Environmental Engineering Reference
In-Depth Information
Future Trends in Commercial Aviation
Engines
'
Combustion
Hukam C. Mongia
Abstract This article gives an overview of the current rich-dome combustion
system design, requirements and challenges; followed by the
first alternative to rich-
domes that have been successfully introduced as products; the lowest levels of
achievable NO
x
(so called entitlement) as determined from small scale rig testing;
summary of recent engine emissions data with
alternative fuels; description
of the 2nd alternative to rich-dome products that may be of interest to the OEM
“
green
”
s for
the N+2 and N+3 generation aviation engines; a brief discussion on the modeling and
correlation accuracy expectations from future efforts in this area; the 3rd alternative to
rich domes which was shown promising for autoignition times closer to 0.2 ms. The
article concludes with a short section on operability and dynamics. Several large
low-NO
x
rich domes
'
takeoff NO
x
emission index is reproduced well by a simple
correlation NO
xRD
−
L
= 0.0303PR
'
2
= 0.9906 including Talon II and
Trent1000. However, the LTO NO
x
is correlated well by a similarly good quality
curve only for
1.9722
w / R
the group of combustors without Trent1000,
DP
/
F
00
=
1.2241
compared to lower value expression for Trent1000 alone given by
DP / F
00
= 0.1292PR
0.6793PR
1.6327
. Consistent with the NO
x
stringency pattern set by
CAEP4, CAEP6 and CAEP8 and longtime goal for achieving 85 % reduction in
takeoff NO
x
at 30OPR, we propose the long-term LTO regulatory standard of CAEP /
18 = -37.763 + 2
effective December 31, 2033. The combustor inlet temperatures for
desired overall pressure ratio at sea-level standard day static condition can be esti-
mated by using T
3,SSS
= 317.544OPR
π
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
0.2704
; 320.1955OPR
cantly increased range of P
3
,T
3
and fuel/air ratio, viz. T
3
: 216.67
-
1084 K; P
3
: 0.33
-
60 atm;
Δ
P:
(0.1
-
1.2)
*
Δ
P
design
; and FAR: FAR
min
- FAR
max
. The numerical values of the dome design
pressure drop (
P
design
), 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. The 1st generation of lean dome products met
Search WWH ::
Custom Search