Emerson Process Management Company (EPMC)announced on April 7th that the world advanced AsianFlow MeasuringCenter, invested and constructed byEPMC,was successfully completed in Nanjing, Jiangsu Province.Despite the se...Emerson Process Management Company (EPMC)announced on April 7th that the world advanced AsianFlow MeasuringCenter, invested and constructed byEPMC,was successfully completed in Nanjing, Jiangsu Province.Despite the severe snowstorm during the construction,展开更多
A new measurement device,consisting of swirling blades and capsule-shaped throttling elements,is proposed in this study to eliminate typical measurement errors caused by complex flow patterns in gas-liquid flow.The sw...A new measurement device,consisting of swirling blades and capsule-shaped throttling elements,is proposed in this study to eliminate typical measurement errors caused by complex flow patterns in gas-liquid flow.The swirling blades are used to transform the complex flow pattern into a forced annular flow.Drawing on the research of existing blockage flow meters and also exploiting the single-phase flow measurement theory,a formula is introduced to measure the phase-separated flow of gas and liquid.The formula requires the pressure ratio,Lockhart-Martinelli number(L-M number),and the gas phase Froude number.The unknown parameters appearing in the formula are fitted through numerical simulation using computational fluid dynamics(CFD),which involves a comprehensive analysis of the flow field inside the device from multiple perspectives,and takes into account the influence of pressure fluctuations.Finally,the measurement model is validated through an experimental error analysis.The results demonstrate that the measurement error can be maintained within±8%for various flow patterns,including stratified flow,bubble flow,and wave flow.展开更多
This study was conducted to investigate the flow field characteristics of right-angled flow passage with various cavities in the typical hydraulic manifold block.A low-speed visualization test rig was developed and th...This study was conducted to investigate the flow field characteristics of right-angled flow passage with various cavities in the typical hydraulic manifold block.A low-speed visualization test rig was developed and the flow field of the right-angled flow passage with different cavity structures was measured using 2D-PIV technique.Numerical model was established to simulate the three-dimensional flow field.Seven eddy viscosity turbulence models were investigated in predicting the flow field by comparing against the particle image relocimetry(PIV)measurement results.By defining the weight error function K,the S-A model was selected as the appropriate turbulence model.Then,a three-factor,three-level response surface numerical test was conducted to investigate the influence of flow passage connection type,cavity diameter and cavity length-diameter ratio on pressure loss.The results show that the Box-Benhnken Design(BBD)model can predict the total pressure loss accurately.The optimal factor level appeared in flow passage connection type II,14.64 mm diameter and 67.53%cavity length-diameter ratio.The total pressure loss decreased by 11.15%relative to the worst factor level,and total pressure loss can be reduced by 64.75%when using an arc transition right-angled flow passage,which indicates a new direction for the optimization design of flow passage in hydraulic manifold blocks.展开更多
During the last three decades, the introduction of new construction materials (e.g. RCC (Roller Compacted Concrete), strengthened gabions) has increased the interest for stepped channels and spillways. However stepped...During the last three decades, the introduction of new construction materials (e.g. RCC (Roller Compacted Concrete), strengthened gabions) has increased the interest for stepped channels and spillways. However stepped chute hydraulics is not simple, because of different flow regimes and importantly because of very-strong interactions between entrained air and turbu- lence. In this study, new air-water flow measurements were conducted in two large-size stepped chute facilities with two step heights in each facility to study experimental distortion caused by scale effects and the soundness of result extrapolation to pro- totypes. Experimental data included distributions of air concentration, air-water flow velocity, bubble frequency, bubble chord length and air-water flow turbulence intensity. For a Froude similitude, the results implied that scale effects were observed in both facilities, although the geometric scaling ratio was only Lr=2 in each case. The selection of the criterion for scale effects is a critical issue. For example, major differences (i.e. scale effects) were observed in terms of bubble chord sizes and turbulence levels al- though little scale effects were seen in terms of void fraction and velocity distributions. Overall the findings emphasize that physical modelling of stepped chutes based upon a Froude similitude is more sensitive to scale effects than classical smooth-invert chute studies, and this is consistent with basic dimensional analysis developed herein.展开更多
Due to piping vibration, fluid pulsation and other environmental disturbances, variations of amplitude and frequency to the raw signals of vortex flowmeter are imposed. It is difficult to extract vortex frequencies wh...Due to piping vibration, fluid pulsation and other environmental disturbances, variations of amplitude and frequency to the raw signals of vortex flowmeter are imposed. It is difficult to extract vortex frequencies which indicate volumetric flowrate from noisy data, especially at low flowrates. Hilbert-Huang transform was adopted to estimate vortex frequency. The noisy raw signal was decomposed into different intrinsic modes by empirical mode decomposition, the time-frequency characteristics of each mode were analyzed, and the vortex frequency was obtained by calculating partial mode’s instantaneous frequency. Experimental results show that the proposed method can estimate the vortex frequency with less than 2% relative error; and in the low flowrate range studied, the denoising ability of Hilbert-Huang transform is markedly better than Fourier based algorithms. These findings reveal that this method is accurate for vortex signal processing and at the same time has strong anti-disturbance ability.展开更多
The double-threshold method has been widely used in ultrasonic flow measurement to determine time-of-flight(TOF)due to its low cost and ease of implementation.Performance of this method is negatively affected by the c...The double-threshold method has been widely used in ultrasonic flow measurement to determine time-of-flight(TOF)due to its low cost and ease of implementation.Performance of this method is negatively affected by the cycle-skip phenomenon which occurs frequently under inconstant working conditions,especially varied fluid temperature.This paper proposes a method to suppress the phenomenon to facilitate reliable determination of TOF in ultrasonic flow measurement.First,the double-threshold method is used to generate a feature point to segment the signal.Second,based on the correlation coefficient and signal power,judgement factors of individual signal periods are calculated to determine signal onset.Finally,a valid zero crossing which has a constant lag from the onset is selected to determine the TOF.Thus,the cycle-skip phenomenon is suppressed.Two additional modifications are proposed to eliminate the influence of varied signal frequency and low sampling rate.The proposed method was validated by an experiment based on an ultrasonic water flow sensor.Results showed that the frequently appearing cycle-skip phenomenon can be successfully suppressed by the proposed method.展开更多
Vortex street flowmeter has been used in steady flow measurement for about three decades The benefits of this type of flowmeter include high accuracy,good linearty,wide measuring range,and excellent reliability Ho...Vortex street flowmeter has been used in steady flow measurement for about three decades The benefits of this type of flowmeter include high accuracy,good linearty,wide measuring range,and excellent reliability However,in unsteady flow measurement,the pressure disturbance as well as the noise from the system or surrounding can reduce the signal to noise ratio of the flowmeter seriously Aimed to use vortex street flowmeters in unsteady flow measurement,the characteristics of the vortex shedding induced hydrodynamic vibration around the prism bluff body in a vortex street flowmeter are investigated numerically and by expriments The results show that the hydrodynamic vibrations with 180° phase shift occur at the axisymmetric points of the channel around the bluff body The most intense vibration occurs at the points on the lateral faces close to the base of the prism The results provide therefore a useful reference for developing an anti interference vortex flowmeter using the different ial sensing technique.展开更多
A kind of signal acquisition circuit and the related signal processing method of the capacitanceelectromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitanceon the...A kind of signal acquisition circuit and the related signal processing method of the capacitanceelectromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitanceon the input impedance of the operational amplifier, and greatly improve the input impedance of the detection circuitto overcome the disadvantage of high signal source impedance. The rotating capacitor filter is a signal processingmethod based on the phase-sensitive detection technology. It can extract the weak signal from the strong and widebandbackground noise, so it is very suitable for the processing of capacitive electromagnetic flow signals. Throughthe comparison of the signal amplitude obtained at different flow rates and the comparison of signal spectrumcomponents before and after the filter, the effectiveness of the bootstrap signal acquisition circuit and rotatingcapacitor filtering method is verified.展开更多
To accurately measure and evaluate the oil-water production profile of horizontal wells, a dynamic measurement experiment of oil-water two-phase flow in horizontal wells and numerical simulation were combined to estab...To accurately measure and evaluate the oil-water production profile of horizontal wells, a dynamic measurement experiment of oil-water two-phase flow in horizontal wells and numerical simulation were combined to establish a method for measuring the partial phase flow rate of oil-water two-phase stratified flow in horizontal wells. An experimental work was performed in horizontal oil-water two-phase flow simulation well using combination production logging tool including mini-capacitance sensor and mini-spinner. The combination tool provides a recording of holdup and velocity profiles at five different heights of the borehole cross-section. The effect of total flow rate and water-cut on the response of spinner and capacitive sensor at five measured positions were investigated. The capacitance water holdup interpolation imaging algorithm was used to determine the local fluid property and oil-water interface height, and the measured local fluid speed was combined with the numerical simulation result to establish an optimal calculation model for obtaining the partial phase flow rate of the oil-water two-phase stratified flow in the horizontal well. The calculated flow rates of five measured points are basically consistent with the experimental data, the total flow rate and water holdup from calculation are in agreement with the set values in the experiment too, suggesting that the method has high accuracy.展开更多
To investigate the conditions under which acoustic resonances occur, staggered arrays of closely spaced rigid tubes were tested in a wind tunnel under various flow velocities. The author investigated the Strouhal numb...To investigate the conditions under which acoustic resonances occur, staggered arrays of closely spaced rigid tubes were tested in a wind tunnel under various flow velocities. The author investigated the Strouhal numbers at which flow periodicities occur, the relation between these Strouhal numbers and those at which acoustic resonances occur, and the effects of Reynolds number and longitudinal tube spacings on the occurrence of acoustic resonance. This investigation showed the following： （1） Acoustic resonance can be produced at a frequency well removed from that of vortex shedding. The results also show evidence of vortex shedding and acoustic resonance existing simultaneously but at different frequencies. （2） Acoustic resonance behavior is consistent with that of a self-excited system. （3） A new model of this phenomenon provides an improved procedure for avoiding acoustic resonances in closely spaced tube banks.展开更多
An experimental investigation of three-dimensional flow field in a film-cooled turbine model is carried out by using particle image velocimeter （PIV） in a low-speed wind tunnel. The effects of different blowing rati...An experimental investigation of three-dimensional flow field in a film-cooled turbine model is carried out by using particle image velocimeter （PIV） in a low-speed wind tunnel. The effects of different blowing ratios （M=1.5, 2） on the flow field are studied. The experimental results reveal the classical phenomena of the formation of kidney vortex pair and secondary flow in wake region behind the jet hole. And the changes of the kidney vortex pair and the wake at different locations away from the hole on the suction and pressure sides are also studied. Compared with the flow field in stationary cascade, there are centrifugal force and Coriolis force existing in the flow field of rotating turbine, and these forces bring the radial velocity in the jet flow. The effect of rotatien on the flow field of the pressure side is more distinct than that on the suction side from the measured flow fields in Y-Z plane and radial velocity contours. The increase of blowing ratio makes the kidney vortex pair and the secondary flow in the wake region stronger and makes the range of the wake region enlarged.展开更多
In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by ...In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.展开更多
The present study,both experimentally and by numerical simulation,concerns the sensitivity of a flow that is driven by a travelling magnetic field(TMF)with respect to a stepwise applied mismatch between the axes of th...The present study,both experimentally and by numerical simulation,concerns the sensitivity of a flow that is driven by a travelling magnetic field(TMF)with respect to a stepwise applied mismatch between the axes of the TMF and of the cylindrical liquid metal column.The TMF is generated by six equidistantly arranged cylindrical coils powered with an AC current having a phase shift of 60℃ between them.Because the flow induced by a TMF is basically of a toms type,vertical velocity components are representative for the motion in the meridional plane.Ultrasound Doppler Velocimetry(UDV)was applied to acquire the velocity component along the beam axis in the centre of the liquid metal column and at various azimuthal positions for a fixed radial coordinate.The measurements are compared to the flow data gained by large eddy simulations.Computations were based on the usual approximations to simplify the magnetohydrodynamic equations,which are low frequency and low induction,and on an analytical expression for the Lorentz force considering the shift between the fluid volume and the field.The results show that even a small shift between the axes may result in a distinct three-dimensional constituent of the flow structure which changes completely the usually assumed axisymmetric toms-type flow.展开更多
Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications.We present the new e...Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications.We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400℃.The parameters of the facility and the dimensions of the test sections will be given,and the possibilities for flow investigations in tundish,submerged entry nozzle and mould will be discussed.In addition,the smaller set-up Mini-LIMMCAST will be presented,which works with the room-temperature liquid alloy GaInSn.The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution.New ultrasonic and electromagnetic techniques for measuring the velocity in liquid metal flows came up during the last decade allowing for a satisfying characterisation of flow quantities in the considered temperature range up to 400℃.First results from LIMMCAST and Mini-LIMMCAST will be presented covering the following phenomena:fully contacfless electromagnetic tomography of the flow in the mould,flow monitoring by a multitude of ultrasonic sensors,and analysis of the flow in the mould under the influence of an electromagnetic brake: intensification of the flow turbulence contrary to the expected flow damping,injection of argon bubbles through the stopper rod:occurrence of pressure oscillations.展开更多
This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale.Experimental...This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale.Experimental results will be presented here which have been obtained using a physical model(mini-LIMMCAST)operating with the low melting point alloy GaInSn.According to the concept of the electromagnetic brake the impact of a DC magnetic field on the outlet flow from the Submerged Entry Nozzle(SEN)has been studied up to Hartmann numbers of about 400.The Ultrasound-Doppler-Velocimetry(UDV)was applied for measurements of the flow pattern in the mould.Local conductivity anemometers were used to measure the turbulent quantities of the flow.The effect of the magnetic field on the flow structure turned out to be manifold and rather complex.The magnetic field causes a deflection of the jet,at which the respective exit angle from the nozzle ports becomes more flat.Thus,both the penetration depth of the discharging flow into the lower part of the mould and the impinging velocity of the jet onto the side wall are reduced.A significant return flow occurs in the adjacent regions of the jet.Specific vortices are formed with axes being aligned with the magnetic field direction.Such vortical structures are typical for quasi-two-dimensional magneto-hydrodynamic(MHD)flows.The flow measurements do not manifest a general braking effect which would be expected as an overall damping of the flow velocity and the related fluctuations all-over the mould volume.Variations of the wall conductivity showed a striking impact on the resulting flow structures.展开更多
The paper demonstrated the feasibility of Lorentz Force Velocimetry for flow rate measurements of weakly conducting electrolytes using experimental results on salt water flow exposed to a permanent magnet system.This ...The paper demonstrated the feasibility of Lorentz Force Velocimetry for flow rate measurements of weakly conducting electrolytes using experimental results on salt water flow exposed to a permanent magnet system.This innovative flow measurement technique allows the non-contact determination of flow rates and relies on the interaction between a magnetic field and a moving conducting fluid.When an electrically conducting fluid moves through the magnetic field a Lorentz force is generated and acts on the measurement system.The present report provides an overview about the experimental setups and the first measurement results.展开更多
Traditional signal processing methods for turbine flowmeter are unable to solve the contradiction between the real-time performance and the accuracy during the aeroengine bench test or hardware in the loop(HIL)simulat...Traditional signal processing methods for turbine flowmeter are unable to solve the contradiction between the real-time performance and the accuracy during the aeroengine bench test or hardware in the loop(HIL)simulation of aeroengine control system.A dynamic flow measurement method based on cycle number of the flowmeter is proposed.And a DSP-based multi-functional dynamic signal processing module for turbine flowmeter is built to validate the method.The developed system can provide three types of output modes including PWM,frequency and D/A.At the same time,the results can be displayed instantly with the module of serial communication interface to obtain dynamic flow signal with good precision.Experimental results show that the stability of flow measurement is greatly improved with precision guaranteed and the real-time response reaches the maximum limit of turbine flowmeter.展开更多
The flow structure in the mould of a continuous caster is of key importance for the quality of the final product. The use of most conventional flow measurement techniques is prevented by the high temperature of the li...The flow structure in the mould of a continuous caster is of key importance for the quality of the final product. The use of most conventional flow measurement techniques is prevented by the high temperature of the liquid steel.For a downscaled physical model of the continuous casting process,we present combined measurements of the flow in the mould by Contacfless Inductive Flow Tomography(CIFT),and of the conductivity distribution in the submerged entry nozzle by Mutual Inductance Tomograpliy(MIT).In addition,we summarize an experiment with a magnetic stirrer around the submerged entry nozzle and its effects on the flow in the mould.Some new developments towards a robust implementation of CIFT at a real caster,including the use of pickup coils and gradiometric probes,are also discussed.展开更多
Hemodynamical evaluation of a coronary artery lesion is an important diagnostic step to assess its functional impact.Fractional flow reserve(FFR)received a class IA recommendation from the European Society of Cardiolo...Hemodynamical evaluation of a coronary artery lesion is an important diagnostic step to assess its functional impact.Fractional flow reserve(FFR)received a class IA recommendation from the European Society of Cardiology for the assessment of angiographically moderate stenosis.FFR evaluation of coronary artery disease offers improvement of the therapeutic strategy,deferring unnecessary procedures for lesions with a FFR>0.8,improving patients'management and clinical outcome.Post intervention,an optimal FFR>0.9 post stenting should be reached and>0.8 post drug eluting balloons.Non-hyperemic pressure ratio measurements have been validated in previous studies with a common threshold of 0.89.They might overestimate the hemodynamic significance of some lesions but remain useful whenever hyperemic agents are contraindicated.FFR remains the gold standard reference for invasive assessment of ischemia.We illustrate this review with two cases introducing the possibility to estimate also non-invasively FFR from reconstructed 3-D angiograms by quantitative flow ratio.We conclude introducing a hybrid approach to intermediate lesions(DFR 0.85-0.95)potentially maximizing clinical decision from all measurements.展开更多
A novel method to measure the flow rate in a wet gas is presented.Due to the presence of liquid,there is a deviation in the measurement of the gas volume flow rate obtained with standard vortex flow-meters.The propose...A novel method to measure the flow rate in a wet gas is presented.Due to the presence of liquid,there is a deviation in the measurement of the gas volume flow rate obtained with standard vortex flow-meters.The proposed method is based on a correction factor determined through the application of an over-reading approach to a bluff body in mist flow.The correction factor is obtained from the slip velocity ratio,i.e.,the ratio of droplet velocity to gas velocity,based on the analysis of the fluid velocity distribution in the pipeline section.It also takes into account relevant theoretical arguments.It is shown that the predicted results fit the experimental results well.展开更多
文摘Emerson Process Management Company (EPMC)announced on April 7th that the world advanced AsianFlow MeasuringCenter, invested and constructed byEPMC,was successfully completed in Nanjing, Jiangsu Province.Despite the severe snowstorm during the construction,
基金Supported By Open Fund of Hubei Key Laboratory of Oil and Gas Drilling and Production Engineering(Yangtze University),YQZC202309.
文摘A new measurement device,consisting of swirling blades and capsule-shaped throttling elements,is proposed in this study to eliminate typical measurement errors caused by complex flow patterns in gas-liquid flow.The swirling blades are used to transform the complex flow pattern into a forced annular flow.Drawing on the research of existing blockage flow meters and also exploiting the single-phase flow measurement theory,a formula is introduced to measure the phase-separated flow of gas and liquid.The formula requires the pressure ratio,Lockhart-Martinelli number(L-M number),and the gas phase Froude number.The unknown parameters appearing in the formula are fitted through numerical simulation using computational fluid dynamics(CFD),which involves a comprehensive analysis of the flow field inside the device from multiple perspectives,and takes into account the influence of pressure fluctuations.Finally,the measurement model is validated through an experimental error analysis.The results demonstrate that the measurement error can be maintained within±8%for various flow patterns,including stratified flow,bubble flow,and wave flow.
基金Projects(51705446,51890881) supported by the National Natural Science Foundation of China
文摘This study was conducted to investigate the flow field characteristics of right-angled flow passage with various cavities in the typical hydraulic manifold block.A low-speed visualization test rig was developed and the flow field of the right-angled flow passage with different cavity structures was measured using 2D-PIV technique.Numerical model was established to simulate the three-dimensional flow field.Seven eddy viscosity turbulence models were investigated in predicting the flow field by comparing against the particle image relocimetry(PIV)measurement results.By defining the weight error function K,the S-A model was selected as the appropriate turbulence model.Then,a three-factor,three-level response surface numerical test was conducted to investigate the influence of flow passage connection type,cavity diameter and cavity length-diameter ratio on pressure loss.The results show that the Box-Benhnken Design(BBD)model can predict the total pressure loss accurately.The optimal factor level appeared in flow passage connection type II,14.64 mm diameter and 67.53%cavity length-diameter ratio.The total pressure loss decreased by 11.15%relative to the worst factor level,and total pressure loss can be reduced by 64.75%when using an arc transition right-angled flow passage,which indicates a new direction for the optimization design of flow passage in hydraulic manifold blocks.
基金Project supported by the National Council for Science and Tech-nology of Mexico (CONACYT)
文摘During the last three decades, the introduction of new construction materials (e.g. RCC (Roller Compacted Concrete), strengthened gabions) has increased the interest for stepped channels and spillways. However stepped chute hydraulics is not simple, because of different flow regimes and importantly because of very-strong interactions between entrained air and turbu- lence. In this study, new air-water flow measurements were conducted in two large-size stepped chute facilities with two step heights in each facility to study experimental distortion caused by scale effects and the soundness of result extrapolation to pro- totypes. Experimental data included distributions of air concentration, air-water flow velocity, bubble frequency, bubble chord length and air-water flow turbulence intensity. For a Froude similitude, the results implied that scale effects were observed in both facilities, although the geometric scaling ratio was only Lr=2 in each case. The selection of the criterion for scale effects is a critical issue. For example, major differences (i.e. scale effects) were observed in terms of bubble chord sizes and turbulence levels al- though little scale effects were seen in terms of void fraction and velocity distributions. Overall the findings emphasize that physical modelling of stepped chutes based upon a Froude similitude is more sensitive to scale effects than classical smooth-invert chute studies, and this is consistent with basic dimensional analysis developed herein.
基金Project(20030335058) supported by the Special Research Fund for the Doctoral Programof Higher Education of China
文摘Due to piping vibration, fluid pulsation and other environmental disturbances, variations of amplitude and frequency to the raw signals of vortex flowmeter are imposed. It is difficult to extract vortex frequencies which indicate volumetric flowrate from noisy data, especially at low flowrates. Hilbert-Huang transform was adopted to estimate vortex frequency. The noisy raw signal was decomposed into different intrinsic modes by empirical mode decomposition, the time-frequency characteristics of each mode were analyzed, and the vortex frequency was obtained by calculating partial mode’s instantaneous frequency. Experimental results show that the proposed method can estimate the vortex frequency with less than 2% relative error; and in the low flowrate range studied, the denoising ability of Hilbert-Huang transform is markedly better than Fourier based algorithms. These findings reveal that this method is accurate for vortex signal processing and at the same time has strong anti-disturbance ability.
基金Project supported by the Science Fund for Creative Research Groups of National Natural Science Foundation of China(No.51821093)。
文摘The double-threshold method has been widely used in ultrasonic flow measurement to determine time-of-flight(TOF)due to its low cost and ease of implementation.Performance of this method is negatively affected by the cycle-skip phenomenon which occurs frequently under inconstant working conditions,especially varied fluid temperature.This paper proposes a method to suppress the phenomenon to facilitate reliable determination of TOF in ultrasonic flow measurement.First,the double-threshold method is used to generate a feature point to segment the signal.Second,based on the correlation coefficient and signal power,judgement factors of individual signal periods are calculated to determine signal onset.Finally,a valid zero crossing which has a constant lag from the onset is selected to determine the TOF.Thus,the cycle-skip phenomenon is suppressed.Two additional modifications are proposed to eliminate the influence of varied signal frequency and low sampling rate.The proposed method was validated by an experiment based on an ultrasonic water flow sensor.Results showed that the frequently appearing cycle-skip phenomenon can be successfully suppressed by the proposed method.
基金This project is supported by National Natural Science Foundation of China(No.59835160).
文摘Vortex street flowmeter has been used in steady flow measurement for about three decades The benefits of this type of flowmeter include high accuracy,good linearty,wide measuring range,and excellent reliability However,in unsteady flow measurement,the pressure disturbance as well as the noise from the system or surrounding can reduce the signal to noise ratio of the flowmeter seriously Aimed to use vortex street flowmeters in unsteady flow measurement,the characteristics of the vortex shedding induced hydrodynamic vibration around the prism bluff body in a vortex street flowmeter are investigated numerically and by expriments The results show that the hydrodynamic vibrations with 180° phase shift occur at the axisymmetric points of the channel around the bluff body The most intense vibration occurs at the points on the lateral faces close to the base of the prism The results provide therefore a useful reference for developing an anti interference vortex flowmeter using the different ial sensing technique.
文摘A kind of signal acquisition circuit and the related signal processing method of the capacitanceelectromagnetic flowmeter (EMF) were introduced. The circuit can eliminate the influence of distributed capacitanceon the input impedance of the operational amplifier, and greatly improve the input impedance of the detection circuitto overcome the disadvantage of high signal source impedance. The rotating capacitor filter is a signal processingmethod based on the phase-sensitive detection technology. It can extract the weak signal from the strong and widebandbackground noise, so it is very suitable for the processing of capacitive electromagnetic flow signals. Throughthe comparison of the signal amplitude obtained at different flow rates and the comparison of signal spectrumcomponents before and after the filter, the effectiveness of the bootstrap signal acquisition circuit and rotatingcapacitor filtering method is verified.
基金Supported by National Natural Science Foundation of China(41474115)Open Fund of Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University)Ministry of Education of China(No K2018-02)Educational Commission of Hubei Province of China(D20141302)
文摘To accurately measure and evaluate the oil-water production profile of horizontal wells, a dynamic measurement experiment of oil-water two-phase flow in horizontal wells and numerical simulation were combined to establish a method for measuring the partial phase flow rate of oil-water two-phase stratified flow in horizontal wells. An experimental work was performed in horizontal oil-water two-phase flow simulation well using combination production logging tool including mini-capacitance sensor and mini-spinner. The combination tool provides a recording of holdup and velocity profiles at five different heights of the borehole cross-section. The effect of total flow rate and water-cut on the response of spinner and capacitive sensor at five measured positions were investigated. The capacitance water holdup interpolation imaging algorithm was used to determine the local fluid property and oil-water interface height, and the measured local fluid speed was combined with the numerical simulation result to establish an optimal calculation model for obtaining the partial phase flow rate of the oil-water two-phase stratified flow in the horizontal well. The calculated flow rates of five measured points are basically consistent with the experimental data, the total flow rate and water holdup from calculation are in agreement with the set values in the experiment too, suggesting that the method has high accuracy.
文摘To investigate the conditions under which acoustic resonances occur, staggered arrays of closely spaced rigid tubes were tested in a wind tunnel under various flow velocities. The author investigated the Strouhal numbers at which flow periodicities occur, the relation between these Strouhal numbers and those at which acoustic resonances occur, and the effects of Reynolds number and longitudinal tube spacings on the occurrence of acoustic resonance. This investigation showed the following： （1） Acoustic resonance can be produced at a frequency well removed from that of vortex shedding. The results also show evidence of vortex shedding and acoustic resonance existing simultaneously but at different frequencies. （2） Acoustic resonance behavior is consistent with that of a self-excited system. （3） A new model of this phenomenon provides an improved procedure for avoiding acoustic resonances in closely spaced tube banks.
基金This project is supported by National Natural Science Foundation ofChina(No. 50406017)
文摘An experimental investigation of three-dimensional flow field in a film-cooled turbine model is carried out by using particle image velocimeter （PIV） in a low-speed wind tunnel. The effects of different blowing ratios （M=1.5, 2） on the flow field are studied. The experimental results reveal the classical phenomena of the formation of kidney vortex pair and secondary flow in wake region behind the jet hole. And the changes of the kidney vortex pair and the wake at different locations away from the hole on the suction and pressure sides are also studied. Compared with the flow field in stationary cascade, there are centrifugal force and Coriolis force existing in the flow field of rotating turbine, and these forces bring the radial velocity in the jet flow. The effect of rotatien on the flow field of the pressure side is more distinct than that on the suction side from the measured flow fields in Y-Z plane and radial velocity contours. The increase of blowing ratio makes the kidney vortex pair and the secondary flow in the wake region stronger and makes the range of the wake region enlarged.
基金supported by the National Natural Science Foundation of China (50606026 and 50736006)
文摘In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.
基金Item Sponsored by "Deutsche Forschungsgemeinschaft" in the framework of the Collaborative Research Centre SFB 609
文摘The present study,both experimentally and by numerical simulation,concerns the sensitivity of a flow that is driven by a travelling magnetic field(TMF)with respect to a stepwise applied mismatch between the axes of the TMF and of the cylindrical liquid metal column.The TMF is generated by six equidistantly arranged cylindrical coils powered with an AC current having a phase shift of 60℃ between them.Because the flow induced by a TMF is basically of a toms type,vertical velocity components are representative for the motion in the meridional plane.Ultrasound Doppler Velocimetry(UDV)was applied to acquire the velocity component along the beam axis in the centre of the liquid metal column and at various azimuthal positions for a fixed radial coordinate.The measurements are compared to the flow data gained by large eddy simulations.Computations were based on the usual approximations to simplify the magnetohydrodynamic equations,which are low frequency and low induction,and on an analytical expression for the Lorentz force considering the shift between the fluid volume and the field.The results show that even a small shift between the axes may result in a distinct three-dimensional constituent of the flow structure which changes completely the usually assumed axisymmetric toms-type flow.
基金Item Sponsored by Deutsche Forschungsgemeinschaft (DFG) in frame of the SFB 609"Electromagnetic Flow Control in MetallurgyCrystal Growth and Electrochemistry"
文摘Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications.We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400℃.The parameters of the facility and the dimensions of the test sections will be given,and the possibilities for flow investigations in tundish,submerged entry nozzle and mould will be discussed.In addition,the smaller set-up Mini-LIMMCAST will be presented,which works with the room-temperature liquid alloy GaInSn.The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements with a reasonable spatial and temporal resolution.New ultrasonic and electromagnetic techniques for measuring the velocity in liquid metal flows came up during the last decade allowing for a satisfying characterisation of flow quantities in the considered temperature range up to 400℃.First results from LIMMCAST and Mini-LIMMCAST will be presented covering the following phenomena:fully contacfless electromagnetic tomography of the flow in the mould,flow monitoring by a multitude of ultrasonic sensors,and analysis of the flow in the mould under the influence of an electromagnetic brake: intensification of the flow turbulence contrary to the expected flow damping,injection of argon bubbles through the stopper rod:occurrence of pressure oscillations.
基金Item Sponsored by Deutsche Forschungsgemeinschaft (DFG) as Part of the Collaborative Research Centre SFB609 "Electromagnetic Flow Control in Metallurgy,Crystal Growth and Electrochemistry"
文摘This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale.Experimental results will be presented here which have been obtained using a physical model(mini-LIMMCAST)operating with the low melting point alloy GaInSn.According to the concept of the electromagnetic brake the impact of a DC magnetic field on the outlet flow from the Submerged Entry Nozzle(SEN)has been studied up to Hartmann numbers of about 400.The Ultrasound-Doppler-Velocimetry(UDV)was applied for measurements of the flow pattern in the mould.Local conductivity anemometers were used to measure the turbulent quantities of the flow.The effect of the magnetic field on the flow structure turned out to be manifold and rather complex.The magnetic field causes a deflection of the jet,at which the respective exit angle from the nozzle ports becomes more flat.Thus,both the penetration depth of the discharging flow into the lower part of the mould and the impinging velocity of the jet onto the side wall are reduced.A significant return flow occurs in the adjacent regions of the jet.Specific vortices are formed with axes being aligned with the magnetic field direction.Such vortical structures are typical for quasi-two-dimensional magneto-hydrodynamic(MHD)flows.The flow measurements do not manifest a general braking effect which would be expected as an overall damping of the flow velocity and the related fluctuations all-over the mould volume.Variations of the wall conductivity showed a striking impact on the resulting flow structures.
基金Item Sponsored by German Science Foundation (Deutsche Forschungsgemeinschaft) in the framework of theResearch Training Group (Graduiertenkolleg) "Lorentz Force Velocimetry and Lorentz Force Eddy Current Testing"(GRK 1567/1)at Ilmenau University of Technology
文摘The paper demonstrated the feasibility of Lorentz Force Velocimetry for flow rate measurements of weakly conducting electrolytes using experimental results on salt water flow exposed to a permanent magnet system.This innovative flow measurement technique allows the non-contact determination of flow rates and relies on the interaction between a magnetic field and a moving conducting fluid.When an electrically conducting fluid moves through the magnetic field a Lorentz force is generated and acts on the measurement system.The present report provides an overview about the experimental setups and the first measurement results.
文摘Traditional signal processing methods for turbine flowmeter are unable to solve the contradiction between the real-time performance and the accuracy during the aeroengine bench test or hardware in the loop(HIL)simulation of aeroengine control system.A dynamic flow measurement method based on cycle number of the flowmeter is proposed.And a DSP-based multi-functional dynamic signal processing module for turbine flowmeter is built to validate the method.The developed system can provide three types of output modes including PWM,frequency and D/A.At the same time,the results can be displayed instantly with the module of serial communication interface to obtain dynamic flow signal with good precision.Experimental results show that the stability of flow measurement is greatly improved with precision guaranteed and the real-time response reaches the maximum limit of turbine flowmeter.
文摘The flow structure in the mould of a continuous caster is of key importance for the quality of the final product. The use of most conventional flow measurement techniques is prevented by the high temperature of the liquid steel.For a downscaled physical model of the continuous casting process,we present combined measurements of the flow in the mould by Contacfless Inductive Flow Tomography(CIFT),and of the conductivity distribution in the submerged entry nozzle by Mutual Inductance Tomograpliy(MIT).In addition,we summarize an experiment with a magnetic stirrer around the submerged entry nozzle and its effects on the flow in the mould.Some new developments towards a robust implementation of CIFT at a real caster,including the use of pickup coils and gradiometric probes,are also discussed.
文摘Hemodynamical evaluation of a coronary artery lesion is an important diagnostic step to assess its functional impact.Fractional flow reserve(FFR)received a class IA recommendation from the European Society of Cardiology for the assessment of angiographically moderate stenosis.FFR evaluation of coronary artery disease offers improvement of the therapeutic strategy,deferring unnecessary procedures for lesions with a FFR>0.8,improving patients'management and clinical outcome.Post intervention,an optimal FFR>0.9 post stenting should be reached and>0.8 post drug eluting balloons.Non-hyperemic pressure ratio measurements have been validated in previous studies with a common threshold of 0.89.They might overestimate the hemodynamic significance of some lesions but remain useful whenever hyperemic agents are contraindicated.FFR remains the gold standard reference for invasive assessment of ischemia.We illustrate this review with two cases introducing the possibility to estimate also non-invasively FFR from reconstructed 3-D angiograms by quantitative flow ratio.We conclude introducing a hybrid approach to intermediate lesions(DFR 0.85-0.95)potentially maximizing clinical decision from all measurements.
基金supported by the Leading Talent Training Project for Young and Middle-Aged Teacher(A2-0265-22-41).
文摘A novel method to measure the flow rate in a wet gas is presented.Due to the presence of liquid,there is a deviation in the measurement of the gas volume flow rate obtained with standard vortex flow-meters.The proposed method is based on a correction factor determined through the application of an over-reading approach to a bluff body in mist flow.The correction factor is obtained from the slip velocity ratio,i.e.,the ratio of droplet velocity to gas velocity,based on the analysis of the fluid velocity distribution in the pipeline section.It also takes into account relevant theoretical arguments.It is shown that the predicted results fit the experimental results well.
