Investigation of concentration limits of flame propagation in ammonia-based gas mixtures

The concentration limits of flame propagation inNH ₃-O ₂,NH ₃-H ₂-O ₂,NH ₃-O ₂-N ₂,and NH ₃-H ₂-O ₂-N ₂ mixtures at temperatures of up to70°C and pressures of up to1.0 MPa were studied experimentally. The lower concentration limit of propagation of ammonia flame in oxygen decreases significantly at elevated temperature and pressure, the effect of temperature being stronger than for organic combustible substances. It is shown that the Le Chatelier rule for the limits ofN ₂-NH ₃-O ₂ mixtures is satisfied with sufficient accuracy.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 5, pp. 3–7, September–October, 1996.     

Concentration limits for flame propagation in fuel-dilutent-nitrous oxide mixtures

Balashikha. Translated from Fizika Goreniya i Vzryva, Vol. 24, No. 3, pp. 48–51, May–June, 1988.     

Effect of an electric field on concentration limits for propane flame propagation in air

Balashikha. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 1, pp. 26–28, January–February, 1991.     

On the limits of flame propagation in a dusty gas

The limits of flame propagation in a gas with suspended inert particles in the presence of external heat removal have been studied. The mathematical model used is based on an unsteady heat-diffusion two-temperature model of gas combustion in the presence of inert particles. The problem is solved by a numerical method. A parametric analysis was performed, and critical values of the parameter that characterizes external heat removal are obtained. Dispersed-phase parameters are determined for which the two-temperature nature of the medium is insignificant. For this case, an analytic estimate for the critical parameters of flame quenching was obtained. At the moment of flame quenching, the normal flame-propagation velocity in a dusty, gas decreases by a factor of compared with the flame velocity in the dusty gas under adiabatic conditions. Tomsk State University, Tomsk 634050. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 4, pp. 14–20, July–August, 1997.     

Maximum explosive pressure and temperature of vapor-air mixtures

For mixtures of air with highly inflammable vapor, the maximum explosive pressure corresponds to superstoichiometric fuel concentrations. The maximum explosive pressure is similar for different classes of compounds and considerably exceeds the handbook values. This must be taken into account in predicting the consequences of explosions.     

Ignition and flame propagation in halocarbon-chlorine mixtures subject to UV radiation

Ignition and flame propagation in halocarbon (difluoromethane, 1,1-difluoroethane) mixtures with chlorine subject to UV radiation is investigated. Depending on initial conditions, the ignition of C₂F₂H₄+Cl₂ mixtures was observed at different distances from the irradiated end of the reaction cell. Data on flame propagation velocities are reported.Moscow. Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 82–84, May–June, 1993.     

Effect of added reactive agents on the flame propagation velocity in rich hydrogen-air mixtures

An approximate analytical method for evaluating the efficiency of the action of an inhibitor on the velocity and propagation limits of a flame in rich hydrogen-air mixtures with small amounts of added propylene and isobutylene inhibitors is proposed. The method is based on the model of a narrow reaction zone and the distinct features of the branching chain mechanism of hydrogen oxidation reactions. Using this method, it is shown that the occurrence of flame propagation limits at higher concentrations of added reactive agents (inhibitors) is caused by the existence of a positive feedback between the flame front velocity and the number of active combustion sites, which break down in the inhibitor-added reaction. According to this feedback, the action of the inhibitor decreases the flame temperature and flame velocity.     

Effect of trimethylphosphate additives on the flammability concentration limits of premixed methane-air mixtures

The effect of small additives of trimethylphosphate (TMP) on the lean and rich flammability concentration limits of CH₄/air gas mixtures were studied using an opposed-flow burner and numerical modeling based on detailed kinetic mechanisms. TMP was found to narrow the flammability concentration limits of premixed CH₄/air mixtures. Modeling using a previously developed model for flame inhibition by phosphorus compounds showed that the model provides a satisfactory fit to experimental results on the effect of TMP additives on the lean concentration limit. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 12–21, January–February, 2008.     

Flame propagation in mixtures of monogermane and oxygen. II. Peculiarities of flame propagation and the structure of combustion waves

Different flame propagation regimes, including a two-wave regime, are studied in a closed pipe with single ignition of GeH₄−O₂ mixtures. It is shown that, depending on the initial conditions and, in particular, on the composition of the initial mixtures, spatially separated chemical reaction waves for oxidation and decomposition of monogermane are observed in certain parts of the reaction vessel which lead to the formation of a two-layer deposit of GeO/Ge. The temporal sequence of the separated combustion wave and wave from which layers of solid products are deposited, as well as the location of the deposition zones in the reaction vessel, are determined by two interacting chain processes—the oxidation and decomposition of monogermane. The thermal relaxation kinetics of the reactive mixture after passage of the combustion waves is determined by the rate of conductive heat transfer from heated solid particles (reaction products) to the gaseous phase. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 1, pp. 77–84, January–February 1999.