External clamp-on ultrasonic flow meter with bubble detection and flow correction and measurement method

Abstract

The application discloses an outer clamping type ultrasonic flowmeter with bubble detection and flow correction and a measuring method. The upper clamp module bottom and the lower clamp module top are connected through a connecting shaft, the upper clamp module and the lower clamp module are both provided with a limiting groove, the two limiting grooves form a pipeline groove, a liquid pipeline is clamped in the pipeline groove, a first acoustic impedance matching layer is arranged between a first ultrasonic transducer and the liquid pipeline, and a second acoustic impedance matching layer is arranged between a second ultrasonic transducer, a third ultrasonic transducer and the liquid pipeline. The method comprises judging whether there is a bubble according to the signal strength received by the ultrasonic transducer, measuring the liquid speed in the liquid pipeline by using the time difference method or the Doppler method, correcting the error caused by the bubble, and obtaining the correct liquid flow. The ultrasonic flowmeter is suitable for liquid single-phase flow and gas-liquid two-phase flow, compensates the liquid flow under the gas-liquid two-phase flow, and makes the flow measurement result more accurate.

Description

Technical Field

[0001] This invention relates to ultrasonic flow meter and method for ultrasonic liquid flow measurement technology, and in particular to an external clamp-on ultrasonic flow meter with bubble detection and flow correction and a measurement method thereof. Background Technology

[0002] Currently, in the field of ultrasonic liquid flow measurement, clamp-on ultrasonic liquid flow meters using the time-of-flight method have been widely used. However, the following problems still exist: under certain operating conditions, bubbles or cavities may appear in the measured liquid, significantly weakening the ultrasonic signal intensity received by the ultrasonic transducer and degrading the signal-to-noise ratio, thus reducing the accuracy of liquid flow measurement. Existing solutions typically employ signal processing methods such as filtering or additional sensors to identify and eliminate the influence of bubbles, but these methods are complex and have certain limitations. While the Doppler method can conveniently measure the flow velocity of gas-liquid two-phase flows, it cannot measure the size of bubbles or cavities to compensate for the liquid flow meter. Therefore, current technology lacks a simplified ultrasonic flow meter with bubble detection and flow correction functions to improve the accuracy and stability of flow measurement. Summary of the Invention

[0003] In order to solve the problems existing in the background art, the purpose of this invention is to design an external clamp-on ultrasonic flow meter with bubble detection and flow correction and a measurement method thereof.

[0004] The technical solution of this invention is as follows:

[0005] I. An external clamp-on ultrasonic flow meter with bubble detection and flow correction:

[0006] The flow meter includes an upper clamp module, a lower clamp module, and a connecting shaft. The upper clamp module is located above the lower clamp module. The rear end of the bottom of the upper clamp module and the rear end of the top of the lower clamp module are movably connected by the connecting shaft. The upper clamp module can be rotatably mounted on the lower clamp module along the axis of the connecting shaft. The front end of the bottom of the upper clamp module and the front end of the top of the lower clamp module are movably connected by bolts. A strip-shaped limiting groove is provided in the middle of the bottom of the upper clamp module and the middle of the top of the lower clamp module. The two strip-shaped limiting grooves together form a columnar pipe groove. The liquid pipe whose flow rate is to be measured is clamped in the columnar pipe groove between the upper clamp module and the lower clamp module. Both the upper clamp module and the lower clamp module are provided with radio frequency coaxial connectors for connection to an external CNC system.

[0007] The lower clamp module includes a lower clamp housing, a first acoustic impedance matching layer, a first ultrasonic transducer, a first lead wire, and a first radio frequency coaxial connector. A first slot is formed in the middle of the upper part of the lower clamp housing, and the first acoustic impedance matching layer is placed in the first slot. A first strip-shaped groove with a semi-circular cross-section is formed on both sides of the top of the lower clamp housing. A first L-shaped hole is formed on one side of the lower part of the lower clamp housing, communicating with the first slot and located below the slot. The first ultrasonic transducer and the first radio frequency coaxial connector are respectively located at the inner and outer ends of the first L-shaped hole, and are connected by the first lead wire. The first radio frequency coaxial connector is connected to an external CNC system via a radio frequency connection wire.

[0008] The upper surface of the first acoustic impedance matching layer is an arc surface. The left and right sides of the upper surface of the first acoustic impedance matching layer are higher than the arc sides of the inner side of the two first strip grooves. The first ultrasonic transducer is in contact with the lower surface of the first acoustic impedance matching layer. The side of the lower surface of the first acoustic impedance matching layer that is in contact with the first ultrasonic transducer is taken as the first standard side. The first standard side and the first ultrasonic transducer have the same tilt angle.

[0009] The upper clamp module includes an upper clamp housing, a second acoustic impedance matching layer, a second ultrasonic transducer, a third ultrasonic transducer, a second lead wire, a third lead wire, a second RF coaxial connector, and a third RF coaxial connector. A second slot is formed in the middle of the lower part of the upper clamp housing, and the second acoustic impedance matching layer is placed in the second slot of the upper clamp housing. Second strip-shaped grooves with semi-circular cross-sections are formed on both sides of the bottom of the upper clamp housing. A second L-shaped hole and a third L-shaped hole are formed on both sides of the upper part of the upper clamp housing, respectively. The inner sides of the second L-shaped hole and the third L-shaped hole are respectively connected to the left and right sides of the second slot. The right sides are connected, and the second L-shaped hole and the third L-shaped hole are both located on the upper side of the second slot. The second ultrasonic transducer and the second radio frequency coaxial connector are respectively located at the inner end and the outer end of the second L-shaped hole, and the third ultrasonic transducer and the third radio frequency coaxial connector are respectively located at the inner end and the outer end of the third L-shaped hole. The second ultrasonic transducer and the second radio frequency coaxial connector are connected by a second lead wire, and the third ultrasonic transducer and the third radio frequency coaxial connector are connected by a third lead wire. The second radio frequency coaxial connector and the third radio frequency coaxial connector are respectively connected to the external CNC system through radio frequency connection wires.

[0010] The lower surface of the second acoustic impedance matching layer is an arc surface. The left and right sides of the lower surface of the second acoustic impedance matching layer are higher than the arc sides of the inner sides of the two second strip grooves. The second ultrasonic transducer and the third ultrasonic transducer are in contact with the left and right sides of the upper surface of the second acoustic impedance matching layer, respectively. The side of the upper surface of the second acoustic impedance matching layer that is in contact with the second ultrasonic transducer is designated as the second standard side, and the side of the upper surface of the second acoustic impedance matching layer that is in contact with the third ultrasonic transducer is designated as the third standard side. The tilt angles of the second standard side and the third standard side are the same as the tilt angles of the second ultrasonic transducer and the third ultrasonic transducer, respectively.

[0011] The first, second, and third ultrasonic transducers are all cylindrical structures. The angle between the circular plane of the first ultrasonic transducer and the horizontal plane is a first typical angle γ, the angle between the circular plane of the second ultrasonic transducer and the horizontal plane is a second typical angle α, and the angle between the circular plane of the third ultrasonic transducer and the horizontal plane is a third typical angle β.

[0012] The radius of the first strip groove cross section and the radius of the second strip groove cross section are both equal to the radius of the liquid pipe to be tested; the number and arrangement of the first strip groove in the lower clamp module and the first strip groove in the upper clamp module are the same and the groove openings are aligned, so that one end of the liquid pipe is set between a first strip groove and a second strip groove, the other end of the liquid pipe is set between another first strip groove and another second strip groove, and the middle part of the liquid pipe is clamped between the upper surface of the first acoustic impedance matching layer and the lower surface of the second acoustic impedance matching layer.

[0013] The first typical angle γ ranges from 30° to 40°; the second typical angle α ranges from 20° to 40°; and the third typical angle β ranges from 30° to 60°.

[0014] The first, second, and third ultrasonic transducers are made of piezoelectric ceramics.

[0015] II. A clamp-on ultrasonic flow measurement method with bubble detection and flow correction includes the following steps:

[0016] Step S1: First, the upper clamp module and the lower clamp module clamp the liquid pipeline to be tested. The CNC system then collects the signal amplitude of the output electrical signals from the first, second, and third ultrasonic transducers in real time.

[0017] If the signal amplitude of the third ultrasonic transducer at time t is not lower than the preset intensity threshold, it is assumed that no bubbles appear in the liquid pipe at time t, and the process proceeds to step S2 to obtain the flow rate Q of the liquid in the liquid pipe at time t.

[0018] If the signal amplitude of the third ultrasonic transducer at time t is lower than the preset intensity threshold, it is assumed that bubbles have appeared in the liquid pipe at time t, and the process proceeds to step S3 to obtain the flow rate Q of the liquid in the liquid pipe at time t.

[0019] Step S2: The flow rate Q of the liquid in the liquid pipe at time t is obtained according to the following formula:

[0020] Q=πd 2 v1 / 4

[0021] Where d is the inner diameter of the liquid pipe, and v1 is the flow velocity measured by the flow meter using the time difference method;

[0022] Step S3: Correct the initial flow rate measured by the flow meter using the second ultrasonic transducer to obtain the corrected final flow rate.

[0023] In step S1, the signal amplitude of the output electrical signals from the first, second, and third ultrasonic transducers is specifically acquired in real time using a numerical control system as follows:

[0024] The CNC system alternately transmits electrical signals to the first and third ultrasonic transducers. After receiving the electrical signal from the CNC system, the first ultrasonic transducer converts it into ultrasonic waves and transmits them to the third ultrasonic transducer. After receiving the ultrasonic waves emitted by the first ultrasonic transducer, the third ultrasonic transducer converts them into electrical signals and transmits them to the CNC system.

[0025] If no bubbles appear in the liquid pipeline, the third ultrasonic transducer receives the electrical signal from the CNC system and converts it into ultrasonic waves, which are then transmitted to the first ultrasonic transducer. The first ultrasonic transducer receives the ultrasonic waves emitted by the third ultrasonic transducer and converts them into electrical signals, which are then transmitted to the CNC system.

[0026] If air bubbles appear in the liquid pipeline, the third ultrasonic transducer receives the electrical signal from the CNC system and converts it into ultrasonic waves, which are then transmitted to the first and second ultrasonic transducers. The first ultrasonic transducer receives the ultrasonic waves emitted by the third ultrasonic transducer and converts them into electrical signals, which are then transmitted to the CNC system. The second ultrasonic transducer receives the ultrasonic waves emitted by the third ultrasonic transducer and converts them into electrical signals, which are then transmitted to the CNC system.

[0027] The specific steps of step S3 are as follows:

[0028] First, the cross-sectional area S of the bubble at time t is obtained using the signal amplitudes of the output electrical signals from the first and third ultrasonic transducers. Then, the flow rate Q of the liquid in the liquid pipe at time t is obtained using the following formula:

[0029] Q=(πd 2 / 4-S)v2

[0030] Where d is the inner diameter of the liquid pipe, and v2 is the flow velocity measured by the flow meter using the Doppler method.

[0031] Working principle of the invention:

[0032] 1. Ultrasonic transducers used for time-of-flight flow detection measure the flow rate of liquids using the time-of-flight method. When the direction of ultrasonic wave propagation is on the same side as the direction of liquid flow, the propagation of ultrasonic waves will be accelerated, and vice versa. By analyzing the ultrasonic signals of the forward and reverse flow, the time delay and liquid velocity can be calculated, and then the flow rate can be calculated based on the cross-sectional area of ​​the fluid.

[0033] 2. There is a huge acoustic impedance between air and most liquids (typically water). When ultrasonic waves pass through the interface between the two phases, most of them are reflected, and only a small portion of the ultrasonic waves pass through the interface and propagate in the original direction. Therefore, by performing amplitude intensity threshold detection on the signal received by the ultrasonic transducer, it can be determined whether bubbles are generated. Furthermore, by establishing the relationship between the threshold level and the cross-sectional area of ​​the bubble perpendicular to the pipe axis, the flow rate of the liquid in the gas-liquid two-phase flow can be corrected.

[0034] 3. When bubbles are detected, an ultrasonic transducer for Doppler flow detection is used. The ultrasonic transducer for Doppler flow detection uses the Doppler method to measure the flow rate of the liquid. According to the Doppler effect, the ultrasonic waves reflected by the moving bubbles will generate a Doppler frequency shift. By performing spectrum analysis on the ultrasonic signal received by the ultrasonic transducer, the corresponding frequency shift and liquid velocity can be obtained. The product of the liquid velocity and the corrected cross-sectional area of ​​the pipe is used as the compensated liquid flow rate.

[0035] Because of the above technical solution, a time-difference flow rate transducer can be used to measure the flow rate of liquids under single-phase flow conditions using the time-difference method. Simultaneously, threshold detection is performed on the intensity of the signal received by the ultrasonic transducer to determine whether bubbles are generated and to detect the size of the bubbles. When bubbles are present, the flow rate of the gas-liquid two-phase flow is measured using an ultrasonic transducer for Doppler flow detection. Furthermore, the flow rate measured by the ultrasonic transducer for Doppler flow detection is corrected using the cross-sectional area of ​​the bubble perpendicular to the pipe axis, as measured by the ultrasonic transducer for time-difference flow detection.

[0036] The beneficial effects of this invention are as follows:

[0037] 1. The ultrasonic flow meter of the present invention is suitable for various working conditions including single-phase liquid flow and two-phase gas-liquid flow. It can compensate for the flow rate of liquid volume under two-phase gas-liquid flow, making the flow measurement results more accurate.

[0038] 2. The ultrasonic flow meter of this invention has a highly sensitive bubble detection capability, enabling timely identification and detection of bubbles or cavities in the fluid. Accurate bubble detection allows for early detection of bubbles and the implementation of appropriate measures, thereby preventing bubbles from interfering with the flow meter's measurement results.

[0039] 3. Based on the results of bubble detection, the ultrasonic flow meter of this invention also has a flow correction function. When bubbles are detected, the flow meter corrects the flow rate according to the characteristics of the bubbles and the fluid motion state to reduce or eliminate the influence of bubbles on the flow measurement results. Flow correction improves the accuracy and stability of the flow meter, ensuring reliable flow measurement data.

[0040] 4. This invention adopts an external clamp design, meaning that the ultrasonic sensor is installed around the fluid pipeline. This design makes installation and maintenance more convenient, without requiring changes to the pipeline structure or direct contact with the fluid, reducing interference and intervention with the pipeline, and improving the reliability and service life of the equipment. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0043] Figure 2 This is a schematic diagram of the upper clamp module;

[0044] Figure 3 This is a schematic diagram of the lower clamp module;

[0045] Figure 4 This is the left view of the present invention;

[0046] Figure 5 For the upper clamp module in Figure 4 Sectional view at point AA;

[0047] Figure 6 For the lower clamp module in Figure 4 Sectional view at point AA;

[0048] Figure 7 This is a comparison diagram of ultrasonic signals received by ultrasonic transducers under single-phase liquid flow and two-phase gas-liquid flow conditions.

[0049] In the diagram: 11. Lower clamp housing; 12. First acoustic impedance matching layer; 21. First ultrasonic transducer; 22. First L-shaped hole; 23. First lead wire; 31. Second ultrasonic transducer; 32. Second L-shaped hole; 33. Second lead wire; 41. Third ultrasonic transducer; 42. Third L-shaped hole; 43. Third lead wire; 51. Upper clamp housing; 52. Second acoustic impedance matching layer; 6. Liquid pipe; 7. Connecting shaft; 8. Nut. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0051] like Figures 1-4 As shown, the flow meter includes an upper clamp module, a lower clamp module, and a connecting shaft 7. The upper clamp module is located above the lower clamp module. The rear end of the bottom of the upper clamp module and the rear end of the top of the lower clamp module are movably connected via the connecting shaft 7. The upper clamp module can be rotatably mounted on the lower clamp module along the axis of the connecting shaft 7. The front end of the bottom of the upper clamp module and the front end of the top of the lower clamp module are movably connected via bolts. A strip-shaped limiting groove is provided in the middle of the bottom of the upper clamp module and the middle of the top of the lower clamp module. After the slots are connected, they together form a columnar pipe groove. The cross-section of the strip-shaped limiting groove is approximately semi-circular. The two strip-shaped limiting grooves form a columnar pipe groove with an approximately circular cross-section. The cross-section is perpendicular to the axis of the liquid pipe 6. The longitudinal section is parallel to the axis of the liquid pipe 6 and parallel to the front and rear sides of the flow meter. The liquid pipe 6 with the flow rate to be measured is clamped in the columnar pipe groove between the upper clamp module and the lower clamp module. Both the upper clamp module and the lower clamp module are equipped with radio frequency coaxial connectors for connection to an external CNC system.

[0052] The flow meter's rear direction is the end closest to the connecting shaft 7, and the flow meter's front direction is the end furthest from the connecting shaft 7. The flow meter's left-right direction is perpendicular to its front-back direction.

[0053] like Figure 3 He Ru Figure 6As shown, the lower clamp module includes a lower clamp housing 11, a first acoustic impedance matching layer 12, a first ultrasonic transducer 21, a first lead wire 23, and a first radio frequency coaxial connector. A first slot is formed in the middle of the upper part of the lower clamp housing 11, and the first acoustic impedance matching layer 12 is placed in the first slot of the lower clamp housing 11. First strip-shaped grooves with a semi-circular cross-section are formed on both sides of the top of the lower clamp housing 11. A first L-shaped hole 22 with an L-shaped longitudinal section is formed on one side (i.e., the left side) of the lower part of the lower clamp housing 11. The inner end of the hole 22 communicates with the first slot, and the first L-shaped hole 22 is located on the lower left side of the first slot. The first ultrasonic transducer 21 and the first radio frequency coaxial connector are respectively disposed at the inner end and the outer end of the first L-shaped hole 22. The inner end and the outer end are respectively the ends of the L-shaped hole that are close to the inner and outer circumferences of the flowmeter. The first ultrasonic transducer 21 and the first radio frequency coaxial connector are connected by the first lead wire 23. The first radio frequency coaxial connector is connected to the external CNC system through the radio frequency connection wire. The first lead wire 23 is disposed in the first L-shaped hole 22.

[0054] The upper surface of the first acoustic impedance matching layer 12 is an arc surface. The left and right sides of the upper surface of the first acoustic impedance matching layer 12 are slightly higher than the arc sides of the inner side of the two first strip grooves. That is, the arc at the left end of the upper surface of the first acoustic impedance matching layer 12 is slightly higher than the right arc at the left end of the first strip groove, and the arc at the right end of the upper surface of the first acoustic impedance matching layer 12 is slightly higher than the left arc at the right end of the first strip groove. The lower surface of the first ultrasonic transducer 21 is in contact with the lower surface of the first acoustic impedance matching layer 12. The side of the lower surface of the first acoustic impedance matching layer 12 that is in contact with the first ultrasonic transducer 21 is taken as the first standard side. The first standard side and the plane where the first ultrasonic transducer 21 is located have the same tilt angle.

[0055] like Figure 2 and Figure 5 As shown, the upper clamp module includes an upper clamp housing 51, a second acoustic impedance matching layer 52, a second ultrasonic transducer 31, a third ultrasonic transducer 41, a second lead wire 33, a third lead wire 43, a second radio frequency coaxial connector, and a third radio frequency coaxial connector.

[0056] A second slot is provided in the middle of the lower part of the upper clamp housing 51. The second acoustic impedance matching layer 52 is placed in the second slot of the upper clamp housing 51. A second strip-shaped groove with a semi-circular cross-section is provided on both sides of the bottom of the upper clamp housing 51. A second L-shaped hole 32 and a third L-shaped hole 42 with an L-shaped longitudinal section are respectively provided on both sides of the upper part of the upper clamp housing 51. The inner sides of the second L-shaped hole 32 and the third L-shaped hole 42 are respectively connected to the left and right sides of the second slot, and both the second L-shaped hole 32 and the third L-shaped hole 42 are located on the upper side of the second slot. The second ultrasonic transducer 31 and the second radio frequency coaxial connector are respectively disposed in the second L-shaped hole 32. The inner and outer ends of the third ultrasonic transducer 41 and the third radio frequency coaxial connector are respectively located at the inner and outer ends of the third L-shaped hole 42. The inner and outer ends are located at one end of the inner and outer circumference of the flowmeter in the L-shaped holes 22, 32, and 42, respectively. The second ultrasonic transducer 31 and the second radio frequency coaxial connector are connected by the second lead 33, and the third ultrasonic transducer 41 and the third radio frequency coaxial connector are connected by the third lead 43. The second radio frequency coaxial connector and the third radio frequency coaxial connector are respectively connected to the external CNC system through radio frequency connection lines. The second lead 33 and the third lead 43 are respectively located in the second L-shaped hole 32 and the third L-shaped hole 42.

[0057] The lower surface of the second acoustic impedance matching layer 52 is an arc surface. The left and right sides of the lower surface of the second acoustic impedance matching layer 52 are slightly higher than the arc sides of the inner side of the two second strip grooves. That is, the arc at the left end of the lower surface of the second acoustic impedance matching layer 52 is slightly higher than the right arc at the left end of the second strip groove, and the arc at the right end of the lower surface of the second acoustic impedance matching layer 52 is slightly higher than the left arc at the right end of the second strip groove. The second ultrasonic transducer 31 and the third ultrasonic transducer 41 are in contact with the left and right sides of the upper surface of the second acoustic impedance matching layer 52, respectively. The side of the upper surface of the second acoustic impedance matching layer 52 that is in contact with the second ultrasonic transducer 31 is taken as the second standard side, and the side of the upper surface of the second acoustic impedance matching layer 52 that is in contact with the third ultrasonic transducer 41 is taken as the third standard side. The tilt angles of the second standard side and the third standard side are the same as the tilt angles of the plane where the second ultrasonic transducer 31 and the plane where the third ultrasonic transducer 41 are located, respectively.

[0058] The first ultrasonic transducer 21, the second ultrasonic transducer 31, and the third ultrasonic transducer 41 are all flat solid cylindrical structures. The angle between the circular plane of the first ultrasonic transducer 21 and the horizontal plane is the first typical angle γ, the angle between the circular plane of the second ultrasonic transducer 31 and the horizontal plane is the second typical angle α, and the angle between the circular plane of the third ultrasonic transducer 41 and the horizontal plane is the third typical angle β. That is, the angle between the first standard side and the horizontal plane is the first typical angle γ, the angle between the second standard side and the horizontal plane is the second typical angle α, and the angle between the third standard side and the horizontal plane is the third typical angle β.

[0059] The radii of the first and second strip grooves are both equal to the radius of the liquid pipe 6 under test, so that the liquid pipe 6 under test is clamped between the two strip grooves. The curvature of the acoustic impedance matching layers 12 and 52 is slightly different from that of the liquid pipe 6 under test, so that the liquid pipe 6 under test can press the acoustic impedance matching layers 12 and 52 tightly after installation. The number and arrangement of the first strip grooves in the lower clamp module and the first strip grooves in the upper clamp module are the same, and the groove openings are aligned vertically. This makes the left end of the liquid pipe 6 set between the left first strip groove and the left second strip groove, and the right end of the liquid pipe 6 set between the right first strip groove and the corresponding right second strip groove. The middle part of the liquid pipe 6 is clamped between the upper surface of the first acoustic impedance matching layer 12 and the lower surface of the second acoustic impedance matching layer 52.

[0060] The first typical angle γ ranges from 30° to 40°; the second typical angle α ranges from 20° to 40°; and the third typical angle β ranges from 30° to 60°.

[0061] The first ultrasonic transducer 21, the second ultrasonic transducer 31, and the third ultrasonic transducer 41 are made of piezoelectric ceramic and are in the shape of a circular plate.

[0062] The lower clamp housing 11 has a first protrusion and a second protrusion on the left and right sides of the top rear end, respectively. The first protrusion has a blind hole, and the second protrusion has a threaded through hole. The lower clamp housing 11 has a first flange in the middle of the top front end, and the first flange has a through hole. The upper clamp housing 51 has a third protrusion in the middle of the bottom rear end, and the third protrusion has a through hole. The upper clamp housing 51 has a second flange in the middle of the bottom front end, and the second flange has a threaded through hole. The third protrusion is located between the first protrusion and the second protrusion. One end of the connecting shaft 7 passes through the second protrusion and the third protrusion in sequence and is fixed at the blind hole of the first protrusion. The other end of the connecting shaft 7 is connected to the second protrusion by a nut 8. The first flange and the second flange are connected by bolts to compress the liquid pipeline 6.

[0063] The inner ends of the L-shaped holes 22, 32, and 42 have a two-step stepped structure, with the upper step being smaller than the lower step. The ultrasonic transducers 21, 31, and 41 are confined within the lower step. The upper step is designed to prevent the ultrasonic transducers 21, 31, and 41 from moving towards the outer ends of the L-shaped holes 22, 32, and 42, while also providing an air backing for the ultrasonic transducers 21, 31, and 41 to absorb vibrations. The thickness of the ultrasonic transducers 21, 31, and 41 is slightly greater than the height of the lower step, causing the ultrasonic transducers 21, 31, and 41 to be pressed against the acoustic impedance matching layers 12 and 52.

[0064] The first ultrasonic transducer 21, the first lead 23, and the first radio frequency coaxial connector constitute the first ultrasonic transducer assembly; the second ultrasonic transducer 31, the second lead 33, and the second radio frequency coaxial connector constitute the second ultrasonic transducer assembly; and the third ultrasonic transducer 41, the third lead 43, and the third radio frequency coaxial connector constitute the third ultrasonic transducer assembly. The second and third ultrasonic transducer assemblies are used for Doppler flow measurement, and the first and third ultrasonic transducer assemblies are used for time-difference flow measurement.

[0065] The first acoustic impedance matching layer 12 is disposed between the first ultrasonic transducer 21 and the liquid pipe 6. The first acoustic impedance matching layer 12 is attached to the outer surface of the liquid pipe 6 through the arc surface and to the surface of the first ultrasonic transducer 21 through the plane where the first typical angle γ is located.

[0066] The second acoustic impedance matching layer 52 is disposed between the ultrasonic transducers 31 and 41 and the liquid pipe 6 being measured. The second acoustic impedance matching layer 52 is attached to the outer surface of the liquid pipe 6 through the arc surface, attached to the surface of the second ultrasonic transducer 31 through the plane of the second typical angle α, and attached to the surface of the third ultrasonic transducer 41 through the plane of the third typical angle β.

[0067] In the ultrasonic transducer assembly used for time-of-flight flow measurement, the first ultrasonic transducer 21 and the third ultrasonic transducer 41 alternately transmit and receive ultrasonic beams along their respective central axes at a typical frequency f; the typical frequency f of the ultrasonic waves is 1MHz to 10MHz.

[0068] In the ultrasonic transducer assembly used for Doppler flow measurement, the third ultrasonic transducer 41 emits an ultrasonic beam at a typical frequency, and the second ultrasonic transducer 31 receives the ultrasonic signal reflected by the bubble.

[0069] like Figure 7This section compares the ultrasonic signals received by the ultrasonic transducer under single-phase liquid flow and two-phase gas-liquid flow conditions. The four different signal intensities received by the ultrasonic transducer 41, ranked from strongest to weakest, correspond to two-phase gas-liquid flow patterns: no bubbles, bubbles with a diameter of 3 / 4 of the pipe's inner diameter, bubbles with a diameter of 1 / 2 of the pipe's inner diameter, and bubbles with a diameter of 1 / 4 of the pipe's inner diameter. By establishing the relationship between the intensity of the ultrasonic transducer's received signal and the cross-sectional area of ​​the bubble perpendicular to the pipe axis, the bubble volume can be calculated from the received signal, thus correcting the liquid flow rate.

[0070] The measurement method of the present invention includes the following steps:

[0071] Step S1: First, the upper clamp module and the lower clamp module clamp the liquid pipe 6 to be tested. The CNC system is used to collect the signal amplitude of the output electrical signals from the first ultrasonic transducer 21, the second ultrasonic transducer 31, and the third ultrasonic transducer 41 in real time.

[0072] If the signal amplitude of the third ultrasonic transducer 41 at time t is not lower than the preset intensity threshold, it is considered that no bubbles appear in the liquid pipe 6 at time t, and the process proceeds to step S2 to obtain the flow rate Q of the liquid in the liquid pipe 6 at time t.

[0073] If the signal amplitude of the third ultrasonic transducer 41 at time t is lower than the preset intensity threshold, it is considered that bubbles have appeared in the liquid pipe 6 at time t, and the process proceeds to step S3 to obtain the flow rate Q of the liquid in the liquid pipe 6 at time t.

[0074] Step S2: Whether bubbles appear or not, the flow rate Q of the liquid in the liquid pipe 6 at time t is obtained according to the following formula:

[0075] Q=πd 2 v1 / 4

[0076] Where d is the inner diameter of liquid pipe 6, v1 is the flow velocity measured by the flow meter using the time difference method; π is taken as 3.14159; t is the time when the flow meter measures the flow rate;

[0077] Step S3: When bubbles appear, the initial flow rate measured by the flow meter is corrected using the second ultrasonic transducer 31 to obtain the corrected final flow rate.

[0078] In step S1, the signal amplitude of the output electrical signals from the first ultrasonic transducer 21, the second ultrasonic transducer 31, and the third ultrasonic transducer 41 is collected in real time using the CNC system, specifically as follows:

[0079] The CNC system alternately transmits electrical signals to the first ultrasonic transducer 21 and the third ultrasonic transducer 41. After receiving the electrical signal from the CNC system, the first ultrasonic transducer 21 converts it into ultrasonic waves and transmits them to the third ultrasonic transducer 41. After receiving the ultrasonic waves emitted by the first ultrasonic transducer 21, the third ultrasonic transducer 41 converts them into electrical signals and transmits them back to the CNC system.

[0080] If no bubbles appear in the liquid pipe 6, the third ultrasonic transducer 41 receives the electrical signal from the CNC system and converts it into ultrasonic waves, most of which are transmitted to the first ultrasonic transducer 21. The first ultrasonic transducer 21 receives the ultrasonic waves emitted by the third ultrasonic transducer 41 and converts them into electrical signals, which are transmitted back to the CNC system. The second ultrasonic transducer 31 receives very few ultrasonic waves. When using the time difference method to obtain the flow rate of the liquid pipe 6, the waveform information of the ultrasonic waves received by the second ultrasonic transducer 31 is not considered.

[0081] If air bubbles appear in the liquid pipe 6, the third ultrasonic transducer 41 receives the electrical signal from the CNC system and converts it into ultrasonic waves, which are then transmitted to the first ultrasonic transducer 21 and the second ultrasonic transducer 31 respectively. The first ultrasonic transducer 21 receives the ultrasonic waves emitted by the third ultrasonic transducer 41 and converts them into electrical signals, which are then transmitted back to the CNC system. The second ultrasonic transducer 31 receives the ultrasonic waves emitted by the third ultrasonic transducer 41 and converts them into electrical signals, which are then transmitted back to the CNC system.

[0082] If no bubbles appear in the liquid pipe 6, the flow velocity v1 in the liquid pipe 6 can be obtained by using the time difference method based on the waveform information of the output electrical signals from the first ultrasonic transducer 21 and the third ultrasonic transducer 41. Thus, the flow rate in the liquid pipe 6 can be obtained.

[0083] Step S3 is as follows:

[0084] First, the cross-sectional area S of the bubble at time t is obtained using the signal amplitude of the electrical signals output by the first ultrasonic transducer 21 and the third ultrasonic transducer 41. Then, the flow rate Q of the liquid in the liquid pipe 6 at time t is obtained according to the following formula:

[0085] Q=(πd 2 / 4-S)v2

[0086] Where d is the inner diameter of liquid pipe 6, v2 is the flow velocity measured by the flow meter using the Doppler method, π is taken as 3.14159, and t is the time when the flow meter measures the flow rate.

[0087] If bubbles appear in the liquid pipe 6, the flow velocity v2 in the liquid pipe 6 can be obtained by using the Doppler method based on the signal frequencies of the output electrical signals from the second ultrasonic transducer 31 and the third ultrasonic transducer 41. The cross-sectional area S of the bubble in the liquid pipe 6 at time t can be obtained by using the threshold method based on the signal amplitudes of the output electrical signals from the first ultrasonic transducer 21 and the third ultrasonic transducer 41. Then, the flow rate in the liquid pipe 6 can be obtained by flow rate correction.

Claims

1. A clamp-on ultrasonic flow measurement method for clamp-on ultrasonic flow meters with bubble detection and flow correction, characterized in that: The external clamp ultrasonic flow meter includes an upper clamp module, a lower clamp module, and a connecting shaft (7); the upper clamp module is located above the lower clamp module, and the rear end of the bottom of the upper clamp module and the rear end of the top of the lower clamp module are movably connected by the connecting shaft (7). The upper clamp module can be rotatably mounted on the lower clamp module along the axis of the connecting shaft (7), and the front end of the bottom of the upper clamp module and the front end of the top of the lower clamp module are movably connected by bolts; a strip-shaped limiting groove is provided in the middle of the bottom of the upper clamp module and the middle of the top of the lower clamp module, and the two strip-shaped limiting grooves together form a columnar pipe groove. The liquid pipe (6) whose flow rate is to be measured is clamped in the columnar pipe groove between the upper clamp module and the lower clamp module; both the upper clamp module and the lower clamp module are provided with radio frequency coaxial connectors for connection with an external CNC system; The lower clamp module includes a lower clamp housing (11), a first acoustic impedance matching layer (12), a first ultrasonic transducer (21), a first lead wire (23), and a first radio frequency coaxial connector; The upper clamp module includes an upper clamp housing (51), a second acoustic impedance matching layer (52), a second ultrasonic transducer (31), a third ultrasonic transducer (41), a second lead wire (33), a third lead wire (43), a second radio frequency coaxial connector, and a third radio frequency coaxial connector. The measurement method includes the following steps: Step S1: First, the upper clamp module and the lower clamp module clamp the liquid pipe (6) to be tested. The signal amplitude of the output electrical signal from the first ultrasonic transducer (21), the second ultrasonic transducer (31) and the third ultrasonic transducer (41) is collected in real time using the CNC system. If the signal amplitude of the third ultrasonic transducer (41) at time t is not lower than the preset intensity threshold, it is considered that no bubbles appear in the liquid pipe (6) at time t, and the process proceeds to step S2 to obtain the flow rate Q of the liquid in the liquid pipe (6) at time t. If the signal amplitude of the third ultrasonic transducer (41) at time t is lower than the preset intensity threshold, it is considered that bubbles appear in the liquid pipe (6) at time t, and the process proceeds to step S3 to obtain the flow rate Q of the liquid in the liquid pipe (6) at time t. In step S2, the flow rate Q of the liquid in the liquid pipe (6) at time t is obtained according to the following formula: Q=πd 2 v 1 / 4 Where d is the inner diameter of the liquid pipe (6), v 1 The flow velocity measured by the flow meter using the time-of-flight method; Step S3: Use the second ultrasonic transducer (31) to correct the initial flow rate measured by the flow meter to obtain the corrected final flow rate; The specific steps of step S3 are as follows: First, the signal amplitudes of the output electrical signals of the first ultrasonic transducer (21) and the third ultrasonic transducer (41) are obtained. The cross-sectional area S of the bubble at time t is obtained using the signal amplitudes. Then, the flow rate Q of the liquid in the liquid pipe (6) at time t is obtained according to the following formula: Q=(πd 2 / 4-S) v 2 Where d is the inner diameter of the liquid pipe (6), v 2 represents the flow velocity measured by the flow meter using the Doppler method.

2. The clamp-on ultrasonic flow measurement method with bubble detection and flow correction according to claim 1, characterized in that: A first slot is provided in the middle of the upper part of the lower clamp housing (11). The first acoustic impedance matching layer (12) is placed in the first slot of the lower clamp housing (11). A first strip groove with a semi-circular cross-section is provided on both sides of the top of the lower clamp housing (11). A first L-shaped hole (22) is provided on one side of the lower part of the lower clamp housing (11). The first L-shaped hole (22) is connected to the first slot and is located below the first slot. The first ultrasonic transducer (21) and the first radio frequency coaxial connector are respectively located at the inner end and the outer end of the first L-shaped hole (22). The first ultrasonic transducer (21) and the first radio frequency coaxial connector are connected by a first lead wire (23). The first radio frequency coaxial connector is connected to an external CNC system through a radio frequency connection wire. The upper surface of the first acoustic impedance matching layer (12) is an arc surface. The left and right sides of the upper surface of the first acoustic impedance matching layer (12) are higher than the arc sides of the inner side of the two first strip grooves. The lower surface of the first ultrasonic transducer (21) and the first acoustic impedance matching layer (12) are in contact. The side of the lower surface of the first acoustic impedance matching layer (12) that is in contact with the first ultrasonic transducer (21) is taken as the first standard side. The first standard side and the first ultrasonic transducer (21) have the same tilt angle.

3. The clamp-on ultrasonic flow measurement method with bubble detection and flow correction according to claim 2, characterized in that: A second slot is provided in the middle of the lower part of the upper clamp housing (51). The second acoustic impedance matching layer (52) is placed in the second slot of the upper clamp housing (51). A second strip-shaped groove with a semi-circular cross-section is provided on both sides of the bottom of the upper clamp housing (51). A second L-shaped hole (32) and a third L-shaped hole (42) are provided on both sides of the upper part of the upper clamp housing (51). The inner sides of the second L-shaped hole (32) and the third L-shaped hole (42) are respectively connected to the left and right sides of the second slot. The second L-shaped hole (32) and the third L-shaped hole (42) are both located on the upper side of the second slot. Two ultrasonic transducers (31) and a second radio frequency coaxial connector are respectively located at the inner and outer ends of the second L-shaped hole (32). A third ultrasonic transducer (41) and a third radio frequency coaxial connector are respectively located at the inner and outer ends of the third L-shaped hole (42). The second ultrasonic transducer (31) and the second radio frequency coaxial connector are connected by a second lead (33). The third ultrasonic transducer (41) and the third radio frequency coaxial connector are connected by a third lead (43). The second radio frequency coaxial connector and the third radio frequency coaxial connector are respectively connected to an external CNC system through radio frequency connection lines. The lower surface of the second acoustic impedance matching layer (52) is an arc surface. The left and right sides of the lower surface of the second acoustic impedance matching layer (52) are higher than the arc sides of the inner side of the two second strip grooves. The second ultrasonic transducer (31) and the third ultrasonic transducer (41) are in contact with the left and right sides of the upper surface of the second acoustic impedance matching layer (52) respectively. The side of the upper surface of the second acoustic impedance matching layer (52) that is in contact with the second ultrasonic transducer (31) is taken as the second standard side surface. The side of the upper surface of the second acoustic impedance matching layer (52) that is in contact with the third ultrasonic transducer (41) is taken as the third standard side surface. The tilt angles of the second standard side surface and the third standard side surface are the same as the tilt angles of the second ultrasonic transducer (31) and the third ultrasonic transducer (41) respectively.

4. The clamp-on ultrasonic flow measurement method with bubble detection and flow correction according to claim 3, characterized in that: The first ultrasonic transducer (21), the second ultrasonic transducer (31) and the third ultrasonic transducer (41) are all cylindrical structures. The angle between the circular plane of the first ultrasonic transducer (21) and the horizontal plane is the first typical angle γ, the angle between the circular plane of the second ultrasonic transducer (31) and the horizontal plane is the second typical angle α, and the angle between the circular plane of the third ultrasonic transducer (41) and the horizontal plane is the third typical angle β.

5. The clamp-on ultrasonic flow measurement method with bubble detection and flow correction according to claim 3, characterized in that: The radius of the first strip groove cross section and the radius of the second strip groove cross section are both equal to the radius of the liquid pipe (6) to be tested; the number and arrangement of the first strip groove in the lower clamp module and the first strip groove in the upper clamp module are the same and the groove openings are aligned, so that one end of the liquid pipe (6) is set between a first strip groove and a second strip groove, and the other end of the liquid pipe (6) is set between another first strip groove and another second strip groove, and the middle part of the liquid pipe (6) is clamped between the upper surface of the first acoustic impedance matching layer (12) and the lower surface of the second acoustic impedance matching layer (52).

6. The clamp-on ultrasonic flow measurement method with bubble detection and flow correction according to claim 4, characterized in that: The first typical angle γ ranges from 30° to 40°; the second typical angle α ranges from 20° to 40°; and the third typical angle β ranges from 30° to 60°.

7. The clamp-on ultrasonic flow measurement method with bubble detection and flow correction according to claim 3, characterized in that: The first ultrasonic transducer (21), the second ultrasonic transducer (31) and the third ultrasonic transducer (41) are made of piezoelectric ceramic.

8. The clamp-on ultrasonic flow measurement method with bubble detection and flow correction according to claim 1, characterized in that: In step S1, the signal amplitude of the output electrical signals from the first ultrasonic transducer (21), the second ultrasonic transducer (31), and the third ultrasonic transducer (41) is collected in real time using a numerical control system as follows: The CNC system alternately transmits electrical signals to the first ultrasonic transducer (21) and the third ultrasonic transducer (41). After receiving the electrical signal from the CNC system, the first ultrasonic transducer (21) converts it into ultrasonic waves and transmits them to the third ultrasonic transducer (41). The third ultrasonic transducer (41) receives the ultrasonic waves emitted by the first ultrasonic transducer (21) and converts them into electrical signals and transmits them to the CNC system. If no bubbles appear in the liquid pipe (6), the third ultrasonic transducer (41) receives the electrical signal sent by the CNC system and converts it into ultrasonic waves, which are then transmitted to the first ultrasonic transducer (21). The first ultrasonic transducer (21) receives the ultrasonic waves sent by the third ultrasonic transducer (41) and converts them into electrical signals, which are then transmitted to the CNC system. If bubbles appear in the liquid pipe (6), the third ultrasonic transducer (41) receives the electrical signal from the CNC system and converts it into ultrasonic waves, which are then transmitted to the first ultrasonic transducer (21) and the second ultrasonic transducer (31). The first ultrasonic transducer (21) receives the ultrasonic waves emitted by the third ultrasonic transducer (41) and converts them into electrical signals, which are then transmitted to the CNC system. The second ultrasonic transducer (31) receives the ultrasonic waves emitted by the third ultrasonic transducer (41) and converts them into electrical signals, which are then transmitted to the CNC system.

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