Study of Gas-Centered Coaxial Injector Using Jet …
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8.06 times of its injection diameter for non-turbulent jet and for turbulent jet it is
five times of injection diameter of jet. In primary atomization, the location of liquid
jet breakup is an important factor. Wu et al. [8] studied the transverse height (Y /d)
and the axial distance of jet breakup (X/d) and proposed correlations for transverse
breakup point (Y /d) and axial breakup point (X/d). For the safe disintegration of
liquid jet, the transverse and axial breakup point will be within the center post of the
injector element. The center post diameter of the injector is designed on the basis of
the transverse breakup point. The distance of the injection orifice from the exit of
the orifice depends on the axial breakup length.
Nozzle geometry design is mandatory that control the characteristic of the liquid
jet. The importance of nozzle parameters on breakup and trajectory of liquid jet was
investigated by Birouk et al. [9]. When the momentum flux ratio increases the effect
of nozzle geometry on the jet’s breakup length becomes more important because the
water jet starts to experience cavitation or hydraulic flip at high values of momentum
flux ratio. It was also observed that when the nozzle’s L/d ratio or the contraction
angle increases then the water jet’s trajectory increases slightly. Song et al. [10]
studied the effect of orifice internal flow of perpendicular to subsonic gas flow and
spray plume characteristic of liquid jet in subsonic cross-flow. The shape of the orifice
entry affected the column trajectory and breakup point [11, 12]. They also studied
how the cavitation and hydraulic flip affected the spray plume characteristic [13–16].
The liquid column diameter is less than that of the orifice due to an air envelope in
the area of hydraulic flip flow inside the orifice. If the orifice length to diameter ratio
is greater than 10 or less than 4 the hydraulic flip does not occur [17–20].
Objective of this work is to design gas-centered coaxial injector elements using jet
in cross-flow mechanism for breakup and study their spray and atomization characteristics under cold flow ambient condition. Malvern Particle Analyzer, a laser-based
equipment is chosen for cold flow atomization studies. Study the atomization and
spray characteristics of injectors at different liquid momentum flux ratio (MFR) and
at different downstream positions using Malvern Particle Analyzer.
2 Experimental Setup
2.1 Details of Injector Hard Ware
Gas-centered coaxial injectors fabricated for the study. The line diagram and specifications of injector are shown in Fig. 1 and Table 1, respectively. In this injector,
the gas (GN 2 ) supplied through the center post pipe (Gas orifice) and liquid (water)
injected through six holes drilled in the center post by two rows. The distance from
last row of liquid injection to injector exit (L exit ), total injector length (L inj ), and center
post diameter (d g ) will change with respect to the MFR. The center post diameter
is depending on the transverse breakup point and L exit depends on the axial breakup
point. At maximum MFR the breakup of liquid jet is mainly due to its momentum
369
8.06 times of its injection diameter for non-turbulent jet and for turbulent jet it is
five times of injection diameter of jet. In primary atomization, the location of liquid
jet breakup is an important factor. Wu et al. [8] studied the transverse height (Y /d)
and the axial distance of jet breakup (X/d) and proposed correlations for transverse
breakup point (Y /d) and axial breakup point (X/d). For the safe disintegration of
liquid jet, the transverse and axial breakup point will be within the center post of the
injector element. The center post diameter of the injector is designed on the basis of
the transverse breakup point. The distance of the injection orifice from the exit of
the orifice depends on the axial breakup length.
Nozzle geometry design is mandatory that control the characteristic of the liquid
jet. The importance of nozzle parameters on breakup and trajectory of liquid jet was
investigated by Birouk et al. [9]. When the momentum flux ratio increases the effect
of nozzle geometry on the jet’s breakup length becomes more important because the
water jet starts to experience cavitation or hydraulic flip at high values of momentum
flux ratio. It was also observed that when the nozzle’s L/d ratio or the contraction
angle increases then the water jet’s trajectory increases slightly. Song et al. [10]
studied the effect of orifice internal flow of perpendicular to subsonic gas flow and
spray plume characteristic of liquid jet in subsonic cross-flow. The shape of the orifice
entry affected the column trajectory and breakup point [11, 12]. They also studied
how the cavitation and hydraulic flip affected the spray plume characteristic [13–16].
The liquid column diameter is less than that of the orifice due to an air envelope in
the area of hydraulic flip flow inside the orifice. If the orifice length to diameter ratio
is greater than 10 or less than 4 the hydraulic flip does not occur [17–20].
Objective of this work is to design gas-centered coaxial injector elements using jet
in cross-flow mechanism for breakup and study their spray and atomization characteristics under cold flow ambient condition. Malvern Particle Analyzer, a laser-based
equipment is chosen for cold flow atomization studies. Study the atomization and
spray characteristics of injectors at different liquid momentum flux ratio (MFR) and
at different downstream positions using Malvern Particle Analyzer.
2 Experimental Setup
2.1 Details of Injector Hard Ware
Gas-centered coaxial injectors fabricated for the study. The line diagram and specifications of injector are shown in Fig. 1 and Table 1, respectively. In this injector,
the gas (GN 2 ) supplied through the center post pipe (Gas orifice) and liquid (water)
injected through six holes drilled in the center post by two rows. The distance from
last row of liquid injection to injector exit (L exit ), total injector length (L inj ), and center
post diameter (d g ) will change with respect to the MFR. The center post diameter
is depending on the transverse breakup point and L exit depends on the axial breakup
point. At maximum MFR the breakup of liquid jet is mainly due to its momentum