WO2009018597A1

WO2009018597A1 - Apparatus for determining flow parameters of a particle-fluid flow

Info

Publication number: WO2009018597A1
Application number: PCT/AT2008/000284
Authority: WO
Inventors: Anton Fuchs; Hubert Zangl; Georg Brasseur
Original assignee: Technische Universität Graz; Forschungsholding Tu Graz Gmbh
Priority date: 2007-08-09
Filing date: 2008-08-11
Publication date: 2009-02-12
Also published as: AT505522A1; AT505522B1

Abstract

Disclosed is an apparatus for determining flow parameters of a particle-fluid flow. Said apparatus comprises a first sensor array (SA1) that reacts to particles and has an equidistant division within planes extending vertical/at an angle to the direction of flow (z) in accordance with the position of the particle path, and an evaluation unit (4) to which the sensor unit signals (e) of the sensor unit are fed that can be attributed to passing particles and which is designed to determine a particle velocity on the basis of said signals. In addition to the first sensor array (SA1), a second sensor array (SA2; SA2'; SA2') is provided which has a different division within planes extending vertical/at an angle to the direction of flow in accordance with the position of the particle path, and the signals of which are likewise fed to the evaluation unit (4). The evaluation unit (4) is designed to determine a particle velocity as a function of the location on planes extending perpendicular to the direction of flow from the signals that both arrays feed to the evaluation unit (4).

Description

DEVICE FOR DETERMINING FLOW PARAMETERS OF A PARTICLE FLUIDUM FLOW

The invention relates to a device for determining flow parameters of a particle-fluid flow, having a particle-responsive sensor array which has an equidistant pitch in planes perpendicular to the flow direction, and an evaluation unit which supplies the signals to the sensor unit to be attributed to particle passages are and which is arranged to determine a particle velocity based on these signals.

In a variety of applications in industry and science, material is transported in the form of two- and multi-phase flows through delivery lines. Typical examples of such transport are the pneumatic conveying of bulk solids and material transport in liquid-solid flows.

The delivery parameters of interest in such transport are material velocity and material concentration. From them the mass flow, i. the amount of material moved by the conveyor section per unit time is calculated.

A device of the type described in the introduction is described, for example, in O. Fiedler et al., "Measurement of Local Particle Velocities and Velocitiy Distributions in Gas-Solid Flows by Means of the Spatial Filter Method", Powder Technology 94, (1997), pp , 51-57, in particular using the example of quartz sand in an air flow, wherein a CCD camera array is used. It is also discussed here that the evaluation can be carried out by using an FFT analysis or by period measurement of the resulting signals. Such speed measurement methods are also referred to as spatial filter methods or "spatial filtering", in which connection reference may be made to document DD 218 170 A1, in which the speed measurement is explained by means of linear CCD arrays using the example of goods moved on a conveyor belt becomes.

An arrangement for measuring the speed of self-luminous, because hot coal particles in a cogeneration plant is in K. Christofori and K. Michel, "Velocimetry with Spatial Filters Based on Sensor Arrays", Flow Meas. Instrum., Vol. 7, No. 3/4 , pp. 265-272, 1996. This arrangement also employs a CCD structure on which an image of the flowing particles is imaged by means of optics already a grid structure inherent, so no special grid in the beam path is required. The literature deals more closely with the transfer function of a spatial filter as well as the signal processing.

It has also become known to use two sensor arrays, as shown by US 2007/083340 A1 (Bailey et al.). The two sensor arrays each have an equidistant division and are arranged on a flow-through pipe, for. one at the bottom of the pipe and one opposite at the top. The sensors respond to pressure fluctuations caused by vortices in the flow and are preferably piezoelectric sensors. In a signal processor, the sensor signals are evaluated in order to obtain information as to whether a sediment layer has deposited at the bottom of the tube or how high such a layer is. In contrast to the state of the art from which the invention proceeds, particles not present in the flow are detected here.

At this point, the terms used in connection with the invention should be defined, if necessary, as follows:

A particle-fluid flow is to be understood as meaning flows which are preferably, but not exclusively, conducted in lines and which consist of gases and / or liquids. The term "particle" is intended to include not only solids, such as grains of sand or grains, but more generally areas entrained by a flow having different physical properties from the actual flow fluid, such properties may be optical and / or electrical or density related "Particles" may thus be, for example, gas bubbles in a liquid or oil pearls in water, and finally also living things in water.

On the other hand, the term "sensor array" is intended to denote an arrangement which, in conjunction with one or more sensors, includes a pattern arranged in the direction of flow, eg a grating or a plurality of sensors, the passage of particles through the area of influence of the sensor array leading to periodic signals, In addition to optical sensor arrays, capacitive sensor arrays should be included, in particular SR Woodhead, JE Amadi-Echendu, "Solid Phase Velocity Measurements Utilizing Electrostatic Sensors and Cross Correlation Signal Processing." Proceedings of the Instrumentation and Measurement Technology Conference, 24-26 April 1995, p. 774-777, and noted that an "array" in the simplest case, only two electrodes or sensors However, using an array with a larger number of electrodes or sensors may result in better signal quality.

In many cases, such as in the production of bulk material, the flow parameters of interest are material velocity and material concentration, as this is simply a measure of mass flow, i. can calculate the amount of material moving through the conveyor section per unit of time. Due to uneven distribution of material speed and material concentration in the delivery line, it would be necessary for a reliable determination of the mass flow to perform a spatially resolving measurement of the two delivery parameters, in other words to determine the distribution profile over the conveyor line cross section. A disadvantage of the known methods and devices is therefore that at best a mean mass flow can be determined, but not a measurement which can provide the distribution of the particles in directions perpendicular to the conveying direction, in other words the distribution profile.

It is an object of the invention to provide a device using a spatial filter method, with the aid of which the distribution profile can be determined without great constructive effort.

This object is achieved with a device of the type mentioned, in which according to the invention, in addition to the first sensor array, a second sensor array is provided which has a different pitch within planes normal to the flow direction, and their signals are also fed to the evaluation, which set up is to determine a particle velocity as a function of the location in planes perpendicular to the flow direction from the signals supplied by both arrays.

Thanks to the invention with its spatial coding of the sensors, an unambiguous assignment of a received measurement signal to a specific region of the cross section is possible, a velocity profile and a concentration profile can be determined, and finally information about the extent and geometry of particles or particle accumulations can be derived.

The term "normal / oblique" is to be understood to mean that the electrodes or their planes are usually normal to the flow direction, but also layers at an angle to the flow direction possible or advantageous under certain measurement conditions or due to local conditions are unavoidable. An easily realizable and less complex embodiment of the invention provides that the first and the second sensor array are arranged in the flow direction at a distance from each other.

It is further possible that the first and / or the second sensor array is formed as an electrode array inside and / or outside the flow, a choice can be made according to the flow to be examined.

One especially with correspondingly clear flows, such as water or gases with not too high particle density, it may be expedient if the first and / or second sensor array has an optical grating, which as well as a flow section in the beam path between a light source and a photodetector.

In a further optical realization can be provided in a meaningful way that the first and / or second sensor array comprises an array of light sources, in the beam path, a flow section and a photodetector Hegen or that the first and / or second sensor array has an array of photodetectors which receives light emitted by a light source and passing through a flow section.

To facilitate the signal processing, it can further be provided that the first have the second sensor array such divisions that the output signals of these arrays are in clearly distinguishable frequency ranges.

The invention together with further advantages is explained in more detail below by way of example embodiments, which are illustrated in the drawing. In this show

1 shows an exemplary, prior art embodiment for determining the speed with the aid of capacitive principles and a sensor array consisting of electrodes distributed equidistantly along the conveyor line,

2 shows an exemplary, quasi-periodic measurement signal (sum signal) for a construction according to FIG. 1 according to the prior art, FIG.

3 with reference to diagrams, the evaluation of the measurement signal by means of Fourier transformation for determining the speed in a structure according to FIG. 1 according to the prior art, 4 is a simple exemplary embodiment of the subject invention using optical principles, wherein after a first equidistant sensor array for Geschwmdigkeitsbestimmung two oblique planes of measurement is provided as a second sensor array for the determination of the particle position,

5 for particle layers within a round or square pipe cross section exemplary measuring signals (sum signals) for a construction according to FIG. 4 for determining the particle velocity and the particle position, FIG.

6 shows a further exemplary embodiment of the subject invention with a fanned-out grating as a second sensor array for determining the particle positions and the exemplary measuring signals for two different particle trajectories,

7 shows exemplary frequency spectra for particles with low velocity and particle positions predominantly in the lower region of a tube cross section and for particles with high velocity and particle positions predominantly in the upper region of the tube cross section,

8 shows a further exemplary embodiment of the invention using capacitive principles, including associated measuring signals,

9 shows a further expedient embodiment of the invention with capacitive sensors, in which the electrodes for coding the particle position in the form of second sensor arrays are provided upstream and downstream of a first sensor array for the speed measurement, and

FIG. 10 shows a flow chart for the determination of the velocity and the particle distribution according to the invention from the frequency spectra of the measuring signals.

The method and a device for determining the particle velocity with the aid of equidistant sensors distributed along the conveying direction according to the prior art will now be made clear with reference to FIGS. 1 to 3. Such a method is also applicable to the industrially frequently used pneumatic Dünnstromförderung in which the solid particles are dispersed in the gas phase.

Thanks to the invention with its spatial coding of the sensors, a clear assignment of a received measurement signal to a specific region of the cross section is made possible, it is possible to have a velocity profile and a concentration profile Finally, information on the extent and geometry of particles or particle accumulations can be derived.

Along the flow direction of the conveyed media, i. in the longitudinal direction of a conveyor line 1, here assumed as z-direction, suitable sensors are mounted at equidistant intervals. In the example shown, a sensor array SA 1 is used which uses transmitting electrodes S1 to S3 and receiving electrodes E1 to E4. An alternating voltage transmission signal s is fed to the transmission electrodes S1, S3 connected to one another via electrical connections 2, a reception signal e is picked up by the reception electrodes El,... E4 which are likewise connected to one another via electrical connections 3 and one here not described in detail, the expert known evaluation unit 4, which can also provide the transmission signal s. Capacitive principles, namely the evaluation of the different relative dielectric constants in the individual phases of the flow, are described, for example, in the aforementioned article by S.R. Woodhead, J.E. Amadi-Echendu described and belong to the skilled person known prior art.

In general, suitable sensors are those that can be influenced by a property of the transported material, wherein fluctuations in the material composition of the transported media, caused by their multi-phase expression, are converted by means of these sensors in evaluable signals. As another example, optical principles may be mentioned, i. the evaluation of the different optical properties, such as optical density and reflection in the individual phases of the flow. Such as. in the DD 218 170 Al or in the already mentioned article by K. Christof ori and K. Michel described.

In Fig. 1, two particles pl and p2 are shown, which lead in their passage through the sensor array SAl to receive signals, namely due to a change in capacitance .DELTA.C, to which reference is made to FIG. The goal of mounting first sensors as the first sensor array SAl is to form a periodically repeating pattern of the sensitivity ranges. A sensitivity range is that region in the delivery line 1 in which a sensor can be influenced by a property of the transported material. A pattern of the sensitivity ranges is the course of the sum of the sensitivities (gradient of change in the sensor output signal relative to a change in the influencing material property) of all sensors along a particle trajectory. The periodically repeating pattern of the sensitivity ranges of the first transducers causes a quasi-periodic signal for the sum of the transducers for media flowing at a constant rate. With slowly moving multiphase flow, the periodicity of the measurement signal will have lower frequency than for a fast moving flow. The speed information can thus be determined from the frequency of the measurement signal, which can be realized in practice by a Fourier transform. A weighting of the sensor signals before the summation can be advantageously used for a pre-filtering in certain applications. Even higher-order functions for transformation, such as rms value generation, may be useful for some applications.

FIG. 3 shows the received signal e or the capacitance change ΔC for two particles p 1 and p 2 moved at different velocities vi and v 2, respectively, and the associated Fourier transforms (on the right in FIG. 3).

The invention is based on a device according to the prior art, as has just been described by means of examples (capacitive, optical).

For precise determination of mass flow, i. the mass of material flowing per unit time through the cross section of a delivery line, it is necessary to determine a velocity profile. The approach of the invention is to distribute sensors in the form of at least one additional second sensor array so that a spatial coding of the line cross-section is realized.

The arrangement of electrodes at equidistant intervals for determining the velocity of the medium being conveyed is thus in the invention by a suitable arrangement of further sensors, e.g. Electrodes upstream of the velocity measurement, extended for spatial coding, whereby a clear assignment of the particle trajectories to the corresponding cross-sectional area of the delivery line can be made.

As shown in Fig. 4, it is possible in the simplest case, to determine a profile of the material velocity over the pipe cross-section with two additional, set to the flow direction measuring planes. The positions or trajectories of the particles can be uniquely determined by the coding in the two measurement planes, as illustrated in FIG. 5 in the time signals for two particle positions. For example, ΔI is the change in luminous flux, generally signal intensity. A coding is realized in the exemplary embodiment shown in FIG. 4 with the aid of optical measuring principles, namely light sources 5, 6 and photodetectors 7, 8. Either the shading of the transported particles (transmitted light method) or the backscattering of light by particles (scattered light method) is evaluated. In the expedient construction according to FIG. 4, the equidistant section of sensors, the first sensor array SA1, is followed by two further obliquely arranged planes, which are rotated by 90 ° relative to one another in the line cross section, as the second sensor array SA2. In b) of FIG. 4, an optical grating 9 is shown by dashed lines, which is arranged in the beam path between the light source 5 and the photodetector 7. Such an arrangement of a single light source and a single photodetector in conjunction with a grating can be used both as a first and as a second sensor array. Furthermore, an array of light sources, eg of laser diodes, can be used for both the first and the second sensor array instead of a single light source, just as either a single photodetector can be used, to which the light of all light sources of an array is fed. or an array of photodetectors.

Due to the inclination of these planes, the distances between the planes inevitably change for an axially parallel transported particle. The time differences Δt _y and Δt _x in the time domain have an effect on different particle trajectories in the pipe cross-section in the form of frequency shifts in the frequency domain and can be detected and evaluated in this way by measurement.

The particle position with regard to the x and y coordinates can be calculated in a structure according to FIG. 4 from:

with d _x and d _y as offset.

It is irrelevant whether the pipe cross-section has a round or a square geometry.

From Fig. 6 shows a further embodiment of the invention, the downstream of a first sensor array, a second sensor array SA2 in the form of a fanned-out grating to Determining the particle positions has, wherein the representations b) and c) of FIG. 6 show exemplary measurement signals for two different particle trajectories or particles pl and p2. With dmm and dmax the minimum or maximum distance between two sensor elements is designated, with ΔS the change of the signal strength.

Reference should be made to a not unimportant in practice embodiment of the first or second sensor array. In the presence of only one output signal, e.g. In the case of capacitive sensor elements, it is often the case to be able to easily separate the output signals of a first from those of a second sensor array, the corresponding arrays are designed so that they receive signals in different, technically easy, e.g. provide frequency bands separable by means of bandpasses. This is made possible by clearly distinguishable lattice spacings-spacings of the sensor elements-and FIG. 6 shows this in an obvious way.

7 shows, with reference to two diagrams, the spectral energy distribution PSD for the case of lower velocity and a higher particle concentration in the lower tube cross section (FIG. 7a) or in the case of a higher velocity and a higher particle concentration in the upper tube cross section (FIG. 7b). ,

As shown in FIGS. 8 and 9, the desired spatial coding can be forward and / or downstream of the equidistant first sensor array SA1 by a unique sequence of wide and narrow distances of sensors. FIG. 8 shows a second sensor array SA2 laying upstream of the first sensor array and the corresponding signals ΔC for four particles p1, p2, p3 and p4, whereas FIG. 9 shows a device according to the invention in which both upstream of the first sensor array SA1 as well as downstream of this first sensor array SAl a second sensor array SA2 'and SA2 "is arranged.

It can be seen that depending on the position or depending on the trajectory of a solid particle transported at a constant speed through the measuring structure pl ... p4 geometry results in a unique signal pattern that can be compressed and stretched according to the speed in the time axis, what to the illustrations of Fig. 8 and 9 under b) is referenced. This signal pattern allows a spatial detection and thus the determination of a velocity profile.

Taking advantage of the fact that small particles contribute to a correspondingly small increase in the dielectric constant of a unit volume, whereas large particles have a greater influence on the relative permittivity and subsequently on the capacitive measurement signal, knowledge of the particle positions and their deterministic sensitivity can be used. For the arrangement of the sensors, the particle sizes and the distribution of the particles can be determined. For optical principles, the particle size also has an influence on the measurement signal. Here shading or backscattering is influenced by the size of the particles. The particle frequencies or their distribution can be estimated from the variance of the measurement signals. For both optical and capacitive measurement principles, the relationship between signal amplitudes caused by flowing particles and the signal power of the measurement signal provides a useful determination of the particle dimensions.

Fig. 10 shows the measuring procedure already described several times above with a device according to the invention again with reference to a basic flow chart. "Analysis frequency range 1 or frequency range 2" is to be understood as the possible splitting of the frequency ranges, as has already been explained above in connection with FIG. 5.

In order to implement a plausibility check, it is also possible to provide a further, redundant downstream level with a second device according to the invention, i. do a duplication and calculate a correlation between upstream and downstream levels. In the case of highly turbulent flow and particle trajectories, which deviate especially from an axis-parallel orbit, the correlation result is very poor and can be discarded. Although the flow will generally be guided within a closed cross-sectional conduit, the invention is applicable to non-all-sided flows , such as a channel open at the top, or a portion of a stream which is not narrowly defined, such as a sea current. Likewise, it is irrelevant for the measuring principle according to the invention which sensors are used in the sensor arrays, wherein the measuring principle of the first sensor array may be different from that of the second sensor array. Of course, the invention is not limited to optical or capacitive measuring principles, but depending on the size and density of the "particles" for their detection in first and second sensor arrays, gamma or beta rays can also be used, for example, or ultrasound.

Claims

A device for determining flow parameters of a particle fluid flow, with a particle - responsive sensor array (SAl) which has an equidistant division in planes normal / oblique to the flow direction (z), and with an evaluation unit (4) which controls the signals due to particle passages (e) are supplied to the sensor unit and that is arranged to detect a particle velocity on the basis of these signals,

characterized in that

a second sensor array (SA2, SA2 ', SA2 ") is provided in addition to the first sensor array (SA1), which has a different pitch within planes normal / oblique to the flow direction, and whose signals are likewise fed to the evaluation device (4) is configured to determine from the signals supplied to it by both arrays a particle velocity as a function of the location in planes perpendicular to the flow direction.

2. Apparatus according to claim 1, characterized in that the first and the second sensor array (SAl, SA2) are seen in the flow direction spaced from each other.

3. Device according to claim 1, characterized in that the first and / or the second sensor array (SA2, SA2 ', SA2 ") is formed as an electrode array inside and / or outside the flow.

4. Device according to one of claims 1 to 3, characterized in that the first and / or second sensor array comprises an optical grating (9) which, like a flow section in the beam path between a light source (5, 6) and a photodetector (7 , 8).

5. Device according to one of claims 1 to 4, characterized in that the first and / or second sensor array comprises an array of light sources, in the beam path, a flow section and a photodetector are.

6. Device according to one of claims 1 to 5, characterized in that the first and / or second sensor array (SAl, SA2) has an array of photodetectors (7, 8) which from a light source emitted, a flow section passing through the light intercepts.

7. Device according to one of claims 1 to 6, characterized in that the first the second sensor array (SAl, SA2) have such divisions that the output signals of these arrays are in clearly distinguishable frequency ranges.