Lean Blowout Detection Techniques for Partially Premixed Flames in a Dump Combustor - Novel Combustion Concepts for Sustainable Energy Development - page 211

Fig. 10 Variation of red and blue color intensities with flame modes for different equivalence
ratios (port 1) (Chaudhari et al. 2013 )

emission band in visible spectrum. As the equivalence ratio is further reduced, the
dominating 700-nm peak in spectrum diminishes and the spectrum shows peak
around 432 nm wavelengths, which is close to blue color emission band wavelength
in the visible spectrum. The results of the spectrometer are consistent with the color
analysis of

flame carried by camera.
We explain this color observation as follows. In the most common hydrocarbon

fl

fl flames, the most important factor determining fl flame color is oxygen supply and the

extent of fuel oxygen premixing which determines the rate of combustion and thus

the temperature and reaction paths, thereby producing different colors. At higher
equivalence ratio (

-

Φ ), the presence of incandescence of very fine soot particles

produced in the flame reddish. With increasing oxygen supply (lean

condition), less soot is produced due to more complete combustion and the reaction
creates enough energy to excite and ionize gas molecules in the

fl ame makes fl

fl flame, leading to

blue appearance of leaner fl ame.

with equivalence ratio for a range of
parameters permitted by our setup to illustrate the consistency of the proposed
metric stated in Eq. ( 2 ) for quantifying LBO proximity.
It is observed that

Here, we first presents the variation of γ

Φ LBO is dependent on L fuel , i.e., the degree of premixing. In
order to explore the applicability of our predictor for various degrees of premixing,
we conducted different tests for a wide range of air fl ow rates and L fuel permitted by

the setup. The color ratio, i.e., , was determined for each decreasing equivalence

ratio condition and reported over a normalized equivalence ratio (

γ

Φ / Φ LBO )in