Environmental Engineering Reference
In-Depth Information
feasibility of one of the most practical techniques, Compliant Matrix Ceramic
(CMC) is reported by Paskin et al. (
1990
,
1993
) which realized approximately 80 %
reduction in the liner cooling.
One of the guidelines for assigning the amount of cooling air required during the
preliminary design phase of a new combustor is illustrated in Fig.
18
which shows
empirical correlation of small reverse
flow combustor products as a function of P
3
.
The NASA CMC combustor for 275 psi inlet pressure was designed to use less than
0.004 lb/s-in
2
(2.8 kg/s-m
2
) realizing approximately 80 % reduction from the
current technology as presented in Paskin et al. (
1990
,
1993
).
Ignition delay times,
fl
flame holding in the premixing systems are
strongly impacted by P
3
,T
3
, and equivalence ratio
fl
ashback, and
fl
. OEMs have empirical know-
how along with highly reliable tools to predict relationships between P
3
and T
3
.
Combustion research community interested in technology-relevant studies needs to
have simpler tools to quickly calculate T
3
for a given P
3
, which was developed as
part of the activities summarized in Kumar et al. (
2012a
,
b
,
c
), and Panda et al.
(
2012a
,
b
). These studies led to a very useful conclusion that simple isentropic
calculations by assuming ideal air properties and isentropic ef
˕
ʷ
isen
approximately 87 % compare well with the publicly available ICAO cycle data on
the N + 1 engines. On the other hand,
ciency
ʷ
isen
value of 89 % is assumed for the N +2
generation aviation engines. We also assume that a typical fully deteriorated
compression system will lose its
ʷ
isen
by approximately 1.0 %. These studies also
led to the recommendation that we can assume
ʷ
isen
approximately 86 and 84 %,
respectively, for the N and the
first generation of modern propulsion engines
'
compression systems; lower set of values should be used for smaller engines.
Further corroboration of these assumptions comes from typical sea-level engine
operating conditions for the
first generation modern engines as summarized in
flow rate (lb./s-in
2
) versus combustor pressure
(psi) of conventional film-cooled liners compared to CMC combustor; reproduced from Paskin
et al. (
1990
)
Fig. 18 Empirical curve of average liner cooling
fl
Search WWH ::
Custom Search