injection duration pulse is 334 ls it is lower than the other four
pulses. Thus, in all the cases, in this phase, the amount of fuel
injected in the last injection pulse is lower than that injected in
the other four injection pulses. We also see that an increase in
the last pulse duration advances the combustion phasing.
Fig. 7 shows the variation of heat release rates for various last
injection pulse durations, when the last injection pulse timing is
at 10 CA before TDC. Here, the last injection pulse occurs after
the cool flame and at the start of main combustion, which disturbs
the main combustion. In this case, the starting of the main combustion occurs almost at the same crank angle position for all the cases
of the last injection pulse durations. As the last injection pulse
duration increases, the main combustion slows down due to its
influence.
Fig. 8 shows the variation of heat release rate for various last
injection pulse durations, when the last injection pulse timing is
at TDC. When the last injection pulse occurs at TDC, the start of
cool flame and the main combustion are not much affected by
the last injection pulse duration. The cool flame and the main combustion occur before the start of the last injection pulse, because of
the four early injections. The third peak in the heat release rate
curve is entirely due to the last injection pulse at TDC. As the last
injection pulse duration increases, the early injection pulse duration decreases, which decreases the heat release rate in the cool
flame and the main combustion. However, in the final combustion
phase the heat release rate depends upon the last injection pulse
duration.