Holography in Dust Erosion Facilities

2014

Extensive application of holographic techniques has been made in the ground test facilities at the Arnold Engineering Development Center (AEDC) for particle-field analysis and flow diagnostics. The instrumentation requirements of dust erosion facilities include a dynamic evaluation of the dust cloud, including size, number density, velocity, and distribution of dust particles. Holography has provided a unique method of performing such an evaluation. The system developed at AEDC and currently in routine use is discussed in detail. Design criteria and system capability are analyzed. It is shown that the holography system provides data which cannot be obtained with other existing instrumentation.

2012

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Powder Technology, 2020

Precise measurement of the minimum ignition energy (MIE) of combustible dust is crucial to safety in the process industries. The development of comprehensive methods for MIE dust cloud characterization is therefore highly desirable. The objective of this study is to investigate the application of high-speed digital in-line holography (DIH) for volumetric and in-situ characterization of dust clouds near the ignition zone of a Kühner MIKE3 MIE device. The dispersion behavior of borosilicate glass and soda-lime glass dust clouds are studied at 20 kHz. Size measurements, with successful detection down to 13 μm, are compared with Beckman Coulter particle size analyzer results. The 5-ms hologram videos also yield new transient particle volume, concentration, and velocity measurements. Sample sizes of 15-150 mg of dust powder are sufficient for each high-speed run. This work showcases new diagnostic capabilities that are accessible to dust explosion research and identifies areas for future research.

Plasma and Fusion Research, 2009

We collected dust particles ranging in size from 1 nm to 10 µm from the Large Helical Device employing two methods: an ex-situ filtered vacuum collection method and an in-situ dust collection method. The size distribution from 1 nm to 10 µm is well expressed by the Junge distribution. Dust particles are classified into three kinds: small spherical dust particles below 1 µm in size, agglomerates consisting of primary particles of 10 nm, and large dust particles above 1 µm in size and irregular in shape; this suggests three formation mechanisms of dust particles: chemical vapor deposition growth, agglomeration, and peeling from walls. In-situ collection shows that agglomeration between dust particles takes place in main discharges. The primary dust particles in agglomerates are around 10 nm in size, suggesting agglomeration between a negatively charged large agglomerate and a positively charged dust particle 10 nm in size. We have also confirmed the important fact that a large number of dust particles move during vacuum vent. Therefore, the in-situ dust collection method is needed to reveal the generation-time and -processes of dust particles and their deposition position during discharges.

Plasma and Fusion Research, 2009

We collected dust particles ranging in size from 1 nm to 10 µm from the Large Helical Device employing two methods: an ex-situ filtered vacuum collection method and an in-situ dust collection method. The size distribution from 1 nm to 10 µm is well expressed by the Junge distribution. Dust particles are classified into three kinds: small spherical dust particles below 1 µm in size, agglomerates consisting of primary particles of 10 nm, and large dust particles above 1 µm in size and irregular in shape; this suggests three formation mechanisms of dust particles: chemical vapor deposition growth, agglomeration, and peeling from walls. In-situ collection shows that agglomeration between dust particles takes place in main discharges. The primary dust particles in agglomerates are around 10 nm in size, suggesting agglomeration between a negatively charged large agglomerate and a positively charged dust particle 10 nm in size. We have also confirmed the important fact that a large number of dust particles move during vacuum vent. Therefore, the in-situ dust collection method is needed to reveal the generation-time and -processes of dust particles and their deposition position during discharges.

Applied Optics, 2004

An in-line holographic system for in situ detection of atmospheric cloud particles ͓Holographic Detector for Clouds ͑HOLODEC͔͒ has been developed and flown on the National Center for Atmospheric Research C-130 research aircraft. Clear holograms are obtained in daylight conditions at typical aircraft speeds of 100 m s Ϫ1 . The instrument is fully digital and is interfaced to a control and data-acquisition system in the aircraft via optical fiber. It is operable at temperatures of less than Ϫ30°C and at typical cloud humidities. Preliminary data from the experiment show its utility for studies of the three-dimensional spatial distribution of cloud particles and ice crystal shapes.

Atmospheric Measurement Techniques, 2013

Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in situ image cloud particles in a well-defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 µm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements.

Fusion Engineering and Design, 2014

Applied Optics, 1967

The basic principles of applying hologram techniques to the problem of particle size determination have received considerable attention over the past year. In this paper the basic principles of the use of the Fraunhofer (far field) hologram are described for both the recording of Factors affecting the sample volumE shown.

1970

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