IEE Colloquium on Advances in Sensors for Fluid Flow Measurement
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 Location: London, UK
 Conference date: 18 April 1996
 Conference number: 1996/092
 The following topics were dealt with: multiphase flows; NMR velocimetry; electromagnetic flowmeters; optical and ultrasonic transducers; electrical, thermal, nuclear and Xray techniques
15 items found

Multiphase flow measurement: current and future developments
 Author(s): T.S. Whitaker
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The history of some of the early developments in multiphase flow measurement are briefly described, leading to an explanation of the technical principles of the currently available technology. The impact of the likely flow patterns to found in the offshore industry on flow measurement is discussed. The status of the current developments in relation to the target uncertainties required by end users is reviewed and the likely future technologies which may be applied to meet more stringent uncertainty criteria are described. Some of the practical problems of offshore and subsea deployment are explained, and the progress in resolving these problems described. (11 pages)

Advances in nuclear radiation detectors for fluid flow measurement
 Author(s): G.A. Johansen and E. Abro
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The needs within experimental nuclear and particle physics and space research have led to substantial advances in radiation detector technology. Here, some of the new detector concepts applicable to gammaray densitometry in fluid flow measurement are presented with respect to the development of more compact, rugged and accurate instrumentation. (3 pages)

Three phase pipe flow imaging using a capacitance tomography system
 Author(s): O. Isaksen
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Several tomography systems for pipe flow imaging have been developed which are based on capacitance sensors measuring the permittivity of the flowing components. Several reconstruction techniques for reconstructing the measured capacitances has been developed. The most commonly used reconstruction algorithm is called the linear backprojection (LBP) algorithm and represents a fast and fairly crude algorithm. In this paper it is shown that in using the LBPalgorithm one must be very careful in interpreting the results. Methods for using a capacitance tomography system based an the LBPalgorithm for three phase oil/water/gas pipe flow imaging is outlined and preliminary results are presented. (6 pages)

Measurement of multiple velocities in multiphase flow
 Author(s): K.H. Albusaidi and G. Lucas
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The work described consists of investigating an entirely novel technique for measuring the velocity of the flowing components in vertically upward, gas/liquid flows in the “Cap bubble” and “Taylor bubble” flow regimes. The technique consists of mounting an array of 64 axially separated conductivity sensors in a vertical pipe through which an air/water mixture is flowing (water is the continuous component). By crosscorrelating the output signals from any two of these conductivity sensors it is possible to obtain the mean Cap bubble (or Taylor bubble) velocity and hence an estimate of the mean gas velocity. The novel element of the work is to demonstrate that by appropriately combining the output signals from the array of 64 conductivity sensors it is possible to determine the output signals that would be obtained from one or more “simulated impedance sensors” that are travelling through the flow at the same speed as the Cap bubbles (or Taylor bubbles). Crosscorrelation of the outputs from two of these simulated conductivity sensors, travelling in between the Cap bubbles, allows the liquid velocity relative to these moving sensors to be determined. Since the velocity of the simulated sensors is known, the liquid velocity can be determined. (4 pages)

Now rate measurement in vertical oilwater flows using conductivity sensors and a void fraction wave model
 Author(s): G.P. Lucas
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To the author's knowledge no attempt has been made to deduce the flow rate of either the continuous of the discontinuous phases in vertically upward, bubbly flows from the measured propagation velocity of naturally occurring kinematic waves. This paper describes an investigation into the feasibility of using the measured wave propagation velocity in this way, in vertically upward, liquidliquid flows in the bubbly flow regime. A 1D kinematic wave model is used and a series of experiments carried out using conductivity flow sensors and output signal crosscorrelation. (3 pages)

Design and fabrication of singlechip intelligent silicon thermal flow sensors in standard CMOS technology
 Author(s): M. Mullins ; R. Bayford ; A. Van Putten ; J. Butcher
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Thermal flow sensors which use thin film thermistors in a microbridge are considered, and configurations which yield optimum sensitivity, power consumption and frequency response are identified. The different biasing modes and transduction mechanisms are also described. The mask layout design and postprocess micromachining step is illustrated for a commercial CMOS process, and lowcost packaging methods are suggested. Integration of interface electronics and signal processing on the same chip as the sensor elements offers many advantages, including improved immunity from interference, reduced interconnection cost and the possibility for complete systems on a chip. As a consequence the performance requirements for the sensor interface circuitry are relaxed. Silicon thermal flowsensors with integrated interface electronics are presented. These have been fabricated in a standard lowcost 2.0 micron double polysilicon, double metal CMOS technology, using a single additional process step demonstrating the feasibility of implementing a complete intelligent sensor system on a single chip at minimal cost. (4 pages)

Evaluation of the performance of dual chevron bluff body vortex flowmeters
 Author(s): J.P. Bentley ; R.A. Benson ; R.S. Jackson
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Vortex flowmeters are less repeatable than turbine flow meters and the latter are normally preferred for high accuracy applications. One method of improving repeatability is to use two bluff bodies in series. Previous work has shown that certain combinations of two rectangular bluff bodies separated by a narrow gap give optimum repeatability. Features of using these bluff bodies suggest the use of chevron shaped bluff bodies. The results are presented of a wind tunnel evaluation of the vortex shedding performance of nine dual combinations based on six bluff body geometries for a range of separations between 3 and 15 mm. (3 pages)

Chemically resolved NMR velocimetry
 Author(s): B. Newling ; S.J. Gibes ; L.D. Hall ; D.E. Haycock ; W.J. Frith ; S. Ablett
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Of particular relevance to process engineering is the potential sensitivity of NMR imaging to fluid displacement, which allows measurement of fluid velocities (in the range mm/s to m/s), even in opaque fluids, in three spatial dimensions (NMR velocimetry). The chemical sensitivity of the NMR technique has often been overlooked in NMR velocimetry implementations, but we present one protocol for the simultaneous measurement of fluid velocity for the separate components of a flowing mixture of chemical compounds. The fluid flow in the expansion/contraction pipe system is found to be fully characterised in three spatial dimensions. Thus, chemically resolved NMR velocimetry allows a fivedimensional (three spatial, one temporal and one chemical shift) measurement to be made, noninvasively and in optically opaque liquids. (4 pages)

Accurate measurement of asymmetric flow by means of a multielectrode induction flowmeter
 Author(s): B. Horner
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Induction flowmeters are relatively accurate noninvasive devices for measuring volume flow of electrically conducting liquids in pipes. Whereas under ideal conditions, axially symmetric flow can be measured to arbitrary accuracy, asymmetric flow (e.g. as caused by bends or valves) leads to significant measurement errors. Thus, a relaxation pipe upstream of the flowmeter must be provided to ensure accurate results. The subject of this work is an improved induction flowmeter that is less sensitive to asymmetric flow and that can be used without relaxation pipes. It is shown that the accuracy of an induction flowmeter subject to asymmetric flow is greatly improved by using more than two electrodes and a second magnetic field direction. In experimental setups with extremely strong asymmetry, a conventional two electrode flowmeter produced measurement errors of up to 90%. A four electrode flowmeter permitted measurements with an error of about 20%. Satisfactory results with an error of approximately 3% were achieved using six or more electrodes. Additional measurements with more realistic flow profiles caused by bends and orifices proved that a six electrode setup is capable of measurement errors below 0.5% in virtually any flow situation. A flowmeter of that type could be installed downstream of bends, valves and orifices without any relaxation pipe. Furthermore, a sensor of that type can be assembled with standard magnetic field systems and only slightly modified transducers. (3 pages)

An electromagnetic flowmeter for measuring rheological parameters and reconstructing the flow profile
 Author(s): A. Trachtler
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A measurement system is presented for measuring rheological properties of nonNewtonian fluids. The system consists of a slightly modified electromagnetic flowmeter and, optionally, of a differential pressure sensor. Its main characteristics are: inline, noninvasive measurement, medium accuracy, very simple to be realized. The estimation of rheological parameters is restricted to laminar, axisymmetric flow. (3 pages)

Investigation into the use of the electromagnetic flowmeter for twophase flow measurements
 Author(s): R. Krafft ; J. Hemp ; M.L. Sanderson
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We investigate the possibility in bubble flows of using an electromagnetic flowmeter to measure simultaneously bubble velocity and velocity of the (conducting) continuous phase. These velocities are different if slip is present. An analysis is presented and an electromagnetic flowmeter with large area electrodes and coil windings designed to produce a uniform magnetic field is constructed. (4 pages)

Usage of the spatial filter method for measurements of local particle velocities in multiphase flows
 Author(s): O. Fiedler ; J. Kumpart ; N. Labahn
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The optical spatial filter method is based upon the evaluation of light distributions by gratinglike structures. The velocity of objects moving through the measuring volume is obtained by determining. the center frequency of a signal delivered by a light receiver observing that volume. The most common realization of this method is laser Doppler anemometry. The measurement volume is located within an intersection of two focused laser beams; a grating results from interference. A single light receiver observes an integral over the intersection area. In our present work, the grating function is performed within the optical receiver. The active gratings simplify the optical arrangement. In order to apply the spatial filter measuring system to multiphase flows with high solid concentrations or optically dense fluids a special probe has been designed. This probe guides light to the measurement volume at its tip and ensures the visibility of particles in this volume for the light receiver. Thus, it is possible to measure the particle velocity at any position inside a gas/solid or fluid/solid flow. The measurement range can be adjusted to the process easily by changing the focal length of the used lens. (3 pages)

Improvement of accuracy in large sewer mean flow measurements using an array of Doppler transducers
 Author(s): A.W. Hughes and I.M. Longair
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The objective of the work was to produce a selfcontrolled, battery powered instrument that could produce velocity profile information across the section of a large sewer. The Doppler Transducer Velocity Array System was produced to meet this and testing has shown that the system functions as designed. Field testing of the system showed that the accuracy of the results recorded was to within 10.9% of an independent propeller meter. The transducer beams were forced to cross at specific positions and thus it was known exactly where in the flow the velocity readings originated. (5 pages)

A novel ultrasonic mass flowmeter for liquids
 Author(s): A.R. Guilbert and M.L. Sanderson
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An alternative technique for determining mass flowrate is to use a volumetric meter in conjunction with a density cell since mass flow m is given by the product of density ρ and volumetric flowrate Q. This usually requires a sampling system to determine density. The meter presented in this paper uses a volumetric flow cell and a density cell, but makes all measurements ultrasonically on flowing liquid without the need for sampling. It was developed initially for use on aircraft but has a wider applicability. The meter is based on an ultrasonic timeofflight cell (the Q cell). This can provide either volumetric flowrate Q or (more typically) the ratio of volumetric flowrate to speed of sound in the liquid squared (Q/c^{2}). in series with this is an ultrasonic cell (the Z cell) capable of determining specific acoustic impedance Z and speed of sound c. Since Z=ρc, equations can be used to determine mass flowrate. The flowmeter is controlled by a fixed point digital signal processor chip (DSP) which also computes volumetric and mass flowrates. Ultrasonic transit times and signal amplitudes are measured and converted to digital values which the DSP processes. To provide the required turndown ratio (about 50:1) and high accuracy at low flowrates, the DSP performs a rolling average on the data. However, it also computes nonaveraged values of mass flowrate to provide a less accurate but faster responding output. This allows the flowmeter to respond rapidly to transients in the flow. (4 pages)

Noninvasive two phase now measurement using soft Xray attenuation
 Author(s): J. Mennell ; B. Byrne ; Y. Yan
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Some of the most difficult problems in multiphase flow measurement lie in the area of pneumaticallyconveyed solids. Many examples exist, of which one of the most important is the conveyance of pulverised coal in the fuel lines feeding power station boilers. In this type of flow, pneumatic suspensions may be extremely dilute, so that radiation attenuation using common radionuclides may be less than 1%. If radiation of much lower photon energy is used, high attenuation in pipe entry and exit radiolucent windows may have to be tolerated. High intensity, soft Xray fields are therefore required in this application. An Xray tube operating at 25 kVp and 0.4 mA can deliver radiation intensity three orders of magnitude higher and attenuations over one order of magnitude higher than are obtainable from a 2 GBq Am241 point source in the same geometry. The paper attempts to evaluate the potential and limitations of this approach for the particular example of dilute pneumatic suspensions of solids. (3 pages)