The paper presents the application of a three component model to the theoretical study of the combustion process of a Diesel engine fueled with sunflower oil and sunflower oil-Diesel fuel mixtures. The model assumes that the working fluid consists of three components: the fresh air, the flame and the burned gases.
The combustion model uses the energy conservation equation:
v
c·Q
c·dξ
α=dU
α+dL
α+dQ
wα, [1]
where v
c is the fuel cyclic dose, Q
c is the fuel heating value, ξ
α=v
cα/v
c, v
cα is the quantity of burned fuel up to the moment α, U
α is the internal energy of the working fluid, Q
wα is the heat exchanged through the cylinder walls and L
α is the mechanical work.
The heat release law was assumed to be a Vibe type one:
ξ
α=R
c·[1−exp(−6.9·A
mPp+1)]+(1−R
c)·[1−exp(−6.9·A
md+1)], [2]
where:
·A
p=(α−α
d)/(α
P−α
d) and A=(α−α
d)/(α
F−α
d);
·α
d-start of combustion angle;
·α
f-end of combustion angle;
·α
P-end of rapid combustion angle.
Using Eqs. [1] and [2] we have obtained the cylinder pressure during combustion, for the vegetable fuels taken into account; the peak values were confirmed during the experiments.
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