Future Trends in Commercial Aviation Engines’ Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 129

Table 4 Typical sea-level combustor relevant values of two small and large first generation
modern aviation engines
Thrust
(kN)

P 3
(atm)

T 3
(K)

Isentropic
ef ciency

FAR Wa

(kg/s)

Wc
(kg/s)

Vr
(m/s)

Small engine combustor from Bruce et al. ( 1977 )
Idle 0.89 1.97 365.4 0.0100 2.31 1.32 10.88

Approach 4.67 5.10 499.8 80.0 % 0.0118 5.76 1.49 14.33

Climbout 14.01 12.45 652.0 81.8 % 0.0150 12.43 1.50 16.53

Takeoff 15.57 13.61 668.7 82.1 % 0.0156 13.38 1.50 16.70

SL ratio 7 1.6 1.14

Opp ratio 41 3.1
Large engine combustor from Bahr and Gleason ( 1975 )
GIDL 7.42 2.96 437.4 <75 % 0.0110 13.93 5.80 18.56

11.2 3.69 463 <75 % 0.0103 17.3 5.94 19.6

15.7 4.55 489 77.2 % 0.0100 21.3 6.10 20.7

FIDL 21.3 5.54 514 79.9 % 0.0099 25.3 6.10 21.4

44.8 9.05 589.0 82.5 % 0.0116 38.6 6.10 22.3

Approach 67.27 11.81 631.9 84.0 % 0.0138 48.17 6.04 23.29

100.9 15.85 691 83.5 % 0.0164 61.00 5.96 24.00

190.5 20.89 745 <85 % 0.0190 76.7 5.90 24.7

Climbout 195.7 25.82 791.9 <85 % 0.0215 90.81 5.83 25.18

206.2 27.49 807 <85 % 0.0224 95.3 5.80 25.3

Takeoff 224.2 29.44 826.3 <85 % 0.0236 100.6 5.79 25.51

SL ratio 10 2.4 1.05

Opp
Ratio

88 3.8

Table 4 . Listed are the sea-level, static, standard-day rated thrust; combustor inlet
pressure and temperature (P 3 , T 3 ); combustor exit fuel/air ratio and air

fl ow rate (FAR,

p

T3 Wa); and corrected air = P 3 ). Combustor reference

velocity is also listed so that it can be related to Fig. 21 for discussion on ignition and
lean blowout LBO FAR. The

fl ow rate (Wc ¼ Wa = 288 : 15

first entry is for a small engine, the TFE731-2 as
reported by Bruce et al. ( 1977 ). NO x emissions of this engine from sea-level to
altitude cruise has been covered in Fig. 14 . The sea-level operation of the small engine
at idle, approach, climbout, and takeoff for P 3 ,T 3, and FAR values changing from
(1.97, 365, and 0.01) to (13.6, 669, and 0.016) may be compared with those of the
large engine entry [viz. the CF6-50 provided by Bahr and Gleason ( 1975 )], namely
(3, 437, and 0.011) and (29.4, 826, and 0.024). Calculated isentropic

ciency
for the large engine varies between 75 % and <85 % as engine operates from several
ground idle (GIDL), two

ʷ isen ef

flight idle (FIDL), three approach, two climbout, and rated
takeoff operating conditions. However, its

fl

ʷ isen for the area of interest for the ICAO

landing - takeoff points (viz. Fig. 12 ) varies between 80 % and <85 %.