Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/74—Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
  • G01F1/662—Constructional details
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
  • G01F1/708—Measuring the time taken to traverse a fixed distance
  • G01F1/7088—Measuring the time taken to traverse a fixed distance using electrically charged particles as tracers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
  • G01F1/86—Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P5/00—Coupling devices of the waveguide type
  • H01P5/08—Coupling devices of the waveguide type for linking dissimilar lines or devices
  • H01P5/10—Coupling devices of the waveguide type for linking dissimilar lines or devices for coupling balanced lines or devices with unbalanced lines or devices
  • H01P5/107—Hollow-waveguide/strip-line transitions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
  • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support

Definitions

• Antenna device for coupling or decoupling microwaves in tubular hollow bodies and device for mass flow measurement by means of such antenna devices is antenna device for coupling or decoupling microwaves in tubular hollow bodies and device for mass flow measurement by means of such antenna devices
• the invention relates to an antenna device for coupling or decoupling microwaves in a tubular hollow body according to the preamble of patent claim 1 and to a device for mass flow measurement in tubular hollow bodies by means of such antenna devices according to the preamble of patent claim 11.
• antenna devices For the transmission of high-frequency energy through the atmosphere or in hollow bodies, antenna devices are known which abstract electromagnetic waves in these media, which can also be picked up again via such antenna devices. Such antenna devices are used to convert electrical signals into electromagnetic waves or electromagnetic waves into electrical signals. These arrangements are used for transmitting information or for assessing the transmission space.
• distances, speeds or the distribution of solids or particles in the dielectric media are frequently detected by using high-frequency waves in the microwave frequency range, and their size or quantity is determined by special evaluation or measuring devices.
• the solids or particles to be measured must reach the emission area or the emission area must be directed onto the measurement objects, the emission being able to take place by means of variously configured antenna devices.
• EP 0 703 447 B1 discloses a method and a device for measuring the volume fraction of a multiphase flow in a pipeline by means of microwave radiation.
• a number of microwave antennas are arranged on the circumference of the flow-through pipeline, which feed microwave energy into the pipeline, wherein the injected microwave energy is simultaneously detected by another microwave antenna.
• the particle volume fraction present in the flow is determined in the propagated microwave field.
• twelve dipole antenna pairs are arranged symmetrically on the circumference of the tube, which irradiate the microwave energy into the through-flowed pipe orthogonally to the flow direction and perpendicular to the radial direction.
• the pairs of dipole antennae are dipoles which are arranged in a crosswise arrangement and consist of a multiplicity of small pipe sections welded together and are arranged on the circumference of the pipe inner wall.
• Such antennas are very complicated to manufacture and can impair a multiphase particle flow flowing through at least for smaller pipe cross-sections, so that such antennas are preferably used with larger pipe diameters.
• Another microwave measuring method for determining the mass flow of a particle stream in a round tubular hollow body is known from DE 101 37 009 C1.
• an opening is provided in the tube wall, in which a horn antenna is left ein ⁇ , is coupled through a waveguide, the microwave energy generated by a Gunndiode in the tube interior Kit ⁇ .
• These electromagnetic waves radiated into the flow channel are reflected by the particle flow and simultaneously received again by the horn antenna and fed to a Schottky diode as a reflection receiver.
• the reflection measure transmits a function of the electromagnetic radiation reflected by the solids fraction From the time course of the measured signal of the differential quotient of time is formed, which is a measure of the concentration of Supplementchen ⁇ distribution in the measuring range.
• the integral is formed mathematically from the derived measurement signal, the magnitude of which is intended to represent a measure of the mass flow in the flow channel.
• the horn antenna radiates the microwave energy essentially only across the cross section into the flow channel, so that only a small measuring range can be exploited in the axial direction with which only a limited accuracy of measurement is likely to be achievable.
• DE 44 06 046 C2 discloses another microwave measuring device with which a powder mass flow in a pneumatic conveying line can be quantitatively determined.
• a microwave resonator is attached to the outer casing of the conveying line, which consists essentially of a resonance space in which a radio-frequency antenna generates a microwave field.
• the delivery line is evidently designed as a plastic tube, the electromagnetic micro waves penetrate the delivery line wall and are dampened in their amplitude by the mass particles passing through and are changed in their resonance frequency.
• the powder mass per unit volume is measured inside the tube '.
• the velocity of the particle stream flowing through is also detected by means of two spaced-apart electrodes, and the flow rate or the flow rate is calculated by means of the measured volume mass.
• Such a microwave coupling has a poor efficiency, since the majority of er ⁇ generated microwave radiation is emitted outside the tube and can not be decoupled for measurement signal evaluation.
• Such a measuring device therefore requires a ver ⁇ relatively high microwave energy for irradiation or a NEN high technical evaluation expenditure in order to achieve a sufficient Meßgenautechnik.
• EP 0 717 269 A2 discloses a further microwave measuring method and a corresponding device, in which the mass flow rate can be detected in a tubular pneumatic delivery line.
• three coupling openings are provided for microwave feed on the circumference of the pipe wall, to which the microwave energy is introduced by means of waveguide, coaxial conductor or strip conductor and can be coupled into the tubular conveying line.
• the Einkop ⁇ pelö Anlagenen more similar Aus ⁇ coupling openings are mounted in the pipe wall, through which the coupled micro wave energy is coupled out again. So that a multiphase fluctuating particle flow over the entire conveyor line cross-section can be detected with sufficient accuracy, three input and three output ports are provided, in which the microwave energy is coupled in and out in pulses.
• the coupled-out microwaves are compared with a reference value without delivery line loading both after their attenuation in the amplitude and after their phase shift.
• the deviation from this reference value is proportional to the loading density on the measuring section.
• the conveying speed is additionally determined, from which by multiplication with the loading density on the measuring section, the delivery rate or the mass flow can be calculated.
• the coupling openings or slots used in this case feed the microwave energy basically evenly into both axial tube directions, so that a maximum of 50% of the injected microwave energy is available for evaluation in the measuring direction.
• relatively high microwave Necessary energy which can also lead to reflections by the undirected propagation, which disturb the measurement signal and can only be reduced by suitable time windows and thus only in a pulsed operation.
• this requires a relatively high outlay for coupling and decoupling the microwave energy and for evaluating it.
• a special antenna device for coupling micro waves into a tubular hollow body for measuring a volume fraction located therein is known from DE 94 12 243 U1, which enables microwave radiation in an axial direction of the hollow body.
• This antenna device is used for level measurement in a tubular container and has a rod radiator antenna which radiates the microwave energy into an axial longitudinal direction of the tubular hollow body whose radiating energy in this direction has a high efficiency.
• this rod antenna would be in the flow and would not only disturb the flow of particles but would also be subject to abrasion therefrom, depending on the abrasion.
• a planar Strahlerele ⁇ element is provided at the front end of a waveguide, which consists essentially of a flat elekt ⁇ risch conductive metal disc, which is applied to a plate-shaped dielectric substrate.
• a plate-shaped dielectric substrate Above the dielectric substrate, an electrically conductive layer or a part of the metallic waveguide back wall is attached, by means of which the high-frequency energy is injected.
• the invention is therefore based on the object of providing an antenna device for coupling or decoupling electromagnetic high-frequency energy into a flow-through tubular hollow body which permits coupling with high efficiency and minimally impairs or alters the interior of the hollow body.
• a device for detecting the mass flow in such a tubular hollow body is to be created with this antenna device.
• the invention has the advantage that the inclusion of patch element pairs in the inner tube wall results in an integration into the hollow body, in which the inner cross section of the flow-through tube remains unchanged. This simultaneously prevents the formation of turbulences when flowing through multiphase powdered or liquid media. which unhindered flow is often necessary for subsequent processes.
• the integration of two oppositely arranged curved patch elements has proved to be advantageous, since it permits uniform propagation over the entire cross-sectional area with microwaves capable of propagation as electromagnetic waves, by means of which the dielectric fluctuations can be precisely detected by multiphase particle flows.
• an integrated antenna device however, other, longer high-frequency transmissions in open, tubular waveguides with high efficiency are also possible, which are in particular less susceptible to interference due to directional coupling.
• By using such integrated patch elements in the inner tube wall for example, by a Koaxialleiteran gleich in a simple way microwave feed or decoupling are made by the relatively little loss, in particular in a directed coupling.
• the feed 'of the microwave energy to provide off-center to the patch element width which has the advantage that carried an axially directed wave propagation in the tubular Hohl ⁇ body, whereby the efficiency in Ausbreitungs ⁇ direction increased and at the same time the disturbances are reduced by a re fllecting wave propagation during decoupling.
• This not only improves the measurement accuracy in the case of a particle distribution or a mass flow determination, but also allows the transmission quality of the microwave propagation in open waveguide structures to be increased. Because even for pure transmission purposes, an efficiency between the coupling and decoupling of well over 50% can be achieved. Therefore, relatively relatively small microwave energies are advantageously used with relatively low coupling-in energies. Transmission distances or high measurement accuracy achievable at predetermined measurement distances.
• Such antenna devices can advantageously also be used as capacities with which conveyed particle fractions can be charged electrostatically and thus can be detected at another point, for example for determining the flow rate.
• FIG. 1 shows a schematic side view of a round hollow conductor with an integrated antenna device
• FIG. 2 is a schematic front view of the circular waveguide with integrated antenna device
• FIG. 3 shows a schematic field line profile of the fundamental wave (TEn mode) in the cross section of the round hollow conductor at the coupling-in point
• FIG. 4 shows a strip line coupling to an antenna device in a circular waveguide.
• an antenna device for Hoch ⁇ frequency feeding or -auskopplung is shown in a tubular hollow body 1 as a waveguide, which consists of so-called patch elements 2, 3, which are integrated in the inner wall 5 of rohr ⁇ shaped hollow body 1.
• the tubular hollow body 1 represents the section of ein ⁇ fold round tube, as it is used for the pneumatic conveying of coal dust in the cement industry, the vor ⁇ preferably consists of metal.
• the hollow body 1 can also represent a waveguide not intended for conveying, as used, for example, for transmitting high-frequency waves in microwave engineering.
• the pulverized coal particles flowing through in the hollow body 1 designed as a conveying tube can be quantitatively determined by means of two antenna devices. With such an antenna device, however, it is also possible to detect other particle or liquid flows which, on the basis of their dielectric properties in the considered frequency range, influence the waves both in their magnitude and in their phase depending on the density of the particle or liquid flow ,
• microwaves in the gigahertz range. For this purpose, it is necessary to couple the microwaves into the conveying tube interior at least at one point and to decouple them again at another point in order to evaluate an influence by the carbon dust and air mixture flowing through with respect to the coupling.
• the invention proposes an antenna device for coupling or decoupling the microwave energy, which is designed as a so-called patch antenna.
• the antenna device contains one or more patch element pairs 2, 3 arranged opposite one another in the tube inner wall 5 and consisting of a rectangular, electrically conductive metal part.
• the individual patch elements 2, 3 have a predeterminable length L and a width W different therefrom, and preferably consist of a substrate with a very highly conductive layer, such as e.g. B. a thin copper sheet, which is ange ⁇ introduced in its longitudinal direction transversely to the longitudinal direction of the conveying tube 1 ange ⁇ .
• the patch element pair 2, 3 is not carried out as usual planar, but conformed to the curved surfaces of the pipe inner wall 5 and inserted in a recess from each other isolated.
• the patch elements 2, 3 are In this case integrated into the tube inner wall 5 such that its radius of curvature is equal to that of the inner wall radius.
• the antenna device is designed as a separate ring-shaped pipe section which can be inserted into an existing pipe system 1 as a small, sleeve-like intermediate piece 4.
• a separate metal ring is provided whose diameter is dimensioned so that the existing För ⁇ derrohrenden can be clamped or screwed therein.
• the described embodiment is based on a Zwi ⁇ rule piece 4 with an inner diameter of about 32 mm, in which preferably microwaves with a frequency from about 5.5 GHz in the fundamental mode (TEn mode) can propagate.
• larger or smaller tubular hollow bodies 1 or intermediate pieces 4 can be used in which correspondingly aus ⁇ spreadable microwaves with lower or higher frequencies are to be coupled.
• this antenna intermediate piece 4 as a tubular hollow body 1 is shown in detail in FIG. 2 of the drawing.
• the two opposing patch elements 2, 3 are mounted symmetrically to a central plane 6 extending in the longitudinal direction of the tube in a recess in the tube inner wall 5 and thus form an antenna pair integrated into the conveyor tube 1.
• the two patch elements 2, 3 are arranged electrically insulated from the outer conductive annular wall or tube outer wall 7 by a dielectric substrate 8.
• the first patch element 2 is provided from the outside with a coaxial connection 9 for feeding the microwave energy
• the outer conductor 10 is electrically connected to the outer ring wall 7 and the inner conductor 11 with the first patch element 2.
• the second patch element 3 of the antenna pair contains no electrical connection and serves essentially for beam shaping and adjustment of the propagation direction of the microwaves.
• an additional microwave feed can also be made in the second patch element 3.
• the feeding of the microwave energy in the first patch element 2 is preferably not initiated centrally at the intersection of its two center lines 12, 13, but off-center in the tube longitudinal direction. Therefore, the inner conductor 11 on the longitudinal center line 13 of the patch element 2, which is orthogonal to a longitudinal edge 14, but offset from the transverse center line 12, which is parallel to the longitudinal edge 14, arranged, resulting in a directed radiation to a longitudinal direction of the conveyor tube 1 results. Therefore, preferably in the second patch element 3, there is also provided an adaptation element 16, which is opposite the inner conductor connection 11 and electrically connects the second patch element 3 for the high-frequency waves to the pipe outer wall 7.
• the antenna device according to the invention can also be used for central injection into the first patch element 2 and without adaptation element 16 for coupling and decoupling the microwave energy.
• the length L of the first patch element 2 is dimensioned such that a standing wave in the base mode (TEn wave) can propagate in the conveying tube 1.
• the length L is calculated can be known from a multiple of half the wavelength ⁇ / 2 and an experimental adjustment because of the curved surfaces, which results in a length of approximately 30 mm for the first patch element 2. Since patch elements fundamentally radiation on all four edges 14, 15 is possible when they are in resonance by their predetermined length, for the width W of the patch elements 2, 3 vor ⁇ preferably only about half the length L is selected.
• the opposite second patch element 3 is provided, with the aid of which the distribution over the entire cross section can be detected precisely in the case of multiphase particle flows, without the need for additional additional microwave inputs distributed around the circumference ren.
• FIG Fig. 3 of the drawing shown A field line profile in the case of a microwave coupling with an external feed with reference to the tube longitudinal direction and with an adaptation element 16 in the second patch element 3 is shown in FIG Fig. 3 of the drawing shown.
• the Feldlinien ⁇ course is shown schematically on the longitudinal edge 14, which shows a directed radiation in a tube longitudinal direction.
• the arrows 17 indicate the direction and strength of the electric field within the conveyor pipe 1. From the strength it can be seen that both patch elements 2, 3 are in resonance.
• the field line course within the conveyor tube 1 corresponds to that of a TEn shaft and thus to that of a shaft capable of propagation within a circular waveguide.
• directed radiation is achieved primarily in only one longitudinal direction of the conveying tube 1, so that almost the entire microwave energy can be traced off in the direction of the measuring path.
• the efficiency is therefore increased with such a directed radiation to more than 90%, which leads to ei ⁇ nem ratio of useful signal to the irradiated micro ⁇ wave component of about 0.9. Since hardly any reflecting microwaves occur with such a directed radiation, the interference signal component is also very small, so that temporally pulsed synchronized coupling in and out is unnecessary.
• Such directed radiation is achieved in that a phase shift occurs between the two longitudinal edges 14 of the first patch element 2 by the off-center coupling. This is caused by the fact that a maximum field strength is applied to the longitudinal edge 14 in the emission direction, while at the opposite longitudinal edge the field strength has a minimum and therefore preferably only one emission in the measurement direction is achieved.
• An amplification of this directivity is effected simultaneously with the matching element 16 in the second patch element 3.
• This matching element 16 is preferably also offset off-center, namely precisely opposite the feed point of the inner conductor connection. As far as this matching element 16 is not in a field strong minimum, this results in a change in the field distribution on the second patch, which leads to a Phasenver ⁇ shift between the radiating longitudinal edges 14.
• an antenna device integrated in the pipe inner wall 5 of a tubular hollow body 1 propagatable electromagnetic high-frequency waves can be coupled in as well as decoupled again after an intended transmission path.
• these antenna devices are preferably used for metrological evaluation of the coupled-in microwave energy. For this reason, in each case at least one antenna pair is provided in at a predetermined tube spacing of several wavelengths of preferably approximately 1 m for the at least one further antenna pair for coupling out the microwave energy. If a mixture of air and coal dust flows through this pipe section as the measuring section, the dielectric properties of the mixture change compared to a reference value in air or vacuum.
• the charge of pulverized coal particles on the measuring path per measuring cycle also changes with load fluctuations, which likewise leads to a change in the damping and a phase shift with respect to the injected microwave energy.
• the proportion of coal dust in the measuring section can be determined.
• a relatively large signal component which is largely free of disturbances, can still be coupled out, so that the attenuation of the microwave amplitude or the phase response Shift is almost only dependent on the coal dust fraction on the measuring section, so that even with simple Auswert ⁇ methods already accurate measurement results can be achieved.
• several pairs of antennas can also be provided for coupling in and out in the tube inner wall. These are preferably offset from one another by 90 ° on the circumference of the tube wall, so that the spreadable microwaves do not influence sötrend.
• the throughflow speed can additionally be determined by means of a flow measuring device. From the carbon dust particle fraction within the measuring section multiplied by the conveying or throughflow velocity, the mass flow can also be determined quantitatively as a delivery rate or in total as a delivery rate at the same time as a corresponding electronic evaluation device. In practical experiments, density measuring accuracies of 0.5% have been achieved with such a device for determining the flow rate, with an average coal dust content of about 5% in air.
• FIG. 4 of the drawing Another embodiment of the antenna device is shown in Fig. 4 of the drawing.
• an antenna pair of two opposing rectangular flat patch elements 2, 3 is also integrated in a tubular hollow body designed as a conveying tube 1. These are likewise formed as already described with reference to FIGS. 1 and 2 and are arranged in a recess in an electrically insulated manner by the electrically conductive tube outer wall 7.
• the antenna device differs from that shown in FIGS. 1 and 2 only by the type of microwave input and output.
• a coupling hole 18 or a coupling slot for so-called aperture coupling is provided in the electrically conductive part of the ring or tubular body is centered or eccentric for the first patch element 2 arranged underneath.
• a frequency of the microwaves is preferably the same in the example. 5.5 GHz with comparable tube cross-section necessary in order to produce propagatable micro waves in the interior of the conveying tube 1.
• the propagation capability of certain microwave frequencies in tubular hollow bodies 1 essentially depends on the high-pass characteristic of the waveguide, according to which lower frequencies below the basic mode are not capable of propagation.
• the coupling of the microwaves in the fundamental mode TE 11 mode has the advantage that no lower frequencies that could interfere with the phase measurement are capable of propagation.
• a further antenna device can be provided for decoupling in a predetermined axial distance, as a result of which a measuring path is created for determining, for example, the pulverized coal density.
• the dust velocity can additionally be determined by means of a flow measuring device, so that the mass flow or the delivery force can be calculated from the dust density and the volume of the measuring section and the product at the flow rate.
• the efficiency in such Aperturkopplung because of the additional radiation outside the tube interior we ⁇ considerably worse than in the coaxial coupling, so that this type of coupling is preferably provided only for cost or space reasons.
• Such an antenna device from the integrated patch element pairs 2, 3 can also be used as a plate capacitor be used because there is air or another dielectric between the two patch elements 2, 3. If one now applies a high electrical voltage to the two patch elements 2, 3, the carbon dust particles passing through, for example, become statically dissolved by the electric field built up between the patch elements 2, 3. These electrical charges can be detected in the conveying direction by further patch element pairs 2, 3 again and z. B. are evaluated for speed measurement as a flow measuring device and the like.

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• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• General Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Measuring Volume Flow (AREA)

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• 2004
  • 2004-11-25 DE DE102004057087A patent/DE102004057087B3/de not_active Expired - Fee Related
• 2005
  • 2005-11-25 US US11/791,630 patent/US7712381B2/en not_active Expired - Fee Related
  • 2005-11-25 BR BRPI0517868-1A patent/BRPI0517868A/pt not_active IP Right Cessation
  • 2005-11-25 WO PCT/EP2005/012603 patent/WO2006056455A1/de active Application Filing
  • 2005-11-25 EP EP05813486A patent/EP1815214A1/de not_active Withdrawn
  • 2005-11-25 CN CNB2005800404131A patent/CN100480640C/zh not_active Expired - Fee Related

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