 6 ] is higher than we expected on the basis of number of K atoms [23][24][25]. Therefore, the presence of Fe atom in the molecule may be responsible for the disagreement between measured and simulated speed of the doped flames. ...
The influence of 1% aerosol of the water solution of potassium ferrocyanide K4[Fe(CN)6] on the flame speed of stoichoimetric methane- air flame, stabilized over the Mache-Hebra burner, has been studied experimentally and by computer simulation. The flame speed was measured at atmospheric pressure and the temperature 93 °C. Addition of the aerosol of the water solution of potassium ferrocyanide results in significantly greater reduction of the flame speed of stoichiometric methane-air flame, compared to aerosol addition without the salt. Modeling the flame speed with the mechanism GRI-Mech 3.0 shows this effect to be caused by the presence of potassium atoms in the composition of this salt. The results obtained account for effectiveness of applying fine aerosol of the water solution of K4[Fe(CN)6] in extinguishing fires.
... However, efficiency of organophosphorous fire suppressant not depends on methods of its delivery to fire source, as was shown in [2]. Thus, combustion suppression effect can be taken into consideration by means of a correction factor for chemical reaction rate, and this fact simplify a numerical modeling of its influence on fire substantially. ...
Numerical calculations of the effect of organophosphorous inhibitor (CF3CH2O)3P and its mixtures with carbon dioxide on propane flames are carried out using the three dimensional Reynolds-averaged Navier-Stokes (RANS) equations in the low Mach number approximation. The k-e model of turbulence, the EDC combustion model and the weighted-sum-of-gray-gases model of radiation are used. The Westbrook global-kinetic scheme with fractional order of reaction was used for the calculation of chemical reaction rate of propane combustion. The empirical expression for the correction factor for the chemical reaction rate was used to model the effect of organophosphorous inhibitor no the reaction. Two series of test calculations for different values of the correction factor are carried out. Dependences of the minimum extinguishing concentration of the inhibitor per carbon dioxide volume concentration in the extinguishing mixtures were obtained. The results of test calculations are shown to agree reasonably with the experimental data. A calculation of the compartment fire extinguishment was carried out using the result of test calculations. Temperature and inhibitor volume concentration fields at the moment of fire extinguishment are obtained. The results of calculation are used to find out the optimum position of the extinguish mixture source.
The comprehensive inhibition mechanism of hydrocarbon/air premixed flames by monoammonium phosphate (NH4H2PO4) powder is studied in this research work using theoretical, experimental and numerical simulation approaches. The critical diameter of the NH4H2PO4 powder particles in the premixed CH4/air flame was calculated to be 30 μm using a predictive mathematical model. Using a Bunsen burner apparatus, the laminar burning velocity of the CH4/air/NH4H2PO4 mixtures, entrained with NH4H2PO4 powder (D90 < 30 μm), was measured over a gas phase equivalence ratio range of 0.9–1.5, powder concentration range of 0–33.8 g/m³, and temperature and pressure conditions of 298 K and 1 bar, respectively. The experimental results show that the laminar burning velocity of the CH4/air/NH4H2PO4 premixed flames decreased non-linearly with the increase of the NH4H2PO4 powder concentration for a constant equivalence ratio. When the NH4H2PO4 powder concentration exceeded a critical powder concentration under a fixed equivalent ratio, a saturation phenomenon appeared. To study this saturation phenomenon and the inhibition mechanism of NH4H2PO4 powder, a gas-phase kinetic model was developed of the NH4H2PO4 powder on the CH4/air premixed flame. Comparing the simulated laminar burning velocity from the kinetic model with the measurements revealed a reasonably good agreement that proves the dominant chemical inhibition characteristics of NH4H2PO4 powder on the CH4/air premixed flame. The gas-phase chemical kinetic analysis shows that H3PO4 plays a major role in reducing the laminar burning velocity of the CH4/air premixed flames by NH4H2PO4 powder; however, the effect of NH3 was negligible. In addition, the catalytic cycles of small phosphorus species (i.e., HOPO2<=>PO2 and HOPO<=>PO2) scavenged the H and OH radicals in the flame, resulting in disappearance of the overshoot of free radicals (i.e., H and OH), production of the saturation effect and reduction of the laminar burning velocity.
Minimum extinguishing concentrations of mixtures of organophosphorus and iodine-containing compounds and inert diluents were measured using the cup-burner and cylinder techniques. The results of these measurements were used to develop and test new effective fire-suppression compositions whose components exhibit a synergetic effect and to estimate the lower temperature limit of their application. The results of laboratory experiments were verified by full-scale tests in which two types of model fire sources were extinguished by salt solution aerosols. The tests demonstrated that short-term action of an aerosol cloud of an aqueous solution of potassium ferrocyanide K3[Fe(CN)6] on the flame front of a surface forest fire led to suppression of gas-phase combustion, and in the case of wood burning, to complete flame extinction. The minimum extinguishing mass concentration of K3[Fe(CN)6] in these experiments was 4.5 g/m3, which is close to that measured in laboratory experiments. In fire suppression by the aerosol, the volumetric flow rate of this fire suppressant was found to be 30 times lower than the standard flow rate of pure water from a fire hose.
The development and investigation of new effective and environmentally clean flame suppressants is a promising direction in
fire extinguishing. Organophosphorus and metal-containing compounds are the most promising candidates for the replacement
of CF3Br. However, for many of these compounds, data on their minimum extinguishing concentration are not available. In the present
work, the minimum extinguishing concentrations for a number of new phosphorus-and metal-containing compounds and some of their
mixtures, solid-propellant gas-generating compositions containing phosphorus additives were determined using the cup-burner
technique and a setup with a turbulent flame source and transient application of flame suppressants.
The minimum extinguishing concentrations of mixtures consisting of organophosphorus and iodine-containing compounds and inert
diluents were measured with the cup-burner and cylinder techniques. The results obtained were used to develop and test new
effective fire-suppressing compositions whose components exhibit a synergetic effect. For these mixtures, the lower temperature
limit of application was estimated.
