Fig. 6. The dependency between the diameter dcof the drop leaving the injector and fluid’s initial velocity vin case of two different diameters d of injector’s opening (d1 = 100 µm, d2 = 300 µm) in case of four different fuel types. The x -axis value range 150-400 m/s corresponds to typical velocities of fuel drops in engine practice.
The dependency between the diameter dc of the drop leaving the injector and fluid’s initial velocity v has been given in Fig. 6 and the diameter dc of the drop leaving the injector and injector’s diameter d has been given in Fig. 7. Here the density of the gas environment was 17 kg/m3 and the physical parameters of the fuels correspond to the temperature 90 °C.
Fig. 6 shows that as the drop’s velocity increases, the drop’s size decreases. Here it is important to point out that the diameter of the injector’s opening does not have a significant effect on the drop’s size. As the drop’s velocity is doubled, its size decreases ~3 times. The physical and chemical properties have an effect on the fuel drop’s size. For example, as the fuel’s kinematic viscosity increases, the drop size increases (starting from gasoline to FAME or HVO fuel). It is important that in case FAME and HVO fuels no drop size difference is evident. This is can be caused by the difference between dynamic viscosities and surface tensions. The dynamic viscosity of the FAME fuel is greater than that of the HVO fuel, however, the surface tension of the HVO fuel is greater than that of the FAME fuel. Therefore, the change of the drop size is within the same magnitude. Fig. 7 shows that the diameter of the injector’s opening does not have a significant effect on the drop size in spray regardless of the spray velocity.