Flow velocity metering system and metering method for large-diameter natural gas pipeline

Abstract

The invention discloses a flow velocity metering system and a flow velocity metering method for a large-diameter natural gas pipeline, and aims to solve the technical problem that the flow velocity measurement deviation is serious due to the fact that the deviation between the center of a transmitting surface of an ultrasonic transducer and the center of the pipeline exceeds 8mm. The metering system comprises n pairs of ultrasonic transducers which are oppositely arranged, each pair of ultrasonic transducers is fixedly connected to the inner wall of the large-diameter natural gas pipeline, and n is equal to 1 or 3; the n pairs of ultrasonic transducers are connected with the controller; the arrangement position of each pair of ultrasonic transducers is vertically deflected by a certain angle on the horizontal basis, and the deflection angle is determined according to the radius of the ultrasonic transducers, so that the problem of flow field deflection caused by deviation between the center of the ultrasonic transducers and the center of the large-diameter natural gas pipeline can be solved, and the gas flow measurement accuracy is improved.

Description

Technical Field

[0001] The invention relates to a method for measuring medium flow in a natural gas pipeline, and in particular to a flow rate measuring system and a measuring method for a large-diameter natural gas pipeline. Background Art

[0002] When ultrasonic flow meters are used in natural gas pipelines, their measurement principle is based on the velocity distribution in the measured area. However, the on-site installation of ultrasonic flow meters will greatly affect the velocity distribution in the pipeline, causing the center airflow point to shift, such as Figure 1 As shown, (a) is the ideal flow field; (b) is the center offset flow field. The traditional ultrasonic flow meter is horizontally set in the natural gas pipeline. Since the diameter of the emitting surface of the transducer in the ultrasonic flow meter is about 16-20 mm, the deviation between the emitting surface center of the transducer in the ultrasonic flow meter and the center of the pipeline exceeds 8 mm during on-site installation, which will lead to serious flow velocity measurement deviation. In addition, when the ultrasonic flow meter is used, it is impossible to effectively overcome the problem of central airflow point deviation, resulting in a large metering deviation. The larger the diameter of the natural gas pipeline, the greater the deviation. Therefore, during the detection or actual use, the ultrasonic flow meter must be repeatedly centered, which is time-consuming and laborious.

[0003] In the existing ultrasonic gas flow rate measurement method, position deviation is unavoidable when the ultrasonic flow meter is installed in a large-diameter pipeline. This position deviation causes the flow field to flow in an offset state when measuring the high-pressure and high-flow gas flow rate in the natural gas pipeline. The accumulated deviation causes a large difference between the actually measured gas flow rate data and the actual gas flow rate data, which will ultimately cause uncontrollable losses to the owner.

[0004] In order to solve the above problems, the prior art often adopts the method of increasing the number of ultrasonic flow meter measurement channels, such as Figure 2 As shown, the measurement accuracy is improved by adding channels; however, this method has the following defects:

[0005] 1) In a large-diameter natural gas pipeline, at least 5-6 sound channels are required. Multiple sound channels require more ultrasonic transducers, resulting in a surge in metering costs;

[0006] 2) Multiple channel measurements cause multiple ultrasonic flow meters to be in a high-power working state for a long time, and the flow field fitting calculation of multiple measurement results puts a lot of pressure on the chip calculation. Ordinary MCU controllers can no longer meet the measurement and calculation requirements, and high-computing DSP chips must be used, which further increases the overall power consumption and material costs.

[0007] 3) Installing multiple ultrasonic transducers in large-diameter natural gas pipelines results in complex installation and processing in the pipelines, high precision requirements, and increased processing difficulty and cost;

[0008] 4) As the more sound channels an ultrasonic flow meter has, the more installation holes it requires. This will increase the pipeline sealing pressure and the risk of accidents, which is not conducive to product reliability and is more obvious in high-pressure products. Summary of the invention

[0009] The purpose of the present invention is to solve the technical problem that when an ultrasonic flow meter is installed in a large-diameter pipeline for measurement, the deviation between the center of the emitting surface of the transducer in the ultrasonic flow meter and the center of the pipeline exceeds 8 mm, which will lead to serious flow velocity measurement deviation, and to provide a flow velocity measurement system and a measurement method for a large-diameter natural gas pipeline.

[0010] The inventive concept of the present invention is to deflect the sound channel angle that is originally parallel to the horizontal center plane of the large-diameter natural gas pipeline, and add a small range of vertical deflection to the multiple pairs of ultrasonic transducers that are originally installed in parallel while maintaining the cross-reflection, so as to increase the measurement range of the measurement sound channel, that is, to add a small amount of vertical measurement part, so as to overcome the flow field center offset problem caused by the deviation between the center of the emitting surface of the transducer in the ultrasonic flowmeter and the center of the pipeline, thereby improving the accuracy of gas flow measurement.

[0011] In order to achieve the above object, the present invention adopts the following technical solution:

[0012] A flow rate metering system for a large-diameter natural gas pipeline comprises n pairs of ultrasonic transducers arranged opposite to each other, and each pair of ultrasonic transducers is fixedly connected to the inner wall of the large-diameter natural gas pipeline, wherein n=1 or 3; the n pairs of ultrasonic transducers are all connected to a controller, and the controller is used for the ultrasonic transducers to receive or send ultrasonic waves; the special features thereof are:

[0013] n virtual surfaces are set along the direction parallel to the axis of the large-diameter natural gas pipeline; when n=1, one virtual surface is a plane along the axial direction; when n=3, the three virtual surfaces are parallel to each other and are equally spaced, and the virtual surface in the middle is a plane along the axial direction; then each pair of ultrasonic transducers corresponds to a virtual surface, and is located on both sides of the corresponding virtual surface, and the distance between the corresponding virtual surface and the corresponding virtual surface is equal, and the connecting line between the center points of the emitting surfaces of each pair of ultrasonic transducers intersects with the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline; the angle between the sound channel between each pair of ultrasonic transducers and the corresponding virtual surface is defined as Φ;

[0014] Then the expression of Φ is:

[0015]

[0016] Wherein, D represents the radius size of the emitting surface of the ultrasonic transducer, and L represents the distance between the center point of the emitting surface of the transducer in the ultrasonic flowmeter and the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline.

[0017] In order to ensure that the ultrasonic transducer still faces the center point of the sound channel after translation, the angle of the ultrasonic transducer is adjusted, that is, the ultrasonic transducer is deflected in a small range on the basis of horizontal radiation. Even if a height deviation occurs during installation, the center airflow point in the pipe can still fall on the sound channel to keep the measurement result unchanged.

[0018] Furthermore, when n=3, the three pairs of ultrasonic transducers adopt the same deflection angle, and the same deflection angle means that the lines connecting the center points of the emission surfaces of each pair of ultrasonic transducers are parallel to each other.

[0019] Furthermore, when n=3, the three pairs of ultrasonic transducers adopt an alternating deflection angle method, and the alternating deflection angle method means that the extension lines of the connecting lines between the center points of the emitting surfaces of each pair of ultrasonic transducers intersect in sequence and are located in the same plane.

[0020] Furthermore, each pair of ultrasonic transducers is a flow meter sensor integrating ultrasonic emission and reception.

[0021] Furthermore, the controller is an MCU controller. When performing fitting calculations on the flow rate of a large-diameter natural gas pipeline, the amount of calculations is reduced, and an ordinary MCU controller can meet the calculation requirements. A high-performance DSP chip is not required, and material costs and product power consumption are further reduced.

[0022] The present invention also provides a flow rate metering method for a large-diameter natural gas pipeline. Based on the above-mentioned flow rate metering system for a large-diameter natural gas pipeline, one of the relatively arranged ultrasonic transducers is turned on, an ultrasonic signal is emitted through the emitting surface of the ultrasonic transducer, the ultrasonic signal is received through another ultrasonic transducer, and the flow rate of the large-diameter natural gas pipeline is obtained based on the received ultrasonic signal.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention discloses a flow rate metering system and a metering method for a large-diameter natural gas pipeline, which adopts a deflected ultrasonic transducer, and the deflection angle is determined according to the radius of the ultrasonic transducer. This can overcome the problem that traditional ultrasonic flow meters cannot cope with the inaccurate flow measurement caused by the deviation of the central flow field, thereby improving the accuracy of gas flow measurement.

[0025] 2. The flow rate metering system for large-diameter natural gas pipelines of the present invention has a simple structure, is easy to implement, can reduce costs and power consumption, and can improve measurement reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of an ideal flow field and a center offset flow field in the background technology;

[0027] Where (a) is the ideal flow field; (b) is the center offset flow field;

[0028] Figure 2 It is a schematic diagram of adding an ultrasonic transducer in a large-diameter natural gas pipeline in the background technology;

[0029] Figure 3 It is a schematic diagram of the position of the ultrasonic transducer when n=1 in an embodiment of a flow rate metering system for a large-diameter natural gas pipeline of the present invention;

[0030] Figure 4 This is a schematic diagram of the position of ultrasonic transducers in an embodiment of a flow rate metering system for a large-diameter natural gas pipeline of the present invention, when n=3, in which the same deflection angle of multiple sound channels is used;

[0031] Figure 5 This is a schematic diagram of the position of an ultrasonic transducer set in an embodiment of a flow rate metering system for a large-diameter natural gas pipeline in which, when n=3, multiple sound channels are alternately deflected at different angles. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] This embodiment is a flow rate metering system for a large-diameter natural gas pipeline, such as Figure 3 As shown, it includes two ultrasonic transducers arranged opposite to each other; both ultrasonic transducers are flow sensors integrating ultrasonic emission and reception; the two ultrasonic transducers are connected to the MCU controller;

[0034] Two ultrasonic transducers are arranged on the inner wall of a large-diameter natural gas pipeline, and a virtual surface is arranged along the direction parallel to the axis of the large-diameter natural gas pipeline; a virtual surface is a plane along the axial direction; each pair of ultrasonic transducers corresponds to a virtual surface, and is respectively located on both sides of the corresponding virtual surface, and the distance between the corresponding virtual surface and the corresponding virtual surface is equal, and the connecting line between the center points of the emission surface of each pair of ultrasonic transducers intersects with the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline; the angle between the sound channel between each pair of ultrasonic transducers and the corresponding virtual surface is defined as Φ;

[0035] Then the expression of Φ is:

[0036]

[0037] Wherein, D represents the radius size of the emitting surface of the ultrasonic transducer, and L represents the distance between the center point of the emitting surface of the transducer in the ultrasonic flowmeter and the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline.

[0038] In this embodiment, when designing the sound channel path, the central radial sound channel angle originally parallel to the flow field is deflected, and the two ultrasonic transducers originally installed in parallel are deflected in a small range while maintaining the cross-reflection. This increases the measurement range of the measurement channel, that is, increases a small amount of vertical measurement part. Figure 3 As shown, it can better cope with flow field deviation. The centering requirement of ultrasonic transducers during on-site installation is relaxed from within 3 mm to within 10 mm, greatly reducing the requirements for on-site installation process.

[0039] According to the setting method of the ultrasonic transducer in this embodiment, even if a height deviation occurs during installation, the central airflow point can still fall on the sound channel to keep the measurement result unchanged.

[0040] An ultrasonic signal is emitted by one of each pair of ultrasonic transducers, and the channel for ultrasonic signal transmission is the measurement channel. Since the deflection of a single measurement channel covers a wider range of flow fields, in large-diameter pipes, the use of a radial center channel in combination with two channels can achieve the measurement accuracy that traditionally requires 5-8 channels.

[0041] The flow rate metering system for a large-diameter natural gas pipeline according to this embodiment can also be designed in a multi-channel manner, that is, multiple pairs of ultrasonic transducers are arranged in the large-diameter natural gas pipeline. When three pairs of ultrasonic transducers are used, Figure 4 As shown, the three virtual surfaces are parallel to each other and are equidistant, and the virtual surface in the middle is a plane along the axial direction; each pair of ultrasonic transducers corresponds to a virtual surface, and is located on both sides of the corresponding virtual surface, and the distance between them and the corresponding virtual surface is equal. The connecting line between the center points of the emitting surfaces of each pair of ultrasonic transducers intersects with the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline; the angle between the sound channel between each pair of ultrasonic transducers and the corresponding virtual surface is defined as Φ;

[0042] Then the expression of Φ is:

[0043]

[0044] Wherein, D represents the radius size of the ultrasonic transducer emitting surface, and L represents the distance between the center point of the ultrasonic transducer emitting surface and the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline.

[0045] In this embodiment, the diameter of the emitting surface of the ultrasonic transducer is generally between 16 and 20 mm, and the radius of the emitting surface of the ultrasonic transducer is mostly between 8 and 10 mm.

[0046] The three pairs of ultrasonic transducers may also adopt an alternating deflection angle method, wherein the alternating deflection angle method means that the extension lines of the connecting lines between the center points of the emitting surfaces of each pair of ultrasonic transducers intersect in sequence and are located in the same plane, such as Figure 5 shown.

[0047] Depend on Figure 4 and Figure 5 It can be seen that using three channels at the same caliber can achieve the same Figure 2 The measurement coverage of the five channels in the middle. The channels far away from the radial channels are used for auxiliary measurement to determine the deviation direction of the central airflow point. In this way, the distribution of the flow field in the entire flow channel can be effectively grasped. Compared with the traditional channel arrangement method in the market, it is not limited by the installation position and can automatically correct the measurement results according to the installation situation. In the scenario of large-caliber natural gas operation, it can effectively avoid the economic losses caused by measurement deviations of the owners.

[0048] In this embodiment, φ is determined according to the radius of the emitting surface of the ultrasonic transducer and the distance between the center point of the emitting surface of the ultrasonic transducer and the central axis of the virtual surface. The larger the diameter of the natural gas pipeline, the smaller φ is. By changing the deflection angle of the emitting surface of the ultrasonic transducer, it is easy to capture the central flow velocity of the flow field in the large-diameter natural gas pipeline, thereby improving the gas flow velocity measurement result in the large-diameter natural gas pipeline. At the same time, the number of ultrasonic transducers used is small, which can reduce power consumption and increase the airtightness of the large-diameter natural gas pipeline.

[0049] The above description is only a specific embodiment of the present invention, and a comparison of the effects of the specific embodiments and the related comparative examples, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A flow rate metering system for a large-diameter natural gas pipeline, comprising n pairs of ultrasonic transducers arranged opposite to each other, and each pair of ultrasonic transducers is fixedly connected to the inner wall of the large-diameter natural gas pipeline, wherein: n=1 or 3; n pairs of ultrasonic transducers are connected to a controller, and the controller is used for the ultrasonic transducer to receive or send ultrasonic waves; the characteristics are: n virtual surfaces are set along the direction parallel to the axis of the large-diameter natural gas pipeline; when n=1, one virtual surface is a plane along the axial direction; when n=3, the three virtual surfaces are parallel to each other and are equally spaced, and the virtual surface in the middle is a plane along the axial direction; then each pair of ultrasonic transducers corresponds to a virtual surface, and is located on both sides of the corresponding virtual surface, and the distance between the corresponding virtual surface and the corresponding virtual surface is equal, and the connecting line between the center points of the emitting surfaces of each pair of ultrasonic transducers intersects with the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline; the angle between the sound channel between each pair of ultrasonic transducers and the corresponding virtual surface is defined as Φ; Then the expression of Φ is: Wherein, D represents the radius size of the emitting surface of the ultrasonic transducer, and L represents the distance between the center point of the emitting surface of the transducer in the ultrasonic flowmeter and the median line on the corresponding virtual surface parallel to the axis of the large-diameter natural gas pipeline.

2. A flow rate metering system for a large-diameter natural gas pipeline according to claim 1, characterized in that: When n=3, the three pairs of ultrasonic transducers adopt the same deflection angle, and the same deflection angle means that the lines connecting the center points of the emission surfaces of each pair of ultrasonic transducers are parallel to each other.

3. A flow rate metering system for a large-diameter natural gas pipeline according to claim 1, characterized in that: When n=3, the three pairs of ultrasonic transducers adopt an alternating deflection angle mode, wherein the alternating deflection angle mode means that the extension lines of the connecting lines between the center points of the emitting surfaces of each pair of ultrasonic transducers intersect in sequence and are located in the same plane.

4. A flow rate metering system for a large-diameter natural gas pipeline according to claim 1, characterized in that: Each pair of ultrasonic transducers is a flow meter sensor integrating ultrasonic emission and reception.

5. A flow rate metering system for a large-diameter natural gas pipeline according to claim 1, characterized in that: The controller is an MCU controller.

6. A flow rate measurement method for a large-diameter natural gas pipeline, characterized in that: A flow rate metering system for a large-diameter natural gas pipeline as described in any one of claims 1 to 5 is used, wherein one of the relatively arranged ultrasonic transducers is turned on by a controller to emit an ultrasonic signal, another ultrasonic transducer is controlled by the controller to receive the ultrasonic signal, and the flow rate of the large-diameter natural gas pipeline is calculated based on the received ultrasonic signal.

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