Vandooren, J., and Van Tiggelen, P.J. (1977)
Reaction Mechanisms of Combustion in Low Pressure Acetylene-Oxygen Flames
16th Symposium (International) on Combustion 1977, p.1133
Abstract
In order to understand the fundamental mechanism of combustion processes, it is necessary to measure the concentrations of all the species throughout the flame front. Molecular beam sampling and mass spectrometric analysis have been used for that purpose. We have determined the molar concentrations of the stable and unstable species for two C2H2/O2 flames: a lean flame and a stoichiometric one. Both flames were burning at 40 Torr.
From all these data, it is possible to deduce the elementary processes occuring in acetylene combustion.
The first step of acetylene removal involves either hydroxyl radicals or oxygen atoms, in different proportions depending on the equivalence ratio (reactions (23) and (108), with rate constants shown below).
The CH2 radical then reacts with molecular oxygen, producing carbon dioxide and molecular hydrogen.
The ketene C2H2O reacts with a hydroxyl radical to form formaldehyde (reaction (A)), and CH2O further reacts with another hydroxyl radical (reaction (121)).
Molecular oxygen then combines with the formyl radical CHO to give carbon monoxide (reaction (168)). The CO and H2, formed in the combustion of acetylene, disappear through the usual elementary reactions.

REACTION RATE COEFFICIENTS SUGGESTED IN THIS WORK:

GRI-Mech
Number
('-' sign
means
reverse)		 Reaction Rate Coefficient
A T^n exp(-E/RT)		 Temperature
Range
(K)
A
(mol,cm3,s)		 n
(T in K)		 E
(cal/mol)
23 O + C2H2 -> CO + CH2 6.7E+13   4000 700-1500
101 OH + CH2O -> HCO + H2O 3.9E+13   1400 300-1600
108 OH + C2H2 -> H + HCCOH 3.2E+11   200 570-890
A OH + C2H2O -> HCO + CH2O 2.8E+13     400-1100