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
Ultrafast X-ray Study of Multi-Orifice Diesel Nozzle Spray : Flow Dynamics and Breakup in the Near-Field
Advanced Photon Source, Argonne National Laboratory
Motivation Deficient information on near-nozzle flow dynamics and breakup of multi-orifice nozzle sprays for validation of conventional breakup models
Objectives Interpretation of near-field flow dynamics and breakup of multi-orifice nozzle spray Provide the validation data for conventional and future breakup models
Overall Flow Development
Principle of X-ray Phase-Enhanced Imaging
Ref.) S. W. Wilkins et al., Nature, 384 (28), 335-338, 1996
DiffractedBeams
Multiple Interference
Interference
sample
Detected Intensity
Broad
Sharp
Polychromatic X-ray Beam
Absorption-contrasted
Phase-contrasted
Branching Multi-Jet Flows Wavy Instabilities and Membrane-Mediated Breakup
Single-Exposed (Side-View) Pinj = 30MPa, Fuel = Biodiesel
Needle Lift = 350 m, Ambient Gas = N2
Two-Orifice Diesel Nozzle
Revolution time: 3.682 s
16 mA
11 mA for each
1.594 s 1.594 s
Hybrid-Singlet Mode
3.682
Time (s)
Current(mA)
1.594 1.594
single-exposure double-exposure
Periodicity : 68ns
Experiments(Setup in XOR 7ID-B, APS ANL)
X-ray Pulses for Single- and Double-Exposure Imaging
Features
Breakup Process of Multi-Jet-Flows
Single-Exposed(Top-View)
1. Wavy Instabilities Thin Membranes
Instability Frequency Instability1 : 2.8 MHz Instability2 : 4.2 MHz
Originated from different inter-nozzle flows
Double-Exposed (Side-View)
x=3.5 mm
Dynamics of Thinned Membranes
Cv Membrane : 0.73 Downflow : 0.84
Air drag exerted on membranes
2. Breakup of Membranes Single-Exposed(Top-View)
Membranes breakup earlier than cylindrical flows.
3. Breakup of Cylindrical Flows Single-Exposed(Side-View)
Cylindrical flows breakup directly into ligaments.
Dynamics of Multi-Jet-FlowsDouble-Exposed
(Side-View) Pinj = 40MPa*
Axial Location (x) = 2.5 mm
Cv(V/Videal) = 0.87
Vx,up = 273.53 m/sVy,up = 8.21 m/s
Vx,down = 273.53 m/sVy,down = -10.94 m/s
Autocorrelation
Local branching flows have same axial velocity but different penetration directions.
Structure of Multi-Jet-Flows
0 100 200 300 400 500 6000.00
0.05
0.10
0.15
0.20
Nor
mal
ized
PD
F
Jet Width [m]
Side-view Top-viewtop-view
side-view
Single-ExposedAxial Location (x) = 3.5 mm
Local cylindrical (1) & tubular (2) Flows
1
2
Elliptical Spray (56 %) : (a) + (d) Stretch of spray up and down Comprised of cylindrical flows
Spray width
Hollow Spray (44 %) : (a) + (b) Hollow region inside spray Comprised of tubular and cylindrical flows
SideView
TopView
Stable elliptical spray was observed from another nozzle with 700 m needle-lift. Full hollow-cone spray was observed with 50 m needle-lift. The sprays with 350 m needle-lift in this study are in transient stage of full hollow-cone to stable elliptical spray.
Top Needle-Lift= 350 m
0 1 2 3 6(mm)
Summary Development and breakup of multi-orifice nozzle spray are dictated by
branching multi-jet-flows induced by complex inter-nozzle flows. In the near-field, branching jet-flows with same axial velocity and have
cylindrical or tubular structures were observed and these formed ellip-tical spray in one case and hollow circular spray in another.
At downstream, wavy instabilities associated with branching jet-flows appear on the spray and develop into thin membranes. The thinned membranes breakup first into ligaments by aerodynamic drag and then cylindrical flows breakup later at farther downstream.
