Fire Safety Science Digital Archive

Results of theoretical and experimental investigations of flammability limits and burning velocity of gaseous mixtures under increased pressures and temperatures are presented. Flammability limits were investigated at temperatures from 20 to 250 C and pressures from 0.1 to 2.0 MPa. Gaseous mixtures included the following components: hydrogen, oxygen, air, steam. nitrogen, argon, carbon dioxide, helium. The burning velocities of gaseous mixtures, containing hydrogen, air and steam were defined experimentally at, temperatures from 20 to 200 C and pressures from 0.1 t o 6.0 MPa. The effect of sign change of pressure index n of burning velocity Su for values of Su much greater, than 0.5 m/c, was found. It means, that the violation of Lewis-Elbe rule for the pressure index o f' burning velocity occures. Numerical modelling of flame propagation in stoichiometric methane-air and hydrogen-air mixtures mas executed with detailed chemical kinetics under room temperature and pressure in the range 0.1-2.0 MPa. The variation of rate constants k of following reactions was made: \. H + H + M -> Hz +, M, ,( 1 ) o + 0 + M -> O 2 + M, (11) H + 0 + M -> HO + M. (111) 2 2 Rate constantes k were reduced by a f'actor K, where K was 0 .1, 1, 10, 100, 1000. The dependence of' burning velocity and its pressure index on a factor K was investigated.