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Numerical simulation has shown that replacing a part of methane by carbon monoxide in a rich mixture while maintaining the equivalence ratio leads to a decrease in the superadiabatic temperature effect due to the competition of chemical reactions. This is explained by a decrease in the H content in the combustible mixture and a decrease in the superequilibrium concentration of water in combustion products. Using numerical tracer simulation and a comparative analysis of the rates of consumption of CH4 and CO, it has been found that the consumption of both fuels in the CH4/CO/air flame is a competitive reaction path and CO monoxide does not act as an inert component in the low-temperature region of the front (contrary to the statements of a number of authors). Furthermore, the rate of consumption of CH4 is much higher than that of CO due to the larger number of consumption reactions of CH4 and their higher rates. The main contribution to the increase in the concentration of H atoms in the flame in passing from a methane–air mixture to a CH4/CO/air mixture is due to the same reactions that increase the heat release rate: O + CH3 = H + CH2O and CO + OH = CO2 + H. The results obtained and their comparison with literature data lead to the conclusion that the increase in the heat release rate and, hence, the flame propagation rate should be greater in rich mixtures since there the thermophysical effect is higher.

In the present paper, the laminar burning velocity and structure of near-stoichiometric premixed laminar flames of methyl methacrylate (MMA) with and without trimethylphosphate (TMP) additives have been studied experimentally and by numerical modeling. The MMA+TMP combustion system is considered as a model system, which simulates gas-phase combustion of polymethyl methacrylate (PMMA) with additive of phosphorus-containing fire retardants (PFRs). The motivation of the present research is to provide a basis for development of a predictive gas-phase chemical kinetic model for inhibition of PMMA by PFRs. The flame sampling molecular beam mass spectrometry was used to determine the spatial variation of the mole fractions of H, OH, PO, PO2, HOPO, HOPO2 and some intermediate hydrocarbons in the one-dimensional burner-stabilized flames. The effect of TMP on the hydrocarbon intermediates in the flames is investigated. The reaction mechanism for combustion of MMA+TMP system has been validated against the novel laminar burning velocity and chemical speciation data. Performances and deficiencies of the kinetic mechanism for MMA flame inhibition are discussed. The sensitivity analysis showed that the insufficiently accurate prediction of mole fraction of H, O and OH results in disagreement for mole fraction profiles of hydrocarbon intermediates in the inhibited flame. Inhibition effectiveness of MMA flame by TMP is compared with that derived from experimental data for other fuels and the observed tendencies are discussed.

This paper deals with the nature of the synergistic effect in flames of methane and formaldehyde mixtures with air. Combustion of mixtures of different fuels is of great practical and fundamental interest. It has been found that the addition of formaldehyde to a rich methane/air flame at a constant concentration of methane first reduces the flame speed and then begins to increase it. The synergism mechanism in this case is due to the predominant and complete consumption of formaldehyde due to its higher reactivity and its negative impact on the rate of methane consumption. The predominant combustion of one of the fuels leads to the existence of two spatially separated heat release zones in the flame. In the first zone, heat release is mainly due to the oxidation of formaldehyde and formyl radical, and in the second zone, it is due to the recombination of methyl radicals. An analysis of the flame speed sensitivity has shown that the key reactions affecting the flame speed are the stages of formation of radicals (mainly hydroxyl) or products that lead to their formation. Reactions that make the main contribution to the heat release generally do not affect the flame speed. It has been found that the interaction of two fuels CH4 and CH2O in a mixture with air leads to a marked increase in the superadiabatic temperature effect.

Chain branching and heat release processes and their influence on the burning velocity of premixed rich and near-stoichiometric methanol–air flames were studied by numerical simulation and sensitivity analysis. The phenomenon of superadiabatic temperatures in these flames due to the kinetic mechanism of methanol combustion was first detected. Comparison of the simulation results of the structure of methanol and formaldehyde flames shows that the formation of water in superequilibrium concentrations in flames does not necessarily lead to superadiabatic temperatures, as believed earlier. It was first found that decreasing the dilution of the CH3OH/O2/N2combustible mixture with nitrogen at a constant equivalence ratio enhances the superadiabatic temperature effect. According to simulation results, in a rich near-limit methanol flame, the role of the chain branching reactions H + O2 = O + OH and O + H2 = H + OH is negligible due to their low rate. At relatively low temperatures, branching occurs mainly in reactions involving HO2and H2O2peroxide compounds, whose concentration is orders of magnitude higher than the concentration of the main chain carriers H, O, and OH. From the sensitivity analysis, it follows that the burning velocity of methanol flames is positively influenced mainly by the reactions of formation of chain carriers and is negatively influenced by the reactions of consumption of chain carriers. reactions having a major contribution to heat release but are not involved in the formation and consumption of radicals have small sensitivity coefficients.

This dissertation is dedicated to the historical review of female mathematics education during the Progressive Era, from 1890 through 1920. This time period is known in the United States for multiple social reforms. Secondary schools experienced rapid expansion in enrollment, and the purpose and direction of education underwent development and change. During this era, a secondary education, which had been available to few, came to be accepted as a necessity for a majority of children in the United States. During this period of development and change, the educational system encountered several challenges. One such challenge was to tailor curricula according to the needs of different students. In parallel with increased enrollment, labor market demands experienced changes as well, and these changes were especially prominent in the urban areas. Historical evidence documents that the purpose of girls’ and boys’ education was often considered to be distinct. This belief stemmed from the idea that girls and boys had different career paths upon high school graduation. Therefore, differentiation of curricula received needed support and allowed schools to provide an elective system of subjects within high schools. This dissertation provides historical analysis of the mathematics education available for girls in the Progressive Era, focusing on the purpose of mathematics education, on curricula differentiation facilitated by an elective system, and on social factors that affected girls’ enrollment into the mathematics classes when the election of mathematics classes was allowed.

As dimethyl ether is being extensively used as an environmentally friendly motor fuel, the issue of its fire and explosion safety is becoming increasingly urgent. In this work, the action of trimethylphosphate, bromotrifluoromethane (CF3Br), trifluoroiodomethane (CF3I) and iron pentacarbonyl (Fe(CO)5) on the upper and lower concentration flammability limits (CFLs) of dimethyl ether/air mixture was studied using the counterflow burner technique and chemical kinetic modeling. Iron pentacarbonyl was shown to extend the lower limit and to have a small inhibition effect on the upper limit. The other additives, even in small concentrations, were shown experimentally to narrow the flammability limits with the effect on the rich limit being greater than that on the lean one. The kinetic mechanisms for flame inhibition by the abovementioned compounds used in the numerical simulations unsatisfactorily predicted the effect of inhibitors on the lower CFL. In addition, modeling greatly overpredicted the inhibiting effect of Fe(CO)5 on the upper limit compared to experimental data. As for the rich limit, the modeling predicted the effect of CF3I and TMP well and underpredicted the inhibition effect of CF3Br. As compared to other inhibitors, CF3I was found to narrow the upper CFL most effectively, whereas TMP is known to have the greatest effect on the speed of freely propagating flames. A possible explanation of the different inhibiting effects of chemically active inhibitors on freely propagating and counterflow flames has been proposed. As, in counterflow flames, the residence time can be less than the characteristic time of chemical reactions, the influence of some reactions on the flame parameters can be different in stretched (counterflow) flames and non-stretched (laminar freely propagating) flames. For TMP, this suggestion has been validated by analysis of the contributions of reactions involving phosphorus species to the rates of production and consumption of H atoms.