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Research Papers: Internal Combustion Engines

The Effects of Diesel Injector Needle Motion on Spray Structure

[+] Author and Article Information
C. F. Powell, A. L. Kastengren

Center for Transportation Research, Argonne National Laboratory, Argonne, IL 60439

Z. Liu, K. Fezzaa

Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439

J. Eng. Gas Turbines Power 133(1), 012802 (Sep 24, 2010) (9 pages) doi:10.1115/1.4001073 History: Received September 25, 2009; Revised November 10, 2009; Published September 24, 2010; Online September 24, 2010

The internal structure of diesel fuel injectors is known to have a significant impact on the steady-state fuel distribution within the spray. However, little experimental or computational work has been performed on the dynamics of fuel injectors. Recent studies have shown that it is possible to measure the three-dimensional geometry of the injector nozzle, and to track changes in that geometry as the needle opens and closes in real time. This has enabled the dynamics of the injector to be compared with the dynamics of the spray, and allows computational fluid dynamics (CFD) simulations to use realistic time-dependent flow passage geometries. In this study, X-ray phase-enhanced imaging has been used to perform time-resolved imaging of the needle seat area in several common-rail diesel injection nozzles. The fuel distributions of the sprays emitted by these injectors were also studied with fast X-ray radiography. Correlations between eccentric motions of the injector needle valve and oscillations in the fuel density as it emerges from the nozzle are examined. CFD modeling is used to interpret the effect of needle motion on fuel flow.

Copyright © 2011This material is declared a work of the US government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.
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Figures

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Figure 1

Schematic of phase-enhanced imaging setup

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Figure 2

Schematic of spray radiography setup

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Figure 3

Static X-ray images of hydroground nozzle from two lines-of-sight 90 deg apart. The relative size and location of the X-ray probe used for the radiography data of Fig. 7 are indicated by the rectangles at the right of the figure.

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Figure 4

Measured axial needle lift for the hydroground nozzle versus time. The dashed lines at 50 mm, 100 mm, and 200 mm lifts indicate the positions at which static CFD simulations of the nozzle flow were performed. The nonground nozzle shows nearly identical axial lift behavior.

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Figure 5

Overall numerical mesh geometry. The nozzle exit is at the left of the image.

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Figure 6

Detailed section view of cells near the nozzle inlet. The orange cells represent the near-wall layer, while the green cells represent the bulk of the mesh.

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Figure 7

Time-resolved measurements of the projected density at three locations near the outlet of the hydroground nozzle. The data shown were measured from the x-y view at an axial distance of 200 μm from the nozzle. The plot in the middle was measured on the injector axis, and the plots on top and bottom were measured 100 μm above and below the axis, respectively.

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Figure 8

Phase-enhanced images of the hydroground nozzle from the x-y view for needle lifts of 50, 100, and 200 μm; the asymmetry of the flow passages (at the upper and lower left of each image) is reflected in the off-axis position of the needle

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Figure 9

Comparison of the oscillations in the projected density (upper plots) with the off-axis motion of the needle (lower plots) for the hydroground nozzle

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Figure 10

Comparison of the oscillations in the projected density (upper plots) with the off-axis motion of the needle (lower plots) for the nonground nozzle

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Figure 11

Coefficients of discharge, velocity, and area for three measured needle lifts, accounting for the measured off-axis needle position

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Figure 12

Pressure distribution in the nozzle hole for 200 μm needle lift with the needle centered (x-y plane, pascals)

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Figure 13

Velocity magnitude in m/s at the exit (y-z) plane at 200 μm lift with the needle centered

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Figure 14

Velocity magnitude distribution in m/s in the sac for 50 μm needle lift with the needle centered

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Figure 15

Velocity magnitude distribution in the sac for 50 μm needle lift with the radial position of the opening phase. The colors represent 100 m/s and above to zero in steps of 5 m/s.

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Figure 16

Velocity vectors at the entrance to the sac, near the bottom left of Fig. 1, showing the flow separation near the sac wall. The needle surface is at the top of the image, with the sac wall at the bottom.

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Figure 17

Distribution of velocity magnitude in m/s at the exit (y-z) plane of the nozzle at 50 μm lift with the needle centered

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Figure 18

Distribution of velocity magnitude in m/s at the exit (y-z) plane of the nozzle at 50 μm lift with the needle at the radial position occupied during the opening phase

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