Experimental Study of Temperature and CH Radical Location in Partially Premixed CH4/Air Coflow Flames.
Experimental Study of Temperature and CH Radical
Location in Partially Premixed CH4/Air Coflow Flames.
(1355 K)
Blevins, L. G.; Renfro, M. W.; Lyle, K. H.; Laurendeau,
N. M.; Gore, J. P.
Combustion and Flame, Vol. 118, No. 4, 684-696,
September 1999.
Sponsor:
Purdue Univ., West Lafayette, IN
Keywords:
premixed flames; temperature; combustion chemistry;
flame structure; temperature measurements; experiments
Abstract:
As part of an ongoing investigation of an exhaust NOx,
emission index minimum measured for partially premixed
flames, radial temperature profiles and CH radical
locations were measured in atmospheric-pressure,
partially premixed, coflow, methane/air flames with
fuel-side equivalence ratios of 1.6, 2.0, and 3.5, at
three axial heights above the burner. The work was
undertaken because of the importance of temperature and
CH radical behavior in NO formation chemistry.
Thin-filament pyrometry was found to be more appropriate
than thermocouple thermometry for temperature
measurements in partially premixed flames. Results
demonstrated that the 1.6-equivalence-ratio flame
exhibited classical double-flame structure, the
2.0-equivalence-ratio flame was a merged flame, and the
3.5-equivalence-ratio flame exhibited diffusion-flame
structure. Signals from CH* chemiluminescence and CH
laser-induced fluorescence provide evidence that, for
the present measurement locations, double flames exhibit
single CH peaks which can be associated with their
premixed component flames. Double CH radical peaks,
which were predicted to occur in low-strain-rate flames,
were not found for the limited number of flame
conditions and locations studied. In the near-burner
region, the premixed and nonpremixed component flames of
the phi b=1.6 double flame diverge radially with
increasing downstream distance and merge together for
larger values.
