Abstract
We have developed an optical technique called ballistic imaging to view breakup of the near-field of an atomizing spray. In this paper, we describe the successful use of a time-gated ballistic imaging instrument to obtain single-shot images of core region breakup in a transient, single hole atomizing diesel fuel spray issuing into one atmosphere. We present a sequence of images taken at the nozzle for various times after start of injection, and a sequence taken at various positions downstream of the nozzle exit at a fixed time. These images contain signatures of periodic behavior, voids, and entrainment processes.
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Abbreviations
- Core region:
-
The near field spray zone that is characterized by large (>100 μm) fluid structures near the axis that generate primary droplets in the process of breakup
- Primary breakup:
-
The destruction of the core region (among some researchers, “primary breakup” implies a specific breakup mechanism, but we make no implication regarding mechanisms)
- Primary droplets:
-
Droplets that have clearly originated from the core
- We ℓ :
-
Weber number of the liquid, We ℓ≡ (ρℓ U 2 L)/σℓ
- Oh :
-
Ohnesorge number, \(Oh\equiv \mu_\ell/\sqrt{\rho_\ell \sigma_\ell L}\)
- ρℓ :
-
Liquid density (kg/m3)
- ρ g :
-
Gas density (kg/m3)
- U :
-
Characteristic velocity (m/s)
- L :
-
Characteristic length (usually nozzle exit diameter) (m)
- σℓ :
-
Surface tension of the liquid (N/m)
- μℓ :
-
Viscosity of the liquid (kg/ms)
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Acknowledgements
Support for this work is provided by a grant from the Army Research Office via ARO Project Number DAAD19-02-1-0221. The equipment used and partial student support were funded by an NSF Major Research Instrumentation Grant number CTS-9711889. The authors wish to thank Lambda Research for free use of the OSLO software through the University Gratis program.
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Linne, M., Paciaroni, M., Hall, T. et al. Ballistic imaging of the near field in a diesel spray. Exp Fluids 40, 836–846 (2006). https://doi.org/10.1007/s00348-006-0122-0
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DOI: https://doi.org/10.1007/s00348-006-0122-0