Pipeline flow measurement method based on real-time zero point compensation

Abstract

The present invention provides a pipeline flow measurement method based on zero point real-time compensation, which adopts an ultrasonic flowmeter for measurement, and adopts a V-method to install the two transducers of the ultrasonic flowmeter, which are mutually transceivers, to be fixed on the same side of the pipeline wall, so as to ensure that the transducers can receive L waves and S waves; the upstream flight time and the downstream flight time of the L wave and the S wave are measured respectively, and the upstream and downstream flight time Δt of the ultrasonic signal in the pipeline wall is obtained for the L wave 1 and Δt 2 , the filtered Δt 1 and Δt 2 Zero point correction is performed to obtain the corrected accurate flow rate; Kalman filtering is performed on the measured flow rate Q to further reduce the interference of random disturbances on the flow rate. The present invention aims to correct the zero point drift of the actual flow rate measured by the S wave by performing zero point measurement on the L wave. Unlike other methods, this method utilizes the characteristic that the L wave does not pass through water, overcomes the difficulty of calibrating the zero point when water flows in the pipeline in actual working conditions, and thus improves the measurement accuracy of the flow meter.

Description

Technical Field

[0001] The invention relates to the technical field of real-time, high-precision measurement of the flow rate of a fluid inside a conveying pipeline by using ultrasonic waves, and in particular to a pipeline flow rate measurement method based on real-time zero-point compensation. Background Art

[0002] With the technological innovation in various fields, the demand for flow measurement in application fields such as energy transportation and water supply and heating has led to a rapid increase in the use of flow meters. When measuring the flow of industrial fluids, traditional electromagnetic flow meters are limited by the working requirements of pipelines and flow meters themselves, and have disadvantages such as difficulty in installation, high cost, and the need to enter the pipe for measurement. Ultrasonic flow meters can be installed on the outside of the pipeline through an external clamp measurement method, which will not cause problems such as environmental damage and energy loss in the pipeline, and are lower in cost than traditional flow meters.

[0003] The time-difference ultrasonic flowmeter is simple and fast. It calculates the flow rate in the pipeline by measuring the time of the S wave flowing downstream and upstream. Among them, the difference in flight time between the upstream and downstream directly determines the measurement accuracy of the time-difference ultrasonic flowmeter system. Therefore, accurately calculating the flight time is a key issue that the entire measurement system needs to deal with. In practical applications, due to the random errors in the process level, circuit line resistance and installation method of the ultrasonic transducer itself, the ultrasonic probe generally has a stable zero point error, which will directly lead to a decrease in the accuracy of the flowmeter. To address this problem, the traditional solution is to calibrate the zero point of the ultrasonic probe under static water conditions. However, in practical applications, different pipe diameters, installation positions, installation angles and installation methods will produce different zero point errors. In addition, in actual working conditions, there are generally no conditions for calibrating the static zero point by stopping water. Summary of the invention

[0004] In view of this, the present invention proposes a measurement method that utilizes the characteristic that ultrasonic waves in the pipe wall do not pass through the water medium in the pipe when the water flow in the pipe is normal, i.e., uninterrupted, and tests the static zero point of the L wave in the pipe wall and uses it for the zero point error correction of the S wave entering the water, thereby dynamically reducing the static error and improving the measurement accuracy of the flow meter.

[0005] The specific technical solutions are:

[0006] The pipeline flow measurement method based on zero point real-time compensation uses an ultrasonic flow meter for measurement and adopts the following steps:

[0007] Step 1: Use the V method to install the two transducers of the ultrasonic flow meter on the same side of the pipe wall, ensuring that the transducers can receive L waves and S waves.

[0008] Step 2: Measure the upstream flight time and downstream flight time of the L wave and S wave respectively, and obtain the corrected flow rate according to the following formula (1):

[0009]

[0010] Among them, t 1 and t 2 are the upstream and downstream flight times measured by the two transducers using S waves, Δt 1 and Δt 2 are the upstream and downstream flight times measured by the two transducers using L waves, D is the inner diameter of the pipe, θ is the emission angle, and K is the compensation coefficient for converting the linear velocity into the surface velocity;

[0011] In step 2, the specific implementation process of zero point real-time compensation is:

[0012] (1) Obtain the flight time Δt of the ultrasonic signal upstream and downstream in the pipe wall for the L wave 1 and Δt 2 ;

[0013] (2)Δt 1 and Δt 2 The following formula (2) is used for filtering:

[0014]

[0015] (3) The filtered Δt 1 and Δt 2 Substitute into formula 1 to perform zero point correction and obtain the accurate flow rate after correction;

[0016] Step 3: Perform Kalman filtering on the measured flow rate Q to further reduce the interference of random disturbances on the flow rate.

[0017] The present invention aims to correct the zero drift of the actual flow measured by the S wave by measuring the zero point of the L wave. Unlike other methods, this method uses the characteristic that the L wave does not pass through water, overcomes the difficulty of calibrating the zero point when water flows in the pipeline in actual working conditions, and thus improves the measurement accuracy of the flow meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 This is a schematic diagram of the working principle of the V method, which takes the V method as an example to show the transducer installation method and the transmission path of the ultrasonic signal.

[0020] Figure 2The schematic diagram of the transducer echo signal shows the front-to-back position relationship between the L wave and the S wave, where t L and t S They are the starting measurement time of the L wave and the S wave, respectively. DETAILED DESCRIPTION

[0021] The propagation speed of ultrasonic waves in the same homogeneous medium is relatively stable. Figure 1 As shown, in the process of measuring flow in a pipeline, the sound wave first enters the pipe wall on the side where transducer A is located, and is reflected and refracted at the interface between the pipe wall and the water flow. The reflected wave (L wave) propagates in the pipe wall, and after several reflections, it reaches another transducer B on the same side. The refracted wave (S wave) enters the water and reaches the inner wall of the opposite pipe wall. After one reflection, it reaches the pipe wall corresponding to transducer B and is refracted again and received by transducer B. The flow rate can be measured by using the two flight times of ultrasonic waves in the downstream and upstream states in the pipeline. The two transducers of the ultrasonic flowmeter are installed in a fixed position on the same side of the pipeline. The two transducers switch the upstream and downstream transmission states to measure the upstream flight time t respectively. 1 and downstream flight time t 2 , and then calculate the flow value by the calculation formula. The time difference flowmeter probe installation methods generally include Z method, V method and W method. Since our method uses L wave to correct the zero point, we only use V method and W method installed on the same side. This article uses V method to explain the principle. The working principle of V method is as follows Figure 1 As shown, A is the upstream transducer, B is the downstream transducer, D is the inner diameter of the pipeline, and θ is the angle between the transmitted signal and the pipeline cross section, that is, the transmitting angle.

[0022] We observed that the sound wave component in the pipe wall will not pass through the water flow, and the propagation speed of L waves in the steel pipe is 3230m / s, and the propagation speed of S waves in water is 1520m / s. The L waves in the pipe wall will reach the receiving end transducer earlier than the S waves, and the received signal will form the following Figure 2 The L wave is in front and the S wave is behind. Therefore, we can measure the zero point error by the L wave first and use it for real-time correction of the S wave zero point.

[0023] Step 1: First, make a pair of transducers with ultrasonic signal transceiver functions to receive and transmit ultrasonic signals. Figure 1 As shown, the angle between the transmitting signal and the pipe cross section (transmitting angle) is 45 degrees. The V method is used to install the two transducers on the same side of the pipe to ensure that the transducers can receive L waves and S waves at the same time.

[0024] Step 2: Measure the upstream flight time and downstream flight time of the L wave and the S wave respectively, and obtain the corrected flow rate according to the following formula 1.

[0025]

[0026] Among them, t 1 and t 2 are the upstream and downstream flight times measured by the two transducers using S waves, Δt 1 and Δt 2 The upstream and downstream flight times measured by two transducers using L waves are filtered, D is the inner diameter of the pipe, θ is the emission angle, and K is the compensation coefficient for converting the linear velocity into the surface velocity.

[0027] In step 2, the specific implementation process of zero point real-time compensation is:

[0028] (1) Figure 2 As shown, the flight time Δt of the acoustic wave signal upstream and downstream in the pipe wall is obtained for the L wave 1 and Δt 2 ;

[0029] (2)Δt 1 and Δt 2 Use the following formula 2 for filtering:

[0030]

[0031] (3) The filtered Δt 1 and Δt 2 Substitute into formula 1 to perform zero point correction and obtain the accurate flow rate after correction.

[0032] Step 3: Perform Kalman filtering on the measured flow rate Q to further reduce the interference of random disturbances on the flow rate, and then obtain the final flow rate.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pipeline flow measurement method based on zero point real-time compensation, characterized in that: The ultrasonic flow meter is used for measurement and the following steps are adopted: Step 1: Use the V method to install the two transducers of the ultrasonic flow meter on the same side of the pipe wall, ensuring that the transducers can receive L waves and S waves. Step 2: Measure the upstream flight time and downstream flight time of the L wave and S wave respectively, and obtain the corrected flow rate according to the following formula (1): Wherein, t1 and t2 are respectively the upstream and downstream flight times measured by the two transducers using S waves, Δt1 and Δt2 are respectively the upstream and downstream flight times measured by the two transducers using L waves, D is the inner diameter of the pipe, θ is the emission angle, and K is the compensation coefficient for converting the linear velocity into the surface velocity; In step 2, the specific implementation process of zero point real-time compensation is: (1) Obtain the flight time Δt1 and Δt2 of the ultrasonic signal upstream and downstream in the pipe wall for the L wave; (2) Δt1 and Δt2 are filtered using the following equation (2): (3) Substitute the filtered Δt1 and Δt2 into formula 1 for zero point correction, and obtain the corrected accurate flow rate; Step 3: Perform Kalman filtering on the measured flow rate Q to further reduce the interference of random disturbances on the flow rate.

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