This work and the use of the APS were supported by US Department of Energy, Office of Science/Basic Energy Science and Energy Efficiency and Renewable Energy/Vehicle Technology

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Feature size [μm]

2MPa

7MPa

Ultrafast X-ray Study of Swirling Hollow-Cone Spraysin the Near-Field

Advanced Photon Source, Argonne National Laboratory, US

Objectives Interpretation of near-field flow development of swirling hollow-cone sprays Physical insight on various types of breakups and atomization process

Pinj = 2 MPa, Ambient Gas = N2,Fuel = Gasoline Calibration Fluid (Viscor 16BR)

Ultrafast X-ray Phase-Enhanced Imaging

Temporal Resolution : 150psHigh Energy X-ray : 9.62keV

Spatial Resolution < 1mm

Temporal Spray Development

Outward-Opening Swirl Injector

Opening -‘Skirts’

Closing – ‘Streaks from Weakened Swirl’

X-ray Tomography from APS, ANLOpening -‘Instability Waves’ Steady – ‘Turbulent Flow from High Swirl’

Nozzle Structure(taken using x-ray phase-enhanced imaging)

1mm

Pinj = 2 MPaSteady-stateWhite-Light

11 ns Exposure

W. Cai et al., Appl. Phys. Lett. 83, 1671 (2003)

1mm 1-5% Transmissionat 1 mm location

Visible Light Image

* Setup in XOR 7ID-B in APS, ANL

A B C

D

A. Opening – ‘Skirts’

500 m Pinj = 5 MPa, 80 s ASOI

Pinj = 2 MPa

Droplet Sizes: 41 ~ 67 m

Low velocity laminar-like flow before swirl motion Dictated by transient pressure and velocity during needle opening

Skirt Ligaments Droplets High injection pressures form thin and long ligaments, and smaller droplets

Pinj = 7 MPa

Droplet Sizes: 35 ~ 50 m

B. Opening – ‘Instability Waves’

Pinj = 2 MPa150 s ASOI

Pinj = 7 MPa120 s ASOI

Instability waves, an indicator of laminar to turbulence transition, appear on the sheet. The wavelengths are dependent to Re.

Wavelength: 40 m

Wavelength : 26 m

C. Steady – ‘Turbulent Flow from Strong Swirl’ D. Closing – ‘Streaks from Weakened Swirl’

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Re DependencyAnalyzed from

non-swirl hollow spray

Concluding Remarks Hollow-cone swirl spray showed four representative stages of flow development with time: (1) skirts and (2) instability waves during opening, (3) turbulent flow

from strong-swirl at steady-state and (4) streaks from weakened swirl during closing. Instability wavelengths, ligament and droplet sizes decrease and number of streaks increases with increase in injection pressure.

Pinj = 2 MPa

500 m 500 m

1 mm

Pinj = 2 MPa, 1.0 ms

Pinj = 5 MPa, 1.19 ms

Pinj = 7 MPa, 1.19 ms 2 MPa 5 MPa 7 MPa0

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Num

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f Stre

aks Number of Streaks at Dotted Boxes

Pinj = 7 MPa

Probability of Feature Size

Turbulent flow from nozzle exit from strong swirl flow Ligaments, droplets and bubbles at downstream Decrease in feature size at higher injection pressure Increase in feature density at higher injection pressure

Streaks with less turbulent flow from weakened swirl Increase in number of streaks at higher injection pressure Streaks are from hydrodynamic instability

500 m