Based on the problem, the method of literature overview and the modeling
of the fuel drops behavior in the spray are chosen. Theoretical
calculations give an opportunity to evaluate experimental results of the
behavior of different biofuels in the fuel spray and explain the
.reasons of the problem.
- Parameters describing fuel drop formation and collision
When fuel is sprayed, the fuel spray is broken down into drops. As the
fuel drops move in the fuel spray, the drops are broken down by air
resistance and the collision of drops occurs, which changes the drop
size dc (Sauter Mean Diameter, SMD -d32 ).
Three dimensionless parameters are used for the modelling of the
decomposition of fuel drops:
Weber number We
\(We=\frac{\rho\bullet\left|v_{1}+v_{2}\right|^{2}\bullet\left(D_{1}-D_{2}\right)}{\sigma}\)(1)
where ρ is the fluid’s density (kg/m3),v1 and v2 are the
respective speeds of smaller and bigger drops (m/s),D1 and D2 are the
respective diameters of the drops (m) and σ is the fluid’s
surface tension factor (N/m).
Impact parameter B
\(B=\frac{2b}{\left(D_{1}+D_{2}\right)}\) (2)
where b is the distance from the centre of one drop to the
relative velocity vector placed to the centre of the other drop (m).B = 0 corresponds to the frontal impact of the drops and B= 1 corresponds to the situation in which the drops graze each other
(Fig. 1).