DE2035545C - Device for measuring the flow rate of a flow medium - Google Patents

Description

The invention is scaled up below with reference to some. The openings 31,32 of the channels 21,22

the drawing illustrated embodiments are in diametrically opposed areas

described. It shows the cylinder 1, approximately in the middle part

F i g. 1 is a schematic view to explain its height. The position of the openings 31,32 relative to

Formation of Karman vortices, 5 flow results in particular from FIG. 2A. The

2A and 2B are schematic diagrams of a flow supplied by the fluid source 5

Leadership example of the invention, medium cleans the surface of the cylinder 1 in

F i g. 3 A is a side view of the embodiment in the vicinity of the openings 31, 32.

example of FIG. 2A and 2B used cylindrical being the cylinder 1 in the flow F within

Flow _{obstacle, l0 of} a channel 10 so immersed that the longitudinal axis of the

F i g. 3 B a cross section along the line XX of the cylinder 1 and the connecting line of the openings 31,

F i g- 3 A, 32 both flies perpendicular to the direction of the flow,

F i g. 3C shows a cross section along the line YY of the so behind the cylinder 1 at regular intervals

F i g. 3 B, stand and alternate vertebrae from both sides

F i g. 4 is a schematic illustration to explain FIG. 15 according to the theory mentioned at the beginning. In the

Operation of the embodiment of FIG. 2, vortex generation changes the flow velocity

F i g. 5 shows a basic illustration of a further expanse of the flow medium along the surface of the

leadership example of the invention, cylinder 1; as a result, it also changes with the

F i μ. 6Λ is a perspective view of another form of vortex formation and the removal of the vortex from Execution of a cylinder 1 which can be used within the scope of the invention, the pressure of the fluid on decylindrical Flow obstacle, opposite sides of the cylinder 1. In the case of the

F i g. 6Ii and 6C cross-sections along the lines X-X illustrated embodiment that flows from the source 5

the F i g. 6 A or along the line K-K of FIG. 6 B, cleaning currents supplied via channels 21, 22

F i g. 7 A, 7 B, 7C and 8 A, 8 B, 8 C further execution means continuously through the openings 31, 32

Cylindrical flow obstacles (clears and cleans the surface of the cylinder 1. The amount

speaking the F i g. 6A, 6B and 6C), the outlet through the openings 31,32 of the channels 21,22

Fig. 9 A another variant (in partially entering fluid depends on the pressure of the

cutaway view), fluid F near the openings 31,32.

F i g. 9 B and 9 C cross-sections along the lines XX Immediately after a vortex e near the opening 31

(Fig. 9A) or K-K (Fig. 9B), 30 is generated (see. Fig. 4) and a vortex develops from

F i g. 1OA has another embodiment (separated in partial cylinder 1 near the other opening 32,

wise sectioned representation), the flow velocity is in the range of

F i g. 10B and IOC cross sections along the lines of the surface of the cylinder on the side of the opening 32

XX (FIG. 10A) or KK (FIG. 10B), larger; the pressure of the fluid F on the

11 to 13 cross-sections through different sides with the opening 32 thus becoming smaller. As a result further Embodiments of the cylindrical flow pass through the opening 32 to prevent more cleaning (as shown in Fluid. On the other hand, in F i g. 10B). in this case the flow velocity of the flow

In the exemplary embodiment of FIG. 2A and 2B determining means F on the side with the opening 31 smaller; the cylindrical flow obstacle 1 is seated (after that of the fluid F on the cylinder 1 in hereinafter also referred to as cylinder) to generate the vicinity of the opening 31 pressure is thus applied the Karman's vertebrae have a circular cross-section. greater; as a result, the reduced by the Channels 11, 22 with a small diameter are, with their opening 31, a quantity of cleaning streams emerging End inserted into the cylinder 1 and point to the medium. As a result, the amount of the opposite sides openings 31,32. By 45 cleaning these exiting through the openings 31, 32 Openings 31, 32 of the channels 21, 22 will be a part of the fluid depending on the formation of the of the fluid F as a function of the eddies on opposite sides of the cylinder I. Pressure changes of the flow ^ by means of F near the The change of the openings from the openings 3I, _32 31, 32 inserted into the channels 21, 22; this the amount of fluid causes a change in the The pressure change is caused by the vortices generated. The channels 21, 22 are - as still by means of in the area of the throttles 41, 42 in the channels is described later —is used for this purpose.a flow 21,22; the number of those formed near the opening31 means for cleaning the surface of the cylinder 1 vortex can thus be determined by performing the Andes. In the channels 21, 22 are throttling tion of the speed or amount of the channel 41,42 provided. The other end of the cleaning fluid permeating channels 21, 22 55 21 is solid connected to a fluid source 5 which is provided, for example by the hot wire 6. the channels 21, 22 with an approximately constant pressure. The electrical signal supplied by the sensor 6 is the Cleaning fluid supplies. A sensor 6, the change in the flow speed of the pure one Detects fluid movement, for example, proportional flow fluid and is over a hot wire, the movement of the StrönuingsmiUels fio the amplifier 7 a (not shown) suitable not obstructed, for example, a measuring device is supplied in the channel 21.

arranges and represents changes in the flow As in the embodiment explained, the cleaning speed or the flow rate in the channel fluid is always on both sides of the zy-21 fixed. An amplifier 7 amplifies the output signal blown out or blown out of the flow obstacle 1. of the sensor 6 and delivers a signal at the output 65 is pressed, a constant cleaning of the takes place connection 8. surface of cylinder 1; this avoids

Figs. 3 A, 3 B and 3 C show the cylindrical that dust or other solid particles are to be «

Flow obstacle 1 of Fig. 2A, 2B create a larger surface and the formation, growth and

interfere with the shedding of the Karman's vertebrae. The F i g. 6 A to 6C so in the fluid F a sensor 6 is arranged in the channel 21 and immersed determined that the longitudinal axis of the cylinder 1 as well as the thus the changes in the flow velocity connecting the openings 35, 36 approximately perpendicularly the always clean cleaning fluid; which lie to the direction of flow of the fluid F, Sensor 6, on the other hand, does not come directly with 5, so it is in the cavities 33,34 through the opening measuring fluid in contact. Even for 35, 36 incoming fluids via this opening thus the fluid to be measured, openings 35, 36, the cavities 33, 34 and the way of connecting If the gas is heavily contaminated, the number of duct 38 may vary depending on the pressure the vortices that are formed can be precisely determined. As a result of the formation of eddies it is displaced Furthermore, the sensor is in a tube outside the cylinder near the openings 35, 36 or as a result of the detachment see flow obstacle 1 is arranged, this vortex prepares to be generated. The cleaning, maintenance or replacement is not difficult. Fluid coming out of openings 31, 32 of the opportunities. Channels 21, 22 exiting into the cavities 33, 34, cleans

In the case of the FIG. 5, these cavities as well as the openings 35, 36 and embodiment contain the channels 21, 22, through which the 15 then allows the cylinder 1. If the fluid is supplied in pure fluid, one of the cavities 33, 34 According to the formation or number of openings 31, 32, which are displaced on opposite separation of the eddies, the dement sides of the cylinder 1 changes in the axial direction and the fluid pressure is arranged in the hollow sequence. Here, too, in the spaces 33, 34. This in turn influences the amount of channels 21, 22 throttles 41, 42 are provided. In both 20 of the cleaning fluid coming out of the channel channels 21, 22, sensors 6, 6 'are arranged here, J ^; e openings 31, 32 from and into the cavities 33, 34-changes in speed of the channels 21, 22 occurs. The number of vortices that are formed can thus be determined by the penetrating cleaning fluid by determining the changes in the fluid. The arrangement also contains two resistors 63, 64 connected in series with the cleaning fluid, between whose free channels 21 are measured. . A DC voltage source 65 is connected at the ends. Since in the case of the explained cylindrical flow, the sensors 6, 6 'and the resistors 63, 64 form an electrical bridge circuit together as an obstacle to sucking in or squeezing out the flow, with the direct voltage source 65 on a diagonal in the area of the openings 35, 36 - depending on the formation and detachment of the eddies is ordered, while the other two diagonals occur, the condition of the eddy formation can be connected to the amplifier 7 by means of points. sucking in and squeezing out the fluid

In the embodiment of FIG. 5 that will be controlled. The formation of eddies can result from cleaning flow means, that from the source 5, which continues because of the presence of strangles, on the circumference of the cylinder 1 in two atmospheric fluctuations and eddies in addition to the other zones facing away from each other are stabilized by several in 35 Karman vortices. When the limit axial Openings 31, 32 distributed in the direction of the .Strömungsmittel along the surface of a blow. In this way, objects of circular cross-section are prepared particularly effectively Dust or other solid particles from the top is to detach from the surface, so this will area of the cylinder 1 removed. Detachment favors when pushing away or away

In this embodiment too, the 40 bubbles of the fluid from the surface of the changes

The flow velocity of the cleaning flow object takes place near the separation point, while

in the channels 21, 22, depending on the rend, the detachment of the boundary layer is hindered or

Thinning of the fluid * F. which is hesitating when near this separation point

Vortices on the two cables of the cylinder 1 alternately - suction of the fluid takes place,

can be generated independently. And the output terminals of Fig. 45 In that shown in Figs. 7A, 7B and 7C

Bridge, as a result, output signals are obtained in a further exemplary embodiment of the invention

Depending on the number of eddies forming, cylindrical flow obstacle 1 on opposite

since the resistance values of the sensors 6, 6 'are located in longitudinally extending slots 35, 36 depending on the sides

ity of the flow rate in the, the openings 35,36 according to the embodiment Change channels 21, 22. 50 Fig. 6 correspond. The openings 31,32 of the channels

Also in the embodiment of FIGS. 6A, 21, 22 open into these slots 35,36. Otherwise ent-6 B and 6 C are the same for identical components speaks the design of the arrangement according to FIG. 6th Reference numerals as in the previously explained embodiments, the cylinder 1 according to FIGS. 7A to 7C used. The openings 31,32 of the channels as well as the arrangement according to FIG. 6 in the 21,22 open into cavities 33,34 in cylinder 1. Submerged in 55 fluid, the flow is opposite Sides are mediated in the axial direction depending on the formation and detachment divides a number of openings 35,36 in the cylinder, the vertebrae through the slots 35,36, the cavities the 1 provided. You stand with the cavities 33, 33,34 and the connecting channel 38 in the partition 34 in connection, so that depending on the 37 displaced. The cleaning fluid will changes in pressure 60 generated by the Karman vortices from the channels 21, 22 through the openings 31, 32 in of the fluid F is injected into the slots 35,36 and then exits the Cavities 33,34 arrives. In a partition wall 37 cylinder 1 from. The flow rate of the A connecting cleaning fluid is also suspended here between the two cavities 33, 34 Extension channel 38 is provided through which the two hollow pressure changes in the slots 35,36 and rooms are connected to each other. In one of the 65 thus on the number of on the outside of the Channels, for example in channel 21, is the feeler 6 of the cylinder 1 forming and separating Karman vortex arranged from. Here, too, the number of developing

If the cylindrical flow obstacle 1 according to the Karman vortex is determined by measuring the change in

The flow velocity in the channels 21, 22 is determined as i? DÄi 6, 6 '.

ATif Ä ™ / *? mi SÄ nuniSlTden "V rbindunjskanal 38 in the partition In the practice, this execution in

From equation (4) it follows that the quantity Q is proportional to the speed to be measured.

As mentioned, in the embodiment according to FIGS. 9 A to 9 C, the discharge pressure P ₁ , with which the cleaning flow from the source 5 is produced

37 displacement or pressure fluctuations fluid, f. Even if som.l the ce-

Here, too, "strömün | smillels" precedes the Z * of the f "dem -bindu ^"

ührimg we! thus the number of vortices formed due to the change in the flow rate in the channel is determined with the aid of sensor 6. i uh the F i g. 9 A to 9C corresponds to im small, so the energy is that in d durcj, d - ^ π «^ ₌ ~

In such a case, the flow rate of the Cleaning Strfimungsm.ttcls automatically reduced, so that this cleaning agent in the Cleaning or removing dust or debris does not interfere with the formation of eddies. Is there-

is cclirfert, e

¹ Dn- ,. of the strand

Si? „I M undΓ S. d» »g _S k _a nals 38 vc, _ä , ä, k ,. In this case «^

mTdem dt Renf ₈ ung, -S, romungs. ₃ S you a "h automatically <1" Slremunismcne. Q des% cclirfert, for example> ut den. Cleaning fluid. so daO dust and / or ¹ d Stags other, ** ^ J * "£

, «, Η ™ £ ^ Z ^ the change de. Flow in de, OftnungM immediately den, U, ^ P of the fluid / · in aen noniräne jj, j «, uct

-nd = n _{r :;} look

"U,"

™ e ° Auslrittäuek density

Relationships:

(P ₀

P)

ssss

_{2 m}

^ _{2 (} 2)

₅ o

where K ₀ and K, are constants.

Since in the embodiment example of ^ 9C the output pressure P _{1 is} approximately equal to the pressure P ₀ of the ^^ üS th to be measured, results from the
following equation (3):

O ^Λ ιΡι

ο s

<y _{ßej the exemplary embodiment of FIG} . 10A to IOC is the free end of a pipe part which is common to the channels21,22 provided with throttles41.42. open to the atmosphere; The sensor 6 for determining the movement of the fluid is arranged in the channel 21. Moreover, the design corresponds to the g in the F \. 9 A to 9 C with the exception of the sensor 9. A special cleaning flow _{fi bej the Ausföhrungsbcisp} i _{el of}

^. _{hi Wegge} i s _ass; the atmosphere is

feel belut. Deftflhler 6 is not in the, canal 38 ν ^^ _{Q p} . _g ^ _{but in the Cana} , ^ _arranged

_The execution of the fig. 1OA to IOC can with

good result if the static

Pressure of the fluid to be measured F is smaller

Print out the flowing rem. flow meter:

to.gt

(4) ^ _{Slrömungsmitt} el _£ F with P, _n its density with _eo, the flow velocity v _0, the atmospheric pressure mil P ,, the density of the atmosphere with ρ ,, the amount of current flowing through the pipes cleaning Strömungsmiltcls mil Q and mean pressure des

309619/79

Allow flow medium in the cavities with P, so set up the following equations:

(P ₀ -P) = K ₀ Lt ₀ (P ₁ - P) = Ii ₁ (j,

where K ₀ and K _{1 are} constants.

If P _{1 is} equal to P ₀ , i.e. if the static pressure P _{0 of} the fluid F corresponds to the atmospheric pressure P ₁ ^{, the following equation 1} is obtained from the above equations (5) and (6):

K ν ² - K f) ² (T)

Solving for Q gives the flow rate of the cleaning fluid flowing through the channels:

Q-

K ₀ Qo

Here, K is a constant corresponding to the root expression.

It can be seen from equation (8) that the flow rate β of the cleaning fluid is proportional to the speed i "of the fluid to be measured Fist.

The mode of operation and advantages of this exemplary embodiment correspond to those in FIG. 9 A to 9 C, so that further explanations are not necessary.

Also in the embodiment of FIGS. 10A to IOC the sensor 6 can be arranged in the channel 38 instead of in the channel 21.

In the embodiment of FIG. 11, a groove or a hole g is provided in the partition 37. The free end or the opening of the single channel 21 through which the cleaning fluid emerges opens into the groove or the hole g, so that the cleaning fluid flows through this hole g of the channel 38 and thereby the hole g and the channel 38 cleans. The sensor 6 for determining the movement of the fluid is arranged in the channel 38 in this exemplary embodiment.

The variant according to FIG. 12 largely corresponds to the arrangement according to FIG. 11; however there are two Sensors 6 and 6 'are provided in channel 38.

According to FIG. 13, two channels 21, 22 are provided for the cleaning fluid, one end of which opens into two bores or semicircular grooves 31a, 32a in the cylinder 1. The free ends of these semicircular grooves 31a, 32a are open at the openings 35, 36, so that the cleaning fluid blown out of the openings of the channels 21, 22 cleans the parts near the openings 35, 36.
In the above explanations it was assumed that

ίο that the end of one or two channels to the The atmosphere is opened or connected to a special cleaning fluid source. Man However, you can also let the ends of the channel open out in pure water and use this pure water as a cleaning fluid use. In this case, there is no need for a separate flow source; the mean pressure in the cavities 33, 34 is also automatically when the flow rate increases in the Voids decreased; the flow rate of the

ao cleaning fluid is thus influenced according to the fluid velocity to be measured, an effective cleaning of the cylindrical flow obstacle 1 is always achieved.

In the explanations, one uses as

The sensor for determining the flow of fluid expediently a hot wire, a thermistor, a strongly temperature-dependent resistor, a thermocouple od. The like. In these cases, the temperature change is used, which is caused by cooling takes place on the part of the fluid. Furthermore, it is not absolutely necessary to use a cylindrical flow obstacle with a circular cross-section; flow obstacles with an elliptical or rectangular cross section can also be used.

Since according to the invention the cleaning of the flow obstacle, the cavities, bores, openings etc. with the pure cleaning fluid and the sensor for determining the fluid movement is located in the tube through which the clean cleaning fluid flows, can determine the number of Karman vertebrae that form safely and precisely with a very simple structure Device can be measured even if the fluid to be measured is itself contaminated. Will the sensor is placed in the channel that is outside the cylinder, so it can be serviced very easily and exchanged if necessary.

For this purpose 3 sheets of drawings

Claims (10)

2 The invention relates to a device for measuring the flow velocity of a flow medium 1. Device for measuring the flow * - with a cylinder speed of a fluid * immersed in the fluid, with a drical flow obstacle to generate cylindrical 5 Karman vortices immersed in the fluid and with emem the number of s.ch see flow obstacles Generation of forming vortices detecting feelers
Karman vortices as well as with a sensor that detects the number of a cylindrical flow change s 1 (cf. Sensor (e.g. 6) which is arranged behind this flow obstacle 1 in a channel (e.g. 21), through which an inward rotating Karman vortex alternates from both sides of the surface of the flow obstacle (1) e generated. This cleaning fluid can be supplied, the eddies e ^{1 of which} lie in two parallel rows against one another - the flow velocity is offset with the formation of the other behind the flow obstacle.
Karman vortex changes. Between the number / those formed per unit of time 2. Apparatus according to claim 1, characterized in that 15 Karman vortices, the flow velocity K of the characterizes that for supplying the cleaning fluid F and the diameter υ ύ · ^. Flow means two, each with a sensor (6, 6 ') cylindrical flow obstacle there is now icversehene channels (21, 22) are provided with the following relationship, where K is a constant: approximately diametrically on the circumference of the cylindrical flow obstacle (1) opposite one another so V
Openings (35, 36) are in communication. D. 3. Apparatus according to claim 2, characterized in that the openings by a number of arranged distributed in the axial direction One can therefore determine the flow velocity de, Individual holes are formed. 25 fluid by measuring deF number / sid. 4. Apparatus according to claim 2, thereby determining the forming Karman vortex. The finding indicates that the openings through one in the number of vertebrae are made by a feeler
axially extending slot formed in a known measuring device of this type miIi ;. will. eier feeler the vortex frequency directly at the 5. Device according to claim 2, characterized in that the surface of the cylindrical flow obstacle indicates that the two channels (21, 22) in each This, however, has the disadvantage that contaminants Cavity (33,34) of the flow restriction cleaning the fluid, for example in the nisses (l) open, whereby between these two fluids contained small solid particles, with the extent of the flow obstacle over the even formation and detachment of the Karmandie diametrically opposed openings in 35 vortices on the surface of the flow obstruction Interconnecting cavities affect the separation and thus also related to the measurement result (37) counterfeit with a connecting channel (38). see is. The invention is therefore based on the object 6. Apparatus according to claim 1, characterized in that a measuring device of the type mentioned at the outset is so designed that, for the supply of the cleaning agent 40, two channels (21, 22) provided impurities in the fluid are reliable even when the fluid is present which takes place in two cavities (33, 34) of the streamline - measurement of the flow velocity,
This object is achieved according to the invention by the circumference of the cylindrical flow obstacle that the sensor is arranged in a channel, opposite openings (35, 36) in 45 through the connection of the surface of the flow obstacle and can be fed from one another by a cleaning fluid whose partition wall (37) is separated and in which a Karman vortex connecting channel (38) which receives the flow velocity changes with the formation of the sensors (6). is provided. By supplying a cleaning flow 7. Apparatus according to claim 1, characterized by means of the surface of the flow obstacle indicates that the pressure with which the cleaning is there is the influence of impurities outflow fluid on the circumference of the cylindrically switched and an even formation and detachment of the see flow obstacle (1) emerges, such as Karman vortices guaranteed. The arrangement of the equal to the static pressure of its sensor in a channel through which the cleaning flow velocity Flow to be measured 5 ;, fluid is supplied, protects the sensor from being held. at the same time against the influence of such solid impurities 8. The device according to claim 1, thereby achieved and thus results in a further improvement in the indicates that the cleaning flow measurement accuracy. The arrangement of the sensor in one medium supplying channel (z. B. 21) a throttle such channel is possible because - like experiments position (e.g. 41). 60 confirmed - the flow rate of the 9. Apparatus according to claim 1, characterized in that cleaning fluid is strictly dependent indicates that the cleaning fluid is changing from the formation of the Karman vortices. Man through Air is formed by atmospheric pressure. is sufficient in this way that the feeler with the flow 10. Apparatus according to claim 1, characterized in that the flow rate of which, characterized in that the cleaning fluid 65 is to be measured, does not come into direct contact at all by a liquid at atmospheric pressure. This results in a long period of maintenance. f _rc j _e service life of the measuring device and a high Measurement accuracy.