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Propylene oxide (C3H6O) is an intermediate product of the oxidation of heavy hydrocarbons and can be used as an additive to conventional fuels to reduce soot emissions. New experimental data on the oxidation of C3H6O at low temperatures were obtained using an isothermal jet-stirred reactor. Experiments were carried out at temperatures of 600–1300 K and a pressure of 1 atm, and the residence time of the gas mixture in the reaction volume was 1 s. Five detailed chemical kinetic mechanisms taken from the literature were tested. The mechanism with the best predictive capability at low temperatures was determined. The mechanisms were also tested against experimental data on the structure of C3H6O flames. It has been found that there is currently no model that can correctly describe the combustion and oxidation of C3H6O at both low and high temperatures. [ABSTRACT FROM AUTHOR]

The total and radiative heat fluxes from the flame to the burning surface of a solid fuel (polymethylmethacrylate) slab for horizontal flame spread over the fuel surface were first quantitatively measured using two water-cooled miniature (2.3 × 2.3 mm) sensors mounted inside the slab. The design of the water cooling of 2 × 2 × 0.5 mm sensors (greenTEG AG) allows their placement directly in the combustion zone. Radiative heat flux was measured by a sensor with a protective ZnSe window, and the total heat flux was measured by a similar sensor without a protective window. The conductive heat flux determined using sensors was compared with that calculated from the data of polymethylmethacrylate flame temperature measurements using thin thermocouples. The maximum radiative and total heat fluxes from the flame to the polymethylmethacrylate surface measured by the heat flux sensors were 30–35 and 70–75 kW/m2, respectively. [ABSTRACT FROM AUTHOR]

Organometallic complexes of transition metals with inorganic anions are considered as promising precursors for the synthesis of nanoscale materials used in various applications including chemical catalysis. In this work, organometallic complexes of nickel, iron, and copper with imidazole as an organic ligand and the nitrate anion as an inorganic ligand were synthesized and characterized. The kinetic parameters of thermal decomposition of the synthesized organometallic complexes were determined by low heating-rate thermogravimetric analysis and high-speed dynamic mass spectrometric thermal analysis. The main gaseous products of thermal decomposition of the complexes under high-speed heating were identified. The chemical and phase compositions of condensed combustion products of the organometallic complexes in air were studied. [ABSTRACT FROM AUTHOR]

Heat and mass transfer processes and the rate of fuel oxidation are the determining parameters of combustion of non-premixed gaseous fuel–oxidizer flows and solid-fuel combustion in a gaseous oxidizer. A correct description of these processes is of both scientific and practical interest. The influence of the kinetics of chemical reactions and diffusion of fuel molecules on the thermal and chemical structure of the flame forming around a polymethyl methacrylate (PMMA) sphere in air under natural convection has been studied by numerical simulation. The three-dimensional gas flow around the solid body has been calculated using the full Navier–Stokes equations for a multicomponent mixture taking into account diffusion and heat transfer between the surface and gas, convection, and radiative heat transfer. The kinetic model represents the conjugate reactions both on the condensed material surface and in the gas phase. The formation of the gaseous fuel methyl methacrylate (MMA) on the surface is described by an effective one-step pyrolysis reaction of PMMA. The oxidation of MMA in the gas phase is described by the global reaction C5H8O2 + 6O2 5CO2 + 4H2O. It has been found that the temperature and species concentration profiles in the flame practically do not depend on the rate constant of this reaction provided that the characteristic reaction time is much less than the characteristic time of MMA diffusion. It has been shown that varying the MMA diffusion coefficient has a significant effect on the thermal and chemical structure of the flame. Increasing the MMA diffusion coefficient increases the maximum flame temperature. The results of the study show that the transport properties of compounds required to calculate their transport coefficients are among the most important parameters for accurate CFD simulation. [ABSTRACT FROM AUTHOR]

Methyl methacrylate (MMA) is the main pyrolysis product of the widely used polymer polymethyl methacrylate; therefore, a compact mechanism of MMA oxidation is of interest for CFD modeling of flame propagation over this polymer. A reduced mechanism of MMA combustion consisting of 263 elementary reactions involving 66 species was developed based on a detailed chemical-kinetic mechanism of MMA oxidation in flames using Chemical Workbench software. The developed mechanism was validated against experimental data on the speed of premixed MMA/air flame at an equivalence ratio and against literature data on the structure of a MMA/O2/Ar ( = 1) flame stabilized on a flat burner at a pressure of 1 atm. The proposed reduced kinetic model for MMA describes the experimental data with satisfactory accuracy, and the modeling results for the full and reduced mechanisms of MMA oxidation are in good agreement with each other in terms of the concentrations of the major flame species and the concentrations of most combustion intermediates, including hydrogen, methane, ethylene, acetylene, propane, acetaldehyde, methyl acrylate, etc. [ABSTRACT FROM AUTHOR]

The structure of premixed ethyl butanoate/O2/Ar flames stabilized on a flat burner at atmospheric pressure was studied by molecular beam mass spectrometry. Mole fraction profiles of the reactants, stable products, and major intermediates and temperature profiles were obtained in flames of stoichiometric (φ = 1) and rich (φ = 1.5) combustible mixtures. Experimental data are analyzed and compared with previously obtained experimental and numerical data for methyl pentanoate flames. The structure of ethyl butanoate flames is simulated using a detailed literature chemical-kinetic mechanism for the oxidation of fatty acid esters. The experimental profiles are compared with the simulated ones, and the conversion pathways of ethyl butanoate are analyzed. Based on a comparative analysis of experimental and simulated data, the main shortcomings of the model presented in the literature are identified and possible ways are proposed to improve the model. The decomposition of ethyl butanoate and methyl pentanoate are discussed based on an analysis of their conversion pathways; similarities and characteristic differences between their oxidation processes due to the structural differences of the molecules of the fuels are outlined. [ABSTRACT FROM AUTHOR]

Interest in the combustion chemistry of multifuel blends is motivated by the need to study the combustion of natural gas, which is known to be a mixture of alkanes. The present study performed using molecular beam mass spectrometry and numerical modeling has shown that the width of the zones of hydrogen and methane consumption in the H/CH/CH/O/Ar flame and the width of the zones of methane and propane consumption in the CH/CH/CH/O/Ar flame differ significantly from each other. The causes of this phenomenon were determined by analyzing the modeling results. It has been found that in the presence of heavier compounds, lighter fuels, such as H and CH, are formed, which reduces the total rate of their consumption and, hence expands the zone of their consumption in the flame. The influence of the presence of hydrogen in the fuel mixture on the concentration of C hydrocarbons has also been studied. It has been established that the addition of hydrogen reduces the maximum concentration of ethane, ethylene, and acetylene in the flame, and the fraction of unsaturated C hydrocarbons with respect to saturated ones also decreases. [ABSTRACT FROM AUTHOR]

The structure of a premixed stoichiometric flame of syngas (H/CO/O/Ar = 0.0667/0.0667/0.0667/0.8) stabilized on a flat burner at a pressure of 5 atm was studied experimentally and by numerical simulation. The mole fraction profiles of the reactants (H, CO, and O) and the major (HO and CO) and intermediate (O, OH, HO, and HO) combustion products were measured by molecular beam mass spectrometry. The experimental data were compared with those calculated using three detailed chemical-kinetic mechanisms proposed in the literature for oxidation of a H/CO mixture. Good agreement was found between the results of the experiment and simulation. Calculations of the structure of the flame of the same composition at a pressure of 1 and 10 atm were performed to establish the effect of the pressure on the chemical reaction kinetics in the syngas flame. The results were explained by kinetic analysis of the mechanisms. [ABSTRACT FROM AUTHOR]

The search for reactive additives capable of reducing the combustibility of dimethyl ether is an important problem due to the widening use of ether as an alternative environmentally friendly motor fuel. This paper presents a numerical study of the autoignition chemistry of mixtures of dimethyl ether with air in the presence of atomic iron. Atomic iron, which is an effective inhibitor of premixed laminar hydrocarbon flames, was found to shorten the induction period. However, the additive affects only the first stage of the induction period. The mechanism of promotion of the low-temperature oxidation of dimethyl ether-air mixtures by atomic iron is the formation of hydroxyls in reactions involving iron compounds. Since the additive hardly changes the duration of the second stage of the induction period, it can be suggested that OH radicals play an insignificant role in the low-temperature oxidation of dimethyl ether at this stage. [ABSTRACT FROM AUTHOR]

This paper presents a numerical and experimental study of the effect of flame-retardant additives on the autoignition of methane behind shock waves. It is shown that at a temperature of 1300-1900 K, the compounds CCl, CFH, and (CHO)PO not only do not suppress ignition but significantly reduce the induction time of methane-oxygen mixtures. A kinetic mechanism is proposed which relates the promoting effect to the reactivity of the pyrolysis products of the additives. [ABSTRACT FROM AUTHOR]

The combustion of ultrahigh molecular weight polyethylene (UHMWPE) in airflow perpendicular to the polyethylene surface (counterflow flame) was studied in detail. The burning rate of pressed samples of UHMWPE was measured. The structure of the UHMWPE-air counterflow flame was first determined by mass spectrometric sampling taking into account heavy products. The composition of the main pyrolysis products was investigated by mass spectrometry, and the composition of heavy hydrocarbons (C-C) in products sampled from the flame at a distance of 0.8 mm from the UHMWPE surface was analyzed by gas-liquid chromatography mass-spectrometry. The temperature and concentration profiles of eight species (N, O, CO, CO, HO, CH, CH, and CH) and a hypothetical species with an average molecular weight of 258.7 g/mol, which simulates more than 50 C-C hydrocarbons were measured. The structure of the diffusion flame of the model mixture of decomposition products of UHMWPE in air counterflow was simulated using the OPPDIF code from the CHEMKIN II software package. The simulation results are in good agreement with experimental data on combustion of UHMWPE. [ABSTRACT FROM AUTHOR]

Molecular beam mass spectrometry was used to measure mole fraction profiles of the reactants, major reaction products and intermediates, including precursors of polycyclic aromatic hydrocarbons, in a premixed fuel-rich (equivalence ratio of 1.75) n-heptane/toluene/O/Ar flame stabilized on a flat burner at atmospheric pressure. The ratio of the liquid volumes in the n-heptane/toluene mixture was 7: 3. The chemical structure of the flame was modeled using a detailed mechanism of chemical reactions tested against experimental data of other authors on n-heptane/toluene flames and comprising the reactions of formation of polycyclic aromatic hydrocarbons. The mechanism was extended with cross-reactions involving derivatives of n-heptane and toluene. Overall, the new experimental data are in satisfactory agreement with the numerical simulation results; however, there are differences between the measured and calculated mole fraction profiles of some species. Analysis shows that in the n-heptane/toluene flame, the main reactions leading to the formation of low-aromatic compounds (benzene and phenyl) are reactions typical of the pure toluene flame. [ABSTRACT FROM AUTHOR]

A PIV study of a conical premixed methane-air Bunsen flame has shown that the inside of the cone has a complex gas-dynamic structure. In this system, the velocity of the gas flow entering the flame front varies in different parts of the flame cone and the stream tubes are not straight. The Landau-Markstein effect is discussed in the interpretation of the experimental data. A method of processing PIV measurement results is proposed that improves the accuracy of determining the burning velocity and allows a quantitative determination of the catalytic effect of submicron TiO particles, which is proportional to the particle surface area. The relative increase in the burning velocity is 2% per each ≈0.01 cm/cm (particle surface/gas volume) of the total specific surface area of the particles. The experimental data are well described by modeling using well-known literature data on the detailed mechanism of chemical reactions and the mechanism of catalytic oxidation of methane with oxygen on metal oxides. [ABSTRACT FROM AUTHOR]

The structure of a premixed methyl decanoate/oxygen/argon flame stabilized on a flatflame burner at atmospheric pressure was studied by molecular beam mass spectrometry. The results of the experiment are compared with the results of numerical simulations using two different mechanisms of chemical reactions proposed in the literature. The main intermediate combustion products of methyl decanoate were identified by gas chromatography-mass spectrometry. Analysis of the primary stages of decomposition of methyl decanoate shows that reactions involving free radicals play a decisive role in its oxidation, which agrees well with the results of the experiments. [ABSTRACT FROM AUTHOR]

Limitations of the spatial and temporal resolution of the particle image velocimetry (PIV) technique in velocity field measurements in a laminar flame have been investigated. The limitations are due to the need to introduce a suspension of tracer particles into the flow. For a methane-air mixture with a stoichiometry coefficient of 0.9, it is determined that at a mass fraction of TiO solid particles over 0.08%, the change in the flame propagation velocity by the particles exceeds 5%. The maximum spatial resolution of PIV for which the influence of the particles is insignificant corresponds to a concentration of 0.03%; in this case, the minimum resolvable scale is limited by a value 200 times larger than the size of tracer particles. Based on analytical estimates and a comparison of measured and numerically calculated particle velocities in the flame, it is concluded that particles smaller than 2 µm adequately track the flow velocity. Under these conditions, the error of the velocity measurement is mainly determined by the limited spatial resolution of PIV. The results of the work can be used to evaluate PIV measurement errors in other experimental studies of flames. [ABSTRACT FROM AUTHOR]

A skeletal mechanism of inhibition and suppression of H/O/N by addition of trimethylphosphate was developed. It includes a mechanism of hydrogen oxidation (13 elementary steps involving 7 species) and two elementary reactions involving trimethylphosphate and its conversion products. This skeletal mechanism adequately predicts the burning velocity of flames with added inhibitor in the range of equivalence ratios studied, and can be used to model fire suppression. [ABSTRACT FROM AUTHOR]

A skeletal mechanism of inhibition and quenching of methane flames by addition of trimethyl phosphate was developed. It includes a mechanism of methane oxidation consisting of 19 elementary steps involving 15 species (including N), and four elementary reactions involving three phosphorus-containing species (PO, HOPO, and HOPO). The developed skeletal mechanism adequately predicts the burning velocity of flames with added inhibitor over a range of equivalence ratio of 0.7-1.4 and can be used to model fire suppression. [ABSTRACT FROM AUTHOR]

The effect of the addition of ethanol (EtOH) to the initial combustible mixture on the concentration of various compounds, in particular, those preceding the formation of polyaromatic hydrocarbons in a fuel-rich (equivalence ratio of fuel ϕ = 1.7) flat premixed ethylene/oxygen/argon flame at atmospheric pressure was studied experimentally and by numerical modeling using a detailed mechanism of chemical reactions. Concentrations of various stable and labile species, including reactants, major combustion products, and intermediates in CH/O/Ar and CH/EtOH/O/Ar flames were measured along the height above the burner using molecular beam mass spectrometry. Experimental mole fraction profiles were compared with those calculated using the previously proposed mechanisms of chemical reactions. This mechanism was analyzed to determine the cause of the ethanol effect on the flame concentration of propargyl, the main precursor of polyaromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

The key combustion reactions of synthesis gas at elevated initial temperatures ( T = 500-700 K) and pressures ( p = 10-30 atm) are identified by analyzing the kinetic mechanism. A reduced mechanism of the oxidation reactions of synthesis gas consisting of 14 elementary reactions involving 13 species is proposed which adequately describes the results of experimental data on the burning velocities of mixtures of synthesis gas with oxygen and inert diluents at T = 300-700 K, p = 10-30 atm, and ratios CO/H = 0.05-0.95, and satisfactorily predicts the flame structure and the dependence of the flammability limits on the initial temperature at atmospheric pressure. [ABSTRACT FROM AUTHOR]

Molecular beam mass spectrometry with photoionizationby synchrotron radiation was used to study the structure of flat premixed flames of CH/O/Ar and CH/CHOH/O/Ar at a pressure of 30 torr (4 kPa) with equivalence ratios ϕ = 1 and 2. It was shown that the replacement of part of ethylene with ethanol in the starting mixture lowered the concentration of a number of intermediate flame species, including soot precursors CH and CH. These data are important for the development, analysis, and further improvement of detailed kinetic mechanisms for combustion of mixtures of hydrocarbon and oxygenated fuels. [ABSTRACT FROM AUTHOR]

The possibility of measuring the concentration of H2O molecules in flames based on the absorption of terahertz free-electron laser radiation was studied. These measurements were performed using the 177.32 cm absorption line in the rotational spectrum of H2O. This line has a low intensity at room temperature, and at about 1000 K, its intensity is comparable to that of the strongest lines. The temperature dependence of the radiation absorption coefficient at a frequency of 77.32 cm was studied theoretically and experimentally. It is shown that the method can be used for measurements in a sooty CH/O/Ar flame, which strongly scatters visible and UV radiation. [ABSTRACT FROM AUTHOR]

The dependence of the lower flammability limit on the initial temperature is studied experimentally and numerically for upward flame propagation at a pressure of 0.1 MPa. It is shown that the Burgess and Wheeler rule, implying a linear dependence of the lower flammability limit on the initial temperature with the intersection of the temperature axis at the point 1300°C, does not hold for N, CHOH, CHO, and CH. For these substances, the intersection of the temperature axis is at the point 900 ± 20°C. The Burgess and Wheeler rule gives overestimated values of the limit which do not reflect the true conditions of explosion safety. [ABSTRACT FROM AUTHOR]

The synthesis of mesoporous nanocrystalline TiO films in a premixed (in vol %) 12.9/14.4/72.7 H/O/Ar flame doped with 0.1% titanium tetraisopropoxide [Ti(OCH)] was studied. Stabilization of the flame and deposition of TiO nanoparticles were carried on the plane of a rotating disk. Spatial distributions of temperature and concentrations of major species in the flame were investigated. The applicability of the employed kinetic reaction scheme and the calculation method to the description of the structure of the investigated flame was tested. It was established that this method can be used to synthesize spherical crystalline nanoparticles of the anatase polymorphic form of TiO with an average diameter of 12 nm and a narrow size distribution ( σ = 1.45), which can be used in the production of solar cells and gas analyzer sensors. [ABSTRACT FROM AUTHOR]

The lower concentration limit of flammability of hydrocarbon-air mixtures has been studied experimentally and by numerical simulation. Simulation using a detailed mechanism of chemical reactions has shown that calculations results are in good agreement with experimental data on the effect of water vapor on the lean concentration limit of flammability of hydrocarbon mixtures with air. The presence of water vapor at low concentrations in the mixture does not affect the lower concentration limit of flammability, but, at the same time, significantly changes the flame propagation velocity. Key words: concentration limits of flammability, opposed-jet premixed flame, hydrocarbons. [ABSTRACT FROM AUTHOR]

This paper presents the measurement and simulation data on the thermal and chemical structure of an atmospheric-pressure premixed H/O/N flame doped with iron pentacarbonyl Fe(CO). Soft ionization molecular beam mass spectrometry was used to measure concentration profiles of the combustion products of iron pentacarbonyl: Fe, FeO, FeOH, and Fe(OH). A comparison of experimental and simulated concentration profiles showed that they are in satisfactory agreement for FeO and Fe(OH) and differ significantly for Fe and FeOH. Thus, the previously proposed kinetic model for the oxidation of iron pentacarbonyl was tested and it was shown that the mechanism needs further elaboration. [ABSTRACT FROM AUTHOR]

The possibility of detecting OH radicals and stable paramagnetic NO species in flames using the effect of rotation of the polarization plane of terahertz radiation (1–10 THz) in a magnetic field (Faraday effect) was experimentally demonstrated. Experimental data on detection of NO in a cell and OH radicals in an atmospheric-pressure H2/O2/N2 flame using this method are given. The proposed method can be used to study highly scattering media which are opaque in the visible region, for example, dusty or sooty flames. [ABSTRACT FROM AUTHOR]

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 showed that short-term action of an aerosol cloud of an aqueous solution of potassium ferricyanide K3[Fe(CN)6] on the flame front of a surface forest fire led to suppression of the gas-phase combustion, and in the case of a model fire source of class A (burning wood) to its complete extinction. The minimum extinguishing mass concentration of K3[Fe(CN)6] in these experiments — 4.5 g/m3 — is close to that measured earlier in laboratory experiments. It was found that, in fire suppression by an aerosol of the aqueous solution of K3[Fe(CN)6], the volumetric flow rate of this fire suppressant was 30 times lower than the standard flow rate of pure water from a fire hose. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper reports results of an experimental study and numerical simulation of the effect of the equivalence ratio ( φ = 0.6–1.6) on the burning velocity of laminar, premixed atmospheric methane-air and propane-air flames without additives and with 0.06% trimethylphosphate (TMP). The effect of the equivalence ratio ( φ = 0.7–4.5) on the burning velocity of hydrogen-air flames without additives and with 0.1% TMP was studied by simulation. The experimental and simulation results show that, in hydrocarbon flames doped with TMP, the inhibition effectiveness decreases sharply with a growth in φ from 1.2–1.3 to 1.4–1.6 and in hydrogen-air flames, the inhibition effectiveness increases with a rise in φ from 1.5 to 4.5. The reactions determining the dependence of the inhibition effectiveness on the equivalence ratio were found by analyzing the flame velocity sensitivity coefficients to changes in reaction rate constants. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The chemical and thermal structure of a Mache-Hebra burner stabilized premixed rich CH4/O2/N2 flame with additives of vapors of triphenylphosphine oxide [(C6H5)3PO], hexabromocyclododecane (C12H18Br6), and ethyl bromide (C2H5Br) was studied experimentally using molecular beam mass spectrometry (MBMS) and a microthermocouple method. The concentration profiles of stable and active species, including atoms and free radicals, and flame temperature pro.les were determined at a pressure of 1 atm. A comparison of the experimental and modeling results on the flame structure shows that MBMS is a suitable method for studying the structure of flames stabilized on a Mache-Hebra burner under near-adiabatic conditions. The relative flame inhibition effectiveness of the added compounds is estimated from changes in the peak concentrations of H and OH radicals in the flame and from changes in the flame propagation velocity. The results of the investigation suggest that place of action of the examined flame retardants is the gas phase. [ABSTRACT FROM AUTHOR]

The propagation velocities of propane-air and methane-air flames of various compositions with and without the addition of 600 ppm trimethyl phosphate were measured and calculated. The flame propagation velocity was determined using the heat flux method, which allows a flame to be stabilized on a flat burner under nearly adiabatic conditions. The experimental results were compared with flame propagation velocities calculated using the PREMIX and CHEMKIN codes for the Westbrook mechanism for the destruction of trimethyl phosphate and the Curran mechanism for hydrocarbon oxidation. The methane-air flame was modeled using the GRI 3.0 mechanism. [ABSTRACT FROM AUTHOR]

The inhibition of atmospheric laminar methane-oxygen flames of various compositions by trimethyl phosphate was studied experimentally and by numerical modeling using mechanisms based on detailed kinetics. The H and OH concentration profiles in flames with and without the addition of trimethyl phosphate were measured and calculated. It was shown that the addition of the inhibitor reduced the maximum (in the reaction zone) concentrations of H and OH in lean and rich flames. The concentration reduction was higher in rich flames than in lean flames. The concentration profiles of the phosphorus-containing products PO, PO2, HOPO, HOPO2, and (HO)3PO in lean and rich flames stabilized on a flat burner were measured and calculated. Tests of the previously developed model of flame inhibition by phosphorus compounds showed that the model provides adequate predictions of many experimental results. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The possibility of using molecular beam mass spectrometry (MBMS) to study the structure of counterflow flames was shown by the example of a CH4/N2-O2/N2 flame. The thermal structure of the flame was studied, and the CH4, O2, and CO2 concentration distributions were measured using a microprobe technique and MBMS. The results of the measurements performed by the two methods were compared. The MBMS technique was used to study the hydroxyl concentration distribution in the flame. The species concentrations and temperature profiles on the burner axis were calculated. [ABSTRACT FROM AUTHOR]