CN114088151B - External clamping type multichannel ultrasonic flow detection device and detection method - Google Patents
External clamping type multichannel ultrasonic flow detection device and detection method Download PDFInfo
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- CN114088151B CN114088151B CN202111166356.9A CN202111166356A CN114088151B CN 114088151 B CN114088151 B CN 114088151B CN 202111166356 A CN202111166356 A CN 202111166356A CN 114088151 B CN114088151 B CN 114088151B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
- G01F1/662—Constructional details
Abstract
The invention provides an external clamping type multichannel ultrasonic flow detection device and method. According to the invention, the group of ultrasonic probes are arranged on the side wall of the pipeline, and the cross section area of the pipeline can be calculated by utilizing the ultrasonic thickness meter and the ultrasonic tomography principle. Two groups of ultrasonic probes are respectively arranged on two sides of the ultrasonic probe, and the flow velocity of the fluid can be calculated by using the improved ultrasonic time difference method through the two groups of ultrasonic probes. Fluid flow can be calculated from the flow rate and cross-sectional area. The ultrasonic information obtained by the method is large in quantity, the calculation method is advanced, the calculation errors of the flow cross section and the flow velocity are reduced, and the accuracy of flow measurement is effectively improved. The improved time difference method and the combined application of the ultrasonic thickness gauge principle and the ultrasonic tomography technology provide a new method for accurately calculating the flow.
Description
Technical Field
The invention relates to the technical field of two-phase flow detection, in particular to an external clamping type multichannel ultrasonic flow detection device and method.
Background
The existing liquid flow meters include electromagnetic flow meters, turbine flow meters, differential pressure flow meters, ultrasonic flow meters, and the like.
The electromagnetic flowmeter mainly comprises a signal converter and a sensor, and mainly utilizes the law of electromagnetic induction, a pair of detection electrodes are arranged in the vertical direction of the axis of a detected tube, when the flowmeter is connected into a liquid medium pipeline, and when a conductive liquid substance moves along the tube axis, the conductive liquid cuts magnetic force lines to move so as to generate induced electromotive force, and the induced electromotive force is detected by the detection electrodes.
The turbine flowmeter is a speed type flow meter and has the advantages of high measurement accuracy, high reaction speed, wide measurement range, low price, convenient installation and the like. The working principle of the device is that when fluid flows along the axis direction of a pipeline and impacts turbine blades, a force proportional to the flow acts on the blades to push the turbine to rotate. While the turbine rotates, the blades periodically cut the magnetic lines of force, and a pulsating potential signal is induced in the coil, the frequency of which is proportional to the flow of the fluid to be measured. The pulse signal output by the turbine transmitter is amplified by the preamplifier and then sent to the display instrument, so that the flow measurement is realized.
The differential pressure type flowmeter is a meter for measuring flow according to differential pressure generated by a flow detection member arranged in a pipeline, known fluid conditions and geometric dimensions of the detection member and the pipeline, and is a metering instrument for measuring flow which is widely used in early stage. The differential pressure flowmeter is composed of three parts: 1) A throttle device for converting the flow rate of the measured liquid into a differential pressure signal; 2) A signal line for transmitting a differential pressure signal; 3) Differential pressure gauge or differential pressure transmitter for measuring differential pressure value and display instrument. Differential pressure flowmeters, such as orifice plate flowmeters, venturi flowmeters, and averaging tube flowmeters, are typically classified in the form of a sensing element.
The ultrasonic waves used in ultrasonic flow meters have two important characteristics: (1) The frequency is very high, the wavelength is short, the light can propagate along a straight line, and the directivity is strong. (2) Ultrasonic energy propagates in a variety of media, such as gases, liquids, solids, or multiphase mixtures. When the ultrasonic wave propagates in the flowing fluid, the signal carries the flow velocity information of the fluid, the flow velocity of the fluid can be obtained by detecting the received ultrasonic wave signal, and then the flow velocity information is converted into flow velocity information through the pipe diameter. At present, ultrasonic flow meters can be mainly classified into a time difference method, a Doppler effect method, a beam shift method and a correlation method.
In an ultrasonic flowmeter, the flow velocity of a fluid can be obtained by detecting a received ultrasonic signal, and then the flow velocity is converted into flow information by pipe diameter. However, the current metering of the channel flow cross section is not accurate enough, and the detection accuracy of the fluid flow is affected.
Disclosure of Invention
The invention aims to provide an external clamping type multichannel ultrasonic flow detection device and an external clamping type multichannel ultrasonic flow detection method, which are used for solving the problem that the actual measurement accuracy of an ultrasonic flowmeter often cannot reach the set accuracy due to the fact that the flow section of the existing ultrasonic flowmeter cannot be accurately measured.
The invention is realized in the following way: an external clamping type multichannel ultrasonic flow detection device has the structure that: three different cross sections are arranged on the pipeline and are respectively marked as a first cross section, a second cross section and a third cross section; the first cross section is positioned between the second cross section and the third cross section, and the first cross section is equidistant from the second cross section and the third cross section; m ultrasonic probes are uniformly distributed on the first cross section, wherein M is an even number; each ultrasonic probe on the first cross section is vertical to the pipe wall; the diameter of the pipeline can be calculated based on the ultrasonic thickness gauge principle and the ultrasonic tomography technology through M ultrasonic probes on the first cross section, so that the cross section area of the pipeline can be calculated;
n ultrasonic probes are uniformly arranged on the second cross section and the third cross section respectively, wherein N is an even number; and N ultrasonic probes on the second cross section and N ultrasonic probes on the third cross section are in one-to-one correspondence on the same bus; each ultrasonic probe on the second cross section and the third cross section forms an included angle theta with the pipe wall, and the value range of theta is 10-80 degrees; each ultrasonic probe on the second cross section corresponds to the ultrasonic probe on the third cross section, and one ultrasonic probe which is symmetrically distributed about the center of the first cross section is always found, and the two ultrasonic probes are called a pair of ultrasonic probes; two pairs of ultrasonic probes can be used for solving one flow velocity, and the average value of the flow velocity can be obtained by averaging a plurality of flow velocities;
the fluid flow may be calculated from the conduit cross-sectional area and the flow velocity average.
In the process of solving one flow rate by two pairs of ultrasonic probes, the forward propagation time of ultrasonic waves in the fluid is measured by one pair of ultrasonic probes, and the backward propagation time of ultrasonic waves in the fluid is measured by the other pair of ultrasonic probes.
In the invention, each ultrasonic probe on the same cross section is installed and fixed through an additional device, the additional device is similar to a binding band structure, through holes are arranged on the additional device at equal intervals, and bayonets are arranged at the through holes so as to fix the ultrasonic probes.
The detection device also comprises a channel control module and a timing module which are connected with each ultrasonic probe, wherein the channel control module and the timing module are also respectively connected with the singlechip; the singlechip is connected with the upper computer through the USB communication module. The channel control module adopts a 74HC4052D chip, the timing module adopts a TDC-GP22 chip, and the singlechip adopts an MSP430FR6047 chip.
The detection method corresponding to the detection device comprises the following steps:
a. providing the ultrasonic probe described above on the side wall of the pipeline;
b. measuring the fluid flow rate based on an ultrasonic time difference method by using ultrasonic probes on the second cross section and the third cross section;
c. measuring the inner diameter of the pipeline based on the principle of an ultrasonic thickness gauge by using an ultrasonic probe on the first cross section, and calculating the average value;
d. c, when the inner diameter of the pipeline measured in the step c does not meet the requirement, measuring the positions and the sizes of scaling and corrosion positions on the inner wall of the pipeline based on an ultrasonic tomography technology by utilizing an ultrasonic probe on the first cross section;
e. solving the cross-sectional area of the pipeline based on the data in step c or step d;
f. and (c) calculating the fluid flow according to the fluid flow rate in the step b and the cross-sectional area of the pipeline in the step e.
The step b is specifically as follows:
b-1, under the control of the singlechip, the channel control module controls the ultrasonic probes to work simultaneously, wherein in each pair of ultrasonic probes, one ultrasonic probe is used for transmitting ultrasonic signals, and the other ultrasonic probe is used for receiving the ultrasonic signals;
b-2, a channel control module and a timing module collect ultrasonic signals transmitted/received by each ultrasonic probe and send the collected signals to a singlechip;
b-3, the singlechip stores and processes the received data and sends corresponding data to the upper computer;
b-4, calculating the flow rate by the upper computer according to the following formula:
in the above formula, T 1 Is the downstream propagation time of ultrasonic signals in the fluid, T 2 The counter-current propagation time of ultrasonic signals in fluid is L, and the distance between two ultrasonic probes on the same bus;
two pairs of ultrasonic probes can be used for solving one flow velocity v, and the flow velocity average value is obtained by solving a plurality of flow velocities.
The step d specifically comprises the following steps:
d-1, measuring the positions and the sizes of scaling and corrosion parts on the inner wall of the pipeline based on an ultrasonic tomography technology by utilizing an ultrasonic probe on the first cross section;
d-2, calculating the sector areas of the scaling and corrosion parts by using the scaling and corrosion part sizes of the inner wall of the pipeline, and calculating the rest sector areas by using the average value of the inner diameter of the pipeline in the step c;
d-3, adding the fan-shaped areas in the step d-2 to obtain the cross-sectional area of the pipeline.
Step d-1 is specifically as follows:
d-11, enabling the ultrasonic probes on the first cross section to sequentially perform one-shot and one-shot;
d-12, assuming that the wave speed attenuation is kept constant in each small grid, and obtaining all ultrasonic rays ti passing through the small grid s (x 0, y 0);
d-13, setting ultrasonic signals to propagate along a straight line, and solving si after wave speed attenuation by utilizing inverse radon transform discretization according to all ultrasonic rays ti passing through the small grid s (x 0, y 0) in the step d-12;
d-14, forming a matrix equation by all sis obtained in the step d-13, solving the equation, and obtaining s (x 0, y 0);
d-15, calculating the positions and the sizes of the scaling and corrosion positions according to s (x 0, y 0).
The step c is specifically as follows:
c-1, enabling the ultrasonic probe to emit ultrasonic signals;
c-2, receiving the primary echo and the secondary echo signal, and calculating the time difference of the primary echo, the secondary echo and the transmitted wave;
c-3, calculating the inner diameter of the pipeline according to the following formula:
wherein:
d, the inner diameter of the pipeline, m;
v-the flow velocity of the ultrasonic wave in the fluid, m/s;
Δt-the time interval between the primary echo and the secondary echo, s;
and c-4, averaging the inner diameter data of the multiple groups of pipelines.
The invention provides an external clamping type multichannel ultrasonic flow measurement method by utilizing an ultrasonic time difference principle and an ultrasonic tomography principle, wherein an ultrasonic array is utilized to perform tomography; according to the error theory, the influence degree of each parameter in the model on the flow measurement accuracy is explored. The ultrasonic information obtained by the method is large in quantity, the calculation method is advanced, the calculation errors of the flow cross section and the flow velocity are reduced, and the accuracy of flow measurement is effectively improved.
The improved time difference method, the application of ultrasonic tomography technology and the accurate flow calculation method are innovations of the invention, and the flow value of the fluid in the pipeline can be obtained with high precision through the combination of hardware innovation and algorithm innovation.
Drawings
Fig. 1 is a schematic diagram of a specific arrangement mode of 24 ultrasonic probes in an embodiment of the present invention.
Fig. 2 is a schematic diagram showing a specific arrangement of 4 ultrasonic transducers for measuring a flow rate in the embodiment of the present invention.
FIG. 3 is a flow chart of a method of measuring the inside diameter of a pipe using the principle of ultrasonic thickness gauge according to the present invention.
Fig. 4 is a flow chart of a method of measuring the inside diameter of a pipe based on the principle of ultrasonic thickness gauge and ultrasonic tomography in accordance with the present invention.
FIG. 5 is a flow chart of a method of measuring the inside diameter of a pipe using ultrasonic tomography in accordance with the present invention.
Fig. 6 is a schematic diagram of an ultrasound tomography technique of the present invention.
Fig. 7 is a schematic view of the structure of an ultrasonic probe attachment device according to the present invention.
Fig. 8 is a schematic structural connection diagram of an external clamp type multi-channel ultrasonic flow rate detection device in the present invention.
Fig. 9 is a block diagram of the hardware module of fig. 8.
FIG. 10 is a diagram showing the connection of crystal oscillators of a test apparatus according to an embodiment of the present invention.
Fig. 11 is a flow chart of the method for detecting the flow rate of the external clamp type multichannel ultrasonic wave in the invention.
Detailed Description
The invention provides an external clamping type multichannel ultrasonic flow standard device based on multichannel time difference method flow velocity measurement and multichannel ultrasonic tomography technology, which realizes accurate modeling of a flow section and accurate measurement of flow velocity by designing an integrated measuring device with a plurality of groups of ultrasonic probes matched for use, and provides a new scheme for a liquid flow standard device.
The invention designs an external clamping type multichannel ultrasonic flow standard device according to the principles of a time difference method and ultrasonic tomography, and ultrasonic signals are generated at the part which is clung to the outside of a pipe wall, and the ultrasonic signals are received by a counter probe. In order to obtain relatively reliable data, eight ultrasonic probes are arranged on a fluid flow section according to an equidistant method, and a tomography technology is utilized to model the cross section of a pipeline. And arranging sixteen other groups of probes at corresponding positions on the cross sections of the other two pipelines, wherein the two cross sections are symmetrically distributed relative to the cross section where the probes for measuring the cross section of the pipeline at the front are positioned. The probes on the two rear sections are consistent with the eight ultrasonic probes of the front measuring section in placement mode, and the probes on the two rear sections are used for measuring the flow velocity by a time difference method. Ultrasonic data are measured through the placed ultrasonic probe, the cross section information and the flow velocity information of the pipeline are calculated, and the flow of the fluid is calculated.
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the specific arrangement mode of 24 ultrasonic probes is shown in fig. 1, so that stable transceiving of ultrasonic signals is ensured, and the influence on the stability of fluid flow in a pipeline is avoided. In fig. 1, (a) is a front view, (b) is a top view, and (c) is a left side view. In the figure, the ultrasonic probes A, B, C, D, E, F, G, H are positioned on the same cross section of the pipeline in the clockwise direction, and the eight ultrasonic probes are uniformly distributed on the side wall of the pipeline. The cross section of the pipe in which these eight ultrasonic probes are located is referred to as a first cross section. The cross section of the pipe is measured by eight ultrasonic probes on the first cross section. The other 16 ultrasonic probes are equally divided into two groups, one group is ultrasonic probes A1-H1, the other group is ultrasonic probes A2-H2, the two groups of ultrasonic probes are respectively positioned at two sides of the first cross section, and each group of ultrasonic probes is evenly distributed on the same cross section of the pipeline. The cross section where the ultrasonic probes A1 to H1 are located is referred to as a second cross section, and the cross section where the ultrasonic probes A2 to H2 are located is referred to as a third cross section. The second cross section and the third cross section are equidistant from the first cross section. And the ultrasonic probes on the three cross sections are in one-to-one correspondence with the same relative position, and the relative positions among the ultrasonic probes on the three cross sections are kept horizontal to the fluid direction, namely: A. a1 and A2 are positioned on the same bus of the side wall of the pipeline, B, B1 and B2 are positioned on the same bus of the side wall of the pipeline, and the other bus is similar. The flow rate of the fluid was measured by 16 ultrasonic probes on the second cross section and the third cross section. The probes on each cross section do not interfere with each other, and relative errors are avoided.
The ultrasonic time difference method is based on the principle of velocity difference. As shown in fig. 2, four ultrasonic transducers, a ', B', C ', D', are disposed on the side wall of the pipeline, and are all transceiver-integrated ultrasonic transducers, so that the transmission and reception of ultrasonic waves can be realized. Wherein the ultrasonic transducers A 'and C' are positioned on the same cross section and are arranged oppositely, namely, the connecting line of the ultrasonic transducers A 'and C' passes through the center of the cross section; the ultrasonic transducers B 'and D' are positioned on the same cross section and are arranged oppositely, namely, the connecting line of the ultrasonic transducers B 'and D' passes through the center of the cross section; the ultrasonic transducers A 'and B' are positioned on the same bus on the side wall of the pipeline; ultrasonic transducers C 'and D' are on the same bus of the side wall of the pipeline. The front end of the ultrasonic transducer is provided with the ultrasonic probe, when the four ultrasonic transducers are installed, the ultrasonic probe and the side wall of the pipeline form a certain included angle, A 'and D' are in a pair, B 'and C' are in a pair, the A 'and D' probes are opposite, the B 'and C' probes are opposite, the signal emitted by the ultrasonic transducer A 'can be received by the ultrasonic transducer D', and the signal emitted by the ultrasonic transducer B 'can be received by the ultrasonic transducer C'. The ultrasonic probes do not interfere with each other. Such a set of ultrasonic transducers (comprising two pairs of ultrasonic transducers) is capable of solving for a fluid flow rate.
In the forward flow, the ultrasonic transducer A 'emits ultrasonic waves, the ultrasonic waves pass through the fluid and are received by the ultrasonic transducer D', and the transit time of the ultrasonic waves at the time is the forward flow propagation time and is marked as T 1 . In the counter flow, the ultrasonic transducer B 'emits ultrasonic waves, the fluid passing through the pipeline is received by the ultrasonic transducer C', and the transit time of the ultrasonic waves at the moment is the counter flow propagation time, which is marked as T 2 。
The flow rate model of the ultrasonic basal meter pipeline is as follows:
the transit time and time difference model ignores the radial propagation time of the ultrasonic wave, the downstream propagation time T of the ultrasonic wave 1 ：
Wherein:
l is the distance between the ultrasonic transducer A 'and the ultrasonic transducer B', and mm;
c-ultrasonic sound velocity, m/s;
v-flow rate of fluid, m/s;
θ—the angle between the upper tube wall and the probe a ', D', in this example set at 60 °.
The formula is deformed as follows:
counter-current propagation time T of ultrasonic wave 2 ：
The formula is deformed as follows:
subtracting formula (2) from formula (4), when θ=60°, it is possible to obtain:
the time difference deltat of the forward and backward propagation is:
ΔT＝T 2 -T 1 (6)
the flow velocity v is:
likewise, the multi-channel measured flow rate may be up to 8 speeds. Less than 4 speed data can be measured with a diameter of 300mm (DN 300), and more than 4 speed data can be measured with a diameter of more than DN 300.
Here, two pairs (i.e. 4) of ultrasonic transducers are required for measurement of one flow velocity v. The two flow velocity measurements can be performed by 8 ultrasonic transducers or 6 ultrasonic transducers; as for the case of using 6 ultrasonic transducers to measure two flow rates, it is necessary to have a pair of ultrasonic transducers that are shared in solving the two flow rates. Therefore, up to three flow rates can be measured in the present invention using 6 ultrasonic transducers. 2-4 flow rates can be measured by adopting 8 ultrasonic transducers; up to 5 flow rates can be measured using 10 ultrasonic transducers. Similarly, 4-8 flow rates can be measured using 16 ultrasonic transducers.
Taking 4 velocity data as an example for illustration, when the included angle θ=60°, the following formula is given:
the average speed was found to be:
according to the ultrasonic probe of the second cross section and the third cross section in fig. 1, when the flow velocity is measured, the A1 transmitting signal is received by E2, the B1 transmitting signal is received by F2, the C1 transmitting signal is received by G2, the D1 transmitting signal is received by H2, the A2 transmitting signal is received by E1, the B2 transmitting signal is received by F1, the C2 transmitting signal is received by G1, and the D2 transmitting signal is received by H1. A1, A2, E1 and E2, the 4 ultrasonic probes are in a group, and one flow rate can be measured. B1, B2, F1 and F2, the 4 ultrasonic probes are combined into a group, and one flow rate can be measured. C1, C2, G1 and G2, the 4 ultrasonic probes are combined into a group, and one flow rate can be measured. D1, D2, H1 and H2, the 4 ultrasonic probes are in a group, and one flow rate can be measured. The 4 flow rates were measured without sharing any pair of ultrasonic probes. In the flow rate measurement, if the ultrasonic probe is used in common, a maximum of 8 sets of flow rates can be measured. When the number of ultrasonic probes provided for the pipe diameter is insufficient, the common ultrasonic probe can be selected for measurement. When enough ultrasonic transducers can be arranged for the large pipe diameter, different ultrasonic probes can be selected during measurement.
In each flow rate measurement, 4 ultrasonic probes are required, the 4 ultrasonic probes are divided into two pairs, and the connecting line of each pair of ultrasonic probes is intersected with the axial lead, namely, each pair of ultrasonic probes is symmetrically arranged about the axial lead. The two pairs of ultrasonic probes, one pair for measuring the forward flow transit time T 1 Another pair is used for measuring the countercurrent transit time T 2 . In the two pairs of ultrasonic probes, the distance between the ultrasonic probes on the same bus is L, and therefore, the flow velocity can be obtained according to the formula (7).
The connecting line between the two ultrasonic probes in each pair forms a specific angle theta with the pipe wall (namely, the axial direction), the value range of the theta is 10-80 degrees, the formula (7) is obtained under the condition that the value of the theta is 60 degrees, and when the theta is uncertain, the flow rate solving formula is as follows:
the flow rate measurement method is described above, and the pipe cross-sectional area measurement method is described below.
Four pairs of eight ultrasonic probes are arranged on the same section according to an equidistant method, and each ultrasonic probe is perpendicular to the pipe wall, so that ultrasonic signals emitted by the ultrasonic probes are received by the opposite ultrasonic probes, namely: the connecting line between each pair of ultrasonic probes forms an angle of 90 degrees with the pipe wall, and the connecting line between each pair of ultrasonic probes passes through the center of the cross section. The MSP430FR6047 singlechip and the channel control module are used for controlling the receiving and transmitting of four paths of ultrasonic signals. Because the ultrasonic wave propagates in the pipe wall at a certain speed, the pipe diameter is measured by utilizing the time intervals of the primary reflected wave, the secondary reflected wave and the emitted wave, and the cross section area is calculated. This is a calculation based on the principle of ultrasonic thickness measurement.
The calculation formula for calculating the pipe diameter by using the ultrasonic thickness gauge is as follows:
wherein:
d, diameter of pipeline, m;
v-the flow velocity of the ultrasonic wave in the fluid, m/s;
Δt-the time interval from the primary echo to the secondary echo, s.
Besides the pipeline diameter measurement by utilizing the ultrasonic thickness gauge principle, the invention also utilizes the ultrasonic tomography technology to accurately measure the pipeline diameter at the scale and corrosion positions of the pipeline, thereby calculating the accurate area in the pipeline. The method specifically comprises the following steps:
the invention utilizes forward transformation and inversion image reconstruction to construct the specific section condition of the pipe wall. The mathematical basis is the radon transform and the inverse radon transform.
(1) Radon transform: the projection function is obtained by integrating the attenuation coefficient s (x, y) reflecting the internal structure of the pipeline along a certain path L.
(2) And (5) carrying out inverse radon transformation: and (3) obtaining attenuation coefficients s (x, y) under the condition that the projection function is known.
Projection formula of radon transform:
t i ＝∫ Ri s(x,y)dl (15)
wherein:
t i -the amplitude of the ith ultrasonic ray received by the ultrasonic probe;
R i -the path taken by the ith ultrasound ray;
s (x, y) -decay coefficient distribution function.
When the cross section of the pipeline is measured, the pipeline diameter is calculated by utilizing the principle of an ultrasonic thickness gauge. The ultrasonic probe is used for transmitting ultrasonic pulses, primary reflection occurs when the ultrasonic pulses pass through the interface between the pipe wall and the fluid, pulse signals pass through the whole fluid and then enter the opposite pipe wall, secondary reflection is performed, and the diameter of the pipe can be calculated by using the time difference of the two reflected echoes. As shown in fig. 3, the calculation of the pipe diameter by using the ultrasonic thickness gauge principle specifically includes: the ultrasonic probe is enabled to transmit ultrasonic waves, the primary echo and the secondary echo are received, the time difference between the primary echo, the secondary echo and the transmitted wave is calculated, and the diameter of the pipeline can be calculated according to the formula (14). For the setting of 8 ultrasonic probes, four sets of data for the pipe diameter can be calculated.
As shown in fig. 4, after four groups of pipe diameters are calculated according to the principle of ultrasonic thickness gauge, it is determined whether the four groups of diameter phase differences (available maximum value minus minimum value) are smaller than a set threshold value; if so, taking the average value of the diameters of the four groups of pipelines as the diameter of the whole pipeline, and further calculating the cross-sectional area of the pipeline; if not, further fine positioning and size determination of pipeline scaling and corrosion conditions are carried out by adopting an ultrasonic tomography technology, corresponding sector areas (the sector can cover the scaling and corrosion positions) are calculated for the scaling and corrosion positions independently, and the rest sector areas are calculated by using pipeline diameter average values; and finally calculating the accurate flow cross-sectional area.
As shown in FIG. 5, the ultrasonic tomography technology is adopted to carry out further fine positioning and size determination of pipeline scaling and corrosion, and the method specifically comprises the following steps: sequentially carrying out one-shot-multi-shot operation on eight paths of ultrasonic probes, setting ultrasonic signals to propagate along a straight line, and carrying out discretization solving on si (the attenuation result on each ray) according to ti (referring to the ith ray) (the solving process applies the radon inverse transform); discretizing the section of the whole pipeline to establish an xy coordinate system; assuming that the wave speed attenuation is kept constant in each small grid, all ti passing through a certain point s (x 0, y 0) are obtained; forming all si corresponding to all ti into a matrix equation, solving the equation, and solving s (x 0, y 0); the scale, corrosion location and size were calculated from s (x 0, y 0).
After precisely obtaining the flow cross-sectional area and flow velocity, flow calculations were performed using the following formula:
Q＝S×v (16)
wherein:
Q—-flow value, m 3 /s；
S-flow cross-sectional area, m 2 ；
v-flow velocity, m/s;
in the invention, for ultrasonic probes on the same cross section, an additional device is used for fixing each probe. As shown in fig. 7, the additional device is similar to a binding band structure, the length of the additional device is adjustable, the longest length is pipe diameter multiplied by pi, through holes are formed at equal intervals, the ultrasonic probe is convenient to place, and bayonets are arranged at the through holes so as to prevent the ultrasonic probe from falling.
In order to make the probe fit tightly to the pipe, a coupling agent is typically applied. In fig. 1, 24 ultrasonic probes are connected into a hardware circuit, as shown in fig. 8, each ultrasonic probe is connected with a hardware module through an ultrasonic connection wire harness, a power supply supplies power to the hardware module through a power connection wire, and the hardware module is connected with a computer host through a USB connection wire.
The structural block diagram of the hardware module is shown in fig. 9, and the hardware module in the invention comprises a singlechip, a channel control module and a timing module, wherein the singlechip adopts an MSP430FR6047 chip, the channel control module adopts a 74HC4052D chip, and the timing module adopts a TDC-GP22 timing chip. The whole system is provided with a chip MSP430F5528 with USB connection and debugging functions.
The single chip microcomputer is connected with the channel control module, and under the control of the single chip microcomputer, the channel control module controls each group of ultrasonic probes to transmit ultrasonic waves and receive corresponding echo signals to the single chip microcomputer. That is, the channel control module may control connection, disconnection, switching, etc. of the ultrasonic transducers, may operate each ultrasonic transducer simultaneously, may operate each ultrasonic transducer individually, or may select several groups of ultrasonic transducers to operate. The timing module collects ultrasonic signals and performs timing, the timing signals are sent to the singlechip, the singlechip uploads data to the computer host through the USB communication module, and the computer host calculates the cross section, the flow velocity and the flow according to corresponding formulas.
The USB communication module is connected to the outside of the singlechip, so that the singlechip is convenient to debug by a computer and outputs a preprocessed ultrasonic signal. The whole system has stable power supply.
As shown in FIG. 10, FIG. 10 is a diagram showing the connection of the crystal oscillator of the detection device of the present invention, which mainly uses the Y3 crystal oscillator of 8MHz to take on the main functions, and assists some capacitors and resistors with high stability. In the principle of measuring the flow velocity by the time difference method, the accurate control of the time point and the accurate measurement of the time difference are of great importance, so the device adopts a crystal oscillator Y3 with high precision, the frequency stability is 5E-9, the phase noise is 140db/Hz at the frequency of 1KHz, and the accurate measurement of the flow velocity is very facilitated.
Fig. 11 is a flow chart of the external clamp type multichannel ultrasonic flow detection method of the invention. The method comprises the steps of self-checking the system, calibrating the system, selecting the sound velocity of the material, measuring the cross section (combining an ultrasonic thickness meter and an ultrasonic tomography), measuring the flow velocity, measuring the flow and displaying the result. Through the steps, the flow measurement result can be accurately obtained on the premise of normal connection of the hardware circuit.
Claims (4)
1. The method for detecting the ultrasonic flow of the external clamping type multichannel is characterized by comprising the following steps of:
a. an ultrasonic probe is arranged on the side wall of the pipeline, and the ultrasonic probe is concretely as follows:
three different cross sections are arranged on the pipeline and are respectively marked as a first cross section, a second cross section and a third cross section; the first cross section is positioned between the second cross section and the third cross section, and the first cross section is equidistant from the second cross section and the third cross section; m ultrasonic probes are uniformly distributed on the first cross section, wherein M is an even number; each ultrasonic probe on the first cross section is vertical to the pipe wall;
n ultrasonic probes are uniformly arranged on the second cross section and the third cross section respectively, wherein N is an even number; and N ultrasonic probes on the second cross section and N ultrasonic probes on the third cross section are in one-to-one correspondence on the same bus; each ultrasonic probe on the second cross section and the third cross section forms an included angle theta with the pipe wall, and the value range of theta is 10-80 degrees; each ultrasonic probe on the second cross section corresponds to the ultrasonic probe on the third cross section, and one ultrasonic probe which is symmetrically distributed about the center of the first cross section is always found, and the two ultrasonic probes are called a pair of ultrasonic probes; two pairs of ultrasonic probes can be used for solving one flow velocity, and the average value of the flow velocity can be obtained by averaging a plurality of flow velocities;
b. measuring the fluid flow rate based on an ultrasonic time difference method by using ultrasonic probes on the second cross section and the third cross section;
c. measuring the inner diameter of the pipeline based on the principle of an ultrasonic thickness gauge by using an ultrasonic probe on the first cross section, and calculating the average value of the inner diameter of the pipeline;
d. c, when the inner diameter of the pipeline measured in the step c does not meet the requirement, measuring the positions and the sizes of scaling and corrosion positions on the inner wall of the pipeline based on an ultrasonic tomography technology by utilizing an ultrasonic probe on the first cross section;
e. solving the cross-sectional area of the pipeline based on the data in step c or step d;
f. calculating the fluid flow according to the fluid flow rate in the step b and the cross-sectional area of the pipeline in the step e;
the step d specifically comprises the following steps:
d-1, measuring the positions and the sizes of scaling and corrosion parts on the inner wall of the pipeline based on an ultrasonic tomography technology by utilizing an ultrasonic probe on the first cross section;
d-2, calculating the sector areas of the scaling and corrosion parts by using the scaling and corrosion part sizes of the inner wall of the pipeline, and calculating the rest sector areas by using the average value of the inner diameter of the pipeline in the step c;
d-3, adding the fan-shaped areas in the step d-2 to obtain the cross-sectional area of the pipeline.
2. The method for detecting the flow rate of the external-clamping type multichannel ultrasonic wave according to claim 1, wherein the step b is specifically as follows:
b-1, under the control of the singlechip, the channel control module controls the ultrasonic probes to work simultaneously, wherein in each pair of ultrasonic probes, one ultrasonic probe is used for transmitting ultrasonic signals, and the other ultrasonic probe is used for receiving the ultrasonic signals;
b-2, a channel control module and a timing module collect ultrasonic signals transmitted/received by each ultrasonic probe and send the collected signals to a singlechip;
b-3, the singlechip stores and processes the received data and sends corresponding data to the upper computer;
b-4, calculating the flow rate by the upper computer according to the following formula:
in the above formula, the number of the groups of groups,T 1 is the downstream propagation time of the ultrasonic signal in the fluid,T 2 is the counter-current propagation time of the ultrasonic signal in the fluid,Lis the distance between two ultrasonic probes on the same bus;
two pairs of ultrasonic probes can solve a flow ratevThe flow velocity average is calculated by solving a plurality of flow velocities.
3. The method for detecting the flow rate of the external-clamping type multichannel ultrasonic wave according to claim 1, wherein the step d-1 is specifically as follows:
d-11, enabling the ultrasonic probes on the first cross section to sequentially perform one-shot and one-shot;
d-12, assuming that the wave speed attenuation is kept constant in each small grid, and obtaining all ultrasonic rays ti passing through the small grid s (x 0, y 0);
d-13, setting ultrasonic signals to propagate along a straight line, and solving si after wave speed attenuation by utilizing inverse radon transform discretization according to all ultrasonic rays ti passing through the small grid s (x 0, y 0) in the step d-12;
d-14, forming a matrix equation by all sis obtained in the step d-13, solving the equation, and obtaining s (x 0, y 0);
d-15, calculating the positions and the sizes of the scaling and corrosion positions according to s (x 0, y 0).
4. The method for detecting the flow rate of the external-clamping type multichannel ultrasonic wave according to claim 1, wherein the step c is specifically as follows:
c-1, enabling the ultrasonic probe to emit ultrasonic signals;
c-2, receiving the primary echo and the secondary echo signal, and calculating the time difference of the primary echo, the secondary echo and the transmitted wave;
c-3, calculating the inner diameter of the pipeline according to the following formula:
wherein:
D-inner diameter of the pipe, m;
v-the speed of the ultrasonic wave circulation in the fluid, m/s;
Δt, the time interval between the primary echo and the secondary echo, s;
and c-4, averaging the inner diameter data of the multiple groups of pipelines.
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