DE10134264B4 - flowmeter - Google Patents

Abstract

Measuring arrangement for guided in a fluid bed of predetermined geometry fluids, comprising
a sensor means (3) comprising
a sensor (3c, 10) for measuring the fluid surface height with respect to a fluid-independent reference point and
a sensor head (3b, 3a) arranged at a predetermined angle to the fluid surface for determining flow height and flow velocity,
and an evaluation circuit for evaluating the signals originating from the sensor means,
wherein the evaluation circuit is designed to
determine a fluid flow profile in response to the sensor means signals
from that lower layers, where a flow velocity is below a certain limit, to be determined as not flowing,
and thus to detect deposits in consideration of the fluid surface height related to the fluid-independent reference point and the given fluid bed geometry.

Description

The The present invention relates to the term claimed above and thus deals with the question of how fluid flows in particular can be measured well.

It gives a variety of applications where it is desired the flow easily and yet accurately measure fluids. This is This is important if the inflow is used for procedural purposes a substance can be detected by a pipe or pressure line must or if information about the fluid flow needed for costing purposes become. The latter is about the case when sewage through Sewer networks directed from one municipality to another to be processed there. In such cases typically pay a fee dependent on the quantity delivered, what the quantity must be determined for.

issues arise first, because the flow over the Cross section of the flow bed usually not constant. Thus, currents flow near walls due to friction slower. Furthermore Deposits result in changes in the fluid bed cross-section both regarding the form as well as re the size of the available cross-section. Corresponding problems also arise in channels, channels, streams and / or small rivers.

A method has already been proposed with which flow profile measurements can be carried out. A related method and apparatus are in the DE 197 40 549 A1 which discloses a method for measuring the flow characteristic of a medium in open channels, partially filled pipes and pressure lines, comprising the following method steps: providing at least one ultrasonic transducer on or in an open channel, partially filled tube or a pressure line; Emitting a first short ultrasonic signal in a direction having a directional component in the flow direction; Receiving first echo signals of portions of the first short ultrasound signal scattered by inhomogeneities in the flow in a predetermined time window corresponding to a first location window in the flow; Digitizing the first echo process; Storing the digitized first echo waveform; Emitting a second short ultrasound signal at a predetermined small time interval to emit the first short ultrasound signal in the same direction; Receiving two echo signals of portions of the second short ultrasound signal scattered in inhomogeneities in the flow in a predetermined time window corresponding to the first location window in the flow; Digitizing the second echo waveform; Image the cross-correlation between one or more regions of the first echo waveform and one or more regions of the second echo waveform; Determining flow velocity (s) in the first location window in the flow from the position of a local maximum of the cross-correlation or of local maxima of the cross-correlations; Repeating the measurement cycle according to the preceding method steps with shifted time windows corresponding to other location windows in the flow, if the detection of the complete flow characteristic in the desired range is not yet completed.

These Application is hereby fully incorporated by reference for purposes of disclosure peripherally incorporated.

A problem with the known method is that although a measurement in several town windows, ie for different height layers, takes place and thus the return flow in the cross-sectional profile can be resolved, but that occur with known sensor arrays problems especially in measurement tasks in which the fluid level varies that is, the flow in fluids must be measured at varying heights. It has been proposed to mount an ultrasonic sensor which operates on the Doppler principle under a float, which in turn is attached via a flexible attachment to a joint at an upper portion of a tube. Now, if the fluid level in the tube varies, the float will rise or fall accordingly. Such a system is used in the FR 2 710 979 A1 described. Thereafter, the sensor should be kept tangent to the water surface at each level; however, the practical implementations of the devices show that attachment at fast flow velocities begin to move transversely to the flow and / or skew to the water surface. A disadvantage of the known arrangement is therefore that the sensor then does not emit in the measurement signals in the same direction as near the fluid bed background. This further increases the measurement inaccuracies.

From the DE 40 27 030 A1 For example, a flow rate measurement method and apparatus is known in which two sensors are fixed in a tube. It is stated that measurement problems occur, inter alia, in cloudy solutions and that one or more arbitrary volumes between the bottom surface and the surface of the flowable medium are to be detected, for example to obtain statements as to whether the flow is laminar or turbulent or whether deposits on the ground or the surface (flotsam) have taken place.

Other fixed measuring devices are for example in the DE 27 03 439 shown.

The JP 57101720 shows a buoyant head, the arrangement should be easy to install and adjust without being affected by a water level change in an open channel.

From the FR 27 10 979 a sensor head is known, which is attached to a rope or the like floating. Attention is also drawn to the corresponding measuring arrangement available on the market, which is designed in a manner closely adapted to the document.

Another device for measuring the volume of liquid flowing through an open channel per time is shown in FIG DE 33 14 260 A1 known, where the height of a float is detected to determine the thickness of a fluid layer flowing below. The practical systems of this type are also unsuitable for deposit measurement.

The DE 40 16 529 C1 also shows a fixedly arranged in a channel flow meter, which has a probe that can be moved in a rectangular coordinate system in the channel. A calibration measurement is to be carried out in order to determine the flow profile and to conclude it by converting from a reference position to an average flow velocity. The calibration phase must be repeated as often as required, in particular with varying water levels or with channel cross sections varying due to deposits.

From the U.S. Patent 5,315,880 is a non-invasive method known. The measurement in the depth and especially in the direction of deposits is not addressed. Only a modeling of the velocities below the surface is made; this applies to corresponding devices on the market. Deposits are not recognized there.

A fluid meter for sewage and the like with ostensibly minimal flow restriction is further from the GB 2 029 030 A known. This meter can be moved in the flow, in a threaded spindle or the like, but this means a lot of effort and also requires long operating cycles.

The DE 196 49 193 A1 concerns the measurement of currents in very wide rivers. It is discussed that in rivers the flow level can vary and also the maximum and minimum flow depths are known at those locations where vertical average flow velocities are to be measured. The DE 196 49 193 does not address the question of how to consider deposits.

The U.S. Patent 5,821,427 relates to a measurement in a pipe or the like, wherein a first sensor arrangement is provided on the tubesheet. Due to the arrangement at the tube bottom, the disclosed device is susceptible to contamination and deposits. Deposits are therefore neither theoretically nor in practical devices measurable. From the DE 195 42 232 A1 An ultrasonic flowmeter for liquid or gaseous media is known, with the Abtragungserscheinungen should be avoided on the Rohinnenwand. For this purpose, two ultrasonic flow meters are attached to the outside of a pipe.

From the DE 32 23 393 A1 For example, a method is known for determining the flow rate of liquid in a channel region through which free liquid flows. Runtime measurements are provided by beams that are directed at the surface.

From the DE 44 43 483 A1 are known method and apparatus for measuring fluid flow, wherein a float is aligned in the flow direction and is directed from one end of the float an ultrasonic signal against the channel bottom, which is received from the other end of the float. The arrangement should be suitable for flow measurement on liquids, gravity channels, etc. Ultrasonic signals are directed by a float on the channel bottom and it is stated that the measuring path between the transmitter and receiver through the entire height or depth of the channel, so that the Flow velocities at all levels affect the ultrasound signal. If different flow velocities exist at different heights above the channel bottom, this should have an effect on the time or frequency of the receiving ultrasonic signal, so that different flow components enter into a measurement result representative of the entire signal height.

The DE 197 40 549 A1 relates to a measuring method in which flow profile measurements in inhomogeneous fluids are performed in real time with an ultrasound system. It is stated that a case of application concerns the flow characteristics in open waters such as in the off-shore area or in the area of marine biology, as well as the industrial process technology, where inhomogeneity concentrations are to be recorded.

From the DE 196 50 621 A1 As is known in the art, a measuring device for detecting the flow rate is known. In this device, a float is hung in a channel on a tether or cable connection, sending echosound signals to the channel ceiling and floor of the channel. It is mentioned that with the sensor arrangement, the flow rate and the flow height is detected. It is further stated that in ground-fixed measuring sensors a functional complication with corresponding incorrect measurements due to dirt deposits and Schmutzzusetzungen due to the preferably moving in the deeper areas of the channel denser or firmer material can occur.

The The object of the present invention is the measurement accuracy without increasing complicated evaluation of several signals.

The The object is achieved by the measuring arrangement according to claim 1 and the Measuring method according to claim 6 solved. Preferred embodiments are in the subclaims.

According to one The first essential aspect of the invention is thus in a measuring arrangement for measuring currents in fluids at varying heights with a sensor head detecting the fluid flow from a specific position and a holder for placing the sensor head in the specific position, suggested that the pivotable support is rigidly formed to the sensor head at least Substantially fluid flow independent in predetermined Angle to the fluid surface to arrange.

In order to First, the present invention teaches that the measurement accuracy the measuring arrangement substantially increased can be done by not simply moving the sensor up and down, but while also maintaining a predetermined orientation to the fluid surface becomes. It is further stated how this can be done in a simple way, namely by a specified mechanical design of the holder. It is so possible the measuring accuracy to increase significantly in particular without complicated electronic evaluation of several Signals or the like.

The sensor head is preferably one with which pulsed signals are transmitted and received, as can be seen for example from US Pat DE 197 40 549 A1 is known. In particular, the emitted and received signals may be pulsed ultrasonic signals. The flow velocity time is determined in response to the echo signature.

The Measuring arrangement is in principle applicable when the fluid flow in guided a predetermined fluid bed is, ie in pressure pipes, pipelines or open channels. While the formation of the measuring arrangement for fluid flow measurements in principle Benefits, a preferred application is the measurement of currents in suspended matter containing fluids such as waste water and the like where the Invention can be used with particular advantages, because here the level heights are strong vary.

In In a particularly preferred variant, the sensor head is at one Float mounted, which in turn as part of the holder via rigid spacers with a solid anchorage verbundne is connected, in particular articulated. The sensor head can be arranged below the fluid surface especially at the bottom of the float.

In In a first variant, the holder is preferably vertical Rail formed along which the float up and down is movable. By a correspondingly elongated guide on the rail will the rigid coupling of the float to the guide and thus the desired angular orientation then received.

Prefers is however a holder with a storkbeak-like Parallel rocker whose one end is hinged to the float and whose other end is hinged to a fixed anchorage. These Training possible it, at fluid levels, which lie below the point of articulation at the fixed anchorage, to keep the rocker at least largely out of the fluid. This is therefore advantageous because so the deposition of material the swingarm is avoided or significantly reduced and also no influence on the fluid flow, in particular near the Sensor head through the bracket is to be feared. This is even more so when the float is streamlined is formed.

In a particularly preferred variant, the sensor will have a means, in particular an evaluation means, in order to determine the flow profile in a height-resolved manner, wherein in particular a layer-by-layer dissolution of the profiles can take place. The measuring arrangement is accordingly particularly preferred for sensors whose signals are evaluated as in DE 197 40 549 A1 described.

If such a means is present, the sensor is preferably formed so that the layer heights variable are so that at low fluid levels, the layers closer together. This elevated the measuring accuracy continues.

The Layer height resolution change can in response to signals from a sensor head made its Signals emitted at an angle to the first sensor head. Especially the sensor head used to determine the layer height resolution can in particular, the distance between the float and the dormant Underground intended to emit vertically downward, while the for the actual fluid flow inserted sensor head diagonally against the current and the fluid surface emitted. The second sensor head is typically down emit. Then it is possible the layer height resolution depends on the height of the flowing fluid set. Alternatively and / or additionally, it is possible to obtain a reference between the fluid surface and a fixed, d. H. not movable in a fluid-level-dependent manner with the holder, Make reference point. This is especially useful in pipes, where the float is a given distance from the upper pipe inside at low fluid level. A measurement both upwards as well as down is meaningful when it is expected that in the fluid bed substances are deposited. It can then be referenced on a firm, d. H. not on the moving part of the holder fluid level dependent mutable attached reference point, be it a given height above the maximum expected fluid height or a predetermined distance to the inner tube top, the absolute water level can be determined above the Fluidbettgrundes and by determining the distance between the fluid surface and the no longer moving fluid background the thickness of the flowing fluid layer be determined. From a difference of both values can then be closed, to what amount are already deposits have formed. This is particularly advantageous when very accurate Wastewater quantity measurements desired and / or an indication of the need to perform a channel clearing is desired.

The Restricted invention but not on it, the accuracy to effect the arrangement only by improving the holder but also teaches how optimal benefit from the increased measurement geometry can be pulled when deposits are expected.

To becomes a measuring method proposed, in which for the measurement of fluid flows in fluids with varying fluid level and / or varying deposits on the Fluid bed reason, including measurement signals directed in the direction of the fluid bed substrate to off the returning one Signals on the flow velocity to close, it is provided that the height of the sensor above the non-flowing fluid bed bottom it is determined this height is divided into a number of layers and a fluid flow measurement for this Layering performed will, so that one of the height of the sensor the non-flowing one Fluid bed dependent Layer thickness results.

This measurement methods is first basically everywhere interesting as where deposits of fluids etc. can occur in fluids. So It can be used to advantage with sensors that are fixed in pipe walls, culverts and the like are installed. The method uses but at the same time in optimal Determine the correct geometric orientation of the sensor in which the sensor is held in a predetermined orientation to the fluid surface becomes.

It is possible in principle, the height above ground to determine with the same sensor, with which also the flow velocity is detected. This is possible, by z. B. a pulsed ultrasonic signals emitted obliquely against the fluid bed background Sensor is used, from the time signature of the echo signal on the flow rates closes. It can be provided that those lower layer heights, at which has a flow velocity is determined below a predetermined limit, as non-flowing and thus identified as a standing fluid bed substrate. The remaining layers can then be redistributed. Preference is, however, if a dedicated Sensor is provided, based on the signal to the height of the sensor above the fluid bottom can be closed.

This elevated the security with which deposits of still flowing fluid are distinguishable.

Especially it is preferred when the height above ground against a fixed reference is determined to be between the absolute Fluid bed substrate and deposits to distinguish. This can a sensor immovably fixed above the fluid surface and their height measure up; through another sensor in the fluid, which measures down then the difference between the deposition height can be determined. alternative and / or additionally Is it possible, to keep the sensor moving on the float and its distance to a fluid independent Reference point, for example, an upper pipe peak to determine.

The Invention will now be described by way of example only with reference to the drawings described. In this shows:

1 a measuring arrangement according to the present invention.

To 1 includes a general with 1 designated measuring arrangement 1 for measuring flows in fluids 2 at varying heights h one from certain position the fluid flow sensing sensor 3 and a holder 4 to the sensor 3 to arrange in the specific position, with the holder 4 is designed to be described manner, the sensor head 3a of the sensor 3 at a predetermined angle α to the fluid surface 2a to arrange.

The measuring arrangement 1 is in a pipe 5 arranged, through which the fluid 2 along the arrow 6 flows.

With the fluid 2 passing through the pipe 5 is conducted, it is in the present case to suspended matter containing wastewater.

The sensor 3 includes a signal generation and evaluation circuit (not shown). This is designed to be on the sensor head 3a To produce pulsed ultrasonic signals and from the time signature of the associated echo signals on the flow rate of the fluid at predetermined levels infer. The sensor 3 also has a second sensor head 3b which emits pulsed ultrasonic signals generally vertically downwards and from the time until the return of the pulse to the height h of the sensor 3 above the non-flowing fluid base 2 B closes. Next is the sensor 3 a pulsed ultrasonic signal upwards emitting sensor head 3c provided, the echo signals are used to the distance l to the upper pipe inner wall 5a that is to the upper vertex of the pipe 5 to determine. The sensor head 3a assigned signal generation and evaluation circuit is per se conventional and as in the DE 197 40 549 A1 described.

The holder 4 includes a float body 7 , a parallelogram swingarm 8th and anchoring 9 , The sensor 3 is on the float body 7 arranged. This has such a buoyancy that the sensor heads 3a . 3b at its bottom 7a are located below the water surface in the water, but the upward-facing sensor head 3c above the fluid surface 2a is arranged. At the float 7 are the two arms 8a . 8b the storkbill-like parallelogram rocker 8th arranged at its upper end 8c at the pipe-anchoring 9 is articulated. At the pipe-anchoring 9 is the level sensor 10 anchored at a height j above the fluid surface 2a that the fluid surface 2a even at maximum expected fluid levels below the sensor surface of the level sensor 10 lies.

The Evaluation circuit (not shown) is adapted to the flow of the Layer by layer to record fluids and the thickness of the layers for which the detection takes place in each case, to change.

The measuring arrangement is used as follows:
First, the distance l between the float and the upper pipe apex is determined. To do this, from the sensor 3c Ultrasonic pulses emitted, determines the time to return the echo and from the running time to the position of the float 7 closed. Then the height of the float 7 above the non-flowing fluid base 2 B certainly. This happens with the sensor 3c or 10 in the same way. In the deposit-free case, it is found that the height l and the height h taking into account the thickness of the float body 7 together give the pipe diameter, which indicates the deposit-free case as such.

In response to the determined height h of the fluid level, a division of the fluid level into 16 equal parts is then carried out and with the sensor head 3b determined for each of these 16 different heights a respective flow velocity. From this flow profile, taking into account the known pipe profile, the total flow rate can be determined.

Now increases the fluid level, so the distance of the float body is reduced 7 to the upper pipe vertex 5a , that is, l becomes smaller, while h, the height of the float body 7 above the non-flowing fluid base 2 B , increases. Alternatively, the distance l or the position of the float body including the sensor 3a and 3b by means of the level gauge 10 be determined. When changing the filling level is always the float body 7 through the stork-beak-like parallelogram wings parallel to the fluid surface 2a held so that for each level the bracket 4 holds the sensor at the predetermined angle α to the fluid surface. There are thus no distortions due to inclinations of the float body 7 or the sensors.

The Sum of the sizes h and l again gives the pipe diameter, indicating that none Deposits are present in the pipe. It will after the rise the fluid level in turn the change in the sizes h and l determined and made an adjustment of the layer height thicknesses and turn with now larger layer thicknesses a measurement of the flow profile for 16 different heights carried out. From the flow profile and the known pipe diameter then becomes the new total flow rate precise certainly.

Now stores substances below the sensor 3b off, as in 1 between fluid background 2 B and pipe 5 indicated, the sum of h and l no longer corresponds to the total pipe diameter, but is smaller. This indicates that a deposit has taken place and this may be the case If necessary, be reported to a control center, if necessary, trigger a removal of the deposits.

The distance between the sensor 3 and the non-flowing fluid background 2 B is again subdivided into 16 parts and a profile of the flow is created, which now only takes into account the heights in which a fluid flow is still present. Again, the total flow rate from the fluid profile can be determined taking into account the tube cross-section and the deposit made therein. When the level h drops below a critical level, either because of very small amounts of fluid flowing through the pipe and / or due to very high deposits, the number of fluid layers for which the flow is determined is reduced from 16 to a smaller number ,

If a defect occurs in the sensor 3c on, the measurement is the height of the fluid surface 2a below the top of the pipe 5a using the level sensor 10 determined and this value used accordingly.

Claims (6)

Measuring arrangement for fluids guided in a fluid bed of predetermined geometry, comprising a sensor means ( 3 ), comprising a sensor ( 3c . 10 ) for measuring the fluid surface height in relation to a fluid-independent reference point and a sensor head arranged at a predetermined angle to the fluid surface ( 3b . 3a ) for determining flow height and flow velocity, and an evaluation circuit for evaluating the signals originating from the sensor means, wherein the evaluation circuit is designed to determine a fluid flow profile in response to the sensor means signals, from which lower layers, where a flow rate is below a certain limit, to determine as not flowing, and thus to detect deposits taking into account the fluid surface height related to the fluid-independent reference point and the given fluid bed geometry. Measuring arrangement according to the preceding claim, characterized characterized in that they for use in a pressure line, pipeline or an open Flume is provided as a predetermined fluid bed. Measuring arrangement according to one of the preceding claims, characterized in that for the arrangement of the sensor head ( 3a . 3b ) at a predetermined angle to the fluid surface a float ( 7 ) provided on a rigid support ( 8th . 9 ), in particular a stork beak. Measuring arrangement according to the preceding claim, characterized in that the sensor means ( 3 ) is designed for measuring the layer heights, fluid heights and deposits. Measuring arrangement according to one of the preceding claims, characterized in that the sensor means ( 3 ) one from the sensor ( 3c ) different, further sensor ( 10 ) for measuring the absolute fluid height and in particular is arranged immovably above the fluid surface. Measuring method for measuring flows in a predetermined fluid bed of fluids with varying fluid level and / or varying deposits in the fluid bed background, wherein the fluid is passed through a predetermined fluid bed and flow altitude and speed-indicative signals with a particular float substantially independent of fluid flow at a predetermined angle to Fluid surface arranged sensor means ( 3 ) and an evaluation circuit fed by its signals, characterized in that a fluid flow profile is determined, from which lower layers in which a flow velocity is below a certain limit value are determined to be non-fluent, the fluid surface height is determined based on a fluid-independent reference point, and then detected for deposits taking into account the fluid surface height related to the fluid-independent reference point and the given fluid bed geometry.