A Review of X-Ray Flow Visualization With Applications to Multiphase Flows

Heindel, Theodore J.

doi:10.1115/1.4004367

Cited by 185 publications

(136 citation statements)

References 160 publications

(225 reference statements)

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“…As stated in Dudukovic (2000), a multiphase flow experimental system should have: (1) high spatial and temporal resolution for local phase fraction measurements, as well as velocity field measurements of all phases, and (2) the capability to provide instantaneous and time history snapshots of the flow. Note, however, that a single experimental system that can satisfy all these needs does not currently exist (Heindel 2011). Despite the recent advances in laser diagnostics, such as ballistic imaging or structured illumination to mitigate the multiple scattering effects (Berrocal et al 2008;Linne et al 2006), their ability to measure fluid density is still limited (Leick et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Despite the recent advances in laser diagnostics, such as ballistic imaging or structured illumination to mitigate the multiple scattering effects (Berrocal et al 2008;Linne et al 2006), their ability to measure fluid density is still limited (Leick et al 2011). Moreover, flows with significant refractive index gradients, such as liquid diesel and vapour, exhibit beam-steering effects that interfere with optical diagnostics by creating uncertainty in the location of the volume under observation (Heindel 2011). Invasive measurement techniques, such as probes, interfere and alter the internal flow field that is under investigation and thus, they cannot be used with the small orifices utilised with fuel injection equipment.…”

Section: Introductionmentioning

confidence: 99%

“…Multiple non-invasive quantitative flow visualisation techniques have been reviewed in the literature over the years (Chaouki et al 1997;Dudukovic 2000;Duke 2015;Heindel 2011;Kastengren and Powell 2014;Yates et al 2002). One of the first applications of X-ray imaging for visualisation of air bubbles in gas-solid fluidised beds was performed in the 1950s and 1960s (Grohse 1955;Rowe and Partridge 1997).…”

Section: Introductionmentioning

confidence: 99%

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Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

et al. 2016

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efficiency of such engines. Among others, the fuel injection equipment (FIE) is a key component for improving the efficiency of environmentally friendly engines. Recent advances dictate the use of extra high injection pressures, of the order of 3000 bar and tiny flow passages (injection holes) of the order of 100-250 μm in diameter, for improved fuel atomisation and combustion efficiency. Under these circumstances, cavitation has been found to develop inside fuel injection nozzles at the early studies of Badock et al. (1999), Bergwerk (1959), Chaves et al. (1995) and Nurick (1976), followed by Arcoumanis et al. (2000), Blessing et al. (2003), Mitroglou et al. (2014) and Roth et al. (2002) in more realistic real-size nozzle geometries offering optical access; equally helpful studies performed in transparent enlarged nozzle replicas [selectively (Andriotis et al. 2008;Arcoumanis et al. 2000;Miranda et al. 2003; Mitroglou and Gavaises 2013;Powell et al. 2000)] also indicate that cavitation plays an increasingly significant role in the nozzle's internal flow structure and development. Cavitation inside an injection hole is believed to enhance spray atomisation, either directly through the implosion of cavitation bubbles or indirectly because it increases turbulence in the nozzle flow (Badock et al. 1999;Walther 2002); unfortunately, under certain circumstances induces erosion (Dular and Petkovšek 2015;Koukouvinis et al. 2016) that may lead to catastrophic failures. Moreover, cavitation inside the injection holes promotes shot-toshot spray instabilities (Mitroglou et al. 2011(Mitroglou et al. , 2012Suh and Lee 2008), which, in turn, are responsible for poor combustion efficiency and increased emissions (Hayashi et al. 2013). Two distinct macroscopic forms of cavitation have been identified, which are referred to as geometryinduced and vortex or 'string' cavitation. The former can be, partially or totally, suppressed by appropriate design of the inlet hole curvature and non-cylindrical injection hole Abstract The flow inside a purpose built enlarged singleorifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and highspeed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can ...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

et al. 2016

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“…X-rays have been used to study gas-solid fluidized beds as well as two and three phase fluidized systems for more than 50 years [8]. They are a commonly employed noninvasive technique because they are safer than other nuclear based techniques which cannot be turned on and off at will, have high resolution, and can be controlled by varying the voltage or current to improve penetration or contrast [9].…”

Section: Introductionmentioning

confidence: 99%

Characterizing Acoustic Fluidized Bed Hydrodynamics Using X-Ray Computed Tomography

Escudero

Heindel

2013

Volume 2, Fora: Cavitation and Multiphase Flow; Fluid Measurements and Instrumentation; Microfluidics; Multiphase Flows: Work I

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Fluidized bed reactors are important assets of many industrial applications because they provide uniform temperature distributions, low pressure drops, and high heat/mass rates. Characterizing the hydrodynamics of a fluidized bed is important to better understand the behavior of these multiphase flow systems. The hydrodynamic behavior in a cold flow 3D fluidized bed, with and without acoustic intervention, using X-ray computed tomography is investigated in this study. Experiments are carried out in a 10.2 cm ID fluidized bed filled with glass beads, with material density of 2600 kg/m 3 and particle size ranges between 212-600 μm. In this study, three different bed height-to-diameter ratios are examined: H/D = 0.5, 1 and 1.5. Moreover, the sound frequency of the loudspeaker used as the acoustic source is fixed at 150 Hz with a sound pressure level of 120 dB. Local time-average gas holdup results show that the fluidized bed under the presence of an acoustic field provides a more uniform fluidization, the bed exhibits less channeling, and the jetting phenomena produced by the distributor plate is less prominent when compared to no acoustic field. Thus, acoustic intervention affects the hydrodynamic behavior of the fluidized bed. KeywordsAcoustic fluidized bed, hydrodynamics, x-ray computed tomography ABSTRACT Fluidized bed reactors are important assets of many industrial applications because they provide uniform temperature distributions, low pressure drops, and high heat/mass rates. Characterizing the hydrodynamics of a fluidized bed is important to better understand the behavior of these multiphase flow systems. The hydrodynamic behavior in a cold flow 3D fluidized bed, with and without acoustic intervention, using X-ray computed tomography is investigated in this study. Experiments are carried out in a 10.2 em ID fluidized bed filled with glass beads, with material density of 2600 kg/m 3 and particle size ranges between 212-600 ~un. In this study, three different bed height-to-diameter ratios are examined: HID = 0.5, 1 and 1.5. Moreover, the sound frequency of the loudspeaker used as the acoustic source is fixed at 150Hz with a sound pressure level of 120 dB. Local time-average gas holdup results show that the fluidized bed under the presence of an acoustic field provides a more uniform fluidization, the bed exhibits less channeling, and the jetting phenomena produced by the distributor plate is less prominent when compared to no acoustic field. Thus, acoustic intervention affects the hydrodynamic behavior of the fluidized bed.

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“…X-ray computed tomography (CT) imagery is used to visualize the three-dimensional Darcy flow in complex porous samples (Heindel, 2011;Wildenschild and Sheppard, 2013;Wildenschild et al, 2002;Zhou et al, 2010). The flowing fluid is doped with an X-ray contrast agent to enhance phase differentiation.…”

Section: Introductionmentioning

confidence: 99%

The use of sodium polytungstate as an X-ray contrast agent to reduce the beam hardening artifact in hydrological laboratory experiments

Nakashima¹

2013

Journal of Hydrology and Hydromechanics

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Iodine is conventionally used as a contrast agent in hydrological laboratory experiments using polychromatic X-ray computed tomography (CT) to monitor two-phase Darcy flow in porous geological media. Undesirable beam hardening artifacts, however, render the quantitative analysis of the obtained CT images difficult. CT imaging of porous sand/bead packs saturated with iodine and tungsten-bearing aqueous solutions, respectively, was performed using a medical CT scanner. We found that sodium polytungstate (Na 6 H 2 W 12 O 40 ) significantly reduced the beam hardening compared with potassium iodide (KI). This result is attributable to the location of the K absorption edge of tungsten, which is nearer to the peak of the polychromatic X-ray source spectrum than that of iodine. As sodium polytungstate is chemically stable and less toxic than other heavy element bearing compounds, we recommend it as a promising contrast agent for hydrological CT experiments.

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A Review of X-Ray Flow Visualization With Applications to Multiphase Flows

Cited by 185 publications

References 160 publications

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

Characterizing Acoustic Fluidized Bed Hydrodynamics Using X-Ray Computed Tomography

The use of sodium polytungstate as an X-ray contrast agent to reduce the beam hardening artifact in hydrological laboratory experiments

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