Lean Blowout Detection Techniques for Partially Premixed Flames in a Dump Combustor - Novel Combustion Concepts for Sustainable Energy Development - page 219

5.

for ′

j = 1 : N

for i 1 = 1 : N

11 −

1

for i 2 = 1 : N − 1

12

x 1 j ) ≥ partition 1 i 1 & x 1 j ) < partition 1 i 1 + 1 &

if ,

x 2 j ) ≥ partition 2 i 2 & x 2 j ) < partition 2 i 2 + 1 ))

p
end

(( i 1 − 1 * ( N − 1 + i 2 = p (( i 1 − 1 * ( N − 1 + i 2 + 1

12 12

end
end

ðÞ= N 0 ;

6. p1 i if N 11 N 12

Use the same partitions for all the states
Determination of Anomaly Measure

ðÞ ¼ pi for1

cos 1 p 0 p 1
p kk p kk
In the present context, the time series of heat release

1. Compute anomaly measure, M ¼

flame (i.e.,
CH signal) captured on photomultiplier tube (PMT) is used for STSA analysis. The
algorithms stated above are applied, and the LBO predictor in the form of anomaly
measure has been deduced to monitor the proximity of imminent blowout. The
same time traces of CH signal which are captured in different experimental runs on
which the preceding optical LBO detecting methods were described are used in the
present analysis. We observed that as

fl fluctuation of fl

approaches to Φ LBO, there is a distinct

Ф

change in the flame dynamics which apparently vary the heat release rate.

Figure 15 a shows the variation of anomaly measure as a function of equivalence
ratio

fl

)
taken as 0.82. In this investigation, alphabet size was taken as 8 for simple parti-
tioning, while for ASSP, the amplitude and phase spaces were divided into 8 and 5
regions, respectively. From Fig. 15 a, it has been found that the anomaly measure

Ф for port 1 (L fuel = 35 cm), Q air = 85 LPM, and the nominal condition ( Ф

first increases sharply as the equivalence ratio decreases from the nominal value but
changes very slowly and acquires a value close to 1 as LBO is approached. Thus, a
sudden change in the slope of the anomaly measure, which is observed at a rea-
sonable distance from LBO, may be useful for LBO prediction. On carefully
observing the trend of anomaly measure, thresholding of the anomaly measure was
found to be very suitable for sensing the proximity of LBO. From Fig. 15 a, the
threshold of 0.7 can be satisfactorily used, which gives enough margin for sensing
the imminent blowout. Once the set threshold value is crossed, the active control
system takes appropriate action for enhancing the stabilization of

flame in com-
bustor so that the incipient blowout could be avoided and LBO limit can be
extended. This can be done either by increasing the pilot fuel or possibly by using
small amplitude fuel modulation.

fl