Begell House Inc.
Atomization and Sprays
AAS
1044-5110
25
5
2015
SPRAY IN AUTOMOTIVE APPLICATIONS: PART II
iv-vi
10.1615/AtomizSpr.v25.i5.10
Sibendu
Som
Energy Systems Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA
MORPHOLOGICAL EXPLORATION OF EMERGING JET FLOWS FROM MULTI-HOLE DIESEL INJECTORS AT DIFFERENT NEEDLE LIFTS
375-396
10.1615/AtomizSpr.2015011058
Seoksu
Moon
Department of Mechanical Engineering, Inha University, Incheon, South Korea
Xusheng
Zhang
Advanced Photon Source, Argonne National Laboratory, Argonne, USA; Merchant Marine College, Shanghai Maritime University, Shanghai, China
Jian
Gao
Advanced Photon Source, Argonne National Laboratory, Argonne, USA; Propulsion Systems Research Lab., General Motors Global Research and Development, Warren, USA
Kamel
Fezzaa
X-Ray Science Division, Advanced Photon Source, Argonne National
Laboratory, Argonne, IL, USA
Eric M.
Dufresne
Advanced Photon Source, Argonne National Laboratory, Argonne, USA
Jin
Wang
Argonne National Laboratory
Xingbin
Xie
Department of Mechanical Engineering, Wayne State University, Detroit, USA
Fengkun
Wang
Department of Mechanical Engineering, Wayne State University, Detroit, USA
Ming-Chia
Lai
Department of Mechanical Engineering, Wayne State University, Detroit, MI 48202, USA
multi-hole nozzle
multi-orifice injector
needle lift
liquid fuel jet
X-ray phase-contrast imaging
The current study takes a morphological approach to interpret the emerging jet flows from multi-hole
diesel injectors. Several types of multi-hole injectors, a six-hole injector and two two-hole injectors with
different needle control mechanisms, were used to investigate the emerging jet flows and related flow
breakup at different needle lifts. A short X-ray pulse with 150 ps duration was used to visualize the nearfield
morphologies of the emerging jet flows using an ultrafast X-ray phase-contrast imaging technique.
A few X-ray pulses with 68 ns periodicity were also used to analyze the dynamics of the emerging jet
flows by tracking the movement of the structures inside the spray. At first, the effects of needle lift on
emerging flow pattern and breakup were investigated using a six-hole injector under practical injection
conditions. A highly expanding spray was observed at the low needle lifts. The degree of flow expansion
was however suppressed with an increase in the needle lift. The higher degree of flow expansion at the
low needle lifts promoted the flow breakup and increased the spray deceleration rate with an increase
in the axial distance. Then, a detailed morphological study of the emerging flows was performed using
two-hole nozzles under low injection pressures to slow down the flow breakup in order to figure out
the intrinsic nature of the emerging flows associated with the nozzle internal flow. The phase-contrast
images revealed clear morphologies of several branching flows inside the spray having different flowing
directions and stretching the spray three-dimensionally that originate from complex nozzle internal flow
pattern. The degree of flow expansion associated with the branching flows appeared differently with the
needle lift with formation of various flow structures: cone shaped, stretched thin, and cylindrical. At
certain needle lifts, the branching flows sometimes formed a couple of microwavelets inside the spray
having different instability frequencies, indicating different origins of each flow associated with nozzle
internal flow. Increasing ambient gas density did not alter the branching characteristics of the flows
significantly, while increasing injection pressure and reducing the fuel viscosity significantly altered the
branching flow characteristics.
A NOVEL SPRAY MODEL VALIDATION METHODOLOGY USING LIQUID-PHASE EXTINCTION MEASUREMENTS
397-424
10.1615/AtomizSpr.2014010377
Gina M.
Magnotti
G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0001 USA
Caroline L.
Genzale
George W. Woodruff School of Mechanical Engineering, Georgia Institute of
Technology, Atlanta, Georgia 30332, USA
diesel spray
model validation
Mie scattering
light extinction
liquid length
local structure
Physical spray models employed in engine computational fluid dynamics (CFD) simulations are not yet fully predictive; therefore, the breadth of conditions under which these simulations yield valid predictions depends strongly on the "tuning" of these models against available spray measurements. Often, these models are validated and calibrated against spray images based on the elastic scattering of light, or Mie scattering, from liquid structures and droplet clouds. However, these measurements do not typically detect the absolute liquid boundary, so employed computational metrics used to define the liquid boundary in the modeled spray can be physically inconsistent with that detected in Mie-scatter images. To more robustly validate fuel spray model predictions against light scattering measurements, direct comparisons can be made between predicted and measured light scattering intensity signals. Such a comparison provides a more quantitative validation of the liquid phase fuel boundary and further offers the potential to validate local spray structure. In this work, we apply the Lorentz−Mie solution to Maxwell's equations to predict extinction signals due to elastic light scattering, informed by droplet diameter and number density distributions, within a predicted diesel spray. The predicted extinction is compared to experimental results from diffused back-illumination and single line-of-sight extinction measurements to generate a calibrated model of the Engine Combustion Network "Spray A" condition that replicates the measured centerline extinction profile. This spray model is used to inform liquid volume fraction thresholds to similarly define the detected liquid boundary from Mie-scatter images.
UNCERTAINTY QUANTIFICATION FOR LIQUID PENETRATION OF EVAPORATING SPRAYS AT DIESEL-LIKE CONDITIONS
425-452
10.1615/AtomizSpr.2015010618
Lyle M.
Pickett
Combustion Research Facility, Sandia National Laboratories, P.O. Box 696,
Livermore, CA 94551, USA
Caroline L.
Genzale
George W. Woodruff School of Mechanical Engineering, Georgia Institute of
Technology, Atlanta, Georgia 30332, USA
Julien
Manin
Sandia National Laboratories, PO Box 969, MS9053, Livermore, CA 94551, USA
diesel sprays
evaporation
liquid length
extinction
light scatter
Seeking to quantify the liquid volume fraction at the measured liquid penetration length for more forthright comparison to CFD results, we compared 10 different light-scatter and extinction diagnostics for measurement of the "liquid length" of an evaporating diesel spray. Results show that light-scatter imaging is sensitive to the orientation of the illumination source, producing different maximum intensity locations depending on the optical setup. However, the scattered intensity from different setups can be normalized to provide similar liquid length values if the appropriate reference intensity is known. Light-extinction diagnostics are more quantitative because of a built-in reference light intensity, but can be sensitive to beam-steering effects due to refractive index gradients. The most quantitative diagnostic in this study is a small laser beam with large collection optics to accommodate beam steering. Using a liquid length defined based on 3% of the maximum scatter intensity and the measured optical thickness at this same axial location, we estimate an expected range of liquid volume fraction at this position for the "spray A" conditions of the Engine Combustion Network. Even though there is a possibility that this condition has supercritical mixtures where distinct droplets do not exist, we apply Mie scatter theory with a range of droplet diameters (0.1−10 µm) to mimic how light may scatter at liquid surfaces where density gradients remain sharp and light effectively scatters as if there were a gas-liquid interface. With a measured liquid path length of 1.4 mm, the upper-bound estimate for the path-length-averaged liquid volume fraction is 0.15%.