DOI: 10.1615/TSFP9
A NEW DOUBLE-SLIT CURVED WALL-JET (CWJ) BURNER FOR STABILIZING TURBULENT PREMIXED AND NON-PREMIXED FLAMES
Краткое описание
A novel double-slit curved wall-jet (CWJ) burner was
proposed and employed, which utilizes the Coanda effect
by supplying fuel and air as annular-inward jets over a
curved surface. We investigated the stabilization
characteristics and structure of methane/air, and
propane/air turbulent premixed and non-premixed flames
with varying global equivalence ratio, ∅, and Reynolds
number, Re. Simultaneous time-resolved measurements of
particle image velocimetry and planar laser-induced
fluorescence of OH radicals were conducted. The burner
showed potential for stable operation for methane flames
with relatively large fuel loading and overall rich
conditions. These have a non-sooting nature. However,
propane flames exhibit stable mode for a wider range of
equivalence ratio and Re.
Mixing characteristics in the cold flow of nonpremixed
cases were first examined using acetone
fluorescence technique, indicating substantial transport
between the fuel and air by exhibiting appreciable
premixing conditions. PIV measurements revealed that
velocity gradients in the shear layers at the boundaries of
the annular jets generate the turbulence, enhanced with the
collisions in the interaction jet, IJ, region. Turbulent mean
and rms velocities were influenced significantly by Re and
high rms turbulent velocities are generated within the
recirculation zone improving the flame stabilization in this
burner. Premixed and non-premixed flames with high
equivalence ratio were found to be more resistant to local
extinction and exhibited a more corrugated and folded
nature, particularly at high Re. For flames with low
equivalence ratio, the processes of local quenching at IJ
region and of re-ignition within merged jet region
maintained these flames further downstream particularly
for non-premixed methane flame, revealing a strong
intermittency.