  The structure of three laminar premixed rich flames has been investigated: a
pure methane flame and two methane flames doped by allene and propyne,
respectively. The gases of the three flames contain 20.9% (molar) of methane
and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure
methane flame. In both doped flames, 2.49% of C3H4 was added, corresponding to
a ratio C3H4/CH4 of 12% and an equivalence ratio of 1.55. The three flames have
been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant,
with a gas velocity at the burner of 36 cm/s at 333 K. The concentration
profiles of stable species were measured by gas chromatography after sampling
with a quartz microprobe. Quantified species included carbon monoxide and
dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne,
allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, isobutene,
1-butyne, vinylacetylene, and benzene. The temperature was measured using a
PtRh (6%)-PtRh (30%) thermocouple settled inside the enclosure and ranged from
700 K close to the burner up to 1850 K. In order to model these new results,
some improvements have been made to a mechanism previously developed in our
laboratory for the reactions of C3-C4 unsaturated hydrocarbons. The main
reaction pathways of consumption of allene and propyne and of formation of C6
aromatic species have been derived from flow rate analyses.
