Lean Blowout Detection Techniques for Partially Premixed Flames in a Dump Combustor - Novel Combustion Concepts for Sustainable Energy Development - page 193

Nomenclature

I(x, y) Image intensity at pixel (x, y)

I r (x, y) Red intensity of the image at pixel (x, y)

I g (x, y) Green intensity of the image at pixel (x, y)

I b (x, y) Blue intensity of the image at pixel (x, y)

L f Premixing length

N Data length captured in experiment

Q Volume fl ow rate

γ Ratio of integrated red to blue intensities

Φ Equivalence ratio

Φ LBO

Equivalence ratio at LBO; LBO limit

R

Number of symbols

1 Introduction

Flames, in different industrial combustion applications, such as gas turbine, aircraft
engine, and burners, are in general partially premixed in nature. These ames are

stable and reliable. Major disadvantage of this type of combustor is production of
unacceptable level of thermal NO x .NO x is found to be a harmful atmospheric
pollutant and causes much environmental degradation such as acid rain, ozone layer
depletion, and human health (Turns 2000 ; Correa 1993 ). During combustion pro-
cess, atmospheric nitrogen, in high temperature, combines with oxygen to form
NO x . The formation in the combustion process is due to the oxidation of atmo-
spheric nitrogen in the high-temperature regions of the post-

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ame gases, which is
chemically described by thermal Zeldovich mechanism (Zeldovich 1946 ).
Due to harmful effects of NO x , stringent environmental pollution norms have
been devised, which recently motivated engine manufactures to develop low NO x
combustors that meet various regulatory emission standards (Correa 1993 ). New
concept for combustion technology like lean premixed (LPM) combustion (or lean
premixed prevaporized [LPP] combustion when liquid fuels are employed) has
been introduced to the gas turbine industry (Lefebvre 1995 ; Correa 1998 ). Lean
premixed combustion appears to be a most promising technology recently because
it offers practical solution to reduce the emissions of nitrogen oxides (NO x ) and its
simplicity in implementation to practical combustors. In LPM combustion, the
temperature of the

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cantly reduced due to excess air present in
combustion zone which consequently eliminates the production of thermal NO x
(Zeldovich 1946 ). In addition, the lean operating condition elevates low mainte-
nance requirements because the lower combustor exhaust temperature increases the
lifetime of turbine blades and other mechanical components (Lefebvre 1999 ).

fl flame is signi