DE2122713C - Vortex generating element for flow rate meters - Google Patents

Description

16 element according to claim 10, characterized in that that in the passage means for measuring the pressure fluctuation prevailing therein are provided.

17 Element according to claim 16, characterized in that that the measuring device is provided in the partition wall passage (52).

18. Element according to one of claims 1 to 15, characterized in that on the outflow surface (14 if) of the element (14) devices (MA) for measuring the pressure fluctuations along this surface are provided (Fig. 3).

W. Element according to any one of claims 1 to 15 characterized in that downstream of the Flements (14) a measuring device is arranged. the means (32, 34) for transmitting a Sound pulse transversely to the direction of movement of the vertebrae and means (30, 36) which on the fluctuations or changes in the transmission times of the caused by the eddies Addressing impulses.

The invention relates to a vortex-generating element for flow velocity meters, which is in has a substantially elongated cylindrical shape and is inserted transversely into a fluid stream is so that it creates alternating eddies on its opposite sides.

/ ο One in the stream of the moving flow

fi. Element according to claim 1, characterized in that it is produced by means of an inserted cylindrical object draws that the cylinder has a circular eddy current Ou section known as the Karman vortex street owns. mung with a certain vortex rate. At a

such vortex street in which the vortices periodically alternate from opposite sides of the cylindrical element, there is a certain relationship between the frequency /

9. Element according to claim 1, characterized in that the cylinder (14 E) has an elliptical cross section.

10. Element according to claim 1, characterized in that between the recessed surface sections (16, 18) there is at least one passage extending through the element (14).

11. Element according to claim 1 (I., characterized in that between the recessed surface sections (16, 18) a number of

the formation of the vortex, the diameter D of the cylinder and the flow velocity V, which is given by the equation

/ = K ■ VID

defines in which K means a constant if the flow is within a speed

3 4

keitsbercichs V lies, and outside this * area K thereby. that the recessed outer surface

represents a function of the speed I · '. Dem- sections each inwards from the edge into the

according to the flow velocity I 'can pass through the face of the element and the edge

Measurement of the excitation frequency f of the vertebrae, closer to the Sirömun ^ center Nirom, an outer one

be measured, the measurement being made directly. 5 approach of the element forms.

if, due to the flow conditions λ ', the element can also be so pronounced.

Is constant. j ^ u, j; _e edge at an angle of 70 to] il5 °

It has been shown that the desired linear / wipe the line connecting the edge to the Z \ lin-

Relationship between the flow velocity Γ dvr-midpoint and the connecting line / wipe and the frequency / the vortex generation not in the io the stagnation point of the fluid * at the Z> lighter

entire area that is arranged in the flow measurement to the center of the cylinder. Continue-

possible conditions. If a Z \ linde "r hildimeen of the invention result from the sub-

in a stream of a river flowing through a dysentery.

Fluid is introduced, and especially when the edges generated by the recesses, the flow rate over a loading 15 ran almost at the location at which the boundary certain value also increased -teilt K no Kd "- layer of the fluid * of the surface of the stante more. the measurement of the Wi-HEL rzeunimn element * when lying in the linear region Stro _he is then no Strümun ^ nv-suns. Although tearing hurry the mur ^ ccschwindigW. the recessed reasons for this discrepancy is not fully or undercut surface .-hen sections are known, it is assumed that they also go inwards from this edge in the flow rate profile of a * a section of the element surface. An outer, interrupted extension of the swellings and the cetien next to the Karman vortex elements above the fluid flow HiI- Straße in St. This arrangement results in the desired linear element flowing over a broader course of the fluid flowing along the cylinder surface of the restricted velocity range Current ratio of the equation explained at the beginning. Another advantage of the invention lies in the fact that it results in a tightness. Support for the control of the boundary layer demolition "" Numerous orders have already been received. 30 for the purpose of generating stable Karman vortex roads erum the Karman range under flow measurement conditions.

making eddy streets more stable. The following are preferred embodiments of the ISA

Patent specification 3 116 63 * described the invention with reference to the drawings.

The cylindrical element has a refined arrangement. It shows

Cross-sectional shape showing the flow resistance 35 F i g. 1 is a schematic representation of a bebei device for generating Karman- and avoids the disadvantageous vortex streets caused by cavitation and the effects of vortex generation for measuring the flow rates. speed.

this cross-sectional shape has a flow-favorable F i g 2 a vertical section through -ein a gen front portion, for example the form 40 fluid flow conducting tube, which is a

a semi-ellipse, and a cut away. Embodiment of the vortex-generating element in

recessed rear section. Supervision shows.

The previously known devices were, however, Fig. 3 a section along the line 3-3 in Fig. _.

not \> »'ιί satisfactory in the" generation of a line of intersection similar to that of FIGS. 4, 5 and 6 of FIG. 3 Relationship between the Strömüngsge- 45 views of modified embodiments of the

speed V and the vortex-generating vortex-generating element,

sequence f. Although regarding the avoidance of F i g. 7 a fig. 2 similar view of a part

Wobble and cavitation problems advantages of a modified cylindrical element,

could be aimed, the deviations from FIG. 8 a fig. 7 similar view of a further

the linearity at high flow velocities 50 modified embodiment of the cylindrical

still exist. Elements.

The task of the establishment is therefore primarily the fig. Q a section along the line W in rig. /, Creation of improved elements for generating F i 2. K) a F i g. Section similar to 9 through von Karmanwirbclstraßen, which enlarges the area of the measurable flow velocity. in the lowering element. 1111 there is a linear relationship between the flow Fig. 11 a section along the line UM in speed and the frequency of the vortex generation. Fig. 12 is a Fig. I similar to a still pending This object is inventively overall further modified embodiment of the eddy solves that the element 60 at its opposite-generating element.

Each side has a recessed surface section from Fig. ■. which has a back surface of the element arranged in a tube through a tube and that these recesses intersect the face of the element in one edge practically at a conventional, cylindrical vortex-producing part at which the boundary layer shows element in the form of a straight circular cylinder C. , of the fluid flow at in the linear region 65, it can be seen that the fluid F breaks away from the top of a stagnation point PI into two flows F 1 and F. divides, which then flow over the surface of the cylinder C. A preferred embodiment is characterized. The flow rate

The cylinder jacket surface increases with increasing The recesses 16, 18 are designed so that the flow is removed from the stagnation point P I until they intersect the inflow surface 14 w of the element 14 in the form of the boundary layer of the fluid at an interruption or edge 20, 22 , detachment point P 2 from the cylinder surface. Downstream, which are practically arranged at the point at the tear-off point P 2, vortices are formed alternately to which the boundary layer of the fluid at lower both sides of the cylinder C, which form the flow velocity of the cylinder surface, which is characteristic of the Karman vortex street. tears, reducing the linear relationship between the

The break-off point P 1 of the boundary layer does not lie in the vortex frequency and the flow velocity

fixed but changed periodically its position is introduced. As shown, for example, in Fig. 3

along the circumference of cylinder C as the erio proceeds, the edges 20 and 22 are under one

the alternating eddy currents and fluctuates at angles of about 75 to 85,

an average b / w. Middle position, which is the case of a The recesses are still arranged in such a way that

predetermined flow velocity is stationary. that they the discharge surface 14t / of the element 14 at

The middle position also changes its position with points 24, 26 which intersect inward of the edges 20.

the flow rate. At lower currents, 15 22 lie, that is, closer to one through the / \ Iin-

The air velocity lies along the average axis of the axis and the slope point P 1

rcißpunkt / '2 are typically on the upstream side of the Pc , which is also the plane of symmetry of the

CylindercrsC and shifts with increasing genes 14 forms. The edges 20. 22 therefore form the

dwindling gradually more towards the flow of water. outermost ans.ii / e around which the flow medium flows

If you wipe the angle with the protrusions or 40, learn ts 14, with read

rcißpunkt Pl connected cylinder radius and the fluid when it hits the element 14

divides the cylinder radius connected to the stagnation point P 1 into two streams F 1 and Fl . The currents / I.

denoted by H, it follows that while the Fl run along the inflow surface 14 "along, h"

eddy-forming flow conditions the position of the edges 20, 22 at which they reach

Tear-off point P1 in an area 75 ° <B <105 ° as the boundary layer of the fluid as a result of the existing

located. Recesses 16. 18 from the surface of the I I

Change in the angle H as a function of mcnts 14 breaks. The 'lurch the recesses 16 18

the speed can also be determined by means of the deformation of the surface.

Rc'tnotdvchcn number R VD Ί \ , in ■ «'·« ämli-iMi-i a / frequent outline of the (ιηι> /

rather V is the flow velocity. D the cylinder layer with resulting inevitable un.i

dcrdurchmcsscr and Vi the kinematic viscosity of stable generation of the Karman vortex street also Ki

dr> mean fluid. When the Reynold- high flow velocities. That with the

see number is less than 10 ^s . If the middle layer has recesses 16. 18 provided element 14 ore »;!

of the tear-off point Pl in a corner across the Karmanwirbclstrasse in a stable manner and far

75 <H <85; on the other hand, if the Reynold- 35 is free from the influences of currents,

Schc number with increasing flow velocity fluctuations and disturbances in the flow and

kcit the value 10 ^s . so the Ahrcißpunkt Pl stops over a wide area of Strömune '-

AhMrörnscite of the cylinder shifted towards where W speed a linear relationship between

is greater than 90. At the lower Reynolds frequency of the vortex removal and the currents

Number stands the frequency of the vortex generation practically 40 speed upright,

table in a linear relationship to the flow velocity. The cross-sectional shape of the recesses 16. 18

digkcit. can be \ ariated. In the embodiment

The vortices generated alternately on the cylinder Γ according to FIG. 3 are the recesses 16, 18 with

move downward from the cylinder where their deburring provided flat surfaces. One of those areas

Standing frequency detected by means of a sensor 12 45 forms the edge 20 or 22 and is perpendicular to the

which is inserted like this. that he depends on the direction of flow. The other part of marriage is in

Vortex is acted upon. The sensor 12 can be seen in one direction of flow - the first surface

known arrangement with an electrically heated downstream and is parallel to the flow F. In

be able to wire, the ends of which with an outside the F i g. 4 to 6 is the element 14 in terms of

of the tube 10 provided measuring circle are rounded. Se shape of its recesses 16, 18 modified. at

which an electrical current flow through the wire of the embodiment according to FIG. 4 has the EIc-

and the change in resistance of the wire ment recesses or bevels 16 A. 18 A

measures that of the one with the passing of the eddy on on. dk in each case by a single flat surface lengthwise «.

Wire-connected fluid displacement formed while a tendon of the cylinder

originates from. 55 in the modified embodiment according to

As mentioned, a conventional cylinder C returns Fig. 5, the member 14 having Ausspaningen 16B, 18 B

is provided according to Fig. 1 at high flow velocities. which have curved surfaces,

not the desired linear relationship between the soft undercut the edges 20. 22. In Fig. 6th

Frequency of the vortex formation and the flow is an element 14 £ of elliptical shape with a

speed. According to FIGS. 2 and 3 creates 60 larger main axis Dl and a smaller main

the invention therefore shows an improved vortex generating axis D 2 , with the flow direction

of element 14, which according to FIG. 2 is typically parallel to the main axis. The recesses

the wall of the pipe I§ is attached. The element 14 16 C .18C are each with two flat Planflächencn

has essentially elongated, cylindrical shapes, of which the direction of flow

stalt. is, however, located in a centrally arranged area parallel to the direction of flow and

borrowed area on opposite sides with two perpendicular to the front surface in the direction of flow

Giving away areas 16, 18 that have been cut out. to the Strümungsrichhing lies, similar to this with ^ er

those in Fic. 3 are shown in cross section. Aiivföhrungsform according to Fig. 3 of the FaI! isi. Dk

7 8

upstream edges 20 and 22 of the pressures prevailing in the recesses 16, 18

Savings 16 C and 18 C are practically also in an alternating manner. This

the point at which the boundary layer of the Stm pressure fluctuations let the fluid flow

medium flow at low flow alternation through the bores 40 through

speed from the surface of an elliptical 5 store or flow, first in one

ZylhiJers with axes D 1 and D 2 tears off. and then in the other direction. The frequency of the

The measurement of the pressure changes generated by the element 14 is the de-piercing frequency of the vortices. The vortex can be measured by means of the sensor 12 according to FIG. 1 proportional, which in turn is proportional to the quantity or, optionally, with the aid of the measuring device MA of the fluid through the tube as shown in FIG. 3 take place. This facility is un- portional. To measure the bores 40 The fluid flowing through the element 14 indirectly on the outflow side 14 can according to FIG attached and has an electrically heated wire F i g. 9 an electrically heated wire 12 r of a measuring run, which the displacement of the along the discharge device in the bores 40 can be arranged measures the area of flowing fluid, its flow and responding to the flow of the fluid, one immediately with the generation of the Karman 15 without hindering it.

wirbclstraßc related change or the holes 40 result in connection with the

Possesses variation. Recesses 16, 18 an improved formation of stable

3 shows a further measuring device I Ib of the Karmanwirbclstralkn. When the limit is met. For the sake of simplicity, the common layer shown in FIG. 3 of a measuring device X1A and 12 /? * o flowing fluids in a state are applied independently of one another. The measuring device finds that it can easily be torn off from the surface. Device 126 measures the passage of the Karman; while a suction of fluid F generated speed compo-mungsmitk! from the boundary layer the outline nenu-n ν 1 and ν 2 (Fig.3). The measuring device 12 B has a retarding effect. As a result, an infrasonic pulse generator 30 blows up. which feeds the arrangement of bores 40 at the edges 20, a transmitter 32, which in turn sends the sound 22 controlling the demolition of the boundary layer, including the pipe 10, towards a through the stability and reliability of the vortex receiver 34 sends out. The receiver 34 is to be further improved on the input of the pulse generator. 10 switched on. In Fig. K, a further modified bypass device sends out a new pulse each time. Guide horn of the invention shown in which when he receives a pulse from the receiver 34. instead of the bores 40 a parallel to the receiver 34 is connected to a frequency axis of the element 14 40 % demodulator 36, the output 35 of which extends between the recesses 16, 18, signal to a counter or computer 38 input Figures 10 and II is a further embodiment. During operation, the measuring device transmits 12 B Approximation form of the invention shown in which the Pulses from transmitter 32 to receiver 34. and the elements 14 on opposite sides with rows for the time required for the transfer depends on the holes 42 and 44. Each Bohab. whether a speed component ν 1 of 40 is within a recess 16 or 18 a vortex, which delays the transmission. at an edge 20 or 22 in a straight row or there is a parallel to the axis of the cylindrical element, which accelerates the transmission, of an accelerating wedge component ν 2. Seconded and communicated with a cavity 46 Depending on this, the receiver 34 generates or 48 inside the element. Signal transmitted through the Karmanwirbelstrasse frequency- 45 The cavities 46. 48 are through a central is modulated. This signal is separated from one another by the demo partition 50, which is provided with a dulator36 demodulated, the output signal of which is provided in bore 52. which as a passage to Speed * providing computer 38 - enabling fluid flow between measurement of the fluid is used. serves the cavities. By equalizing the pressure

7 to 12 further illustrate the cavities 46, 48 about the axis converted embodiment forms, in which the element 14 distributed uniformity of the streams 14 with passages' can be seen. which are sandwiched and thus bear regardless of a variable view of the spans 11, 18 and the velocity distribution over the diameter of fluid fluctuations between them over the pipe 10 for the stable formation of the cartridges manwirbclstraßen over the axial distance /, row of itself between the recesses extend- at. According to Fig. 10, the alternating flow bores 40, which close to the edges 20. mung through the bore 52 by a measuring device 22, at which the boundary layer rupture occurs, in a device with a straight row arranged in the bore parallel to the axis of the elements 14 trisch heated wire can be determined. Are arranged according to. According to FIG. 9, the flow medium flow F , which acts on the element 14 through slots, divides the rows of bores As and 44s can be replaced and the hole provided in the two streams F1 and F 2 on whose boundary layers dividing wall consists of a row at the edges Ζβ, 22 of the surface of the EIe of element arranged parallel to the axis of the element 14 tear off. As soon as vertebrae from element 14 consist of bores 52A.

go, corresponding pressure fluctuations arise 6 ₅ In addition to the various measurement or fullness in'ich-

near the adjacent mouths of the holes lines according to FIGS. I. 3, 9 and 10 can 40. As the eddies alternate from opposite- measurement of the velocity of flow at with

the sides of the element I ^ go out, the cavities vary: 46, 48 provided elements 14 also

take place by measuring devices, which are connected to the cavities in one, but of these remote chamber are arranged.

In addition, the measurement can also be carried out using the Wirbcl interference scheme, which consists of two

10

elements 14 arranged one behind the other are generated one of which is upstream of the other, with either or both of these elements the in the F i g. 2 to 12 illustrated manner are.

1 sheet of drawings

Claims (7)

Patent claims: 1. Vortex generating element for flow velocity meters, that is essentially elongated; has a cylindrical shape and transversely in a fluid stream is used. so that it alternates on its opposite sides occurring eddies generated, thereby characterized in that the element (14) on its opposite sides each have a recessed surface section (16, 18) and that these recesses the inflow surface (14 m) of the element in an edge (20. 22) prakli ^ -cii cut at a point where the boundary layer of fluid flow at im flow velocities lying in the linear range tears from the surface of the element. 2. Element according to claim I. characterized «indicates, that the recessed obscure sections (16. 18 ^ each inwards from the edge (20. 22) into the flow area (24 if) of the element (14) pass and the edge opposite the fluid flow an outer approach of the Elements forms. 3. Element according to claim 1, characterized in that aie edge (20, 22) wipe at an angle H of 70 to 105 ° 1. «The connecting line of the edge (20, 22) to the cylinder center and the connecting line between the stagnation point (P ₁ ) of the fluid (F) is arranged on the cylinder to the cylinder center. 4. Element according to claim 3, characterized in that the angle Θ in the range of 75 up to 85 °. 5. Element according to claim 1, characterized in that each recessed surface portion (16, 18) has at least one flat surface. 6. Element according to Ansp.uch 5, characterized in that each recessed surface section (16, 18) consists of two flat surfaces (16, 18; 16 / j, 16 C, 18C) , of which the rear in the flow direction parallel to the flow direction of the Flow center lies and the front in the flow direction is arranged perpendicular to the flow direction of the fluid. 7. Element according to claim 1, characterized in that each recessed surface section (16, 18) is formed by a curved surface (16 ß. 18 »). arranged parallel to the axis of the element (14)
Bohruneen (40) are provided. P element according to claim 10, characterized in that two cavities (46, 48) are provided in the interior of the cylinder (14). _the are interconnected through a passage (s2) in a partition (50) ""}? jnit the ^ oesparten Oberflächenabschniuen (16, 1t ") are through openings (42 44) in combination. 11 element according to claim 12, characterized in that that the openings (42, 44) are each a row of bores ... are (Fig. 1 I). 14 element according to claim 12, characterized in that that the openings are each formed by a slot (42.v, 44.?) (Fig. 1_). Is element according spoke 12. characterized in that the partition wall passage (= 2) consists of a series of bores (52 n) out