CN112747260B - Ultrasonic flow measuring device capable of preventing noise interference - Google Patents

Abstract

The invention discloses an ultrasonic flow measuring device for preventing noise interference, wherein an upstream pipeline of a measured fluid is connected with a slow vibration structure and a downstream pipeline through a tee joint, the fluid enters the downstream after the upstream interference noise of the fluid is eliminated by the slow vibration structure, enters an energy converter and a display device for measurement after passing through a rectifying distributor, and the interference is eliminated by reflecting and absorbing ultrasonic noise generated due to external reasons in the fluid flow, so that a favorable measuring environment is provided for an ultrasonic flow meter, and high-precision and stable flow data are obtained.

Description

An Ultrasonic Flow Measuring Device Against Noise Interference

technical field

The invention belongs to the technical field of flow measurement, and in particular relates to an ultrasonic flow measurement device for preventing noise interference.

Background technique

In the field of modern industry, pressure, flow, and temperature are identified as the three important detection parameters of industrial automation. Flowmeters are widely used in metallurgy, chemical industry, natural gas transportation, petroleum transportation, and civil water meters. Whether it is industrial production or commercial trade, the demand for flow measurement is constantly increasing.

Traditional flowmeters measure flow based on the functional relationship between the resistance characteristics of the fluid in the flow process and the flow velocity, such as Venturi flowmeters and orifice flowmeters. Their similar characteristics are that the fluid is in direct contact with the measurement structure, the pressure loss is large, and the measurement Small range. The biggest disadvantage of this type of flowmeter is that it is very sensitive to the wear of the firmware and the measurement accuracy is not high. With the development of ultrasonic technology and sensor technology, the use of sound wave measurement technology has become more and more widely used. Ultrasonic flowmeter has no moving parts, non-contact, digital and electronic, and generally has high measurement accuracy, good linearity, wide range ratio, high reliability and easy maintenance in terms of performance, so ultrasonic flowmeter It is gradually entering the field of various measurement and measurement.

However, in different application places, the ultrasonic flowmeter will be affected by the roughness of the inner wall of the upstream straight pipe section, gas composition, length of the upstream straight pipe section, fluid flow state upstream of the flowmeter, water pump and other noise interference, air flow pulsation, etc. , thus affecting the measurement accuracy. In order to overcome the external influence, although the filter can overcome part of the interference, its effect is limited, so other means are needed to reduce the noise interference to improve the measurement accuracy.

Contents of the invention

The invention provides an ultrasonic flow measurement device that prevents noise interference, which eliminates interference by reflecting and absorbing ultrasonic noise generated by external causes in fluid flow, provides a favorable measurement environment for ultrasonic flowmeters, and obtains high-precision flow data.

In order to achieve the above object, an ultrasonic flow measurement device for preventing noise interference according to the present invention includes an ultrasonic flowmeter installed on the pipeline to be measured and a damping structure, the damping structure includes a damping chamber, and the damping chamber A damping film is arranged in the middle, and the damping chamber is filled with air or inert gas.

Further, the damping structure is installed close to the noise source.

Further, the damping structure is connected to the measured fluid pipeline through a three-way joint, and the measured fluid pipeline includes an upstream pipeline and a downstream pipeline, and the three interfaces of the three-way joint are respectively connected to the upstream pipeline, the downstream pipeline and the damping room.

Further, the damping chamber is provided with an on-off valve.

Further, the damping membrane is a movable piston or a fixed flexible plate.

Further, a damping material coating is provided on the vibration-damping membrane.

Further, a rectification distributor is installed on the upstream pipeline of the ultrasonic flowmeter, and the rectification distributor includes a plate body. The shape of the plate body is the same as the shape and size of the longitudinal section of the measurement fluid pipeline. hole.

Further, the ultrasonic flowmeter includes a first transducer, a second transducer and a display device for measuring and displaying the flow rate of the measured fluid.

Compared with the prior art, the present invention has at least the following beneficial technical effects:

The invention provides an ultrasonic measurement device for preventing noise interference. The damping film and the damping chamber constitute a damping system. Using the compressibility of the gas, when the noise is transmitted, the energy of the vibration wave acts on the vibration-damping film. The micro-distance movement or vibration of the diaphragm is transmitted to the gas in the damping chamber, and the gas is compressed and converted into heat energy to realize the energy dissipation of noise and sound waves. By setting up the noise elimination mechanism, it can reflect and absorb the ultrasonic noise mixed in by fluid flow itself, fluid interception, pump and other sound sources, eliminate interference, provide a favorable measurement environment for ultrasonic flowmeters, and obtain accurate flow data. Compared with the existing ultrasonic flowmeter, the anti-interference ability is stronger, and the measurement accuracy and stability are effectively improved.

Further, the damping structure is installed in the direction close to the noise source, so as to improve the noise reduction effect.

Further, the damping chamber is provided with an on-off valve, which can conveniently inflate or deflate the damping chamber.

Furthermore, a damping material coating is provided on the vibration-damping membrane to further improve the vibration-damping effect.

Further, a rectification distributor is installed upstream of the ultrasonic flowmeter, and the rectification distributor includes a plate body whose shape is the same as the shape and size of the longitudinal section of the measurement fluid pipeline. The elbow of the measuring fluid pipeline causes eddy currents to be rectified, shortening the requirements for installing the straight section before the ultrasonic flowmeter.

Description of drawings

Accompanying drawing 1 is the principle structural diagram of a kind of anti-noise interference ultrasonic flow measuring device of the present invention;

Accompanying drawing 2 is A-A direction sectional view among Fig. 1;

Accompanying drawing 3 is ultrasonic flowmeter measurement schematic diagram;

Accompanying drawing 4 is a schematic diagram of an ultrasonic flowmeter.

In the attached drawings: 1. Upstream pipeline, 2. Tee joint, 3. Mounting flange, 4. Damping film, 5. Damping chamber, 6. On-off valve, 7. Rectifier distributor, 8. Ultrasonic flowmeter, 9. Downstream pipe, 10. Through hole, 11. First transducer, 12. Second transducer, 13. Through hole.

detailed description

In order to make the purpose and technical solution of the present invention clearer and easier to understand. The present invention will be further described in detail below in conjunction with the drawings and embodiments. The specific embodiments described here are only used to explain the present invention, not to limit the present invention.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", " The orientations or positional relationships indicated by "vertical", "horizontal", "top", "bottom", "inner" and "outer" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and Simplified descriptions, rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and thus should not be construed as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, unless otherwise specified, "plurality" means two or more. In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

The main principle of anti-noise interference of the present invention is to use the characteristics of sound wave propagation reflection and damping absorption, and set a vibration-reducing film with reflection and absorption functions in the main direction of noise sound wave propagation to reflect and absorb the transmitted energy of noise sound waves.

Example 1

Referring to Fig. 1, an ultrasonic flow measurement device for preventing noise interference, including a measuring fluid pipeline 1, a tee joint 2, a mounting flange 3, a vibration damping film 4, a damping chamber 5, a switching valve 6, a rectifying distributor 7 and Ultrasonic flowmeter 8. The ultrasonic flowmeter 8 includes two transducers and a display screen.

The measurement fluid pipeline includes an upstream pipeline 1 and a downstream pipeline 9. The upstream pipeline 1 is connected to the damping structure and the downstream pipeline 9 through a three-way joint 2. The ultrasonic flowmeter 8 is installed on the downstream pipeline 9. The fluid passes through the damping structure to eliminate upstream interference noise. After that, it enters the downstream pipeline 9, and enters the ultrasonic flowmeter 8 for measurement after passing through the rectifying distributor 7. When there is noise source interference in the downstream direction of the fluid flow, similar devices can also be installed to dampen the downstream noise. The upstream of the measurement fluid pipe 1 communicates with the inlet of the three-way joint 2 .

The damping structure includes a damping chamber 5, a damping membrane 4 and a switching valve 6. The damping chamber 5 and the upstream part of the measurement fluid pipeline 1 are coaxially arranged; the damping chamber 5 is installed on the tee joint 2 through the mounting flange 3. At the first outlet, the damping membrane 4 can be a piston type that moves freely along the inner wall of the damping chamber 5, or it can be a fixedly installed flexible plate with a relatively large damping coefficient. Inflate air or inert gas into the damping chamber 5 through the switch valve 6, the inflation pressure is approximately equal to the fluid pressure, specifically, the fluid pressure of plus or minus 20% is taken; its function is to balance the fluid pressure, and at the same time form an elastic compression space. The choice of gas needs to consider extreme accidents, that is, when the vibration damping film is damaged, it will leak to the mainstream working fluid, so as not to cause the accident to expand. The noise from upstream of the fluid propagates along the fluid, and the sound waves are reflected and absorbed by the damping membrane 4 after arriving at the damping membrane 4 .

The vibration damping film 4 and the damping chamber 5 form a damping system. Using the compressibility of the gas, when the noise is transmitted, the vibration wave energy acts on the vibration damping film, and is transmitted to the The gas in the damping chamber 5 is compressed and converted into heat energy, so as to realize the energy dissipation of noise and sound waves.

Preferably, a damping material coating can also be added on the vibration-damping membrane 4 to further improve the vibration-damping effect.

A rectification distributor 7 is installed on the downstream pipeline 9, and the rectification distributor 7 is used to rectify the eddy current caused by the pipe elbow of the measured fluid, shortening the requirement for the straight section before the ultrasonic flowmeter 8 to be installed. According to the requirements of the installation space and the actual situation of the site, the rectifier distributor 7 may not be installed.

Referring to FIG. 2 , the rectifying distributor 7 includes a plate body whose shape is the same as the longitudinal section shape and size of the measuring fluid pipeline, and a plurality of circular through holes 13 are opened on the plate body.

The fluid in the measured fluid pipeline 1 is a liquid or gas single-phase medium, and no phase change occurs in the fluid pipeline and the flowmeter. The measured fluid pipe 1 is a round pipe or a square pipe.

Referring to FIG. 3 , the ultrasonic flowmeter 8 includes a first transducer 11 , a second transducer 12 and a display device for measuring and displaying the flow rate of the measured fluid.

According to the measurement principle, ultrasonic flowmeters are divided into: propagation velocity difference method (abbreviated as velocity difference method), Doppler effect method, noise method, correlation method, etc. The commonly used ones are velocity difference method and Doppler effect method. The Doppler method uses the principle of acoustic Doppler to determine the fluid flow rate by measuring the ultrasonic Doppler frequency shift scattered by the scattering body in the inhomogeneous fluid. It is suitable for flow measurement of two-phase flow containing suspended particles and bubbles. Velocity difference methods include: direct time difference method, time difference method, phase difference method, and frequency difference method. The method overcomes the error caused by the change of sound velocity with the temperature of the fluid, and has high accuracy, so it is widely used. Ultrasonic gas flowmeters generally use the speed difference method. The speed difference method is mainly used in the measurement of single-phase fluid.

The following is a brief introduction to the basic measurement principle of the ultrasonic gas flowmeter by taking the time difference method as an example:

On the measuring pipe section of the instrument, a pair of ultrasonic transducers are obliquely installed: the first ultrasonic transducer 11 and the second transducer 12, which alternately transmit and receive ultrasonic pulses, as shown in Figure 3. In Figure 3: C is the sound velocity in the fluid medium; V is the flow velocity of the fluid medium in the pipeline; L is the sound path length; θ is the angle between the transducer and the pipeline axis; D is the pipeline diameter.

On the sound path L, the propagation speed of the ultrasonic wave is the superposition of the sound speed and flow speed components. The propagation times t ₁ and t ₂ in the downstream and upstream directions are respectively:

After measuring the propagation time t ₁ and t ₂ in the direction of forward flow and reverse flow respectively, the flow velocity V can be calculated:

Because the measured forward and reverse propagation times t ₁ and t ₂ include the inherent electro-acoustic delays τ ₁ and τ ₂ generated by circuits, cables and transducers, etc., their effects must be deducted, so formula (3) can be rewritten as:

Due to the friction and viscosity of the pipe wall and the inside of the fluid, the actual fluid velocity has a velocity distribution on the surface of the pipeline. For a single-channel ultrasonic flowmeter on the center line, the measured flow velocity v is actually the inner diameter of the pipeline section. The average linear velocity of the pipe, and the measurement of the flow requires the surface average velocity V _m of the inner section of the pipe, and they are not equal. According to the theory of fluid mechanics, when the Reynolds number is greater than 4000, the fluid is in a state of turbulent flow. At this time, there is a dynamic factor K between the average velocity of the line and the average velocity of the surface (the function of the Reynolds number Re of the pipeline, which can be calibrated in the flowmeter in engineering. Obtained by actual measurement), that is:

Thus, the instantaneous volume flow Q _{instantaneous} can be obtained:

In continuous measurement, as long as the measured Q _{instantaneous} value is integrated with time one by one, the accumulated flow Q _accumulation in any time period can be obtained. After the volume flow is compensated by pressure and temperature, the mass flow Q _quality can be obtained:

In the formula: ρ ₀ is the density of the gas medium in the standard state; P ₀ and P are the pressures in the standard and actual state respectively; T0 and T are the temperature in the standard and actual state respectively; Z is the gas compression coefficient. It can be seen from formulas (4) and (6) that the measurement of sound time t ₁ and t ₂ is the key to flow measurement. After the parameters D, L, θ, τ ₁ , τ ₂ and K are determined, as long as the accurate measurement t ₁ and t ₂ , the flow velocity V and _{instantaneous} flow Q in the pipeline can be accurately obtained, and then the cumulative flow Q _accumulation and mass flow Q _quality can be obtained.

The schematic diagram of the ultrasonic flowmeter is shown in Figure 4: the first transducer 11 and the second transducer 12 are respectively installed on both sides of the fluid pipeline with a certain distance apart, and the ultrasonic emission is mainly composed of a master oscillator and a switcher. , to transmit ultrasonic waves, the sawtooth wave voltage generator is processed by the main control oscillator to obtain the sending pulse signal required by the transducer, and the first ultrasonic transducer is driven to emit ultrasonic signals, and the inductance-capacitance matching circuit is used to make the transducer in the state of When resonating, piezoelectric ceramics generate enough vibration energy to send out high-power ultrasonic signals. The function of the switch is that the transceiver control circuit controls the transmission and reception of the pulse signal. After the ultrasonic signal emitted by the first transducer 11 is transmitted to the second transducer 12, the switch of the switch controls the second transducer 12. , the second transducer 12 obtains the receiving ultrasonic signal, passes through the receiving amplifier and the output gate, and carries out the logic processing of the digital circuit by the receiving waveform and the transmitting waveform through the peak detector, the differential amplifier, etc., obtains the time signal, and performs data processing and calculation , and finally get the traffic data and display it.

The above content is only to illustrate the technical ideas of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solutions according to the technical ideas proposed in the present invention shall fall within the scope of the claims of the present invention. within the scope of protection.

Claims (6)

1. An ultrasonic flow measuring device for preventing noise interference is characterized by comprising an ultrasonic flow meter (8) and a vibration damping structure, wherein the ultrasonic flow meter is installed on a measured pipeline, the vibration damping structure comprises a vibration damping chamber (5), a vibration damping film (4) is arranged in the vibration damping chamber (5), and air or inert gas is filled in the vibration damping chamber (5);

the damping structure is connected to a measured fluid pipeline through a three-way joint (2), the measured fluid pipeline comprises an upstream pipeline (1) and a downstream pipeline (9), and three interfaces of the three-way joint (2) are respectively connected with the upstream pipeline (1), the downstream pipeline (9) and a damping chamber (5); the vibration damping chamber (5) and the upstream pipeline (1) are coaxially arranged; the ultrasonic flowmeter (8) is mounted on a downstream pipeline (9);

the damping membrane (4) is a movable piston or a fixed flexible plate.

2. An ultrasonic flow measurement device against noise interference according to claim 1, wherein the vibration attenuating structure is installed in a direction close to the noise source.

3. An ultrasonic flow measuring device for preventing noise interference according to claim 1, wherein the damping chamber (5) is provided with a switching valve (6).

4. An ultrasonic flow measuring device for preventing noise interference according to claim 1, wherein the damping membrane (4) is provided with a coating of damping material.

5. An ultrasonic flow measuring device for preventing noise interference according to claim 1, wherein the rectifying distributor (7) is installed on the upstream pipeline of the ultrasonic flow meter (8), the rectifying distributor (7) comprises a plate body, the shape of the plate body is the same as the shape and the size of the longitudinal section of the pipeline for measuring the fluid, and a plurality of through holes (13) for the fluid to flow through are formed on the plate body.

6. An ultrasonic flow measurement device for noise immunity according to claim 1, wherein the ultrasonic flow meter (8) comprises a first transducer (11), a second transducer (12) and a display device for measuring and displaying the flow of the measured fluid.

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