Future Trends in Commercial Aviation Engines’ Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 116

Fig. 8 Typical CO emission
index versus fuel/air ratio of
the TFE731-2 engine data
from an altitude tank at
simulated altitude operation
from idle to maximum power;
reported by Diehl and
Biaglow ( 1974 )

points; whereas for the other altitudes, the testing included two flight Mach num-

bers, namely 0.6 and 0.8. Therefore, the data covers a broad range of operation in
terms of fuel/air ratio, combustor inlet pressure and temperature, namely
207 ≤ P 3 ≤ 1,150 kPa, 416 ≤ T 3 ≤ 670 K, and 0.0045 ≤ FAR ≤ 0.0185. Com-
bustion ef

fl

ciency (%) is calculated from the measured gaseous emissions of CO
and unburned hydrocarbons HC expressed as EI, g/kg of fuel, namely

g C ¼ . This means that approximately

43 g of CO/kg fuel accounts for one percent decrease in combustion ef

100 ð 0 : 1 EIHC þ 0 : 02334 EICO Þ

ciency,
whereas 10 g of unburned fuel expressed as g CH 2 /kg fuel has similar impact.
Therefore, Mongia in pursuit of all of his technology programs has used 30EI for
CO and 3EI for HC at sea-level idle operation conditions as his long-term goal since
his

first program (Bruce et al. 1977 ), giving an idle combustion ef ciency of 99 %.

Fortunately, most of the GE ' s modern rich-domes ' idle HC and CO are represented

well by EIHC idle ¼ 0 : 1498EICO idle 1 : 4585 (Mongia 2013a ) which justi es

Mongia ' s assumption for correlation between CO and HC at idle.