Environmental Engineering Reference
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geometries, which can sometime become quite complex, are used in a majority of
liquid fuel combustion systems.
A fourth process known as effervescent atomization (EA) injects high-pressure
gas directly into the liquid in a mixing chamber upstream of the injector discharge
ori
ce (Sovani et al. 2001 ). The injected gas bubbles into the liquid and produces a
two-phase mixture that
ce, the gas
bubbles expand rapidly to shatter the surrounding liquid into droplets. The liquid
breakdown mechanism with EA atomization relies on potential energy unlike the
kinetic energy-driven AB and air-assist atomizers. The EA process requires small
atomizing air
fl
flows through the ori
ce, and upon exiting the ori
fl
ow rate to produce a spray with
fine droplets, the atomizer perfor-
mance is relatively insensitive to the liquid
'
is kinematic viscosity, and the larger
diameter of the injector ori
es fabrica-
tion. However, in the EA process, the spray angle is small, air must be pressurized to
the liquid
ce alleviates clogging problems and simpli
s pumping level, and the spray produced can exhibit unsteadiness because
of the long residence time for the two-phase
'
fl
flow between the mixing chamber and
injector discharge ori
ce.
We have employed a novel process initially presented by Ganan-Calvo ( 2005 ),
so-called
exible combustion. As
illustrated in Fig. 2 , the FB mechanism consists of a liquid supply tube and a
circular ori
fl
flow blurring (FB), to achieve low-emission, fuel-
fl
ce in a plate oriented perpendicularly to the axis of the tube and situated
downstream of the tube exit. The tube outer wall is tapered at the outlet, and the
sharpened edge of the ori
ce in the plate is the same diameter as the inner diameter
of the tube (d). When the axial distance between the tube and the ori
ce (H) is about
the size of the tube diameter (H/d *
1), the liquid and gas interact similar to an AB
atomizer. However, for shorter distances (H/d *
0.25), the atomizing gas enters a
short distance into the liquid tube where it bubbles and mixes with the liquid. The
resulting bubbly two-phase mixture exits the injector ori
ce, where the gas phase
rapidly expands to create
fine liquid droplets. FB atomization is similar to the EA
process, although the two-phase mixing in a FB atomizer occurs only at the tip of
the liquid tube as dictated by the geometry (H/d). Following the introduction by
Fig. 2 Working principle of
the
Spray
flow-blurring (FB)
injector
fl
Atomizing Air
Atomizing Air
Fuel Inlet
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