RU82320U1 - PROBE VORTEX FLOW SENSOR - Google Patents

Abstract

1. A probe vortex flow sensor, comprising a flow transducer and a computing unit, respectively located at the ends of a hollow rod equipped with a sealing unit relative to the pipeline and reciprocating axial movement of the flow transducer in a direction perpendicular to the flow of the measured medium, the flow transducer housing being made in a rectangular ( in plan) with a measuring window-channel in which a trapezoidal flow body is placed, the lower end of which is rigidly fixed in the lower part of the housing of the flow transducer, two piezosensitive elements electrically connected by conductors to the computing unit, characterized in that a cylindrical insert with two through holes is installed in the upper part of the housing of the flow transducer to be flush with the lower surface of the cylindrical insert (upper surface of the measuring channel window ), respectively, of two piezosensitive elements with the possibility of direct contact with the measured medium and located sim metrically relative to the longitudinal axial line of the flow body past its upper end in the flow direction, with the cylindrical insert on top made with an annular flange, the surface of which is mated to the flow transducer body, fastened to the last weld, with a guaranteed gap (Δ) determined by the flanging size. ! 2. The probe vortex flow sensor according to claim 1, characterized in that the dihedral angles (γ) on the lower and upper surfaces of the measuring channel window at the inlet and outlet of the flow are sharp, and on both sides

Description

The utility model relates to measuring equipment, namely: to flowmeters of gaseous substances, and can be used to account for consumption, for example, compressed air, steam, hydrocarbon gases, etc. when transporting them through pipelines.

The well-known design of the sensor [1], consisting of a flow-through housing integrated in the pipeline, into the channel of which the body flows around is cantilevered, mainly in the form of a prism placed perpendicular to the channel axis (and flow), which vibrates in the direction perpendicular to the flow under the influence of pressure pulsations on its lateral sides. The sensor signal about the flow rate is the vibration frequency of the flow around the body in the stream, which is recorded and transmitted to the measuring device by transforming the bending stresses into the corresponding electrical signal, for example, using strain gauges or piezoelectric elements built into the flow body.

A significant drawback of such sensors is the fact that when switching to measuring the flow rate of a measured medium in pipes of large diameter (up to 1000 mm and more), the natural vibration frequency of the flow body is close to the frequency of the useful signal, which virtually eliminates the possibility of using this sensor design. The known design of flowmeters for large diameters of pipelines is very material intensive. The use of such flowmeters in such pipelines is limited due to the increased measurement error with large sizes of casings and channels. In addition, the complexity of installation, commissioning, verification, replacement is great.

The closest technical solution (prototype) to the claimed solution is a vortex gas flow meter [2], designed to measure the flow of gas and steam in pipelines. The operation of the sensor-flowmeter is based on the dependence of the frequency of pressure pulsations that occur in the stream behind the flow body during the vortex formation process, on the flow rate of the measured medium in the pipeline.

A known gas flow meter consists of a flow housing integrated in the pipeline and a flow sensor containing a flow body in the form of a trapezoidal prism rigidly fixed with ends in the channel of the housing perpendicular to its axis and two piezosensitive elements that are placed in the housing flush with the surface of the channel of the housing behind the flow around the body different sides of the latter. The electronic computing unit is located either directly on the housing, or taken out some distance from it and connected to the flow sensor via a hollow rod and cable.

The practice of long-term operation of these flowmeters has shown that the cause, if not the main, increased measurement error is due to vibrations of masses connected to the sensor (pipelines, risers, etc.), including external short-term impacts in the form of shocks [3].

Thus, the goal of creating the inventive design of a probe vortex flow sensor (otherwise, the required technical result) is to provide a well-known technical solution of higher consumer properties, namely: to ensure reliable information signal while minimizing the design dimensions and material consumption of the sensor for pipelines with diameters from 100 mm and up to a maximum of 2500 mm.

The required technical result is achieved by the fact that in the inventive probe vortex flow sensor, according to the prototype, comprising a flow transducer and a computing unit located, respectively, at the ends of the hollow rod equipped with its sealing unit

relative to the pipeline and the reciprocating axial movement of the flow transducer in the direction perpendicular to the flow of the measured medium, moreover, the flow transducer housing is made with a rectangular (in plan) measuring window-channel, in which the trapezoidal flow body is placed, the lower end of which is rigidly fixed in the lower part of the housing flow transducer, two piezosensitive elements electrically connected by conductors to the computing unit, to the upper part of the transducer housing In addition, a cylindrical insert with two through-holes is additionally integrated for placement flush with the lower surface of the cylindrical insert (upper surface of the measuring channel window), respectively, of two piezosensitive elements, with the possibility of direct contact with the measured medium and located symmetrically with respect to the longitudinal axial line of the flow around the upper its end along the flow, and, on top of the cylindrical insert is made with an annular flanging, the surface Otori is associated with a flow transducer housing is fastened to the last weld, the clearance (Δ), determines the size of flange.

The dihedral angles (γ) on the lower and upper surfaces of the measuring window-channel at the inlet and outlet of the flow are sharp, and chamfers are made on both side walls of the measuring window-channel at the inlet of the flow.

A gap (h) is organized between the end surface of the upper end of the flow body and the upper surface of the measuring channel window.

The drawing (figure 1) shows the design of the probe vortex flow sensor mounted on a large diameter pipeline (conditionally); in figure 2 is an enlarged scale of the flow transducer, in figure 3 is a section bB in figure 2, in figure 4 is a section bb in figure 3.

The probe vortex flow sensor (see figure 1) contains a flow transducer 1 and a computing unit 2,

respectively, at the ends 3 and 4 of the hollow rod 5, equipped with a unit 6 for sealing it relative to the pipeline and reciprocating axial movement of the flow transducer in the direction perpendicular to the flow of the measured medium. The housing 7 (see FIG. 2) of the flow transducer 1 is made with a rectangular (in plan) measuring window-channel 8, in which a trapezoidal flow body 9 is placed, the lower end of which is rigidly fixed in the body of the housing 7 of the flow transducer 1. To the upper part of the housing 7 of the flow transducer, a cylindrical insert 10 with two through holes (not numbered in the drawing) is built in, which are flush with the lower surface of the cylindrical insert (with the upper surface of the measuring channel window), respectively, two ezochuvstvitelnyh member 11, conductors 12 electrically connected to the computing unit 2, with the possibility of direct contact with the measured medium and arranged symmetrically about the longitudinal center line of the body 9 for wrapping the upper end thereof downstream. The cylindrical insert 10 on top is made with an annular flange 13, the surface of which is interfaced with the housing 7 of the flow transducer 1, is fastened to the last weld 14, with a guaranteed clearance (Δ) determined by the size of the flanges. The piezosensitive elements 11 from above (from the side of the conductors 12) are fixed (pressed) by the threaded elements 15.

The dihedral angles (γ) on the flow transducer case at the flow inlet (outlet) into the measuring channel window are sharp, and chamfers 16 are made on the side walls of the measuring channel window at the flow inlet (see figures 3 and 4). The hollow rod 5 (bottom) is rigidly connected to the upper part of the housing 7 of the flow transducer 1 using a threaded cap sleeve 17 (see figure 1).

A gap (h) is organized between the end surface of the upper end of the flow body and the upper surface of the measuring channel window.

The probe vortex flow sensor operates as follows. When a medium flows around a measured medium, tearing vortices alternately arise on both sides of the body around the flowing body 9, which are the so-called Karman “vortex track”. The pressure pulsations in the Karman “track” are perceived by the piezoelectric sensors 11, converted by each of them into electrical signals, which are then sent to the processing unit and to calculate the flow rate, after which the information is presented to the user in the form of a corresponding indication in standard flow rate units.

On real objects, in operating conditions, interference is caused by an electric (informational) signal caused by the influence of hydraulic pulsations of the measured medium in the pipeline, as well as disturbing vibrations of significant connected masses (pipelines) on piezosensitive elements. The task is to minimize the intensity of the influence of interference sources: pulsations of the measured medium and the vibrations of the attached masses on the piezosensitive elements and, ultimately, on the useful (information) signal. This problem can be solved in two ways:

- the selection of a useful signal against the background of noise by adaptive filtering methods implemented by electronic circuits involving one or another element base [4];

- a decrease in the influence of mechanical influences excited by external sources of vibrations (attached masses) due to changes in the design of the object.

It should be noted that the implementation of the first path will be all the more effective the more successfully the design problems are solved, namely, the more the piezosensitive elements are protected from the influence of extraneous disturbances.

From these positions, we consider the design of the probe vortex flow sensor (see figure. 1), which from the point of view of the theory of oscillations

represents a physical pendulum, that is, a pendulum with a distributed mass. On an elastic hollow rod 5, from one end 4 (top) rigidly fixed in the pipeline, a load (flow transducer 1) is suspended, which, under the influence of disturbing influences, the source of which (in our case) is the pipeline vibrations and hydraulic pulsations of the medium being measured, forced oscillations, the amplitude of which is proportional to the amplitude of the driving force and substantially depends on the ratio between the frequency of this force ω and the natural frequency of the oscillating system (the attached mass of the pipeline section + flow sensor) ω ₀ [5]. Moreover, as in each oscillatory system, in this design, the amplitude of the oscillations of the system will be a function of the angular frequency of the disturbing force. But when the angular frequencies of the perturbing force and the natural oscillations of the system are equal, a resonance arises, an indicator of which is a sharp drop in the damping coefficient and, as a consequence of the latter, a correspondingly sharp increase in the oscillation amplitude. An important characteristic of an oscillatory system is its Q factor Q, which is determined by the ratio of the total energy of the system at resonance to the energy loss in one period:

where W is the total energy of the oscillatory system at resonance;

W _p - energy loss in one period. For a mechanical system, we can write [6]: (2)

where k is the coefficient of elasticity of the system;

β is the attenuation coefficient;

m is the mass of the system.

From the determination of the quality factor of the oscillatory system it follows (formula 1) that, firstly, the probability should be excluded as much as possible in the design

the appearance of resonance, and, secondly, if it appears, maximize the energy loss in one period. And from formula (2) it follows which way all this can be implemented.

Thus, the problem of reducing the oscillations of the probe vortex flow sensor from the disturbing influences of the external environment and fluctuations of the measured medium by changing its design must be solved in the following ways [7]:

- elimination of resonance phenomena;

increased dissipation of mechanical energy in the system (structural damping);

- dynamic damping (compensation) of oscillations;

- Introduction to the design of the oscillatory system of vibration isolation elements.

Ultimately, dampers, dynamic dampers and vibration isolators together form vibration-protective devices designed to one extent or another to reduce the influence of external disturbances on the vibrational activity of the structure, or in other words, as in our case, on the measurement process.

It is known [7] that the introduction of mechanical stresses into the design of concentrators in the form of threaded and welded joints (dampers) can significantly increase the energy loss inside the (vibrational system) of the structure, namely: weaken the influence of the energy of external disturbing vibrations due to its partial absorption, or, in other words, due to the work being done to overcome the friction forces. In the design of the probe vortex flow sensor (see figure. 1) there are three stages of vibration protection of the structural damping method:

1. rigid fastening of the hollow rod 5 (on top) using a union nut (not shown in the drawing) in the sealing unit 6;

2. fastening the bottom 3 of the hollow rod to the external thread of the upper part of the housing of the Converter 7 using a threaded cap sleeve 17 (see figure 2);

3. the suspension (decoupling) of the piezosensitive elements 11 (see figure 2), placed in the through holes of the cylindrical insert 10, fastened on top with the housing of the transducer 7 by means of a weld 14 with the simultaneous fixation of the guaranteed clearance (Δ).

Passive dynamic damping (compensation) of vibrations in the design of the probe vortex flow sensor is provided by an increase in the mass of the bottom of the flow transducer housing, which is made all-metal. The physical essence of dynamic dampers consists in counteracting object vibrations due to reactions transmitted to it by an additional attached body (mass), or in other words we can say that in order to maintain the regime of forced object vibrations, additional energy of an external oscillation source is required. It is natural to assume that the inclusion of dynamic dampers in the form of an attached mass in the oscillatory system makes it difficult for the system to transition to a resonance state. It should also be noted that the method of dynamic damping is more effective, the smaller the ratio of the masses of the oscillation source and the dynamic damper.

The introduction of a gap (h) between the end surface of the upper end of the flow body 9 (see FIG. 2) and the upper surface of the measuring window-channel 8 into the design of the probe vortex flow sensor is due to the need to unload the cylindrical insert with the sensing elements placed in it from the influence of extraneous disturbances, including from vibrations of the housing of the flow transducer connected to the main source of disturbing vibrations - the pipeline.

At its core, the design of the probe vortex flow sensor is a flow body (transducer housing 7, suspended

on a hollow rod 5), behind which vortices are formed along the general flow (Karman’s “vortex track”). At the same time, a measuring window-channel 8 is formed in the body of the flow transducer body, in which a trapezoidal flow body 9 is placed, which is the main source of pressure pulsations (vortices), the oscillation frequency of which is proportional to the flow rate of the measured medium, partially removed from the main stream to the measuring channel. The leading edges (the boundary of the body of the flow around and the measuring channel) are sources of additional turbulization of the flow — vortices that pass into the measuring channel and naturally interfere with the formation of stable pulsations (Karman's “vortex tracks”), which also causes an additional error in the measurement of the flow rate of the measured medium. The effect of introducing sharp edges into the structure (see Fig. 4) on the lower and upper surfaces of the measuring channel window in the form of sharp dihedral angles (y) can be explained by the example of the flow around a plate installed along a stream [8]. In this case, a boundary layer of the measured medium appears along the plate, the transverse dimensions of which increase along the flow. It is the boundary layer that is, ultimately, the cause of the formation of vorticity of the flow [9]. Sharp edges in the form of a dihedral angle on the lower and upper surfaces of the measuring channel window tighten or delay both the time and distance the formation of the boundary layer both on the upper (and, naturally, in the zone of contact with the measured medium of the piezoelectric sensors) and the lower surfaces of the measuring window -channel, and, therefore, its separation.

Chamfers 16 on the side walls of the measuring window-channel 8 also contribute to a smooth entry of the flow into the measuring channel (see figure 3).

Introduction to the design of the probe vortex flow sensor of sharp edges formed on the lower and upper surfaces of the measuring window channel in the form of sharp dihedral angles (γ) and chamfers 14 (see figure 3

and 4), contributes to the formation of a laminar boundary layer [8], which creates favorable conditions for the operation of piezoelectric elements 11.

The required technical result is ensured by the combination of the essential features (characterizing the proposed design of the flow sensor) of the above distinctive features, and the non-detection in public sources of patent and technical information of equivalent technical solutions with the same properties with undoubted industrial applicability of the claimed object implies its compliance with the criteria of the “utility model” , and implies legal protection by the relevant title of protection (patent) of the Russian Federation.

SOURCES OF INFORMATION TAKEN INTO ACCOUNT WHEN DRAWING UP A DESCRIPTION OF A USEFUL MODEL:

1. Kremlin P.P. Flow meters and quantity counters. - L .:

Mechanical Engineering, 1989.-701 p. (P. 367);

2. TU 39-0148346-001-92 “Vortex gas counters SVG. Technical conditions ”(Appendix B) of the CSA (No. 13489-00 in the State Register of Measuring Instruments of the Russian Federation) (prototype);

3. Zolotarevsky S. About the applicability of various methods of measuring flow for commercial gas accounting // Gas. Specialized Journal -2006, No. 3 (p. 14);

4. Baranov S.L., Boldin B.C., Abramov G.S., Zimin M.I. A new generation of vortex flowmeters // NTZh. Automation, telemechanization and communications in the oil industry. - M .: VNIIOENG OJSC, 2002. - No. 6 (p. 9-15);

5. Landau L.D., Akhiezer A.I., Livshits E.M. General physics course. Mechanics and molecular physics. Ed. "Science", Main Edition of the Physics and Mathematics Literature, 1969. - 400 p. (P. 109);

6. Sen A.S. Units of physical quantities and their dimension. - M .:

Publishing house "Science", 1977. - 336 p. (P. 136);

7. Vibrations in technology: Reference: In 6 vols. T. 6. 2nd ed., Rev. and Dop.-M.: Engineering, 1995. Protection against vibration and shock. - 456 p. (P. 33, 34, 148);

8. Altshul A. D., Kiselev P.G. Hydraulics and aerodynamics. Textbook for universities. Ed. 2nd, rev. and additional - M: Stroyizdat, 1975 .-- 323 p. (p. 235.236);

9. Marsden J. E., Chorin A. - Mathematical foundations of fluid mechanics. - M.-Izhevsk: Research Center “Regular and chaotic dynamics”, 2004. -204 p. (P. 92, 93).

Claims (3)

1. A probe vortex flow sensor containing a flow transducer and a computing unit, respectively located at the ends of a hollow rod equipped with a sealing unit relative to the pipeline and reciprocating axial displacement of the flow transducer in a direction perpendicular to the flow of the measured medium, the flow transducer housing being made in a rectangular ( in plan) by a measuring window-channel in which a trapezoidal flow body is placed, the lower end of which is rigidly fixed in the lower part of the housing of the flow transducer, two piezosensitive elements electrically connected by conductors to the computing unit, characterized in that a cylindrical insert with two through holes is installed in the upper part of the housing of the flow transducer to be flush with the lower surface of the cylindrical insert (upper surface of the measuring channel window ), respectively, of two piezosensitive elements with the possibility of direct contact with the measured medium and located sim metrically relative to the longitudinal axial line of the flow body past its upper end in the flow direction, with the cylindrical insert on top made with an annular flange, the surface of which is mated to the flow transducer body, fastened to the last weld, with a guaranteed gap (Δ) determined by the flanging size. 2. The probe vortex flow sensor according to claim 1, characterized in that the dihedral angles (γ) on the lower and upper surfaces of the measuring window-channel at the inlet and outlet of the flow are made sharp, and on both side walls of the measuring window-channel at the flow inlet chamfers. 3. The probe vortex flow sensor according to claim 1, characterized in that a gap (h) is arranged between the end surface of the upper end of the flow body and the upper surface of the measuring channel window.