Activation energies in high temperature combustion

Fenn, John B.; Calcote, H.F.

doi:10.1016/s0082-0784(53)80029-9

Cited by 23 publications

(7 citation statements)

References 4 publications

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“…Equilibrium partial pressures of hydrogen atoms, hydroxyl radicals, and oxygen atoms were calculated by the method of Huff and Calvert [13] . The activation energy, E, was taken as 26 kcal/g mole [14].…”

Section: Comparison Of Experiments With Theoriesmentioning

confidence: 99%

Measurement of flame speeds by a nozzle burner method

Halpern¹

1958

J. RES. NATL. BUR. STAN.

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The literature records a great many meas urements, using stationary flames on burners of the speed with which flame moves through combustible mixtures of gases. D espite th~ fact that the method itself seems reasonably simple, the results obtained by various invcstigato:s often are not in good agreement. One of the phases of a program of research on combustIOn has been a study of some of the r easons for the differences among recorded values of flame speed measured by the burner method. The primary objective of this task has been to develop the precautions t hat should be observed in applying t he method, rather than to e volve numerical values of flame speed . This paper describes progress that has been made since the apparatus was described originally in 1951, and presents val ues of flame speeds of methane-air mixtures obtained s ince then, together with comparisons of these val ues with those obtained by two flame theories.

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Section: Comparison Of Experiments With Theoriesmentioning

confidence: 99%

Measurement of flame speeds by a nozzle burner method

Halpern¹

1958

J. RES. NATL. BUR. STAN.

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“…(13) is obtained by expanding the perturbed Arrhenius exponent in a series and neglecting terms of order higher than one. In subsequent manipulations, extensive use is made of the perfect gas relationships a 2 = kRT and C P /R = k/(k -1).…”

Section: Discussionmentioning

confidence: 99%

Combustion stability in an annular gas combustor.

Bonnell

1968

AIAA Journal

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The conditions for either stable or oscillatory combustion are determined analytically for a burning mixture of ideal gases in an annular combustion zone. The mixture, flowing steadily in the axial direction, is perturbed by a small-amplitude, tangentially propagating pressure disturbance. The rate of energy release is described by an Arrhenius function. The stability of the system is governed by an amplif cation coefficient that reflects the effects due to the rate of energy release and the convective transport of energy. The stability criterion is employed to evaluate the effects of changes in the system parameters on the combustion stability. A critical value of the Arrhenius exponent is determined which exists at a line demarcating regions of stable and oscillatory combustion; it is a function of the flowfield variables, the specific-heat ratio, and the reaction rate frequency factor. A partial, qualitative verification of the stability trends predicted by the analysis is provided by the known stability behavior of premixed gases burned in cylindrical and annular combustors.Mach number m = mean molecular weight n = wave number for tangential mode of oscillation p -static pressure p i} p. 2 = amplitude constants r = mean radius of annulus, radial coordinate R -gas constant R u -universal gas constant t = time T = static temperature v = velocity vector v$j v z = tangential and axial velocity components, respectively Xij Xj = mass fractions of components i and j z = axial coordinate & = na/r Sij 5 2 = constant phase angles e = activation energy 0 = angular coordinate p = density

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“…A : frequency factor Dam : Damköhler number E H 2 : overall activation energy of hydrogen-air reaction (67 kJ/mole (11) , 75 kJ/mole (12) ) E CH 4 : overall activation energy of methane-air reaction (109 kJ/mole (11) Table 1 shows an example of the composition and properties of off-gas from a fuel cell. The main combustible components are hydrogen and methane, of which the volumetric fractions are 16 -38% and 4 -3%, respectively, in accordance with the changes in the fuel utilization ratio.…”

Section: Nomenclaturementioning

confidence: 99%

Flame Stability Limit and Exhaust Emissions of Low Calorific Fuel Combustion in Turbulent Diffusion Combustor for a Small-Scale Fuel Cell

Koseki

2004

JSME international journal. Ser. B, Fluids and thermal engineer

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This paper describes an investigation conducted on flame stability and exhaust emissions from a turbulent diffusion combustor, fueled with low-calorific gas, for a small-scale fuel cell. It is important to maintain flame stability in the combustor, even under lean fuel conditions, and to suppress CO emission in the exhaust gas. An imitation off-gas, in which hydrogen and methane were diluted by adding nitrogen, with Wobbe indices ranging from ca. 4 400 -8 700, corresponding to the fuel utility ratio of 90% -60% in the fuel cell, was supplied to the combustor, and the blow-off limits, CO, and NO x emissions were experimentally investigated. The results show that the blow-off excess air ratios increases with an increasing Wobbe index and with decreasing fuel input to the combustor, and that they are proportional to the hydrogen concentration in the fuel to the power of 0.5 -1.0. In addition, it was found that the Damköhler numbers at blow-off limits decreased with decreasing fuel input and with increasing Wobbe indices, and that the product of (0.5 was constant at blow-off limits. Furthermore, NO x emissions from the combustor were low, less than 20 ppmV (O 2 = 0%), it was also found that the apparent activation energy of NO x emission derived from Arrhenius plots was almost equal to that of prompt NO in the combustion of imitation off-gas.

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Activation energies in high temperature combustion

Cited by 23 publications

References 4 publications

Measurement of flame speeds by a nozzle burner method

Measurement of flame speeds by a nozzle burner method

Combustion stability in an annular gas combustor.

Flame Stability Limit and Exhaust Emissions of Low Calorific Fuel Combustion in Turbulent Diffusion Combustor for a Small-Scale Fuel Cell

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