Environmental Engineering Reference
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Fig. 12 Pressure, heat release rate, n-heptane vapor, and methane mass pro
les with respect to
crank angle for the 0 % (100 % n-heptane), 90 and 97 % methane cases. Vertical lines in b indicate
crank angles at ignition
combustion zones. In a similar way, HO
2
plots can be used to examine the lean
combustion zone. Thus, for the two dual-fuel cases, HO
2
contours at 0 and 4
°
ATDC (cf. Figs.
14
and
15
) indicate the presence of a lean combustion zone,
characterized by a propagating
flame. However, the corresponding contours for the
single-fuel case do not show this lean combustion zone (cf. Fig.
13
).
The three combustion zones for the dual-fuel combustion can be qualitatively
identi
fl
ed by deconstructing the HRR diagram based on the temporal mass pro
les
of some relevant species. Figure
16
presents the mass pro
les of several such
species for the 97 % methane case. As indicated, the rich premixed combustion
mostly occurs between
ATDC and is characterized by the consumption
of n-heptane and the production of C
2
H
2
, CO, and other intermediate species, such
as H
2
. As indicated in Fig.
16
a, C
2
H
2
and CO species attain their peak values during
this period. Based on this observation, a HRR pro
−
5
°
and 3
°
le corresponding to rich pre-
mixed combustion can be constructed and is shown in Fig.
16
b. Similarly, from the
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