indicates regions of lower fuel mixture density and the downstream part of the spray has an unclear shape. The spray tip contour gets more visible and the downstream part has elliptical shape at higher pressures.

Figure 5.1.1: Inial stages of spray evolution for different nozzle types (experimental conditions: 1.5 ms injection duration, 50 MPa injection pressure, 3 MPa ambient pressure and 300 K ambient temperature)

The injection pressure has significant effect on spray liquid penetration. The effect of increasing pressure on spray tip penetration is depicted in Figure 9(b). The spray tip penetration gets longer as the injection pressure increases. This result is related to both higher quantity and higher velocity of the droplets at higher injection pressures. When the spray lost its momentum related to lower quantity or lower injection pressure, the difference of the penetration lengths got longer at the downstream region of the spray. Proportional to injection pressure, the spray penetrates faster at higher injection pressures.

The injection duration effect and nozzle type effect on spray tip penetration are presented in Figure 4.5.1.3. The injection duration seems to have little effect on spray penetration. Even though all the conditions are equal in Figure 4.5.1.3 (a), the penetration length is shorter at 0.4 ms injection duration than the others. This effect may be attributed to the lower injection quantity at 0.4 ms injection duration.