Using Petroleum and Biomass-Derived Fuels in Duel-fuel Diesel Engines - Novel Combustion Concepts for Sustainable Energy Development - page 261

Fig. 18 Heat release rate (a), pressure (b), and IHR (c) profiles with respect to crank angle for the
single fuel (n-heptane), and 90 and 97 % methane dual-fuel, and 95 and 98.5 % syngas dual-fuel
cases

Results for the syngas dual-fuel cases are shown in Fig. 18 , which plots the
HRR, pressure, and IHR pro les for all the ve cases. The HRR and pressure

pro les for the low-load cases (90 % methane and 95 % syngas) indicate more rapid

combustion and higher heat release for 95 % syngas compared to that for 90 %
methane. Consequently, as indicated in Table 3 , IMEP and engine ef ciency are

higher for 95 % syngas compared to those for 90 % methane. Differences between
the syngas and methane become signi

cantly more pronounced at high-load con-
dition (97 % methane and 98.5 % syngas). The HRR and pressure pro les for

syngas indicate nearly spontaneous combustion with a very sharp rise in heat
release and pressure but a gradual combustion process for methane. The total heat
release is also noticeably higher for syngas compared to that for methane. These
differences are primarily due to the much faster flame propagation in syngas-air

mixture compared to that in methane-air mixture, even though the equivalence
ratios for the two mixtures are nearly the same (Table 3 ).
The

fl

flame propagation behavior is illustrated in Fig. 19 , which presents the HO 2
contours for the 95 and 98.5 % syngas cases. Similar to the methane case, the
contour plots are cut through the peak

fl

value location. As expected, the plots

ϕ