Fig. 5. Dependency between the diameterdc of the drop leaving the injector and fluid’s
dynamic viscosity µf at two different velocitiesv of the spray (v1 = 200 m/s,v2 = 400 m/s), for four different fuel types. Thex -axis value range 0-3600 µPa·s corresponds to typical
viscosities of fuels at temperatures 40 °C and 90 °C (Table 1).
Equation 11 contains the member ΛKH , which
contains the fluid’s dynamic viscosity µf .
Therefore, it is possible to represent graphically the dependencydc of the drop leaving the injector and fluid’s
dynamic viscosity µf for various fuels (Fig. 5).
The diagrams of Fig. 5 presume that the surface tension and density of
fuel does not change. The density of the gas environment is 17
kg/m3, injector’s opening’s diameter 100 µm. According
to sources \cite{Chh13,Keg18,Wan06,Boh17,Mel14,Fen16,Sah17}, the physical parameters of the fuels correspond to the
temperature 90 °C.
Fig. 5 shows that as the dynamic viscosity increases, the drop size in
the air-fuel mixture also increases. An important factor having an
effect on the drop size is the velocity of the fuel spray. The higher
the velocity of the fuel spray, the smaller the diameter of the drop.
Dynamic viscosity has a bigger effect on the change of fuel drop size in
case of lower velocity fuel spray. For example, in case of the velocity
of 400 m/s of the drop of any fuel, the change of fuel drop size is
relatively smaller than compared to the speed of 200 m/s. Likewise, the
physical and chemical properties of fuels have an effect on the drop
size mostly at the lower velocity of the spray v1= 200 m/s. When we compare the fuel spray of gasoline and HVO fuel at
spray velocity of 200 m/s, then, for example, we can see that at the
dynamic viscosity’s value of 1600 µPa the difference of drop size is
~1 µm (25%). At drop velocity ofv2 = 400 m/s the change of drop size is 0.2 µm
(16%).