Elementary reaction rates from post-induction-period profiles in shock-initiated combustion

Abstract

Elementary reaction rates were measured by following the reaction profiles in the transition zone between the exponential growth and recombination zones in the shock-initiated combustion of H 2 :O 2 :Ar=10:1:89, H 2 :O 2 :Ar=1:10:89, H 2 :O 2 :CO:Ar=1:5:3:91, and H 2 :O 2 :CO 2 :Ar=5:1:4:90 mixtures in the temperature range 1200°–2500°K. Rate-constant expressions for the reactions O H + H 2 = ⋅ H 2 O + H , O H + O H = H 2 O + O , O H + C O = C O 2 + H , were found to be 5.2×10 13 exp (−6.5 kcal/ RT ) 5.5×10 13 exp (−7.0 kcal/ RT ), and 4.0×10 12 ×exp (−8.0 kcal/ RT ) cm 3 /mole/sec, respectively. None of these expressions extrapolate linearly on an Arrhenius graph to the room-temperature data. Possible interpretations of nonlinear Arrhenius graphs are discussed.