Burning Velocities Of Methane Research Articles

A Kinetic Mechanism for CF3I Inhibition of Methane–Air Flames

ABSTRACT The influence of CF3I on the burning velocity of methane–air flame is experimentally and numerically studied. Experimental results demonstrate that the inhibition effectiveness of CF3I is very close to that of CF3Br. A detailed kinetic model of flame inhibition by CF3I is presented, based on an updated version of a previous model. The kinetic model contains 1072 reactions with 115 species including 10 iodine-containing species. Modeling results demonstrate good agreement with experimental data, and both experiments and calculations show that CF3I is only slightly less effective at reducing the burning velocity than CF3Br. The flame structure predicted from numerical simulations is analyzed and shows that main reactions of the inhibition cycle of CF3I are as follows: H+ HI = H2 + I; H + I + M = HI+M; I + I + M = I2 + M; H+ I2 = HI+I; I+ CH3 + M = CH3I+M; H+ CH3I = CH3+ HI; I+ HCO = HI+CO; HI+OH = H2O+I and O+ HI = I+ OH.

Determination of laminar burning velocity of methane/air flames in sub atmospheric environments

The global energy demand enhances the environmental and operational benefits of natural gas as an energy alternative, due to its composition, mainly methane (CH4), it has low polluting emissions and benefits in energy and combustion systems. In the present work, the laminar burning velocity of methane was determined numerically and experimentally at two pressure conditions, 0.85 atm and 0.98 atm, corresponding to the city of Medellín and Caucasia, respectively, located in Colombia. The environmental conditions were 0.85 atm, 0.98 atm, and 295±1 K. The simulations and experimental measurements were carried out for different equivalence relations. Experimental laminar burning velocities were determined using the burner method and spontaneous chemiluminescence technique, flames were generated using burners with contoured rectangular ports to maintain laminar Reynolds numbers for the equivalence ratios under study and to reduce the effects of stretch and curvature in the direction of the burner's axis. In general, the laminar burning velocity fits well with the numerical results. With the results obtained, a correlation is proposed that relates the laminar burning velocity with the effects of pressure, in the form SL=aPb, where a and b are model constants. Sensitivity analysis was performed using the GRI-Mech 3.0 mechanism which showed that the most sensitive reaction was H+O2=O+OH (R38). Additionally, it was found that the reactions H+CH3 (+M)=CH4 (+M) (R52), 2CH3 (+M)=C2H6 (+M) (R158), and O+CH3=H+CH2O (R10) dominate the consumption of CH3 which is an important radical in the oxidation of methane, this analysis is carried out for equivalence ratios of 0.8 and 1.0, and atmospheric pressures of 0.85 atm and 0.98 atm

メタン-水素予混合火炎の OH 濃度と燃焼速度 (第一報)

メタン-水素予混合火炎の OH 濃度と燃焼速度 (第一報)

High pressure laminar burning velocity measurements and modelling of methane and n-butane

A constant volume vessel has been used in conjunction with a numerical multi-zone model to calculate laminar burning velocities of methane and n-butane in the ranges φ = 0.8–1.4, T u = 320–470 K, p u = 1–15 bar from the pressure record. This multi-zone model has been compared with the analytical model of Luijten and de Goey. For methane, the experimental data have been compared with modelling data generated using the MIXFLA program of Warnatz. The MIXFLA data have further been used to examine the form of the correlation fitted to the experimental data, confirming the form used by Clarke. For methane, good agreement was found between the current experimental data and the literature at high pressures. For n-butane, poor agreement was found with the one data set available. However, the data from this reference did not compare well with other authors for methane.

The Effects of Enrichment by Carbon Monoxide on Adiabatic Burning Velocity and Nitric Oxide Formation in Methane Flames

The present paper discusses the fundamentals of specific fuel mixtures as they may be used in lean premix flames in power installations. Experimental measurements of the adiabatic burning velocity and NO formation in (CH4 + CO) + (O2 + N2) flames are presented. The carbon monoxide content in the fuel was varied from 0 to 15%. The oxygen content in the air was varied from 20.9% to 18%. These ranges are typical for addition of reformer gas to methane burners. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. The Heat Flux method was used to determine burning velocities under conditions when the net heat loss of the flame is zero. An overall accuracy of the burning velocities was estimated to be better than ±1 cm/s in the whole range of enrichment by carbon monoxide. The relative accuracy of the equivalence ratio was found to be below 1.6%. Adiabatic burning velocities of methane + carbon monoxide + nitrogen + oxygen mixtures were found in satisfactory agreement with the modeling. The concentrations of O2, CO, CO2 and NO in these flames were measured in the burnt gases at a fixed distance from the burner using probe sampling. Enrichment by carbon monoxide leads to the increase of NO formation in lean and stoichiometric mixtures. Dilution by nitrogen decreases [NO] at any equivalence ratio. Numerical predictions and trends were found in good agreement with the experiments. The results of enrichment by CO on adiabatic burning velocity and nitric oxide formation in methane flames are discussed and compared with similar flames enriched by hydrogen. Experimental peculiarities due to contamination of the fuel mixtures with metal carbonyls are described.

317 メタンおよびプロパンの燃焼速度に及ぼす圧力,温度,濃度の影響(燃焼)

317 メタンおよびプロパンの燃焼速度に及ぼす圧力,温度,濃度の影響(燃焼)

Erratum: “A Correlation for the Burning Velocity of Methane–Air Mixtures at High Pressures and Temperatures” (Journal of Engineering for Gas Turbines and Power, 1987, 109, pp. 439–442)

Erratum: “A Correlation for the Burning Velocity of Methane–Air Mixtures at High Pressures and Temperatures” (Journal of Engineering for Gas Turbines and Power, 1987, 109, pp. 439–442)

A Correlation for the Burning Velocity of Methane–Air Mixtures at High Pressures and Temperatures

A formulation for the burning velocity of methane–air mixtures was developed over a range of equivalence ratios at temperatures and pressures high enough to cover conditions encountered in a typical operating spark ignition engine using the experimental data of Babkin and Kozachenko [1]. An example involving the use of such data in a diagnostic program to yield information about the characteristics of flame propagation in an engine fueled with methane is shown.

Laminar Burning Velocities of Methane-Oxygen-Diluent Gas Mixtures

The burning velocities of methane--oxygen--diluent mixtures were determined at atmospheric pressure by use of bunsen flames under laminar flow conditions. The fuel-lean region was investigated at theoretical flame temperatures of 2000, 2250 and 2500/sup 0/K employing nitrogen, helium and argon as diluents. By maintaining constant calculated flame temperatures for the different mixtures, evaluation of the effects of the properties of the diluent and of O/sub 2//CH/sub 4/ ratio was greatly simplified. The dependence of burning velocity on O/sub 2//CH/sub 4/ ratio was not in accord with the approximate theories of combustion. Therefore, an empirical expression was developed to describe the effect of diluent, O/sub 2//CH/sub 4/ ratio, and flame temperature on burning velocity. The evaluation of this expression is discussed in terms of effective transport properties and concentrations.

The determination of burning velocities of slow flames

Measurements of the burning velocities of methane, ethane, propane, butane, ethylene, carbon monoxide and cyanogen mixtures with air, in the range about 4 to 8 cm, are made by the flat-flame burner method with an accuracy of 2 to 3%. The results can be represented by a straight-line relationship between composition and burning velocity except for carbon monoxide which is sensitive to the percentage of water vapour present. Extrapolated values agree well with recent measurements of faster flames. Measurements are also made on binary mixtures with air of the gases, including hydrogen. The mixture law holds except with mixtures containing carbon monoxide. Limits of inflammability are also determined and the burning velocities at the limits average 3⋅6 cm/s. The mixtures obey the Le Chatelier rule accurately, except for carbon monoxide mixtures. The burning velocities of the hydrocarbons can be represented approximately by a straight-line relationship with the heat generated and with the maximum flame temperature, but correlation is best when thermal conductivity is introduced. At a given velocity the excess energy maintained by the flame appears to be constant for all the hydrocarbons investigated, except methane, which behaves slightly differently. The burning velocities of the hydrocarbons are controlled by a reaction which provides reasonable values of the activation energies and probably precedes the sudden development of chain branching.