Environmental Engineering Reference
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Fig. 6 Schematic of high-shear injector showing subcomponents for optimizing the design;
reproduced from McKinney et al. ( 2007 )
the CF6-80C2 LEC engine emission test in 1995 (Mongia 1997 ). Subsequently, all
new GE rich domes have used LEC technology comprised of new mixers with
variations in the air
fl
ow splits between the primary and secondary swirlers, carbon
sweep air, and
flare air, followed by closer spacing between primary and dilution jets
along with optimized distribution of primary, dilution, and cooling air in order to
meet all the design requirements as described in Sects. 2.2
fl
2.5 (Mongia 2013a , b , c ).
The mixer or injector and dome-mounted swirler designs have played a key role
in producing low exhaust smoke as the residence time of the zone between the
primary and dilution jets (intermediate zone) is minimized in order to get lower
high-power NO x . Some OEM
-
is seem to indicate that it is possible to achieve lower
PF with a single row of primary/dilution jets downstream of a rich primary zone
burning at
'
1.5, a value normally considered reasonable for RQL concepts
to produce competitive high-power NO x and exhaust smoke levels. If it were true,
then the OEM has developed a new technological capability than demonstrated
previously in the 1980s for high
˕ ≥
1.4
-
Δ T combustors (Mongia 2011a ).
The importance of idle CO tradeoff versus high high-power NO x has been
known since the early 1970s, and Fig. 7 represents a typical example from a low
emission technology program as described by Fear ( 1976 ) and Bruce et al. ( 1977 )
which showed strong correlation between idle CO and HC. A critical evaluation of
all low-emissions combustion technology and product development efforts should
point to a key observation: idle CO is a function of takeoff NO x whereas idle HC is
a function of idle CO (Mongia 2013a , b , c ). Therefore, advances in low emissions
technology should be measured conceptually by the technology arrow direction
shown in Fig. 7 thereby implying that none of the
five modi
cations investigated
for this particular combustor (identi
ed as Concept 2) has made any improvement
over the baseline con
guration; the latter has certainly achieved improvement over
the production combustor. In other words, one has to make substantial changes in
the design in order to impact the CO-NO x characteristics. Therefore, several swirl
cup con
gurations have been developed by the GE combustion teams over the
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