The aforementioned studies revealed some important mechanisms
for initial breakup. However, the relationship between the
flow regime in the injector hole and the mushroom-shaped spray
jet has not been deeply studied although the development of the
mushroom head has been fully described in [4,5]. The fuel dispersion
quality in the near field has not been quantified either. With
the aim to address these unknown questions, a long tube realtime
mass flow rate measuring instrument was first adopted to calibrate
the injection characteristics, allowing the mass flow rate
(MFR) measurement at the initial injector opening stage. A long
distance microscope together with an ultra-high speed CCD camera
was then employed to study the spray primary breakup. One
novelty of the present paper is the theoretical and experimental
study of the fundamental forming regime of the mushroom head
by the combination of photography and mass flow rate measurement.
Another novelty is that the flow regimes during the early
stage are studied by calculating the boundary thickness in the nozzle
to stress the importance of flow regimes for the formation of
‘mushroom’. In addition, the quantification of dispersion quality
in the near field by the application of imaging and fuel flow rate
measurement is quite original.