Laser Focus Displacement Meter Research Articles

Two-Phase Swirling Flow in a Gas-Liquid Separator

Air-water swirling flows in a one-fifth model of a steam separator in a boiling water nuclear reactor are measured to obtain a database for modeling and verification of numerical methods for predicting swirling flows in the separator. Flow patterns, liquid film thicknesses, separated flow rates and the ratio Ws* of the separated flow to the total liquid flow are measured using a high-speed camera, a laser focus displacement meter and flowmeters. Main conclusions obtained are as follows: (1) liquid transfer from droplets to liquid film is caused not only by droplet deposition but also by the collection of droplets on the vanes of the swirler, (2) Ws* increases with the gas volume flux JG and does not depend on the liquid volume flux JL so much because a large centrifugal force caused by the swirler makes most of droplets in the gas core deposit on the liquid film before the separation and (3) a local peak appears in the axial distribution of film thickness, the position of which corresponds to the location where the droplet deposition caused by the centrifugal force has completed.

Experimental study on axial development of liquid film in vertical upward annular two-phase flow

Accurate measurements of the interfacial wave structure of upward annular two-phase flow in a vertical pipe were performed using a laser focus displacement meter (LFD). The purpose of this study was to clarify the effectiveness of the LFD for obtaining detailed information on the interfacial displacement of a liquid film in annular two-phase flow and to investigate the effect of axial distance from the air–water inlet on the phenomena. Adiabatic upward annular air–water flow experiments were conducted using a 3 m long, 11 mm ID pipe. Measurements of interfacial waves were conducted at 21 axial locations, spaced 110 mm apart in the pipe. The axial distances from the inlet ( z) normalized by the pipe diameter ( D) varied over z/ D = 50–250. Data were collected for predetermined gas and liquid flow conditions and for Reynolds numbers ranging from Re G = 31,800 to 98,300 for the gas phase and Re L = 1050 to 9430 for the liquid phase. Using the LFD, we obtained such local properties as the minimum thickness, maximum thickness, and passing frequency of the waves. The maximum film thickness and passing frequency of disturbance waves decreased gradually, with some oscillations, as flow developed. The flow development, i.e., decreasing film thickness and passing frequency, persisted until the end of the pipe, which means that the flow might never reach the fully developed state. The minimum film thickness decreased with flow development and with increasing gas flow rate. These results are discussed, taking into account the buffer layer calculated from Karman’s three-layer model. A correlation is proposed between the minimum film thickness obtained in relation to the interfacial shear stress and the Reynolds number of the liquid.

Interfacial area concentration in annular two-phase flow

Accurate prediction of the interfacial area concentration is essential to successful development of the interfacial transfer terms in the two-fluid model. The interfacial area concentration in annular flow and annular-mist flow is especially relevant to the transition process to the liquid film dryout, which might lead to fatal problem in the safety and efficient operation of boiling heat transfer system. However, very few experimental and theoretical studies focusing on the interfacial area concentration in annular flow region have been conducted. From this point of view, measurements of annular flow parameters such as one-dimensional interfacial area concentration of liquid film and local interfacial area concentration profile of liquid film were performed by a laser focus displacement meter at 21 axial locations in vertical upward annular two-phase flow using a 3-m-long and 11-mm-diameter pipe. The axial distances from the inlet ( z) normalized by the pipe diameter ( D) varied over z/ D = 50–250. Data were collected for preset gas and liquid flow conditions and for Reynolds numbers ranging from 31,800 to 98,300 for the gas phase and 1050 to 9430 for the liquid phase. Axial development of the one-dimensional interfacial area concentration and the non-dimensional local interfacial area concentration profile of liquid film were examined with the data obtained in the experiment. Total interfacial area concentration including liquid film and droplets was also discussed with help of the existing drift-flux model, entrainment correlation, and droplet size correlation.

1804 水・蒸気系環状流中における局所液膜厚さの計測(G06-1 伝熱(1),G06 熱工学)

The surface structure of the liquid film was investigated in steam-water annular flow. Film thickness was measured using a laser focus displacement meter. A high-speed camera was used to visualize disturbance waves. These were carried out about 300mm above the end of heated section. The frequency and velocity of the disturbance waves were measured through image analysis.

Measurement of liquid film in microchannels using a laser focus displacement meter

This paper presents a new method for measuring the interfacial displacement of a liquid film in microchannels using a laser focus displacement meter (LFD). The purpose of the study is to clarify the effectiveness of the new method for obtaining detailed information concerning interfacial displacement, especially in the case of a thin liquid film, in microchannels and minichannels. To prevent the tube wall signal from disturbing that of the gas–liquid interface, a fluorocarbon tube with a water box was used; the refraction index of this device is the same as that for water. With this method, accurate instantaneous measurements of the interfacial displacement of the liquid film were achieved. The error caused by refraction of the laser beam passing through the acrylic water box and fluorocarbon tube was estimated analytically and experimentally. The formulated analytical equation can estimate the real interface displacement by using the measured displacement in a fluorocarbon tube of 25 μm to 2.0 mm I.D. A preliminary test using fluorocarbon tubes of 1 mm and 2 mm I.D. showed that the corrected interface displacement calculated by the equation agreed with the real displacement to within a 1% margin of error. It was also confirmed that the LFD in the system could measure a liquid film of 0.25 μm at the thinnest. We made simultaneous measurements of the interface in fluorocarbon tubes of 0.5 mm and 1 mm I.D. using the LFD and a high-speed video camera with a microscope. These showed that the LFD could measure the interface of a liquid film with high spatial and temporal resolution during annular, slug, and piston flow regimes. The data also clarified the existence of a thin liquid film of less than 1 μm in thickness in the slug and annular flow regimes.

Measurement of Interfacial Structure on Liquid Film in Annular Flow Using Laser Focus Displacement Meter (1st Report, Measurement Accuracy and Axial Development of Liquid Film)

Accurate measurements of interfacial wave-structure of upward annular two-phase flow in a vertical pipe were performed using a laser focus displacement meter (LFD). The purpose of this study was to clarify the effectiveness of the LFD for obtaining detailed information concerning the interfacial structure of a liquid film in annular two-phase flow and to investigate the effect of axial length on the phenomena. We made simultaneous measurements of the liquid film interface in an acrylic rectangular pipe with 3-mm width using LFD and high-speed video camera to check the measuring accuracy of the LFD. These showed that the LFD could measure the interface of liquid film with high spatial and temporal resolution in various flow conditions. Adiabatic upward annular air-water flow experiments were conducted using a 3 m-long, 11 mm-ID pipe. Measurements of interfacial wave were conducted at 21 axial locations. The axial distances from the inlet (L) normalized by the pipe diameter (D) varied L/D=50-250. The results revealed that the maximum film thickness decreased gradually with some oscillations as flow developed. The flow development, i. e. decreasing of film thickness, existed till the pipe exit which means that the flow might never reach a fully developed condition.

Measurement of Interfacial Structure on Liquid Film in Annular Flow Using Laser Focus Displacement Meter (2nd Report, Disturbance Wave Frequency and Local Minimum Film Thickness)

In this study, a precise database of microscopic interfacil wave-structure was obtained for annular two-phase flow developing in a vertical pipe. Using a laser focus displacement meter (LFD), measurements of such local properties as the minimum film thickness and passing frequency of the waves along the pipe were conducted. The results showed that the passing frequency of disturbance waves decreased gradually with some oscillations in the pipe axial direction, whose phenomena had a similarity with those of maximum film thickness reported in the 1st report. These unique phenomena were also discussed from a view of pressure resonant interactions based on the experimental results of pressure propagation in the pipe. Minimum thickness of the film decreased with flow development and with increasing gas flow rate. These results were discussed taking into account the buffer layer calculated from Karman's three-layer model. Correlation was proposed for obtained minimum film thickness in regarding to interfacial shear stress and the Reynolds number of the liquid. This correlation expressed the minimum film thickness obtained from the experiment withis 5% deviation.

Measurement of Interfacial Displacement of a Liquid Film in Microchannels Using Laser Focus Displacement Meter

This paper presents a new method for measuring the interfacial displacement of a liquid film in microchannels using a laser focus displacement meter (LFD).The purpose of the study is to clarify the effectiveness of the new method for obtaining detailed information concerning interfacial displacement, especially in the case of a thin liquid film, in micro- and mini-channels. To prevent the tube wall signal from disturbing that of the gas-liquid interface, a fluorocarbon tube with water box was used ; the refraction index of this device is same as that for water. With this method, accurate instantaneous measurements of interfacial displacement of the liquid film were achieved. The error caused by refraction of the laser beam passing through the acrylic water box and fluorocarbon tube was estimated analytically and experimentally. The formulated analytical equation can estimate the real interface displacement using measured displacement in a fluorocarbon tube of 25μm to 2.0 mm I.D. A preliminary test using fluorocarbon tubes of 1 and 2 mm I.D. showed that the corrected interface displacement calculated by the equation agreed with real displacement within a 1% margin of error. It was also confirmed that the LFD in the system could measure a liquid film of 0.25 μm at the thinnest. We made simultaneous measurements of the interface in fluorocarbon tubes of 0.5 and 1 mm I.D. using the LFD and a high-speed video camera with a microscope. These showed that the LFD could measure the interface of a liquid film with high spatial and temporal resolution during annular, slug, and piston flow regimes. The data also clarified the existence of a thin liquid film less than 1 pm in thickness in slug and annular flow regions.

レーザーフォーカス変位計による細管内液膜界面の計測(FR2 計測制御の最先端)

This paper presents a new method for measuring the interfacial displacement of a liquid film in minichannels using a laser focus displacement meter (LFD). The purpose of the study is to clarify the effectiveness of the new method for obtaining detailed information concerning interfacial displacement, especially in the case of a thin liquid film, in micro- and mini-channels. To prevent the tube wall signal from disturbing that of the gas-liquid interface, a fluorocarbon tube with water box was used; the refraction index of this device is the same as that for water. With this method, accurate instantaneous measurements of interfacial displacement of the liquid film were achieved. The error caused by refraction of the laser beam passing through the acrylic water box and fluorocarbon tube was estimated analytically and experimentally. The formulated analytical equation can estimate the real interface displacement using measured displacement in a fluorocarbon tube of 25 μm to 2.0 mm I.D. A preliminary test using fluorocarbon tubes of 1 and 2 mm I.D. showed that the corrected interface displacement calculated by the equation agreed with real displacement within a 1% margin of error. It was also confirmed that the LFD in the system could measure a liquid film of 0.25 μm at the thinnest. We made simultaneous measurements of the interface in fluorocarbon tubes of 0.5 and 1 mm I.D. using the LFD and a high-speed video camera with a microscope. These showed that the LFD could measure the interface of a liquid film with high spatial and temporal resolution during annular, slug, and piston flow regimes. The data also clarified the existence of a thin liquid film less than 1 μm in thickness in slug and annular flow regimes.

HEMOCOMPATIBILITY OF HYDRODYNAMIC LEVITATION BLOOD PUMPS

PURPOSE: Non-contacting bearing is the key technology for long-term implantable artificial hearts. We are developing a centrifugal pump whose impeller is levitated by original hydrodynamic bearings without any complicated control or sensing modules. METHODS: Using groove type hydrodynamic bearings for thrust and radial bearings, centrifugal pumps (HH1, HH2, HH4, HH5) were made. The impeller diameter was commonly 50 mm and the bearings act as hardening springs. The sum of the upper and the lower gaps of the thrust bearings were 25 mm (HH1) and 68mm (HH2, HH4, HH5), respectively. Special deep grooves were carved on HH4 and HH5 to increase the bearing-gap flow for antithrombogenicity. RESULTS: Sufficient pump performance (100 mmHg, 5L/min at 1900 rpm) and silent operation were verified for all the pumps. Gap measurement, carried out with a laser focus displacement meter, clarified that the minimum gap were 6 mm for HH1 and 34 mm for HH2, respectively, over 1000 rpm. Consequently the hemolysis level compared to HH1 became 1/6 (NIH=0.018) for HH2. Computational fluid dynamic analysis is predicting a certain increase of the bearing gap flow for HH4 and HH5. CONCLUSION: The hemolysis level of the hydrodynamic levitation pumps was reduced by expanding the bearing gap and adjusting the gap pressure. Improvement of the bearing-gap flow would attain the antithrombogenicity. Therefore, the hydrodynamic levitation pump would be expected to fit for implantable artificial hearts.

Simultaneous measuring system for free surface and liquid velocity distributions using PIV and LFD

In order to predict the free surface phenomena in a pool, the interaction between the liquid flow field and free surface should be evaluated. In this study, we aimed at developing a new three-dimensional measurement system for surface elevation and liquid velocity profiles in pool water using an image-processing technique and a laser focus displacement meter. The purpose of the experiments was to confirm the effectiveness of this new technique for obtaining temporal and spatial information on surface elevation and inclination as well as three-dimensional liquid velocity distribution. We confirmed that the free surface position and inclination were measured by this technique within 0.1 mm and 0.7° deviation. A data set for free surface and three-dimensional liquid velocity distribution was obtained through this study.

2133 レーザーフォーカス変位計による FEP マイクロチャンネル内液膜界面の計測

This paper presents a new method for measuring the interface of a liquid film in microchannels using a laser focus displacement meter (LFD). To prevent the tube wall signal from disturbing that of the gas-liquid interface, a fluorocarbon tube with water box was used; the refraction index of this device was the same as that for water. Simultaneous measurements of the interface in fluorocarbon tubes of 0.5 and 1mm I.D. using the LFD and a high-speed video camera with a microscope showed that the LFD could measure the interface of a liquid film with high spatial and temporal resolution during annular, slug, and piston flow. The data also clarified the existence of a thin liquid film less than 1μm in thickness in slug and annular regimes.

Relationship between Fracture Modes and Fractality of Fracture Surfaces

The fracture modes are classified into two categories ; ductile fracture and brittle fracture. This paper presents the study on the relationship between the fracture mode and the fractality of the fracture surface. Using iron and steel changing the carbon contents, the three-point bending fracture experiments were conducted. The critical stress intensity factor K IC was calculated as the macroscopic parameter. Furthermore, from the microscopic viewpoint, the fractality of the fracture surface was investigated using the surface profile curve obtained by the laser focus displacement meter, comparing with the SEM photographs of the fracture surface as the microscopic observation. The fractality of fracture surface depends on the fracture mode, which is explained by the facture mechanism. The final purpose of this study is to identify the fracture mode by quantifying the fracture surface using the concept of fractality.

1210 PIV による自由界面と液流速の同時計測システム : LFD と模擬粒子を用いた誤差評価

In order to predict the free surface phenomena in pool, the interaction between the liquid flow field and free surface should be evaluated. In this study, we aimed at developing a new three-dimensional measurement system for surface elevation and liquid velocity profiles in pool water using an image processing technique and a laser focus displacement meter. The purpose of the experiments was to confirm the effectiveness of this new technique obtaining temporal and spatial information of surface elevation and inclination as well as particle positions. As a result, it was confirmed that the free surface position and inclination could be measured accurately by this technique.

603 Degradation of Materials by High Energy Atomic Oxygen

The degradation of structural materials exposed in space is a new problem since various kinds of materials have been used for structures in low earth orbit (LEO). This paper presents an experiment of degradation on the ground and a simulation by the molecular dynamics (MD) method. In the experiment, atomic oxygen produced at a plasma torch is accelerated fluid-dynamically with working gas. Graphite, C/C (carbon/carbon) composite and Si-C. C. (silicon impregnated C/C composite) were used as the target materials. The mass loss per unit area depends strongly on the temperature of the material surface. The eroded surfaces of materials were observed with SEM (scanning electric microscope) and laser focus displacement meter. In case of C/C composite, the matrix region erodes substantially more than carbon fiber. The mass loss of Si-C. C. is less than that of corresponding C/C composite and only the C/C region erodes deeply with almost no erosion in Si and SiC regions. In order to investigate the degradation caused by high energy atomic oxygen, numerical simulation was performed for graphite using the MD method. The simulation model explains the influence of the impact energy of AO on the degradation of materials.

319 Relationship between Fracture Modes and Fractality of Fracture Surfaces

The fracture modes are classified into two categories; ductile fracture and brittle fracture. This paper presents the study on the relationship between the fracture mode and the fractality of the fracture surface. Using S45C, S55C and FC20,the three-point bending fracture experiments are conducted. The critical stress intensity factor K_<IC> is calculated as the macroscopic parameter and the fracture mode is investigated comparing with the SEM photographs of the fracture surface as the microscopic observation. Furthermore, from the microscopic viewpoint, the fractality of the fracture surface was investigated using the surface profile curve obtained by the laser focus displacement meter. The final purpose of this study is to identify the fracture mode by quantifying the fracture surface using the concept of fractality.

341 動圧浮上遠心式血液ポンプの溶血特性

A centrifugal blood pump, whose impeller is suspended without contact by hydrodynamic bearing, being developed by AIST. Measurement of impeller levitation was conducted with a laser-focus displacement meter. Expansion of axial gap of the thrust bearing, from 6 to 34 micro meters, lead to sufficient reduction of hemolysis, which indicates close relation between the axial gap to hemolysis.

Deposition layers formed by a turbulent aerosol flow of micron and sub-micron particles

The particle deposition layers formed by a turbulent aerosol flow have been studied as a simultaneous phenomenon of particle deposition and reentrainment. The experiments were conducted in a rectangular channel using alumina powders of Dp50=0.5–3.3 μm. The state of the deposition layer was observed through a video microscope, and the surface profiles were measured with a scanning laser focus displacement meter. The experimental results showed that micrometer-sized particles formed a striped-pattern deposition layer as well as a filmy deposition layer, while sub-micron particles only formed a filmy deposition layer; the difference in the formation of these deposition layers was described in detail. Furthermore, a theoretical analysis taking account of the balance of the adhesive strength and the separation strength was carried out to explain the thickness of the deposition layer.

Measuring interfacial waves on film flowing down tube inner wall using laser focus displacement meter

To elucidate details of the fascinating nonlinear phenomena of waves on a film, spatial temporal knowledge of the interfacial waves is essential. This paper presents a new method for measuring waves on a film flowing down the inner wall of a vertical tube, using a laser focus displacement meter. The purpose of the study was to clarify the effectiveness of the new method for obtaining detailed information of film thickness or wave characteristics, and to investigate the effect of film entry length on the phenomena. With this method, accurate measurements of film thickness in real time, with sensitivity of 0.2 μm and 1 kHz, were achieved. The error caused by refraction of the laser beam passing through an acrylic tube, whose outer wall surface was flat, and water was estimated. As the entry length increased, the ripple on the flowing film grew to a solitary wave of about 0.5 mm in height, then the wave became a two-wave system. In the entry region, the wave amplitude decreased as the flow rate increased, in the same manner as that in a film flowing down a plate wall.

407 低温プラズマ処理を利用したGF/PP複合材料の接着に関する研究(GS-11 複合材料(2))

The adhesive strength properties of glass fiber/polypropylene controlled by using low temperature plasma treatment are investigated. It is clear from contact angle measurement test that the surface energy of GF/PP composite can be improved by this treatment. The adhesive strength is assessed with single lap joint specimen. The strength is remarkably increased by the plasma treatment. XPS data shows that the amounts of oxygen can be increased on the surface and functional groups ; -OH and =CO etc., are introduced. From measurement of surface by laser focus displacement meter, it is confirmed that the surface of GF/PP composite is roughened from exposing oxygen plasma for long time.