Advanced Photon Source, Argonne National Laboratory

1. Ultrafast X-ray Study of Multi-Orifice Diesel Nozzle Spray : Flow Dynamics and Breakup in the Near-Field Advanced Photon Source, Argonne National Laboratory Principle of X-ray Phase-Enhanced Imaging • Motivation • Deficient information on near-nozzle flow dynamics and breakup of multi-orifice nozzle • sprays for validation of conventional breakup models PolychromaticX-ray Beam • Objectives • Interpretation of near-field flow dynamics and breakup of multi-orifice nozzle spray • Provide the validation data for conventional and future breakup models Two-Orifice Diesel Nozzle X-ray Pulses for Single- and Double-Exposure Imaging Experiments (Setup in XOR 7ID-B, APS ANL) Top Needle-Lift = 350 m • Structure of Multi-Jet-Flows Overall Flow Development Single-Exposed (Side-View) Pinj= 30MPa, Fuel = Biodiesel Needle Lift = 350 m, Ambient Gas = N2 Single-Exposed Axial Location (x) = 3.5 mm (mm) 0 1 2 3 6 Side View 1 Spray width • Elliptical Spray (56 %) : (a) + (d) • Stretch of spray up and down • Comprised of cylindrical flows Top View • Hollow Spray (44 %) : (a) + (b) • Hollow region inside spray • Comprised of tubular and • cylindrical flows 2 Local cylindrical (1) & tubular (2) Flows • Branching Multi-Jet Flows • Wavy Instabilities and Membrane-Mediated Breakup • 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. Features • Dynamics of Multi-Jet-Flows • Breakup Process of Multi-Jet-Flows 1. Wavy Instabilities  Thin Membranes 2. Breakup of Membranes Double-Exposed (Side-View) Pinj= 40MPa* Axial Location (x) = 2.5 mm Single-Exposed (Top-View) Single-Exposed (Top-View) • Instability Frequency • Instability1 : 2.8 MHz • Instability2 : 4.2 MHz • Originated from different • inter-nozzle flows Autocorrelation Cv(V/Videal) = 0.87 Vx,up= 273.53 m/s Vy,up= 8.21 m/s Vx,down= 273.53 m/s Vy,down= -10.94 m/s Dynamics of Thinned Membranes • Membranes breakup earlier than cylindrical flows. • Local branching flows have same axial velocity but different penetration directions. 3. Breakup of Cylindrical Flows Single-Exposed (Side-View) Double-Exposed (Side-View) x=3.5 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 elliptical 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. • Cv • Membrane : 0.73 • Downflow : 0.84 • Air drag exerted • on membranes • Cylindrical flows breakup directly into ligaments.