Combustion Science and Technology

WELDON, J.; SENKAN, S. M.

doi: 10.1080/00102208608923875pmid: N/A

Abstract The oxidation of CH3Cl in air using a commercially available Cr2O3 catalyst was studied in a packed-bed, isothermal reactor in the temperature range of 340-470°C and at I atm. Reaction rates were independent of the concentration of oxygen for CH3Cl partial pressures below 0.043 atm. A non-linear second order rate model was satisfactory in correlating the data.

SKOCYPEC, R. D.; WALTERS, D. V.; BUCKlUS, R. O.

doi: 10.1080/00102208608923876pmid: N/A

Abstract The radiant emission from gas and particulate mixtures is of interest in many combustion processes. This work presents total hemispherical emittance values for media representative of combustion applications in terms of measurable or known parameters. The charted solutions apply to gas mixtures of carbon dioxide and water vapor, and particulate which scatters radiant energy. The values of total hemispherical emittance are presented in terms of the particulate absorption coefficient, system length, tcmperaturc, and particulate scattering coefficient. Methods to evaluate these parameters as well as the emittance arc presented.

Bray, K. N. C.; Libby, Paul A.

doi: 10.1080/00102208608923877pmid: N/A

Abstract An earlier analysis of the characteristic scales associated with the mean reaction.rate in a premixed turbulent flame is extended by revising an important modeling assumption. In the previous work the distribution of passage times of burned and unburned gas packets is represented by an exponential probability density function which is analytically convenient but inapplicable at small passage times. The present analysis employs a gamma two distribution which removes this shortcoming and is in good agreement throughout the range of such times with the limited experimental data currently available. Modified expressions are obtained for the distributions of the time autocorrelation function, the mean reaction rate and the normalized time scale through a planar flame. Further experiments are required to test these predictions.

ROTZOLL, G.

doi: 10.1080/00102208608923878pmid: N/A

Abstract Abstract– A molecular beam source reactor is used to study the oxidation of methane at temperatures from 1170 to 1460 K, pressures above 1000 mbar and residence times of about 3 msec. The mixtures investigated range from lean to rich conditions. The products detected in the induction phase or the reaction up to the ignition point arc H2O, H2, CH2O, C2H6, CO, C2H4. CO2, C2H2 and C2H2O. A recent flame chemistry reaction model is extended by elementary reactions important for the induction phase and used to simulate the experimental data. The general agreement is good, although quantitative discrepancics remain. Analysis of the major reaction pathways shows that the reactions of the methyl radical in the induction phase up to high conversions are distinctly different from the ones in flames: CH3 is mostly oxidized by the HO2 radical, with minor contributions from the reactions with O2 and O.

Joulin, G.; Deshaies, B.

doi: 10.1080/00102208608923879pmid: N/A

Abstract Abstract–We employ asymptotic techniques to study the propagation of a planar premixed flame in a gaseous mixture sceded with small, inert particles. Assuming that: i) the particles to gas heat capacity ratio is very small, ii) the phases are in local thermal and mechanical equilibrium, iii) the attenuation to conduction-convection length ratio is very large. iv) the radiant to convective energy flux ratio is small, v) the activation to thermal energy ratio is large we get the changes in flame structure and its increase in speed due to radiative (self-) preheating. The theory is applied first to steady flames, by using differential approximations of the radiative transfer equation. It is then extended to take account of a better description of radiative exchanges. including scattering and spectral effects, and is used to investigate the propagation of unsteady, planar flames.

MURPHY, MICHAEL J.

doi: 10.1080/00102208608923880pmid: N/A

Abstract Abstract–A well-stirred combustor (WSC) was constructed capable of burning natural gas, and residual fuel oil at equivalence ratios of 0.4 to 1.8 and residence times of 50 or 175 ms. gold-flow tests verified the well-stirred condition. NOy emissions produced by burning these fuels in the WSC were higher than previous WSCs with 1-10 ms residence time, but generally lower than industrial boilers.