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Cornell High Energy Synchrotron Source — CHESS

W. Cai, C. F. Powell, Y. Yue, S. Narayanan, J. Wang
     Argonne National Laboratory, Argonne, Illinois 60439

M.W. Tate, M.J.Renzi, A.Ercan, E. Fontes, and S. M. Gruner
     Cornell University, Ithaca NY 14853

The power of x-rays as tools to visualize the insides of dense bodies was one of the first applications of x-ray beams more than 100 years ago.  In this present study, two groups brought together a new, fast x-ray area detector and large, high intensity synchrotron x-ray beams to capture streaming images with microsecond resolution of the high-pressure liquid fuel sprays like those found in internal combustion engines.  Quantitative spray characterization has been difficult for a number of reasons, including the need for microsecond time resolution, submillimeter-scale spatial resolution, penetration through dense fuel sprays, lack of multiple scattering, and lack of perturbation of the in-situ spray.  The lack of penetration and multiple scattering have limited optical studies.

The detector used in this work, a Pixel Array Detector, or PAD, was highlighted in a previous CHESS Annual Report.  Each pixel uses charge accumulation from x-ray deposition and on-chip shift registers to acquire multiple images in microsecond timeframes.  The image readout is longer, but subsequent images can be synchronized with the pulsing beam from the storage ring to record a full stream of “video” images.

fuel spray

The resulting radiographs show striking details.  The mosaic figure at right shows the geometry of the x-ray beam traversing the fuel cone jet (top left), the resulting full-field images (top right, bottom left) and the density profiles taken at four different angles (bottom right).  Images like these show striking details in the dynamic characteristics of the hollow-cone gasoline spray.  These include a “sac” (small volumes of fuel near the spray leading edge due to transient nonequilibrium pressures at the instance of the injection pintle lift), density waves (due to a hydrodynamically driven instability in pintle axial motion), heavy asymmetry (due to pintle asymmetric radial motion), and local streaks (due to nozzle surface finish).  Each of these features was amazingly reproducible under identical injection conditions.

This study demonstrated that it is possible to measure the time- and spatial-resolved distribution of fuel mass, in liquid or vapor form, in highly transient gasoline direct injec-tion sprays.  These results should help engineers to design even more efficient injectors in the future.  The same methodology can also be generalized to study fluid dynamics of other high-speed liquid sprays in situations that cannot use visible light methods, such as in dense plasmas, spray coaters, and ink-jet apparatus.

See Publications:

MacPhee AG, Tate MW, Powell CF, Yue Y, Renzi MJ, Ercan A, Narayanan S, Fontes E, Walther J, Schaller J, Gruner SM, and Wang J.; "X-ray Imaging of Shock Waves Generated by High-pressure Fuel Sprays", Science 2002;295 (5558):1261-3

Renzi MJ, Tate MW, Ercan A, Gruner SM, Fontes E, Powell CF, MacPhee AG, Narayanan S, Wang J, Yue Y, and Cuenca R.; "Pixel Array Detectors for Time Resolved Radiography", (invited). Review of Scientific Instruments 2002;73 (3):1621-4

Cai WY, Powell CF, Yue Y, Narayanan S, Wang J, Tate MW, Renzi MJ, Ercan A, Fontes E, and Gruner SM.; "Quantitative Analysis of Highly Transient Fuel Sprays by Time-resolved X-radiography", Applied Physics Letters 2003;83 (8):1671-3

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