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.