Igor V. Dyakov

Measurement of adiabatic burning velocity in methane-oxygen-nitrogen mixtures

Experimental measurements of the adiabatic burning velocity in methane-oxygen-nitrogen mixtures are presented. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. The oxygen content in the artificial air was varied from 16 percent to 21 percent. The Heat Flux method was used to determine burning velocities under conditions when the net heat loss of the flame is zero. Major attention in this work has been paid to the identification of possible uncertainties and errors of the measurements. The overall error of the burning velocities is estimated to be smaller than ± 0.8 cm/s. Experimental results are in very good agreement with recent literature data for methane-air mixtures. They also agree well with detailed chemical model predictions.

Measurement of adiabatic burning velocity in ethane-oxygen-nitrogen and in ethane-oxygen-argon mixtures

Abstract Experimental measurements of the adiabatic burning velocity in ethane–oxygen–nitrogen and in ethane–oxygen–argon mixtures are presented. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. Dilution ratio O 2 /(O 2 +N 2 ) was varied from 15% to 21%; dilution ratios O 2 /(O 2 +Ar) were 15% and 16%. A heat flux method was used to determine burning velocities under conditions when the net heat loss from the flame to the burner is zero. An overall accuracy of the burning velocities was estimated to be better than ±0.8 cm/s. Experimental results are in a good agreement with recent literature data for ethane–air mixtures. New measurements of the adiabatic burning velocity in diluted ethane–oxygen–nitrogen and in ethane–oxygen–argon mixtures extend the basis for validation of detailed reaction schemes. Predictions of the detailed chemical mechanism developed in this laboratory agree well with the measurements. The influence of the inert diluent on the flame burning velocity is discussed.

EXPERIMENTAL STUDY OF ADIABATIC CELLULAR PREMIXED FLAMES OF METHANE (ETHANE, PROPANE) + OXYGEN + CARBON DIOXIDE MIXTURES

Abstract Experimental studies of adiabatic cellular flames of CH4 + O2 + CO2, C2H6 + O2 + CO2, and C3H8 + O2 + CO2 are presented. Visual and photographic observations of the flames were performed to quantify their cellular structure. Non-stretched flames of methane and propane were stabilized at atmospheric pressure on a perforated plate burner of improved design. New measurements are compared with recent results from this group. A Heat Flux method was used to determine propagation speeds under conditions when the net heat loss of the flame is zero. Under specific experimental conditions the flames become cellular; this leads to significant modification of the flame propagation speed. The onset of cellularity was observed throughout the stoichiometric range of the mixtures studied. Cellularity disappeared when the flames became only slightly sub-adiabatic. Increasing the oxygen content in the artificial air and increasing the temperature of the burner plate led to increase of the number of cells observed. No direct proportionality between the number of cells and propagation speeds in CH4 + O2 + CO2 flames was observed. Dependence of the number of cells as a function of equivalence ratio clearly showed a local minimum in the stoichiometric mixtures.

Nitric oxide formation in premixed flames of H2+CO+CO2 and air

Burning velocity and probe sampling measurements of the concentrations of O 2 , CO 2 , CO, and NO in the postflame zone of the flames of H 2 +CO+CO 2 and air are reported. The heat flux method was used for stabilization of laminar, premixed, non-stretched flames on a perforated plate burner at 1 atm. Axial profiles of the concentrations of major species were used to evaluate the influence of the ambient air entrainment and downstream heat losses. The influence of the downstream heat losses to the environment has been included in the modeling. The numerical predictions of the concentrations of O 2 , CO 2 , and CO in the postflame zone are in a good agreement with the experiment. The amount of the NO formed in the adiabatic flame front is significantly higher than that formed downstream. It is shown that in rich mixtures, where the NNH route forming NO is dominant, the heat losses do not affect significantly the calculated [NO]. The comparison of the experimental data with the detailed flame structure modeling strongly suggests a reduced value of the rate constant k 1 for the reaction NNH+O=NH+NO. The calculations with k 1 =(1±0.5)×10 14 exp(−16.75±4.2 kJ/mol/ RT ) cm 3 /mol s bring the modeling close to the measurements not only in rich but also in stoichiometric and lean flames. The rate constant proposed in the present study is consistent with earlier evaluations within uncertainty limits.

PROBE SAMPLING MEASUREMENTS OF NO IN CH4+O2+N2 FLAMES DOPED WITH NH3

ABSTRACT Probe sampling measurements of the concentrations of nitric oxide in the post-flame zone of methane + oxygen + nitrogen flames doped with ammonia (0.5% of the fuel) are reported. The goal of this work was to analyze formation of NOx from fuel-N under well-controlled conditions. A Heat Flux method was used for stabilization of non-stretched flames on a perforated plate burner at atmospheric pressure. Dilution ratios of oxygen, O2/(O2 + N2), were varied from 0.16 to 0.209. The concentrations of O2, CO, CO2 and NOx were measured by means of a non-cooled quartz probe at different axial distances from the burner. Measured burning velocities for these flames and concentrations of the major species (O2, CO, CO2) agree well with those of the flames of methane + oxygen + nitrogen within an experimental accuracy. The concentrations of NOx in the post-flame zone have a maximum near the stoichiometry. These measurements were compared to predictions of detailed kinetic models and to similar experiments in flames of methane + oxygen + carbon dioxide doped with ammonia. In (CH4 + NH3) + O2 + CO2 mixtures the modeling over-predicts the measured concentrations of NOx however the experimental trends are well reproduced. In (CH4 + NH3) + O2 + N2 mixtures the plots of the concentrations of NOx in the post-flame zone as a function of the stoichiometric ratio differ qualitatively from that in (CH4 + NH3) + O2 + CO2 mixtures. The modeling is in satisfactory agreement with the experiments in lean flames, while in rich flames it is not.

EXPERIMENTAL MEASUREMENTS AND MODELING USING CESFAMB TM SOFTWARE OF THE PRODUCT GAS COMPONENTS ON THE 2MW TH GASIFIER PLANT

The work assesses the performance of a prototype 2M Wth plant as an auxiliary source of energy based on biomass gasification using wood pellets as a fuel. During steady operation, process temperature, proce ss pressure and concentrations of components in the pr oduct gas have been measured the measurements are compared to the simulation results obtained with th e CeSFaMB software. The underlying model in this software is also used to determine the sensitivity of the simulated concentrations to various paramete rs of the gasification process. The results of modeling are i n general agreement with those obtained experimenta lly.

The effects of composition on the burning velocity and NO formation in premixed flames of C{sub 2}H{sub 4} + O{sub 2} + N{sub 2}

Experimental measurements of the adiabatic burning velocity and NO formation in C2H4 + O2 + N2 flames are presented. The oxygen content in synthetic air varied from 18% down to 14%. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. A heat flux method was used to determine the burning velocities under the conditions when the net heat loss of the flame is zero. Adiabatic burning velocities of ethylene + nitrogen + oxygen mixtures were found in good agreement with the modeling. Sampling measurements were performed at 10–20 mm from the burner and concentrations of stable species, CO, CO2, O2 and NOx were recorded. The concentrations of CO, CO2 and O2 were compared with the modeling to reveal that the range of the flame conditions was less affected by the ambient air entrainment. The dependencies of [NO] as a function of equivalence ratio clearly possess two maxima: in stoichiometric mixtures due to Zeldovich thermal-NO mechanism and in rich mixtures at equivalence ratio close to 1.4 due to Fenimore prompt-NO mechanism. Dilution by nitrogen decreases [NO] at any equivalence ratio. Numerical predictions of the concentrations of NO in a post-flame zone of lean and stoichiometric flames are in good agreement with the experiments when downstream heat losses to the environment were taken into account. The predictions of the Konnov mechanism in rich ethylene flames reproduce trends of the experimental data with an under-prediction of about 10–15 ppm.