Figure 2. Drop-drop collision mechanisms \cite{Kim09}.
  1. Fuel drop size after leaving the injector
The size of the fuel drop after leaving the injector can be expressed as follows \cite{Pos02}:
\(d_{c}=\frac{2\pi B_{d}\sigma\lambda_{m}}{\rho_{a}U_{T}^{2}}\) (5)
where Bd is a parameter that depends on the injector nozzle’s geometry. In previous works \cite{Bra85} the value ofBd was chosen Bd = 0.62,σ – fluid’s (gasoline, DF, HVO, FAME) surface tension factor (N/m), λ m – fluid’s Taylor viscosity parameter,ρ a – density of outer or gas environment (kg/m3), U T – velocity of the fastest unstable wave of the spray (m/s), wherebyUT is in linear correlation with the initial velocity of the injected spray. Here U T = 0,25 ∙U 0, where U 0 is the initial velocity of the spray (m/s).
It is possible to obtain the mean diameter of drops leaving the injector or Sauter mean diameter (SMD ) by using equation 5 and data listed in sources \cite{Qia97,Sie98}. Table 2 presents some illustrative SMD values according to various authors.
Table 2. Values of SMD from chosen authors.