JPS5834319A - Eddy type flowmeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vortex bIL type flow meter, in particular to a vortex bIL type flow meter which is configured to produce an output signal with a frequency proportional to the fluid flow rate to be measured.
The vortex generator/sensor unit has a vortex generator/sensor unit that is torsionally supported 8'ft in the flow tube by a torque tube connected to an external torque transducer by a sensor link assembly, and provides a It also relates to a vortex #L-type flowmeter that can measure the density of the vortex.

It is well known that under certain conditions, if there is an obstruction in a flow tube, a vortex will periodically occur. When the Reynolds number is small, the downstream flow is laminar, but as the Reynolds number increases, a regular vortex pattern known as a Karman vortex results. The frequency of these vortices is a function of flow rate.

Various control functions? This phenomenon has been exploited in the development of flowmeters that measure the volumetric flow rate of fluids being processed or delivered. Flow needles operating on this principle are disclosed in US Pat. Nos. 3,116,639 and 3,650,152. Eddy current flowmeters, such as those disclosed in U.S. Pat. No. 3,888,120 and U.S. Pat. 20. .

Here, I will limit the content to IW for reference only, but I will explain how the fluid vibrations generated by the vortex generator attached to the flow tube are pivoted by a torsional suspension that makes only small movements of the vanes. The present invention discloses an eddy current flowmeter that is sensed by a downstream balanced vane sensor. This vortex generator diverts the incoming fluid flowing tL through it, and both 11
(Vortices are generated alternately in the flow rate of the flow rate of the fluid to be measured. The vortices passing through both sides of the valve generate a fluid force that alternately generates clockwise and counterclockwise torques, with a frequency proportional to the flow rate of the fluid to be measured. , Sen-9-i mechanically vibrated.

The details will be kept here for reference only, but a sensor that operates with a tension lever equipped with a pair of parallel legs installed symmetrically with respect to the axis of the flow tube is used to generate vortex generators. A vortex style needle has been proposed which is twistedly supported behind the .

In a sensor operating with a tensile deer, the vortices leave the vortex generator (5) one after another and appear alternately on both sides of the gap between the #J'tl organism and the downstream cell, so that each The low pressure region created by the vortex displaces the stagnant region created in this gap as a result of fluid flow through the vortex generator at the forward position of the sensor leg on the side closer to the vortex, and then passes all the way around the other leg of the sensor, creating a torque about the pivot axis. This torque alternately causes the torsionally supported sensor to oscillate at a frequency dependent on the flow rate.

The vibrations of the torsionally supported sensor are detected by a trans-no-length, a sophisticated strainer whose one end is attached to a trunnion or shaft that projects through the flow tube and whose other end is attached to a fixed resilient beam. be done. The deformation of the beam that occurs when the shaft oscillates is converted by strainage into a corresponding electrical signal whose frequency is representative of the flow rate.

V of a vortex flowmeter with a torsionally supported sensor
The key advantage is that this device is effective and precise for circular flowmeter measurements of liquids and gases.
Although N, type flow needles are significantly superior to conventional eddy current instruments (6), the T,I configuration of these torque transducers has certain drawbacks that make them less than ideal. I can't say that.

Proposed Torque Transducer (1) In the configuration H1 eddy current flowmeter, a torque transducer combined with a torsionally supported sensor comes very close to the ideal requirements of the purchased detection system. . These ideal requirements are:

Person: The instrument must have a complete detection system with sensitivity that makes it effective in measuring low-pressure gases.

B. Inherent robustness f: $, output system must have to make the instrument suitable for fluid flow measurement that can withstand adverse conditions.

The detection system must be insensitive to mechanical vibrations, shocks, and acceleration forces that the C1 flow meter receives.

D. The detection system is capable of operating over the wide temperature range and very wide frequency range commonly encountered in gas and liquid measurements.

E. The detection system is virtually immobile and the problem does not limit mounting or mounting of the torque transducer.

F. The detection thread is relatively inexpensive and has a compact structure.

In the proposed torque transducer configuration, the transducer cooperates with an axial extension having two parallel flat surfaces on either side of which the torsionally supported sensor of the eddy current instrument is pivoted. do. The transducer assembly is in a common plane and has an axis IJrf, one surface of the long part,
a first pair of parallel-connected piezoelectric elements provided between the first preload blocks; constituted by a second pair of parallel connected pressure 1! elements provided rl
1. The movement of the extension is limited to the extent that it is provided by a preloaded element - Ans so that the extension moves very little.

Two pairs of parallel connected elements are connected to the output terminal rL1
As polarized with respect to the plane of the shaft extension, the alternating clockwise and counterclockwise torques cause the interconnected elements to generate alternating current pressures of the same frequency.

In the proposed vortex flow meter, the sensor in each case is torsionally supported on a shaft that projects through the hole in the flow tube, the free end of this shaft being connected to an external transducer to control the vibration of the sensor. 1 corresponding to vJ! Convert to air signal. To prevent fluid from leaking through this hole,
The shaft has an elastic seal therethrough, made of Neozolene or a material with similar elasticity and physical properties.

Even when measuring very hot or very cold corrosive fluids.
Although resilient seals function effectively under normal operating conditions, under extreme conditions they are unsatisfactory.
Resilient seals may fail under extremely high operating conditions, such as with steam or liquid salts, or at cryogenic temperatures with cryogenic liquids, such as liquid nitrogen or acid salts, or liquefied natural gas. Put it away.

The content here is kept for reference only, but the torsional support of the sensor in the proposed eddy current flowmeter is as follows:
The configuration connects the sensor (9) to an external transducer without the need for an elastic tube, therefore the flow tube remains undisturbed and the instrument remains highly effective even under extreme conditions. can operate.

The sensor is supported in a torsional manner on a pivot perpendicular to the flow direction axis of the flow tube behind and downstream of the vortex generator, the torsion support being inserted into a hole in the flow tube. , with a torque tube welded thereto, and the tip of the torque tube is
It is welded to one end of the sensor to form a sealed structure that prevents fluid from leaking from the flow tube.

In operation, as the incoming fluid stream is diverted by the vortex generator and flows through it, vortices fall from the vortex generator one after another, appearing alternately on either side of the sensor and alternating directions around the pivot axis. generates a torque that changes, causing the senna to vibrate at a frequency proportional to the fluid #, -:. These vibrations are converted into corresponding electrical signals by an external torque transducer connected to the sensor by a link assembly that extends coaxially into the torque tube and has a rod ii at its tip.

(lO) Thus, this proposed flowmeter has no seal,
Therefore, sealing problems that occur under extreme temperature + W conditions do not occur. However, this instrument requires two separate pieces, as it has both a fixed vortex generator and a torsionally supported sensor positioned one aft of the other in the flow tube, making it possible to This is contrary to the aim of simplifying the structure and obtaining a compact and low-cost instrument.

In view of the above, the main object of the present invention is that the necessary vortex generation and detection functions are integrated into a single torsionally supported body (hereinafter referred to as vortex generator/sensor unit). An object of the present invention is to provide a vortex flow meter.

Although the invention is preferably practiced in a sealless splitter having a link assembly to an external transducer, a torsional attachment that eliminates the need for a resilient seal, the invention is not limited thereto; It is also applicable to a type of arrangement in which the shaped body extends through a hole in a thread or flow tube and is supported on a shaft with a resilient seal.

An important advantage of a flow meter according to the present invention that utilizes a torsionally supported vortex generator/sensor unit is that it lends itself to a compact, low cost instrument, yet has separate vortex generators and sensors. It inherently has the operating characteristics and advantages of an eddy current meter.

Briefly, these objectives are achieved in a vortex flow meter that is capable of precisely measuring the flow of a liquid or gas even under extreme operating conditions. The fluid to be measured is guided through a flow tube having a vortex generator/sensor unit 1 which is twisted and supported on a pivot axis perpendicular to the flow direction axis of the flow tube. The torque tube is inserted into the hole of the vortex generator/sensor unit and its tip is welded to one end of the vortex generator/sensor unit to form a sealed structure that prevents leakage of fluid from the tube. It is equipped with

In operation, as the incoming fluid stream is diverted by the unit and flowed through it, vortices flow from the unit alternately on either side thereof, creating an alternating redirection torque around the pivot axis; The unit oscillates at a frequency proportional to the fluid flow rate, so the cono unit acts both as a vortex generator and as a vortex sensor. These vibrations are converted into corresponding electrical signals by an external torque transducer connected to the unit by a sensor link assembly that extends into the torque tube and has a rod welded to its tip. .

BRIEF DESCRIPTION OF THE DRAWINGS In order to provide a better understanding of the invention, as well as other objects and features thereof, the invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 1, which schematically shows a first embodiment of a vortex generator/sensor unit according to the invention, it can be seen that the unit shown in end view has a trapezoidal cross section.

The unit is torsionally supported transversely to the flow tube 11 along a pivot axis passing through its center of gravity CG (j), so that the unit, statically and dynamically balanced, I can freely vibrate around the vertical axis.

In operation, the unit (10) acts as an obstruction in the flow tube and branches (13) the fluid flow to be measured, alternating from the -10,000 side to the other side at a repetition rate proportional to the fluid flow rate. create a vortex.

As a result of this vortex-generating action, the moving vortices migrate to the left and right sides of the flow tube and pass on both sides of the unit.

In Figure 1, vortex Ll appears on the left near the leading edge of the unit, and vortex L! shows the state at a specific moment when it appears on the right side near the trailing edge of the unit.

Since the vortex in the fluid stream creates a low pressure region within it, the low pressure created by the vortex L1 on the left side creates a fluid force F' t f on the right side of the unit, and this force F.

is applied to the leading edge of the unit in a direction that causes the unit to rotate clockwise around the pivot @CG. at the same time,
The low pressure region created on the right side by the vortex L2 generates a fluid force Fxf on the left side of the unit, and this force F! is applied to the trailing edge of the unit in a direction that attempts to rotate the unit 9 times clockwise around the pivot axis.

Therefore, the forces F1 and F! generates a large clockwise torque.

The position +gi B in Figure 81 is the vortex L3 and L for the unit.
The relationship of 4 is the opposite relationship (1
4) shows the subsequent instantaneous state in . Since the vortex L3 creates a low pressure area on the right side, the resulting force F3 is applied to the left side with respect to the leading edge of the unit, thus tending to rotate the unit counterclockwise about the pivot axis. Vortex L
4 creates a low pressure area on the left side, the resulting force F4 is applied to the right side with respect to the trailing edge of the unit and thus tends to rotate the unit counterclockwise, causing force F3
and F4 are in a cooperative relationship.

The unit 10 is mounted in a very rigid torque tube, as described below, or is otherwise torsionally mounted, so that it is extremely susceptible to movement << of the unit kJJ'f1. in either direction from the neutral position. However, it only makes small vibrations. Mechanically, this unit therefore functions effectively as if it were fixed. This is because although it is sufficient to excite the transducer to produce a flow electrical signal, the micromotion is small and therefore does not counteract the fluid vortex generation process.

In other words, the reason why it has been thought that it is necessary to separately provide a fixed vortex generator that generates periodic vortices and a flexible sensor that detects vortices in an eddy current flowmeter is as follows. This is because accurate flow measurement requires that the position of the vortex generator remain virtually unchanged. However, by providing an integrated vortex generator/sensor unit according to the present invention, it is possible to perform both seven functions in a single unit. This is because the minute movement required for detecting a vortex is compatible with the vortex generation function.

In FIG. 2, the integrated vortex generator/sensor unit 12 has a T-shaped cross-section, with a pivot (not shown) coincident with the center of the unit and perpendicular to the axis of fluid flow. , twisted and supported within the flow tube.

Again, the relationship of the vortex to the instantaneously existing force shown in position gives rise to clockwise motion around the pivot axis,
A subsequent instant, denoted by 1 iM B, produces a counterclockwise movement.

In Figure 3, an integrated vortex generator/sensor unit 1
3 has a triangular cross section, clockwise motion occurs at position +RA and counterclockwise motion occurs at position B.

Longer vortex generators are preferred, but torsional forces are created around all but the cylindrical body with circular cross section. Therefore, the present invention is also applicable to non-cylindrical vortex generator/sensor unit shapes other than those shown in FIGS. 1-3, which have a rectangular cross section. Torsively supported sensors have the advantage of being immune to all forces other than those causing torsional motion, and thus serve to minimize noise signals caused by vibrations and other external forces.

Referring to FIGS. 4, 5, and 6, there is shown a single-piece eddy flow meter according to the present invention.

The instrument includes a cylindrical flow tube 14 having end flanges 14A and 14B. In fact, the end flange is inserted into the Zoroses line that transports the instrument or gas! IF bolts are tightened to the end flanges of the upstream pipe and downstream pipe (17).

The integrated vortex generator/sensor unit 15 is connected to the flow tube 1
4, this unit has a wide front face for the incoming fluid, and a rear face with an intermediate beam 15B of rectangular cross section, the same width as the beam and the same width as the front member. A rectangular grate front member 15 connected to a rectangular par rear member 15C at its center band.
It has A.

This unit 15 is torsionally supported on a pivot that coincides with its center of gravity and is perpendicular to the longitudinal axis X of the flow tube 14. The incoming fluid stream impinging on the unit 15 is separated there, creating Karman vortex turbulence.

It is housed in the intermediate beam 15B and is pivotally supported by upper and lower torque tubes on a pivot axis.

The lower torque tube 16 has a stepped base portion 16A inserted into and welded to a similarly shaped hole in the flow tube 14, and a tip 16B welded to the lower edge of the intermediate member 15B. . As seen in FIG. 5, the upper torque tube 17 has its stepped base portion 17A inserted into a similarly shaped hole extending through the wall of the flow tube 14 (18).
The end of the pace section is arranged to be welded to the flow tube. The distal end 17B of the torque tube 17 is inserted into a socket formed at an upper level of the intermediate member 15B of the unit and welded thereto.

This unit is connected to an external torque transducer by a link assembly that transmits the torsional movement of the upper torque tube 17 to the torque transducer 18. Preferably, the transducer is of balanced piezoelectric construction. Transceiver v18 is a stationary preload
Melon! A pair of sub-assemblies 1 are respectively inserted between the lock and each side of the rod extension 19 of the link assembly, each sub-assembly 1 comprising a pair of side-by-side piezoelectric elements. The rod extension 19 is connected by a connecting member 20 to a main rod 21 which extends into the torque tube 17 and is anchored to and welded to the distal end of the tube.

The coupling member 20 is constituted by a pair of opposed cup-shaped flexible diaphragms welded together such that their circular flanges form a cell similar to that of an aneroid barometer. The torque transducer 18 is
Cut into an annular upper part 22 of the separator, this upper part 22 is connected by a cylindrical intermediate part 23 to an annular lower part 24, and a connecting member 20 is provided within said separator. The lower part 24 is fixed to the flow tube 14 by a screw clamp f (not shown).

Transducer 8 detects movement of unit 15 as unit 15 oscillates around the pivot and generates a signal with a frequency proportional to the flow rate of the distal leg fluid. The torsional suspension of the unit provided by the torque tubes 16 and 17 limits the rotational motion to extremely large torques to minute movements on the order of 1 micron in either direction from the neutral position. Therefore, the unit is virtually stationary during operation.

In this instrument construction, the torsional force produced by the torsionally supported unit 15 is applied to the outside of the upper torque tube 17 which is interposed in the flow tube 14. Due to the resulting torsional movement V of the torque tube 17, ') by the main rod 21, the connecting member 20 and the rod extension 19 of the link assembly,
It is transmitted to an external piezoelectric torque transducer 1B.

Therefore, with this construction there is no need for seals. This is because the flow tube is kept clear by the welded torque tube structure.

However, although this structure solves the problems that occur when using elastic seals and allows the flowmeter to operate under extreme temperature conditions, the sealless structure is not effective as an actual flow measurement device. A whole new set of problems arises that must be solved for instrumentation.

First, the torque tube must be strong enough to withstand internal flow needle pressure and to withstand the forces encountered at maximum fluid flow. At the same time, the torque tube must be sufficiently stiff to provide unit 15 with a resonant frequency characteristic that is sufficiently higher than the maximum operating frequency of the instrument over the range of expected flow rates. This latter requirement is necessary because if the resonant frequency of the unit is near the maximum ξ operating frequency of the flowmeter, the unit will resonate and cause a large disturbance to the output signal. Deroru.

No problems arise with steel or other suitable metal torque tubes that meet these strength and hardness requirements.

-The torque sensing system must be sensitive to low-speed fluid flows. A sensing system that meets strength and hardness criteria will act to dampen the force transmitted to the torque transducer by several orders of magnitude.

The gain of the electronic system that receives and processes the flow-to-flow signal from the piezoelectric torque transducer can be increased to compensate for the signal attenuation caused by the required stiffness of the torque tube; Background or noise generated from sources other than fluid flow throughout the pipe can result in an unfavorable signal-to-noise ratio. This is because the noise component is now relatively large with respect to the attenuated flow meter 1d.

Therefore, in order to improve the +m-to-noise ratio, the noise (22
) component must be attenuated. But 1! Before explaining how the active member 20 and the separators (22, 23, 24) perform this damping action, we must first consider the noise source. flow of
In this case, the torsionally supported unit 15 is connected to the flow tube 14.
The mounting is relatively close to Franz 14A and 148. Therefore, when the flow tube 14 is inserted into the flow path by delt-tightening the seven flanges of the upstream and downstream tubes of the entire flow tube flange S), a very large force is applied to the flanges 14A and 1411. Thus, if the upstream and downstream tubes are in an industrial process line where vibration is easy, the surfaces of the flow tubes 14A and 14B will be subjected to vibrational forces.

If an external torque transducer 18
If it is attached directly to the Bib, it will be transmitted to the flow tube.
Most of the force is also transmitted to the transducer,
The resulting noise component of the signal will be very large.

The balanced piezoelectric torque transducers are X, Y.

/Q'J) It has excellent signal removal ability on the second side, but
Even with L, there is undesirable noise caused by vibration. If you do this, you will reach a considerable level in the trenches. Next, we will explain how to attenuate the force caused by these vibrations.

It can be seen in the drawing that the upper beam 22 of the separator is relatively thick and therefore stiff. However, the cylindrical intermediate portion 23 and the annular lower portion 24 are intentionally quite thin and flexible. As a result, no matter how small the outer part 1114 is bent, the cylindrical middle part 23 and the annular F side part 24 will bend, causing the upper part 22 of the separator to which the transnozer 18 is attached to be bent. I can only apply a moderate force. As a result, the vibrational force transmitted to the transducer 18 is reduced, and the noise component in the signal is thereby cut.

With a properly designed separator structure, the forces transmitted by the separator to the transducer 18 will be several orders of magnitude smaller than the forces present in the instrument body. In turn, the effectiveness of the flexible lower side 24 of the separator is increased by giving it a convoluted or corrugated diaphragm shape to more effectively absorb forces applied to it.

Furthermore, this separator structure plays a role in the thermal characteristics of the instrument detection system. Because the thin lower and intermediate metal parts 24 and 23ii, the instrument body (i.e. flow tube 14)
and a transducer 18 attached to the upper section 22.
An extension path with poor heat conduction is formed between the two. This extension effectively insulates the transducer 18 from rapid temperature changes, allowing the transducer 18 to operate at near ambient temperatures despite its proximity to the instrument body.

The connecting member 20L of the sensor printer assembly is connected to the main rod 21 and the rod extension 19.

It functions as a torsional force connection that minimizes the effects of bending and misalignment forces. This connection s@20 serves to dampen the impact when the torque tube 17 is bent by a force acting on the unit 15, thereby attenuating the bending force (25) generated on the sensor link assembly, and these bending forces from reaching the transducer 18.

Also, does the connecting member 20 play a certain role in the thermal characteristics of the detection system?
Fulfilling. As in the case of the separator, the connecting member 20θ
1. Extends the thermal conduction path between the unit 15 and the transducer 18, thus insulating the transducer from sudden temperature changes.

Furthermore, the connecting member 20 performs a more important function.

This is because when a sudden temperature change occurs in the flowmeter, the torque tube 17 and sensor link assembly
) temperature level? present. As a result, the expansion/contraction difference caused by the temporary temperature difference causes a large force to be applied to the transformer saucer 15 in the absence of the connecting member 20. However, by providing a coupling member between the transducer 18 and the torque tube 17, the differential expansion and contraction caused by the temporary temperature difference is largely absorbed by the coupling member, so that no significant force is applied to the transducer.

Although a preferred embodiment of an eddy current flowmeter having a single vortex generator/sensor unit according to the invention has been shown and described (26), many variations and modifications can be made without departing from the spirit of the invention. One thing will be understood.

[Brief explanation of the drawing]

FIG. 1 shows a vortex generator according to the invention having a trapezoidal cross section/
Schematic view from the end of one embodiment of the sensor unit, at an instant when the force exerted by the vortex produces a clockwise torque, on the order of 1!1 tA, and then at subsequent moments when the force produces a counterclockwise torque. Figure 2 shows the unit in position B. Figure 2 shows the T-type 1u? FIG. 3 is a schematic end view of a second embodiment of a vortex generator/sensor unit according to the invention, indicated at positions A and B, having a triangular cross-section; FIG. 4 is a schematic view taken from the end of a third embodiment of a vortex generator/sensor unit according to the invention, indicated at positions A and B, FIG. A plan view of the vortex flow needle structure including the fourth embodiment of the unit, FIG. 5 is a cross-sectional view taken along the plane shown in FIG. It is an isolated perspective view of the unit. t o , t 2 , 1 a , 15... unit, 11° 14... flow tube, 14A, 14B... flange, 16° 17... torque tube, 1 Day... Transju?, 19... Rod head section, 20... Connecting member, 21... Main rod, 22.23.24... Separator. 41 Applicant Fisher End -y - Takashi Kusano, 11 members of the company

Claims (9)

[Claims] (1) (4) a flow tube into which the fluid to be measured is introduced along the flow direction axis; -gn. Therefore, the fluid is blocked and vortices are generated alternately on both sides, and the vortices vibrate the circumference of the pivot shaft at a frequency proportional to the flow rate. , a torque tube is connected to one end of the unit to prevent fluid leakage A'i from inside the torque tube, and the vibration is caused by micro-movement so that there is no interference between the vortex-generating action and the movement of the unit. a vortex generator/sensor unit that is restricted; a main rod connected to the transducer, extending into the torque tube and connected to the distal end of the torque tube, and transmitting torque tube motion to the transducer via the rod; (2) The flow tube is provided with a flange at its end that can be delt-fastened to the end flanges of the upstream tube and the downstream tube of the line for transporting the fluid. Eddy current flowmeter. (3) The vortex flow meter according to claim 1, wherein the support body includes a second torque tube whose tip end is connected to the unit at the other end and whose pace is connected to the flow tube. . (4) The eddy current flowmeter according to claim 3, wherein the torque tube is made of metal with high strength and is relatively hard. (5) The torque tube has a hardness that provides the unit with resonance characteristics whose resonance frequency is sufficiently higher than the maximum frequency in the operating range of the flowmeter. . (6) The main rod is connected to the transducer, and the vortex flow according to claim 1 further comprises a rod extension connected to the main rod.
-Elbow. (7) The Rondo extension part is connected to the diaphragm ↑,
7. The vortex vIL type flow gauge according to claim 6, wherein the vortex VIL type flow gauge is connected to the front and main shafts by a material II to attenuate the transmission of bending force applied to the front and first torque tubes. (8) The unit is constituted by a single body with a trapezoidal cross-section, whose +11 diameter is larger than its superior surface, and which impedes the inflowing fluid. ．． 'i 4f of patent claim
ii. Section 1. First eddy flow mIt. (9) +41J fl unit has a wide curved surface of 7
The first area of interest is formed by a unitary body with a rectangular front part facing the fluid, and this front part is connected to the rear part by a beam passing through said pivot axis.
Flowmeter described in section. al The unit has a triangular cross section with the base facing the incoming fluid. Search range 1
The eddy current flowmeter described in Section 1.