Future Trends in Commercial Aviation Engines’ Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 121

takeoff NO x (see Fig. 7 ), and idle HC as a function of idle CO (Mongia 2013a , b , c ).
Consequently, very interesting conclusions emerge as summarized in Fig. 13 which
shows that several of the recent large rich-dome engines produced by GE, P&W, and
RR have very similar characteristics in terms of the takeoff EINO x versus SLSS
takeoff pressure ratio. The resulting empirical correlation identi

ed by the legend

0303PR 1 : 9722

2

RD-L in Fig. 13 EINO xRD L ¼ 0 : w = R ¼ 0 : 9906 gives good agree-

2 = 0.9906, root-mean-square

ment with the data; namely the correlation coef cient R

errors ( ) of 0.87 g/kg and 2.7 % which is comparable with the measurement

repeatability as determined by the average standard deviation of the LTO NO x .
Figure 13 also shows takeoff NO x emissions of the CFM56-2/3 engine family to
which belongs the engine tested by Bulzan et al. ( 2010 ); its combustion ef

˃

ciency
data was presented in Fig. 11 with more to follow in Figs. 38 , 39 and 40 for NO x and
particulate emissions along its SLS engine operating line. It is interesting to see that
takeoff NO x of the CFM56-2/3 tested in 1983 is approximately 20 % higher than the
best group of rich domes including Trent1000 tested in 2009, as shown by the dotted
green curve which represents 1.2 time RD-L values. The author is hopeful that the
N + 1 generation GTF TALON-X combustor will show signi cant lower takeoff

NO x than RD-L. Otherwise, we will have to conclude that rich-domes takeoff NO x
levels have settled down to the entitlement level given by the empirical correlation
EINO xRD L ¼ 0303PR 1 : 9722

:

w = R

2

:

9906 and that it is only17 % lower than
the CFM56-2/3 engine tested in 1983; albeit we have learned to scale up from
25 - 45 OPR engines during the last 30 years.
We should be interested in estimating mission NO x emissionswhich depends on
the knowledge of engine operating points (viz. P 3 , T 3 , and fuel

0 ¼ 0

fl flow rates) along the

airplane flight path. We rely on engine performance models and weather conditions

to make accurate predictions for the fuel burn; it will be equally desirable to have
simple models for mission NO x calculations as discussed next.

fl

Fig. 13 Combined large rich-dome technology of GE, P&W, and RR identi ed as RD-L showing
takeoff EINO x plotted as a function of SLSS takeoff pressure ratio; also shown the CFM56-2/3 and a
dotted green curve showing 1.2 × RD-L trendline line which is given by EINO xRD L ¼

0 : 0303 OPR 1 : 9722