Environmental Engineering Reference
In-Depth Information
Several of the TFE731-2 engine operating points at cruising altitude (viz.
13,200 m with FAR
0.016) have CO and HC levels close to 15EI and 0.2EI
*
giving combustion ef
ciency of 99.6 %, considered very acceptable level in the
1970s. However, for the leading N + 1 generation engines, this number has notched
up to 99.9 %.The minimum acceptable combustion ef
ciency levels during altitude
relight, and for avoiding
flameout during inclement weather (viz. hail storm) vary
from engine to engine models, but 80 % is considered a good guideline.
Potential air quality bene
fl
ts and global climate impact are the primary reasons
for interest in the alternative fuels in addition to other factors including price
volatility and lack of diversity of the sources of conventional fuels. Carter et al.
( 2011 ) provides a good summary of the viability of some of the selective
approaches for producing synthetic fuels including Fischer
Tropsch (FT) coal- or
biomass to liquid and Hydroprocessed Renewable Jet (HRJ) processes. Research on
quantifying combustion characteristics of synthetic fuels has been active since the
middle 1970s (Longwell 1977 ). Recent emphasis (viz. Bester and Yates 2009 ;
Bulzan et al. 2010 , Chisty et al. 2011 ; Corporan et al. 2004 ; Davison and Chisty
2011 ; Moses and Roets 2008 ; Wey and Bulzan 2013 , etc.) has been on investi-
gating the impact of alternative fuels or their blends with conventional fuels on
engines performance, emissions, operability, and durability in order to qualify drop
in fuels.
We summarize combustion efficiency data of the CFM56-2C engine (which was
ICAO emissions tested in 1983) reported by Bulzan et al. ( 2010 ) reproduced here as
Fig. 11 showing that for its sea-level operating line, the
-
five fuels tested (viz. JP 8,
Fig. 11 Combustion ef ciency (computed from gaseous emissions) versus fuel
flow rate of the
CFM56-2C1 engine sea-level operation with the base fuel (JP8), two FT fuels and their blends;
reproduced from Bulzan et al. ( 2010 )
fl
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