Environmental Engineering Reference
In-Depth Information
shows a pressure atomizing injector surrounded by an axial swirler followed by a
converging diverging venturi in order to further improve atomization and fuel/air
mixing. The shape of the venturi is optimized to ensure no spray impingement on
its wall unlike swirl cup venturi. The conditioned spray and air mixing stream is
further improved by another concentric axial swirler followed by a diverging
passage to help continue further fuel/air mixing with minimal spray impingement
on the walls. The fraction of fuel impinging on the walls increases slightly with
power because when the pilot fuel is cut back at approach and higher power points,
we would like to have the equivalence ratio
˕
of the pilot recirculation zone only
slightly higher than
ameout. In other words, we want to have the spray concen-
trated on the outer peripheries of the pilot so that it helps continued
fl
flame sustaining
in the pilot/cyclone interaction zone (viz. Fig. 23 ) which is also impacted by the
fuel/air ratio, velocity, and turbulence pro
fl
les at the main exit plan, namely item
124 in Fig. 25 . Several geometrical features including items 156, 158, and 204 have
a direct bearing on the annular pilot/cyclone interaction zone
s performance and
stability. Several features of the cyclone (viz. 170, 172, 174, 182, 190, and 194)
in
'
fl
uence swirl number and mixing characteristic,
fl
flame holding, and
fl
ashback
characteristics of the main mixer.
In order to further reduce NO x and improve operability characteristics, several
changes will be required for the TAPS4 technology; only limited details are
illustrated in Fig. 26 . For example, there is provision for having two fuel circuits for
the pilot, one for the pressure atomizing tip and the other one to inject into
cross
ow; the latter is added to increase the operating envelope of the pilot and
improve its operability including protection against hail storm and dynamics
abatement. The main cavity is fed through a combination of axial and radial in
fl
ow
swirlers generally counter-rotating in order to improve fuel/air mixing and lower
overall swirl strength of the main. The plane fuel jets in cross
fl
fl
ow (JIC) have been
augmented by coaxial air streams which signi
cantly impact the hardware details of
the fuel circuit as shown. Moreover, the axial location of JIC is optimized relative to
the shear layer formed between the counter-rotating main swirlers with attendant
impact on mixedness and NO x emission.
3.2.2 GEnx TAPS Engine Emissions
The TAPS1 technology substantiationwas completed in 2003 (viz. Mongia 2003) and
the
ed data was completed
on October 2009 for the 13 engine models with a wide range in SLSS takeoff pressure
ratio and thrust, namely BPR: 8
first aviation engine product (viz. GEnx) emissions certi
-
9.4; OPR: 35.1
-
46.5; F 00 : 255
-
345 kN; and margin
from CAEP8:60
35 %. The product team worked very hard and vigorously since
2004 in order to produce a reliable second generation lean dome engine that meets all
the design requirements 6 years after technology substantiation. Its takeoff NO x as a
function of pressure ratio is shown in Fig. 27 which is presented well by an empirical
correlation EINO xGEnx ¼
-
10 5 OPR 3 : 971
2
1
:
079
w = R
¼
0
:
991. This expression
may be compared with the low rich-dome large engines
'
takeoff NO x presented earlier
Search WWH ::




Custom Search