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