Lean Blowout Detection Techniques for Partially Premixed Flames in a Dump Combustor - Novel Combustion Concepts for Sustainable Energy Development - page 212

Fig. 11 Spectrometer spectrum for different Φ / Φ LBO clearly shows the variation of colors from

their different dominating wavelength peak as Φ approaches to Φ LBO (Q air = 80 LPM,L fuel = 35 cm)

(Chaudhari et al. 2013 )

Fig. 12 . Again, for each selected L fuel and air ow rate (Q air ), three different runs

have been taken to estimate the percentage error. It is found that error percentage
for most of the readings lies within

fl

10 %.
From Fig. 12 , it is clearly observed that irrespective of the L fuel and the air

±

fl ow

condition used, γ decreases monotonously with equivalence ratio, which justi es

the choice of as LBO detection metric for sensing the proximity of combustor to

blowout. As evident from the

γ

figure, a set threshold ( c thresh ) on the value of γ would

be suf cient to detect proximity to blowout for this particular con guration. Setting

c thresh 0 : 3 would provide a reasonably safe margin of / Φ LBO ≈ 1.2 1.3 for all

Ф -

the flow rates and premixing lengths considered, with the higher ratio corre-

sponding to the more premixed configuration (L fuel = 35 cm). Since premixed
fl

fl

flames are more susceptible to lean blowout, a higher safety margin for this con-

figuration is advantageous. A single threshold value for different con figuration and

fl flow condition would simplify the development of controller for preventing

blowout. Again, selection of threshold value ( c thresh ) is not limited to fixed value

and can be varied depend upon the safety margin required. Another advantage of