CN103196504A - Method and device for measuring multi-channel ultrasonic flow - Google Patents

Abstract

The invention discloses a multi-channel ultrasonic flow measurement method and device. The number of transducers is installed on the pipe section twice the number of sound channels, and the connection of two transducers corresponds to a sound channel, and the axis of the sound channel and the pipe section is 15°~75°; a pressure sensor is arranged at the front end of the pipe section , which is equal to the distance from the axial center position of each channel; the corresponding channels of each transducer are divided into chord channel and radial channel, three or more chord channels on the axial section Projected as a regular polygon. According to the real-time detection of the pressure status of the flow field by the pressure sensor, the pressure variance value of the flow field within a cycle is compared with the initial value, and then the time interval of the channel measurement is increased or decreased to realize the multi-channel measurement time interval. Real-time adjustment, especially suitable for occasions where the flow field changes suddenly. There are both radial channels and chord channels in each channel. By comparing the two measured velocities, it can be judged whether the current state of the flow field is in laminar flow or turbulent flow.

Description

A multi-channel ultrasonic flow measurement method and device

technical field

The invention relates to a flow measurement method and device, in particular to a multi-channel ultrasonic flow measurement method and device.

Background technique

Ultrasonic flowmeter is a kind of measuring instrument that uses the signal modulation effect of fluid flow on ultrasonic pulse or ultrasonic beam, and obtains volume flow by detecting the change of signal. The measurement principles of ultrasonic flowmeters can be divided into time difference method, Doppler method, beam offset method, correlation method and noise method. What this patent is aimed at is an ultrasonic flow measurement method using the time difference method for measurement. This flow measurement method can measure common liquids, gases, etc.

In the process of fluid transmission, it is inevitable to use devices such as sudden expansion pipes, single bend pipes, double bend pipes, shut-off pipes, valves, etc., which will cause unstable flow fields such as eddy currents in the flow field. The disturbance of the flow field has a great influence on the measurement accuracy of the transit-time ultrasonic flow measurement method. In order to ensure measurement accuracy, multi-channel methods are usually used. A good channel layout can not only improve the accuracy of measurement, but also effectively improve the anti-interference ability of the flowmeter and the adaptability to special flow fields. The multi-channel design is to reduce the sensitivity of the flowmeter to the fluctuation of the flow field. The multi-channel ultrasonic flowmeter can compensate the influence of the flow field fluctuation on the accuracy through the unique channel design, thereby reducing the stringent requirements for the installation environment and flow field conditions. Therefore, the design of the sound channel layout scheme has an extremely critical impact on improving the measurement accuracy and adaptability of the flowmeter.

The existing multi-sonic ultrasonic flowmeter usually adopts two types of typical sound channel layout schemes. The traditional solution (1) is: using one radial channel or two radial channels interlaced at 90 degrees, and two or four chord channels that reflect twice each, the two or four chords The projection to the channel line is a regular triangle or two staggered regular triangles on the axial plane; the traditional scheme (2) is: there are one channel or two staggered planes on multiple planes perpendicular to the axial section channel. Due to the possibility of eddy currents or sudden changes in the flow field, the measurement intervals between the channels of the above two schemes are fixed, but in the case of sudden changes in the flow field, the flow field conditions of each channel are quite different when measuring , which in turn leads to a large deviation between the measured results and the actual flow field.

Contents of the invention

The purpose of the present invention is to provide a multi-channel ultrasonic flow measurement method and device. Based on the specially set channel layout, the measurement time interval between channels can be controlled in real time with the real-time detection of the pressure sensor.

In order to achieve the above-mentioned purpose of the invention, the technical scheme adopted in the present invention is as follows:

One, a multi-channel ultrasonic flow measurement method, the steps of the method are as follows:

(1) Arrange a pressure sensor at the front end of the sound channel measurement area, and the distance between the pressure sensor and the axial center position of each sound channel is equal;

(2) Install transducers twice the number of sound channels on the pipe section, where the connection of every two transducers constitutes a sound channel, and the axis of the sound channel and the pipe section is 15°~75°;

(3) The channels corresponding to each transducer are divided into chord channels and radial channels, that is, there is one radial channel and at least three chord channels, and each chord channel is divided into The projection on the axial section is a regular polygon;

(4) According to the measurement results of the pressure sensor, the measurement time interval between each channel is adjusted in real time. While the flow rate of each string channel is measured, the signal processing module reads the pressure sensor data and calculates the measurement time of all string channels The corresponding pressure sensor measurement result variance; if the pressure sensor measurement result variance is less than the set value A0, the measurement results of each string channel are considered valid; if the pressure sensor measurement result variance is greater than the set value A0, each string channel measurement result is considered If the result is invalid, reduce the measurement time interval between each channel and measure again until the variance of the pressure sensor measurement results is less than the set value A0, then the measurement results of each chord direction flow velocity at this time are valid;

(5) Average the flow velocities measured by all string channels as the average flow velocity measurement result, calculate the ratio between the average flow velocity measurement result and the flow velocity value measured by the radial channel, and use this ratio to judge the flow field status.

When the regular polygon is a regular triangular chord channel, for the four-channel arrangement of the regular triangular chord channel+diameter channel: when the ratio is less than k1=3/4, it is determined that the flow field is in a laminar flow state, and the laminar flow The flow correction model calculates the volume flow rate from the average flow velocity measurement results; when the ratio is greater than k2=4/5, it is determined that the flow field is in a turbulent flow state, and the turbulent flow correction model is used to calculate the volume flow rate from the average flow velocity measurement results; the ratio is between k1 and When k2 is between, the flow field is in the transition state between laminar and turbulent flow, and the transition state flow correction model is used to calculate the volume flow rate from the average flow velocity measurement; the laminar flow correction model and turbulent flow correction model are obtained in advance through flow calibration experiments.

When the regular polygon is a square chord channel, for the five-channel arrangement of the square chord channel+diameter channel: when the ratio is less than k1=0.5, it is determined that the flow field is in a laminar flow state, and a laminar flow correction model is adopted, The volume flow rate is calculated from the average flow velocity measurement results; when the ratio is greater than k2=0.84, the flow field is determined to be in a turbulent flow state, and the turbulent flow correction model is used to calculate the volume flow rate from the average flow velocity measurement results; when the ratio is between k1 and k2, the flow field The field is in the transition state between laminar turbulent flow, and the transition state flow correction model is used to calculate the volume flow rate from the average flow velocity measurement; the laminar flow correction model and turbulent flow correction model are obtained in advance through flow calibration experiments.

2. A multi-channel ultrasonic flow measuring device:

The present invention arranges and installs transducers whose number is twice the number of channels on the pipe section, wherein the connection of every two transducers constitutes a sound channel, and the axis of the sound channel and the pipe section is at an angle of 15°~ 75°; a pressure sensor is arranged at the front end of the sound channel measurement area, and the distance between the pressure sensor and the axial center position of each sound channel is equal; the sound channels corresponding to each transducer are divided into chord sound channels and radial sound channels , that is, it is composed of one radial channel and three chord channels, and the projection of each chord channel on the axial section according to the number of channels is an equilateral triangle, and the radial channel is parallel to the base of the equilateral triangle; or It is composed of one radial channel and four chord channels. The projection of each chord channel on the axial section according to the number of channels is a square, and the radial channel is parallel to one side of the square.

The beneficial effects that the present invention has are:

(1) According to the real-time detection of the pressure status of the flow field by the pressure sensor, the pressure variance value of the flow field within a period can be compared with the initial value, and then the time interval of the channel measurement can be increased or decreased to realize multi-channel Real-time adjustment of channel measurement intervals. This enables the flowmeter to adapt to occasions where the flow field changes suddenly, and the measurement result is more realistic and accurate. In the traditional method, the measurement time interval between each sound channel cannot be adjusted according to the working conditions, and there is no existing method for adjusting according to the real-time monitoring results of the pressure sensor.

(2) There are radial sound channel and chord sound channel in each sound channel of the present invention. By comparing the two measured velocities, it can be judged whether the current flow field state is in laminar flow or turbulent flow.

(3) The projection of the chord sound channel of the present invention on the axial plane is an equilateral triangle or square, which are all regular and completely symmetrical sound channel arrangements, which can effectively eliminate the radial velocity component of the flow field for the actual axial direction. influence of fluidity.

(4) In the two channel arrangement schemes disclosed in the present invention, although the four-channel arrangement of "equal triangle chord channel + radial channel" has an axial projection of the chord channel is also a regular triangle, which is different from the traditional scheme ( 1) The same, but in the present invention, each side of an equilateral triangle or square in the axial projection is an independent sound channel, and the axial distance between the center position of the sound channel corresponding to each side and the pressure sensor is equal to ensure The pressure sensor has the same spatial and temporal reference for each channel, while in the traditional solution (1), the three sides of each regular triangle are the same channel with two reflections, and the axial center position of each side is also different .

Description of drawings

Fig. 1 is the front view of the four-channel arrangement of the present invention "equal triangle chord channel+diameter channel".

Fig. 2 is an axial projection diagram of the four-channel arrangement of "equal triangular chord channel + radial channel" in the present invention.

Fig. 3 is a front view of the five-channel arrangement of "square string channel + radial channel" in the present invention.

Fig. 4 is an axial projection diagram of the five-channel arrangement of "square string channel + radial channel" in the present invention.

Fig. 5 is a flow chart of real-time adjustment of the measurement time interval between each sound channel according to the measurement result of the pressure sensor in the present invention.

In Fig. 1 and Fig. 2: 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B are all transducers for transmitting and receiving. 1, 2, and 3 are chord sound channel lines, 4, radial sound channel lines, 5, pressure sensor, 1, 2, and 3 sound channels are arranged in an equilateral triangle on the axial section.

In Fig. 3 and Fig. 4: 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 6A, and 6B are all transducers for transmitting and receiving. 1, 2, 3, and 6 are chord-direction channel lines, 4, radial channel lines, and 5, pressure sensors. Channels 1, 2, 3, and 6 are arranged in a square shape on the axial section.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Fig. 1 and Fig. 2, the present invention arranges and installs two transceiving dual-purpose transducers as a group of three chord sound channels and radial sound channels every 120° on the pipe section, that is, two transceiving transducers The connection of the used transducers 1A and 1B constitutes the first sound channel, and the connection of the transducers 2A and 2B for sending and receiving constitutes the connection of the second sound channel and the transducers 3A and 3B for both sending and receiving. The line constitutes the third channel, 4A and 4B constitute the radial channel; the projection of the three channels on the axial section is an equilateral triangle, that is, the three channels 1A (3B), 2A (1B) and 3A (2B) The radial sound channel is parallel to the base of the regular triangle, and each sound channel line is 15°~75° to the axis of the pipe section. A pressure sensor 5 is arranged on the front end pipe section of the sound channel measurement area. The pressure sensor 5 The distance from the axial center position of each channel is equal.

As shown in Fig. 3 and Fig. 4, the present invention arranges and installs two transceiving dual-purpose transducers as a group of four sound channels and radial sound channels at intervals of 90° on the pipe section, that is, the transceiving dual-purpose transducers The connection of transducers 1A and 1B constitutes the first sound channel, the connection of transducers 2A and 2B for both transmission and reception constitutes the second sound channel, and the connection of transducers 3A and 3B for both transmission and reception constitutes The connection between the third sound channel and the transducers 6A and 6B for transmitting and receiving forms the fourth sound channel, and 4A and 4B form the radial sound channel; the projection of the four sound channels on the axial section is a regular quadrilateral, namely 1A (6B), 2A (1B), 3A (2B) and 6A (3B) channels form a regular quadrilateral, the radial channel 4 is parallel to one side of the regular quadrilateral, and each channel line is 15° to the axis of the pipe section ~75°, a pressure sensor 5 is arranged on the front end pipe section of the sound channel measurement area, and the distance between the pressure sensor 5 and the axial center position of each sound channel is equal.

In Figures 1 to 4, the pressure sensor is located in the front section of the entire sound channel test area, and is used to obtain pipeline pressure information and monitor changes in the flow field in the pipeline in real time. The axial projection is an equilateral triangle or each side of a square is an independent sound channel, and the center position of the sound channel corresponding to each side is equal to the axial distance between the pressure sensor to ensure that the pressure sensor has an Same spatial and temporal reference.

As shown in Figure 5, the measurement time interval between each sound channel is adaptively adjusted through the real-time detection of the flow field by the pressure sensor. A pressure test is required at the same time as each sound channel measurement, and under normal working conditions only the chord direction sound channel needs to be measured. Use the mathematical model of discrete random variables to find the variance of these three pressure values. If the variance of these three pressure values is less than the set value A0, it is considered that the flow field condition of this measurement is stable, and the obtained sound channel measurement value If the requirements are met, the next measurement will be performed after the predetermined sleep time TS has elapsed. If the variance of the measured pressure value is less than 0.8 times the set value A0, increase the measurement time interval between the channels to 120% of the initial value T0. If the variance of the measured pressure value is greater than the set value A0, reset the measurement, and reduce the measurement time interval between each channel to 80% of the initial value T0, without going through the sleep time TS directly The time interval restarts the measurement. If the variance of the measured pressure values after the measurement time interval between the channels is changed is less than the set value A0, it is considered that the flow field at this moment is stable, and the obtained channel measurement values meet the requirements. If not, then reduce the measurement time interval between each channel to 60% of the initial value T0, and restart the measurement of each channel in turn without going through the sleep time TS. By analogy, if the variance of the measured pressure value still does not meet the requirement of being less than the set value A0 after the measurement time interval is changed, then reduce the time interval between the measurement channels to 40% of the initial value T0, 20%, 10% or even less, until the variance of the pressure test values measured by two consecutive complete measurements is less than the set value A0, it is considered that the flow field is in a stable state, the state of the flow field has not changed, and the string channel measurement The result works.

When the measurement result of the string channel is valid, perform a measurement of the radial channel to judge whether the transition of laminar turbulence occurs in the flow field. As shown in Figure 1 and Figure 2, the 4-channel measurement is performed after the 1, 2, and 3-channel measurements are completed. As shown in Figure 3 and Figure 4, the 4-channel measurement is performed after the 1, 2, 3, and 6-channel measurements are completed. The flow velocity information measured by all string channels is averaged as the average flow velocity measurement result. Calculate the ratio between the average flow velocity measurement and the flow velocity value measured by the radial channel. For the four-channel arrangement of "equal triangle chord channel + radial channel": when the ratio is less than k1=3/4, it is determined that the flow field is in a laminar flow state, and the laminar flow correction model is used to calculate from the average flow velocity measurement results Volume flow; when the ratio is greater than k2=4/5, it is determined that the flow field is in a turbulent state, and the turbulent flow correction model is used to calculate the volume flow from the average flow velocity measurement results; when the ratio is between k1 and k2, the flow field is in laminar turbulence For transition states between flows, a transition state flow correction model is used to calculate volume flow from average flow velocity measurements. For the "square string channel + radial channel" five-channel arrangement, the value of k1 is 0.5, and the value of k2 is 0.84. The laminar flow correction model and the turbulent flow correction model are obtained in advance through flow calibration experiments.

Claims (4)

1. A multi-channel ultrasonic flow measurement method is characterized in that the steps of the method are as follows: (1) Arrange a pressure sensor at the front end of the sound channel measurement area, and the distance between the pressure sensor and the axial center position of each sound channel is equal; (2) Install transducers twice the number of sound channels on the pipe section, where the connection of every two transducers constitutes a sound channel, and the axis of the sound channel and the pipe section is 15°~75°; (3) The channels corresponding to each transducer are divided into chord channels and radial channels, that is, there is one radial channel and at least three chord channels, and each chord channel is divided into The projection on the axial section is a regular polygon; (4) According to the measurement results of the pressure sensor, the measurement time interval between each channel is adjusted in real time. While the flow rate of each string channel is measured, the signal processing module reads the pressure sensor data and calculates the measurement time of all string channels The corresponding pressure sensor measurement result variance; if the pressure sensor measurement result variance is less than the set value A0, the measurement results of each string channel are considered valid; if the pressure sensor measurement result variance is greater than the set value A0, each string channel measurement result is considered If the result is invalid, reduce the measurement time interval between each channel and measure again until the variance of the pressure sensor measurement results is less than the set value A0, then the measurement results of each chord direction flow velocity at this time are valid; (5) Average the flow velocities measured by all string channels as the average flow velocity measurement result, calculate the ratio between the average flow velocity measurement result and the flow velocity value measured by the radial channel, and use this ratio to judge the flow field status. 2. A kind of multi-channel ultrasonic flow measurement method according to claim 1, characterized in that: when the regular polygon is a regular triangular chord channel, for the four-channel arrangement of the regular triangular chord channel+diameter channel In terms of: when the ratio is less than k1=3/4, it is determined that the flow field is in a laminar flow state, and the laminar flow correction model is used to calculate the volume flow rate from the average flow velocity measurement results; when the ratio is greater than k2=4/5, it is determined that the flow field is turbulent In the flow state, the turbulent flow correction model is used to calculate the volume flow rate from the average flow velocity measurement results; when the ratio is between k1 and k2, the flow field is in the transition state between laminar turbulence, and the transition state flow correction model is used to calculate the volume flow rate from the average flow velocity The volumetric flow is measured and calculated; the laminar flow correction model and the turbulent flow correction model are obtained in advance through flow calibration experiments. 3. A multi-channel ultrasonic flow measurement method according to claim 1, characterized in that: when the regular polygon is a square string channel, for the five-channel arrangement of the square string channel+diameter channel : When the ratio is less than k1=0.5, it is determined that the flow field is in a laminar flow state, and the laminar flow correction model is used to calculate the volume flow rate from the average flow velocity measurement results; when the ratio is greater than k2=0.84, the flow field is determined to be in a turbulent flow state, and the turbulent flow is used The flow correction model calculates the volume flow rate from the average flow velocity measurement results; when the ratio is between k1 and k2, the flow field is in the transition state between laminar turbulence, and the transition state flow correction model is used to calculate the volume flow rate from the average flow velocity measurement; layer The current flow correction model and the turbulent flow correction model are obtained in advance through flow calibration experiments. 4. a kind of multi-channel ultrasonic flow measuring device of method as claimed in claim 1, is characterized in that: Arrange and install transducers with twice the number of sound channels in equal space on the pipe section, where the connection of every two transducers forms a sound channel, and the axis of the sound channel and the pipe section is 15°~75° ; Arrange a pressure sensor at the front end of the channel measurement area, and the distance between the pressure sensor and the axial center position of each channel is equal; the corresponding channel of each transducer is divided into a chord channel and a radial channel, namely It is composed of one radial channel and three chord channels, and the projection of each chord channel on the axial section according to the number of channels is a regular triangle, and the radial channel is parallel to the bottom of the regular triangle; or by a The radial channel and four chord channels are formed. The projection of each chord channel on the axial section according to the number of channels is a square, and the radial channel is parallel to one side of the square.

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