Figure 3 and figure 4 represent the effect of brake power
on the brake thermal efficiency for without EGR and
with EGR condition respectively for all fuel blends. It is
observed that, initially with increasing brake power, the
brake thermal efficiencies for each fuel (diesel,
diesel-biodiesel blends) increased due to reduction in
heat loss and increase in power developed with increase
in load. The maximum brake thermal efficiency was
obtained at around 5.0 to 5.5 kW and then tends to
decrease with further increase of load.
For the B10 fuel the brake thermal efficiency is
improved compared to pure diesel and for B15 fuel, it is
almost same of pure diesel. The possible reason for this
improvement is the molecules of biodiesel contain some
amount of excess oxygen which takes part in the
combustion process. It is noticed from the figures that,
with EGR the brake thermal efficiency increases a bit,
due to increase of the combustion velocity, caused by
higher intake charge temperature. Disassociation of
carbon dioxide to form free radicals can also be credited
to this improvement in efficiency.