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observed due to the irregularly large-sized dro-
plets.
3.2 Mean droplet size of intermittent spray
Figure 7 shows the SMD of the 5-hole and the
single-hole nozzle with radial distance at the
three axial positions of Z/dn=31, 63 and 94.
Here, the time window, applied for calculating
the SMD, is 20 ms from SOl. This time window of
20 ms isrelatively longer duration than the injec-
tion periods of 1.1 and 0.8 ms for the 5-hole and
the single-hole nozzle, respectively. Hence, the
SMD distribution shown in Fig. 7 would repre-
sent the whole spray characteristics during the
single injection event.
In the case of the 5-hole nozzle, as shown in
Fig. 7 (a), the SMD decrease with the increase in
the axial distance, and finally, at Z/dn=94, it
reaches approximately 30/zm near the spray axis.
in addition, the SMD decreases gradually with
the increase in the radial distance and shows
about 20/zm from at R/dn>7-8. In the case of the
single-hole nozzle, as shown in Fig. 7(b), the
SMD decrease with the increase in the axial
distance, but it is quite high near the spray axis,
compared with that of the 5-hole nozzle. In the
variation of the SMD along with the radial dis-
tance, the SMD decreases rapidly with the in-
crease in the radial distance, and the constant Intermittent Atomization Characteristics of Multi-Hole and Single-Hole Diesel Nozzle 1699
value is obtained at R/dn>6, which is a little
smaller than that in the 5-hole nozzle. There is
the large difference between the inner region,
which is defined as the region near the spray axis
including the central part and trailing edge of the
spray, and the outer region of the spray in the
SMD, especially near the nozzle tip. These
smaller SMD distributions near the outer region
of the spray indicate that the fine droplets are
produced through the disintegration processes of
the inner region of the spray.
Figure 8 shows the SMD along the centerline of
the spray for the 5-hole and single-hole nozzle,
The time window of 20 ms was used to calculate
the SMD at the given axial positions.
After showing the maximum value near the
nozzle tip, the SMD distributions show a rapid