Environmental Engineering Reference
In-Depth Information
The combustor inlet temperatures for desired overall pressure ratio at sea-level,
standard-day,
static
condition
can
be
estimated
by
using
T
3
;
SSS
¼
1955 OPR
0
:
272
, respectively, for the N + 1 and N +2
generation engines. This along with generally accepted requirements for combustor
operability, we have to manage signi
544 OPR
0
:
2704
317
:
;
320
:
cantly increased range of P
3
, T
3,
and fuel/air
-
-
Δ
P:
-
Δ
P
design;
and
ratio, viz. T
3
: 216.67
1,084 K; P
3
: 0.33
60 atm;
*
(0.1
1.2)
FAR: FAR
min
-
FAR
max
. The numerical values of the dome design pressure drop
(
P
design
), and the minimum and maximum fuel air ratios (FAR
min
and FAR
max
)
depend upon the combustion system design and its potential applications. We will
assume typical values of these variables, respectively, 3
Δ
-
5 %, 0.005
-
008, and
0.025
-
0.040 for the aviation engines.
first generation of lean dome products met their original objectives of
achieving lower NO
x
within the speci
The
ed design constraints including cooling
technology. They were immediately followed by the second generation lean dome
products known popularly as TAPS in GEnx in addition to planned LEAP-X and
GE9X. The
takeoff EINO
x
of GEnx is given by EINO
xGEnx
¼
1
:
079
10
5
OPR
3
:
971
2
w
=
R
¼
0
:
991. These products will be able to meet the proposed
long-term LTO NO
x
regulatory standard within the generally accepted design
modi
nement process. TALON-X and recently introduced P&W
concept (viz. Lee et al.
2013
) will provide credible alternatives to TAPS; an
interesting technological competition. However, the second generation lean domes
produce an order of magnitude lower exhaust smoke number than the rich domes.
For all other design requirements, both the lean and rich domes have comparable
characteristics; the dynamics topic will be covered separately. For future technol-
ogists, lean dome NO
x
entitlement as given in Figs.
36
and
37
are proposed. The
effect of FT fuel blends on combustion ef
cation and re
ciency, EINO
x
is very small; but its
bene
ts in regard to particulate emissions are enormous in terms of both the number
density and mass emissions due primarily to signi
cantly lower aromatic and sulfur
contents. Future CFD and semi-empirical model should be developed with the
proposed long-term accuracy goal expressed in term of the standard deviation
˃
goal: 3 % of takeoff EINO
x
, 7.5 and 15 %, respectively, of idle CO and HC
emission indices.
Acknowledgments The author would like to express his gratitude for the support and encour-
agement he has received from his colleagues, friends, customers, bosses, and mentors since 1972.
References
Acosta WA (1987) Liner cooling research at NASA Lewis Research Center. AIAA paper 1987-
1828
Ajmani K, Breisacher K (2014) Simulations of NO
x
emissions from low emissions discrete jet
injector combustor tests. AIAA paper 2014-3524
Ajmani K, Mongia HC, Lee P (2013a) Evaluation of CFD best practices for combustor design: part
I
—
non-reacting
fl
ows. AIAA paper 2013-1144
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