RU170705U1 - VICHREACOUSTIC FLOW CONVERTER - Google Patents

Abstract

The utility model relates to means for measuring the flow rate and amount of fluids, namely to vortex flowmeters. The vortex-acoustic flow transducer includes a measuring nozzle, in the cross section of which a poorly streamlined body is installed, an inlet conical transition from a round section to a square, an outlet conical transition from a square section to a round and an exchangeable unit with ultrasonic heads. The nozzle is made in the form of a section of a square pipe with a thickening in the middle parts with two flat contact pads located in the recesses on opposite walls of the nozzle behind the flow body, the width of the recesses being equal to the width of koby. The wall thickness of the pipe at the locations of the contact pads is an integer number of half-wavelengths of ultrasonic vibrations at the resonance frequency of the piezoelectric element. The diameters of the conical transitions are equal to the length of the diagonal of the pipe, and the taper angles are 10 °. The replacement unit includes a U-shaped bracket with holes, two ultrasonic heads with the same piezoelectric elements, signal wires, two flat springs, two rotary stoppers, an electrical connector, captive screws and acoustic grease. Ultrasonic heads are located in the holes of the bracket on the same axis with the possibility of movement. The rotary stoppers are designed so that in the extreme position they hold the springs in the depressed state, and when the stopper is rotated, the springs are released and the ultrasonic heads are pressed against the protective bottoms. EFFECT: provision of the possibility of on-line mounting / dismounting of ultrasonic ones without reducing the accuracy and reliability of measurements. 3 ill.

Description

The utility model relates to means for measuring the flow rate and the number of fluids, namely to vortex flowmeters, and can be used in cases where, under operating conditions, the flowmeter should be serviced without stopping the flow with limited access to the flow transducer or when severe time limits are imposed restoration of efficiency after failure of the flow transducer.

Known vortex-acoustic flowmeter of the flowmeter "Ultra yewflo-UYF200" company "Yokogawa" [1], containing a measuring pipe (body) with a flowing part of a circular cross section, a vortex generator (vortex shedder) in the form of a poorly streamlined body with a trapezoidal cross-section mounted symmetrically relative to the walls nozzle, two inserts (plug) in the form of cups welded into holes in the nozzle wall, two removable ultrasonic emitter / receiver (sensor, ultrasonic transmitter / receiver) with flat piezoelectric elements, two connecting cables. The plane-parallel protective bottom of the insert has a thickness that is a multiple of half the length of the ultrasonic wave, which ensures the maximum value of the receiving signal. The acoustic contact of the piezoelectric elements with the bottom is provided by silicone grease. The emitters / receivers are mounted in the housings with screws.

The above-described flow transducer is designed for use in particularly difficult operating conditions: it is insensitive to vibrations and shocks, and its design allows inspection and replacement of emitters / receivers without stopping the process. To do this, remove the screws, remove the emitters / receivers from the inserts, remove the old silicone grease, apply fresh silicone grease to the new emitters / receivers (or replace the grease with old ones), install the emitters / receivers in the housings and fix them with screws. A disadvantage of the known flow transducer is that for mounting / dismounting the emitters / receivers it is required to have free access from at least two sides of the nozzle, which is not always possible at the facility, for example, when the flow transducer is mounted on a unit with a tight layout. In addition, the places where the inserts exit into the stream, as well as the places where the flow around the body is embedded in the wall of a pipe of cylindrical shape, are sources of disturbances that reduce the stability of the vortex formation process and, as a result, the measurement accuracy.

Closest to the claimed utility model is a vortex acoustic flow transducer according to US patent No. 5,747,701 [2]. It contains a measuring nozzle made in the form of a piece of circular pipe with a thickened central part with two flat contact pads located in recesses on opposite walls of the nozzle, a removable U-shaped bracket with four pairwise coaxial holes, two removable ultrasonic heads with identical piezoelectric elements and a rod -fixer, and the width of the recesses is equal to the width of the bracket.

According to the description of the patent, this converter is designed to periodically control the flow rate in the pipeline, after which the bracket with emitters is removed before the next measurement session (the pipe itself remains on the pipeline). For mounting / dismounting ultrasonic heads on the nozzle, it is necessary to have access to it from the side and from the top. During installation, it is necessary: put the bracket on top of the nozzle, fix the bracket on the side with a retainer, threading it through the two lower holes, apply acoustic grease to the ultrasonic heads, insert the ultrasonic heads into the two upper holes in the bracket and fix them. When dismantling the heads, it is necessary to remove the retainer from the lower holes, remove the heads, remove the bracket by moving it up. Thus, for mounting / dismounting ultrasonic heads it is required to have access to the flow transducer from two sides, which is not always possible at the facility. In addition, despite the fact that there are no flow distortions at the installation site of the emitters, there is a strong attenuation of the ultrasonic signal due to the refraction of ultrasonic rays on the cylindrical wall during their transition from the nozzle to the working fluid. This leads to a deterioration of the signal-to-noise ratio of the reception signal and, accordingly, to a decrease in the reliability of the flow converter.

The problem to which the claimed technical solution is directed is to improve operational characteristics and increase the accuracy and reliability of measurements.

The problem is solved in that in a vortex-acoustic flow transducer, including a measuring tube, in the cross section of which a poor-flowing body is installed, a U-shaped bracket with two coaxial holes, two ultrasonic heads with the same piezoelectric elements, signal wires and acoustic grease in which the pipe is made in in the form of a pipe segment with a thickening in the middle part with two contact pads located in the recesses on opposite walls of the pipe behind the flow body, ultrasonic traps are located in the holes of the bracket, and the width of the recesses is equal to the width of the bracket, the input conical transition from round to square is introduced, the output conical transition from square to round, two flat springs, two rotary stops, an electrical connector and captive screws, and the pipe is made with square cross-section, U-shaped bracket, ultrasonic heads, springs, stoppers, connector, signal wires and captive screws are made in the form of a removable assembly, ultrasonic heads are installed in the holes of the brackets with the possibility of axial movement, the rotary stoppers are designed so that in the extreme position they hold the springs in the depressed state, and when the stopper is rotated, the springs are released and the ultrasonic heads are pressed against the contact pads, and the wall thickness of the pipe at the contact pad locations is an integer number of half-wavelengths ultrasonic vibrations at the resonance frequency of the piezoelectric element, while the diameters of the conical transitions are equal to the length of the diagonal of the pipe, and the taper angles are 10 °.

The technical result achieved by the combination of the above characteristics is the possibility of rapid mounting / dismounting of ultrasonic heads with access to the flow transducer on only one side of the nozzle and restrictions on the time of mounting / dismounting operations without compromising the accuracy and reliability of measurements.

The technical solution is illustrated by drawings: in FIG. 1 shows an eddy-acoustic flow transducer assembly; in FIG. 2 shows a conduit branch pipe arrangement; in FIG. 3 - removable node.

The vortex-acoustic flow transducer (see Fig. 1) contains a measuring pipe 1 with input 2 and output 3 conical transitions from a circular cross section to a square and removable unit with two ultrasonic heads 4. The pipe 1 (see Fig. 2) has a thickening in the central part in which a poorly streamlined body 5 is installed and two recesses are made with flat contact pads 6, 7 (the second platform 7 is not shown) located on opposite walls behind the flow body 5 into which a removable assembly 4 with ultrasonic heads is inserted. The thickness h of the walls of the pipe 1 at the locations of the contact pads 6, 7 is equal to an integer number of half-waves of the ultrasonic signal generated by the ultrasonic heads. The body of the flow around 5 is made in the form of a cylinder, for example, a trapezoidal section.

The removable assembly 4 (see Fig. 3) includes a U-shaped bracket 8 with two coaxial holes, two ultrasonic heads 9, 10 with disk piezoelectric elements 11 and 12 (piezoelectric element 12 not shown) installed in the bracket holes, acoustic grease 13, 14 applied to the piezoelectric elements 11, 12 (grease not shown), two flat springs 15 and 16 (spring 16 not shown), two rotary stoppers 17 and 18, four captive screws 19-22 (two screws not shown), connecting wires 23, 24 (one wire not shown) and electrical connector 25. Ultrasonic heads 9, 10 are installed in the holes staples 8 on the same axis with the ability to move and are meshed with flat springs 15, 16. Connecting wires 23, 24 connect the piezoelectric elements 11, 12 to the contacts of the connector 25. Captive screws 19-22 provide fastening of the bracket 8 to the pipe 1. The width of the bracket 8 removable node 4 is equal to the width of the recess in the pipe 1.

Vortex-acoustic flow transducer operates as follows. When the medium flows through the measuring pipe 1 behind the body of the flow around 5, a Karman vortex path is formed. An electrical excitation signal is supplied from the electronics unit (not shown in the figures) to the connector 25, which is fed through the wire 23 to the piezoelectric element 12 of the ultrasonic head 11. The excitation signal is converted by the piezoelectric element 12 into an ultrasonic probe signal, which passes through the acoustic lubricant layer 13, the housing wall 1 , the vortex track, through the opposite wall of the housing 1, the lubricant layer 14 and enters the piezoelectric element 12 of the ultrasonic head 10, which converts it into an electrical receiving signal. The receive signal on wire 24 is supplied to connector 25, and from the connector to the electronics unit. The delay time of the reception signal with respect to the excitation signal is variable and fluctuates around the average value with the frequency of vortex formation. Using an electronic circuit, the frequency of these oscillations is measured, which is proportional to the flow rate.

If it becomes necessary to quickly replace the removable assembly 4 with ultrasonic heads, the electronics block is undocked from the connector 25, the captive screws 19-22 are unscrewed, and the removable assembly 4 is removed from the notches of the measuring pipe 1 by moving upward with little effort. Installation of the removable node 4 in place is carried out in the following order:

- the old grease is removed from the piezoelectric elements 11, 12 and contact surfaces;

- the springs 15, 16 are wrung out and stoppers 17, 18 are inserted into the gaps between the heads and springs, which fix the ultrasonic heads 9, 10 in the retracted state;

- on the surface of the piezoelectric elements 11, 12 is applied a new acoustic lubricant;

- the bracket 8 is installed in place and secured with screws 19-22, while the recesses in the pipe 1 are used as guides;

- the stops 17, 18 rotate, while the ends of the stoppers 17, 18 come out of the gaps and the springs 15, 16 are released, pressing the piezoelectric elements 11, 12 to the contact pads of the pipe 1. Due to the clamp, the lubricant uniformly fills the space between the piezoelectric elements 11, 12 and the contact pads pipe 1, providing reliable acoustic contact;

- the electronic unit is connected to connector 25: the flowmeter is ready for operation.

To perform all the above operations, it is enough to have access to the pipe from above.

Due to the square cross-section of the nozzle, the level of disturbances at the site of embedment of the flow body is reduced. Reducing the level of disturbances generated at the points of transition from the circular section of the pipeline (and flange) to the square section of the pipe ensures conical transitions, and the diameters of the flanges must be equal to the diagonal of the pipe section, and a taper angle of 10 ° ensures an uninterrupted flow regime. Due to the above design features of the inventive flow Converter compared with the prototype increases the stability of the frequency of vortex formation and, as a result, the accuracy of the measurements.

Due to the fact that the wall of the pipe at the locations of the contact pads (at the location of the fit of the piezoelectric elements) is equal to an integer number of half-waves of the ultrasonic signal at the resonant frequency of the piezoelectric element, the acoustic transparency of the wall is ensured. In this case, compared with the prototype, there is a significant increase in the transmission coefficient (the ratio of the amplitudes of the reception and excitation signals), thereby increasing the reliability of the flow converter.

Conducted at the flowmeter test bench of the proposed flow Converter showed:

- to perform operations on replacing a removable unit with ultrasonic heads, it is sufficient to have access to the flow transducer on one side (from above);

- the time required to replace the removable unit does not exceed 5 minutes;

- in comparison with the prototype of the proposed Converter provides an increase in the stability of the frequency of vortex formation by 1.5-2 times.

Information sources

1. Ultrasonic vortex Flowmeter "Ultra yewflo-UYF200". T. Kawano, Y. Matsunaga, T. Andoh, A. Yasumatsu. Yokogawa Technical Report. English Edition. No. 25 (1998), p. 23-26.

2. US patent No. 5, 747,701 C2, IPC G01F 1/32, NKI 78 / 861.23, publ. 05/05/1998.

Claims (1)

Vortex-acoustic flow transducer, including a measuring tube, in the cross section of which a poor-flowing body, a U-shaped bracket with two coaxial holes, two ultrasonic heads with the same piezoelectric elements, signal wires and acoustic grease are installed, the pipe being made in the form of a pipe section with a thickening in the middle part with two flat contact pads located in the recesses on opposite walls of the nozzle behind the flow body, the ultrasonic heads are located in holes with Generally, and the width of the recesses is equal to the width of the bracket, characterized in that it includes an input conical transition from round to square, an output conical transition from square to round, two flat springs, two rotary stops, an electrical connector and captive screws, and the nozzle made with square cross-section, U-shaped bracket, ultrasonic heads, springs, stoppers, connector, signal wires and captive screws made in the form of a complete removable assembly, ultrasonic heads are installed in the hole axles with the possibility of axial movement, rotary stoppers are made in such a way that in the extreme position of the stoppers the springs are kept in a depressed state, and when the stoppers are turned, the springs are released and press ultrasonic heads to the contact pads, and the wall thickness of the pipe at the locations of the contact pads is an integer the half-wavelengths of ultrasonic vibrations at the resonance frequency of the piezoelectric element, while the diameters of the conical transitions are equal to the length of the diagonal of the pipe, and the taper angles are 10 .

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