C₁/C₂ Chemistry in Fuel-Rich Post-Flame Gases I. Experimental Results and Pool Modelling

Abstract

An experimental study of C₁ and C₂ hydrocarbon species in the post-flame zones of fuel-rich ethylene-air flames at atmospheric pressure and temperatures from 1700 to 1940 K is reported. Most hydrocarbon oxidation occurs via

C₂H₂ + OH. → ((CH₂CO + H) (Rl)

Reaclion (Rl) is effectively irreversible under post-flame conditions. Based on this study and other post-flame and shock-lube studies, the rate constant for (Rl) is, independent of pressure,

k₁ = 1.1 × 10¹³ exp (−30000Jmol⁻¹RT)cm³ mol⁻¹1 s⁻¹

with an estimated uncertainty factor less than 2 in the temperature range 1650 to 1950 K. Oxidation of ketene and CH³ by OH also occurs to some extent. The reaction

CH₃ + OH → (CH₂OH + H) (R2)

is very fast, with k₂ ⩾1.50 × 10¹³ cm³ mol ⁻¹ s⁻¹ A new mode of C₁/C₂ interaction is found to be important under richer conditions:

CH₂CO + CH₃ → (C₂H₅ + CO) (R6)

The occurence of (R6) limits the formation of C₁, species.

Key words:

• Acetylene oxidation
• ketene
• flames
• kinetics