X-Ray Imaging Techniques to Quantify Spray Characteristics in the Near Field

Heindel, Theodore J.

doi:10.1615/atomizspr.2019028797

Cited by 41 publications

(40 citation statements)

References 60 publications

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“…X-ray beam can be produced in two types of devices: a tube source and a synchrotron. A detailed comparison between these two kinds of X-rays and the corresponding measurements for multiphase flows is provided by Heindel (2018). For cavitating flows, the tube source X-ray attenuation technique is used to measure local void fraction because of the absorption difference between water and vapor.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of internal two-phase flow structures and dynamics of quasi-stable sheet cavitation by fast synchrotron x-ray imaging

et al. 2020

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The quasi-stable sheet cavitation produced in a small Venturi channel is investigated using a fast synchrotron X-ray imaging technique aided with conventional high speed photography. The use of X-rays instead of visible light solves cavitation opacity related issues, and X-ray phase contrast-based edge enhancement enables high-definition visualization of the internal two-phase morphology. The simultaneous acquisition of time-resolved velocity and void fraction fields through post-processing the recorded X-ray images reveals, for the first time, the complex diphasic flow structures inside the sheet cavity, which is essentially divided into 6 characteristic parts. Distinct from the current mainstream view, the globallysteady sheet cavitation is found to be characterized by a weak but constantly-existing re-entrant flow that can penetrate the entire cavity. The turbulent velocity fluctuations inside the sheet cavity are also investigated. The turbulence level in the reverse flow region is observed to be as low as in the outer main flow demonstrating the relatively steady status of the reentrant flow. Unlike the streamwise and cross-stream fluctuations, the shear stress appears to be weakly correlated with the velocity gradient. The collapse of vapor phase and the vaporization at the upstream cavity interface are found to be the primary causes of shear stress intensification.Partial cavitation has two main forms of appearance: sheet and cloud cavitation (Pelz et al. 2017). The former generally appears as a quasi-stable sheet cavity with only small vapor shedding at its closure region, i.e. with an open closure. While in the latter case, the cavity is highly unstable as a consequence of periodic shedding of large vapor structures.The transition from sheet to cloud cavitation is, in a classic view, related to the motion of a re-entrant jet that breaks off the sheet cavity from the leading edge and consequently causes a large cavitation cloud to shed (Knapp, 1955). The existence of the re-entrant jet in periodic cloud cavitation was confirmed through the method of dye injection (Le et al. 1993). Kawanami et al. (1997) placed a small obstacle on the suction side of a hydrofoil to prevent the re-entrant jet from moving upstream, and the large cloud shedding disappeared, demonstrating the dominant role of the re-entrant jet. The conditions necessary for the development of the re-entrant jet has been explored by Callenaere et al. (2001). They showed the critical role of adverse pressure gradient at the cavity closure in the onset of the re-entrant jet instability.Regarding the relatively stable sheet cavitation, Gopalan & Katz (2000), Callenaere et al. (2001) and Laberteaux & Ceccio (2001) described that no clear re-entrant jet was observed or only the weak reverse flow existed at the trailing edge

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Section: Introductionmentioning

confidence: 99%

Experimental investigation of internal two-phase flow structures and dynamics of quasi-stable sheet cavitation by fast synchrotron x-ray imaging

et al. 2020

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“…Ballistic imaging and X-ray radiography have recently shown the potential for insights because they can penetrate the dense multiphase flow with visible light and X-ray photons, respectively [Linne et al, 2009;Yue et al, 2001;Heindel, 2011]. Synchrotron X-rays, like the ones produced at Argonne National Laboratory's Advanced Photon Source (APS), provide a high-flux collimated beam that can be used to probe the spray with high spatial and temporal resolution, even in its densest regions [Kastengren and Powell, 2014;Heindel, 2019]. This study uses the unique capability of synchrotron radiography to image the dense near-field region of a canonical coaxial two-fluid atomizer.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron radiography characterization of the liquid core dynamics in a canonical two-fluid coaxial atomizer

Machicoane

Bothell

et al. 2019

International Journal of Multiphase Flow

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The liquid core of a canonical two-fluid coaxial atomizer has been characterized using synchrotron X-rays. The high energy photons allow for high-speed imaging of attenuation through the dense liquid-gas jet core, resolving the internal structures that include entrapped air bubbles and the formation of liquid ligaments and bags. When the gas-to-liquid momentum ratio increases, the liquid core transitions from an intact column, where primary break-up happens several liquid diameters downstream, to a hollow crown with a downstream span comparable to the liquid diameter that disintegrates by shedding ligaments from its rim. At high gas momentum ratios (limited by the sonic velocity at the gas nozzle exit), this crown suffers partial dewetting and, when angular momentum is added to the gas, it dewets on a large section of the liquid injection needle circumference. This partial crown exhibits azimuthal motions along the circumference, on timescales much longer than the rele

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“…The near-field region is generally optically dense, increasing the difficulty of characterizing the spray in this region using optical or laser-based techniques (MacPhee et al, 2002). X-ray based techniques, with weak scatter and strong penetration, can provide alternative measurements for effective spray characterization (Heindel, 2018). X-ray radiography is a common X-ray imaging method which produces a shadow-like image of an object where the intensity of the "shadow" is a function of X-ray power and the object's X-ray attenuation (Heindel, 2011).…”

Section: Introductionmentioning

confidence: 99%

Time-Averaged Spray Analysis in the Near-Field Region Using Broadband and Narrowband X-Ray Measurements

Bothell

Morgan

et al. 2019

Atomiz Spr

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The characterization of a spray in the near-field region is challenging because of its high optical density in this region. X-ray based techniques, with weak scatter and strong penetration properties, can provide better characterization than optical assessment techniques in this region.In this work, the effects of various operating parameters on the evaluation of the optical depth (defined as the accumulated liquid thickness in the beam path times the X-ray attenuation coefficient) and spray profile of an atomizing spray in the near-field region are evaluated based on time-averaged X-ray analysis techniques. Controlling parameters in the spray structure include swirl ratio, liquid phase Reynolds number, and gas phase Reynolds number. Data from the broadband X-ray radiographs obtained using a tube source at Iowa State University and from focused beam measurements at the Advanced Photon Source at Argonne National Laboratory are compared. The X-ray tube source at ISU was operated at two different energy levels, which reveals that the X-ray tube source energy influenced the magnitude of the optical depth but did not change the shape of the distribution. For the no swirl condition, gas flow rate and liquid flow rate had opposite effects on the spray profile, where the spray widens as the gas flow rate increases and narrows as the liquid flow rate increases. As the swirl ratio increases from 0 to 1, the spray widens and then narrows, which indicates that the effect of swirl being more dramatic

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X-Ray Imaging Techniques to Quantify Spray Characteristics in the Near Field

Cited by 41 publications

References 60 publications

Experimental investigation of internal two-phase flow structures and dynamics of quasi-stable sheet cavitation by fast synchrotron x-ray imaging

Experimental investigation of internal two-phase flow structures and dynamics of quasi-stable sheet cavitation by fast synchrotron x-ray imaging

Synchrotron radiography characterization of the liquid core dynamics in a canonical two-fluid coaxial atomizer

Time-Averaged Spray Analysis in the Near-Field Region Using Broadband and Narrowband X-Ray Measurements

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