Study on Vertical Bubbly Flows Using Laser Doppler Measurements : 1st Report, Simultaneous Measurement of Local Liquid Velocity and Void Fraction

謙吉, 大場; 光信, 小笠原; 次明, 上村; 純一, 佐藤

doi:10.1299/kikai1938.42.3560

Cited by 3 publications

(2 citation statements)

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“…Some of these sensors are based on X-ray absorption variation [5,12,13,14] or ultrasonic wave damping rate modulation [5,15,16,17] due to the bubble presence. Laser methods [5,18,19,20] however need the presence of optical view-ports and uses the reflectance of a laser beam over the gas bubbles to determine their volume. Finally, sensors based on capacitive variation of the medium [21] are characterized by an enhanced sensitivity and low noise if properly designed.…”

Section: State-of-the-artmentioning

confidence: 99%

Void fraction measurement in cryogenic flows. Part I: Design and validation of a void fraction capacitive sensor

et al. 2018

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This manuscript presents the design of a capacitive void fraction sensor for cryogenic LN2 two phase flows and its validation at room conditions. The capacitive void fraction sensor is first designed by means of Electric Field Analysis (EFA) simulations taking into account specific technical constraints coming from the test section in which it should be accommodated. Then it is manufactured and validated using a proper combination of fluids (Polydimethylsiloxane (PDMS) and air) having a dielectric constant ratio similar to the one encountered in LN2/GN2 two phase flows. The validation is performed through comparison with void fraction measured by means of optical visualizations and shows how the capacitive measurement technique robustness allows obtaining reasonable accurate values of void fraction also for the substitute fluid case. The sensor presented in this manuscript was used to evaluate the void fraction during LN2 chilldown of a rectangular cooling channel and the results are presented in the second part of this work.

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Section: State-of-the-artmentioning

confidence: 99%

Void fraction measurement in cryogenic flows. Part I: Design and validation of a void fraction capacitive sensor

et al. 2018

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“…In this table, experimental studies on the flows in narrow rectangular ducts with a large aspect ratio are excluded. Profiles of several local flow parameters along a bisector only in the cross-section have been measured [14][15][16][17][18][19]. However, to understand geometry effect on the flow, data in a whole symmetric area including a corner which characterizes the geometry effect in a noncircular cross-section are inevitable.…”

Section: Introductionmentioning

confidence: 99%

Upward air–water bubbly flow characteristics in a vertical square duct

Sun

Kunugi

Shen

et al. 2013

Journal of Nuclear Science and Technology

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In nuclear engineering fields, gas-liquid bubbly flows exist in channels with various shape and size crosssections. Although many experiments have been carried out especially in circular pipes, those in a noncircular duct are very limited. To contribute to the development of gas-liquid bubbly flow model for a noncircular duct, detail measurements for the air-water bubbly flow in a square duct (side length: 0.136 m) were carried out by an X-type hot-film anemometry and a multi-sensor optical probe. Local flow parameters of the void fraction, bubble diameter, bubble frequency, axial liquid velocity and turbulent kinetic energy were measured in 11 two-phase flow conditions. These flow conditions covered bubbly flow with the area-averaged void fraction ranging from 0.069 to 0.172. A pronounced corner peak of the void fraction was observed in a quarter square area of a measuring cross-section. Due to a high bubble concentration in the corner, the maximum values of both axial liquid velocity and turbulent kinetic energy intensity were located in the corner region. It was pointed out that an effect of the corner on accumulating bubble in the corner region changed the distributions of axial liquid velocity and turbulent kinetic energy intensity significantly.

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Study on Void Fraction Measurement of Cryogenic Two-Phase Flow by Image Analysis

Okada

Satô

Kobayashi

et al. 2015

AEROSPACE TECHNOLOGY JAPAN, THE JAPAN SOCIETY FOR AERONAUTICAL

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The hypersonic air-breathing engine, which is currently under development by Japan Aerospace Exploration Agency (JAXA), uses liquid hydrogen as the fuel. In order to accurately control the fuel flow rate during the start-up, it is essential to measure the heat transfer and pressure drop of the two phase flow. These two characteristics depend on void fraction, flow velocity and flow regime; thus, measurement methods for these values are required to be established. In this study, the void fraction measurement method by the high-speed image analyses has been developed. Two images taken from top and side directions by high-speed cameras of 1000 fps are used for two-direction semi-automatic analysis . We also develop One-direction full automatic analysis which uses only the side view as a full-automatic and high sampling rate method with little accuracy deterioration. The preliminary verification test using vertical pipe and acrylic ball shows favorable results within 2.2% error against the theoretical value. A cryogenic experiment using two-phase nitrogen flow was also conducted. Sampling rate of One-direction full automatic analysis can be up to 1000 Hz. The difference between the results of two methods was as minor as 5% when the void fraction was below 30%.

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Study on Vertical Bubbly Flows Using Laser Doppler Measurements : 1st Report, Simultaneous Measurement of Local Liquid Velocity and Void Fraction

Cited by 3 publications

References 0 publications

Void fraction measurement in cryogenic flows. Part I: Design and validation of a void fraction capacitive sensor

Void fraction measurement in cryogenic flows. Part I: Design and validation of a void fraction capacitive sensor

Upward air–water bubbly flow characteristics in a vertical square duct

Study on Void Fraction Measurement of Cryogenic Two-Phase Flow by Image Analysis

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