Ethanol flame structure investigated by molecular beam mass spectrometry

The oxidation of ethanol was studied in low-pressure, premixed flat flames using molecular beam mass spectrometry (MBMS) in combination with electron impact ionization (EI) and resonance-enhanced multiphoton ionization (REMPI). Flame temperature profiles were measured by laser-induced fluorescence (LIF) of seeded NO. Two ethanol/oxygen/argon flames with stoichiometries of ϕ=1.00ϕ=1.00 and ϕ=2.57ϕ=2.57 were investigated at 50 mbar by EI-MBMS. Profiles of a variety of stable and radical species were measured as a function of height above the burner. The benzene profile in the fuel-rich ethanol flame was obtained by REMPI-MBMS. The same technique was used to determine the dependence of the benzene concentration on the ethanol/propene ratio in low-pressure flames with blended fuels (propene/ethanol/oxygen/argon). The C/O ratio of all blends was kept constant at C/O=0.773C/O=0.773 or C/O=0.600C/O=0.600. Ethanol addition ranged from 0 to 15% for flames with C/O=0.773C/O=0.773, and from 0 to 100% for flames with C/O=0.600C/O=0.600. In both data sets, a decrease of the benzene concentration with increasing ethanol percentage was observed. Qualitative information on some other aromatic species with higher mass was also obtained.