X-Ray Diagnostics of ECN Injector Geometry, Needle Motion, and Spray Behavior

1. X-Ray Diagnostics of ECN Injector Geometry, Needle Motion, and Spray Behavior Alan Kastengren, Christopher Powell, F. Zak Tilocco, Kamel Fezzaa, Seoksu Moon, Xusheng Zhang: Argonne National Laboratory Daniel Duke: Monash University DOE Vehicle Technologies Program Team Leader: Gurpreet Singh

2. Overview • ECN Nozzle Geometry • ECN Needle Motion • Radiography at cold “Spray A” conditions Engine Combustion Network Workshop, Ventura, CA, May 2011

3. X-Ray Phase-Contrast Imaging • Previous measurements: injectors 210675, 210679, 211201 • New measurements: injectors 210677, 210678 • Geometry images at improved resolution • 2 µm pixel resolution vs. 4 µm previously • Test pattern image resolution: 3 µm radial, 5 µm axial • Geometry images from six different viewing angles • Complements, but doesn’t replace, tomography • Allows us to correct the orientation angle of the tomography measurements • Substantial analysis of phase-contrast images and tomography for A&S paper Engine Combustion Network Workshop, Ventura, CA, May 2011

4. Nozzle Geometry: Nozzle Targeting • All nozzles have been drilled significantly offset from the injector axis • Minimum is 30 µm for 210678, maximum is 40 µm for 210675 • Orientation of offset is virtually identical in all nozzles: maximum offset at +10° orientation angle • Misalignment of jig during machining • The exact amount of offset matters because the sac is not hemispherical • Flat area at the very tip of the sac • Easily seen in three-hole nozzle, since there is no hole at tip of sac • Also evident at hole inlet for some orientations and nozzles • Hole direction aligned with injector to within 0.5° Nozzle 211201 Nozzle 210677, 0° Engine Combustion Network Workshop, Ventura, CA, May 2011

5. Nozzle Geometry: Inlet Condition • Turning angle at inlet influences potential for vena contracta, recirculation, and cavitation • Use phase-contrast images and look at three nozzles with high-res images • Significant variation around nozzles due to hole offset for all nozzles • Very high turning angle for 210677 and 210679 around 180° orientation angle • Hole inlet covers up entire flat area at sac tip for 210678 • 210677 and 210679 are more offset, so this flat area becomes apparent at inlet, leading to turning angles close to 90° • Inlet radius: really hard to measure • Somewhere around 17-20 µm Engine Combustion Network Workshop, Ventura, CA, May 2011

6. Nozzle Geometry: Diameter vs. Axial Distance 210678deviates from others ~ 200 µm from tip Inlet d = 115 µm, so nozzles KS 2.5 – KS 3 Convergence not linear: faster near inlet Fast convergence near tip: 3 µm 210678 5-6 µm 210677 and 210679 210677and 210679 Virtually Identical Engine Combustion Network Workshop, Ventura, CA, May 2011

7. Nozzle Geometry: Tomography Diameter Profile • Tomography data show smaller diameters, but same trends • Use measured nozzle exit diameter from microscopy as baseline for phase-contrast images • Phase effects leading to errors in tomography? • Same trends • 210677 and 210679 are virtually identical • 210678 converges less quickly < 200 µm • Tip convergence greater for 210677 and 210679 than 210678 • Different trend throughout nozzle for 210675: faster convergence early, flatter near the tip • Waves from tomography not in phase-contrast images: artifacts? Diameter vs. Axial Position Tomography Measurements Engine Combustion Network Workshop, Ventura, CA, May 2011

8. Nozzle Geometry: 210678 Unusual Behavior Engine Combustion Network Workshop, Ventura, CA, May 2011

9. Nozzle Geometry: Conclusions • All nozzles drilled off-center but generally axially • Significant variations in inlet turning angle around the circumference of the inlet and between nozzles • Diameter profile down nozzle • K-factor much greater than specification • Non-linear convergence • Significant convergence within last 50 µm of nozzle • Odd behavior of 210678 in radiography due to coking? • Unanswered questions • If 210677 and 210679 are so similar in geometry, why are the injected quantity values so different? Internal leakage? • How can we get better values of the inlet radius? • How can we get measurements of surface finish? Engine Combustion Network Workshop, Ventura, CA, May 2011

10. Needle Motion Measurements • In conjunction with geometry imaging, x-ray phase-contrast imaging has been used to examine needle motions • High-speed movies of needle motion, both axial and lateral • Resolution: 4 µm/pixel, 20 µs per frame • Previous measurements: injectors 210675, 210679, 211201 with 750 µs commanded duration • New measurements: injectors 210677, 210678, 211201 with 795 µs commanded duration • Still processing data Example Needle Motion Movies Injector 210677, 0° Engine Combustion Network Workshop, Ventura, CA, May 2011

11. Needle Motion Measurements: Axial Motion • General trends are very similar to what we have seen in previous measurements • All single hole nozzles lift on virtually identical curves • Three-hole nozzle a little slower • Some variation in timing of reversal of motion • Old measurements reach slightly smaller lift due to different commanded duration • As stated at workshop, we can probably develop a single lift curve that is universally applicable Axial Needle Position vs. Time after Commanded SOI Engine Combustion Network Workshop, Ventura, CA, May 2011

12. X-Ray Radiography • Use x-rays to probe the mass distribution in the near-nozzle region of the sprays • Uninhibited by scattering from spray droplets, since x-rays scatter very little from phase interfaces • High resolution: 3.68 µs time resolution, down to 5 µm spatial resolution • As with all of our other measurements, these experiments were at room temperature in N2, but with the same density at the Spray A specification • Performed measurements from 0.1 to 12 mm from the nozzle for all single hole nozzles at four different viewing angles each • Judge the repeatability of the measurements • Perform 3-D reconstruction to understand underlying density distribution Schematic of Beamline Layout Engine Combustion Network Workshop, Ventura, CA, May 2011

13. X-Ray Radiography: Initial Results • Measurements are the most challenging we’ve ever attempted • Due to high injection pressure, a normal shock is formed at the spray tip, which interferes with seeing spray tip in more downstream locations • Pressure fluctuations in chamber that must be corrected • Significant asymmetry fro 210675 injector • Some very non-ideal (bimodal) distributions for 210678 and 210679 • 210678: due to coking? • 210679: ??? Engine Combustion Network Workshop, Ventura, CA, May 2011