A method for calculating the flow rate of a pulsating flow by a vortex flowmeter

Abstract

The present application relates to vortex flowmeter, specifically to a kind of vortex flowmeter measurement pulsating flow flow calculation method, set high level threshold and low level threshold, according to high level threshold and low level threshold to the vortex digital signal of collection point by point scanning, and the effective pulse number in point by point scanning process is counted, the flow of pulsating flow is calculated based on effective pulse number;The technical scheme provided by the present application can effectively overcome the defects that pulsating flow with sparse change cannot be accurately measured in the prior art.

Description

Technical Field

[0001] This invention relates to vortex flow meters, and more specifically to a method for calculating the flow rate of pulsating flow measured by a vortex flow meter. Background Technology

[0002] Vortex flow meters are flow instruments based on the principle of fluid oscillation and are widely used in process measurement and control systems. Currently, research on vortex flow meters is based on steady-state flow conditions, calculating the corresponding volumetric flow rate by measuring the vortex shedding frequency over a period of time. However, in industrial flow measurement, unsteady-state flow conditions are widespread, such as pulsating flow. Pulsating flow refers to a flow whose parameters change periodically over time. In industrial production, the fluids output from rotary, reciprocating, and various moving conveyor equipment are all pulsating flows.

[0003] Measuring pulsating flow using a vortex flowmeter is a challenging task. Fang Min, in her master's thesis "Application Research of HHT and Wavelet Transform in Vortex Pulsating Flow Signal Processing," proposed using HHT (Hilbert-Huang Transform) to denoise pulsating flow signals. Huang Yunzhi and Xu Kejun, in their paper "Estimation of Instantaneous Frequency of Vortex Signal under Pulsating Flow Conditions," used wavelet transform based on IIR filter banks to perform binary decomposition of the signal, and then performed Hilbert transform on the decomposed vortex signal to estimate the instantaneous frequency.

[0004] In summary, current publicly available literature still relies on simulation for processing pulsating flow signals. It assumes the existence of a steady-state vortex shedding signal within the sampling period, only superimposed with some interference signals. The goal of signal processing is to extract the steady-state vortex shedding signal. However, in real-world operating conditions, such as the vortex shedding signal generated by a Dürer pump in oil and gas recovery, the signal is not steady-state. Figure 2 As shown in the figure, the signal is sparsely varied, and the above method is ineffective for such signals. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a method for calculating the flow rate of pulsating flow using a vortex flow meter, which can effectively overcome the defect of the prior art in being unable to accurately measure sparsely varying pulsating flow.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for calculating the flow rate of pulsating flow using a vortex flowmeter involves setting a high-level threshold and a low-level threshold, scanning the acquired vortex digital signal point by point based on the high-level threshold and the low-level threshold, counting the number of effective pulses during the point-by-point scanning process, and calculating the flow rate of the pulsating flow based on the number of effective pulses.

[0010] Preferably, the step of scanning the acquired vortex shear digital signal point by point according to a high-level threshold and a low-level threshold, and counting the number of effective pulses during the point-by-point scanning process, includes:

[0011] S1. Determine whether the signal voltage value is less than the low-level threshold. If the signal voltage value is less than the low-level threshold, proceed to S2; otherwise, proceed to S3.

[0012] S2. Determine whether both high and low level flags are set. If both high and low level flags are set, check the validity of the pulse segment, set the interval counter to 0, count the number of valid pulses, and return to S1. Otherwise, set the low level flag if it is not set, increment the interval counter, and return to S1.

[0013] S3. Determine if the signal voltage value is greater than the high-level threshold. If the signal voltage value is greater than the high-level threshold, proceed to S4; otherwise, increment the interval counter and return to S1.

[0014] S4. Determine if the high-level flag is set. If the high-level flag is set, increment the interval counter and return to S1. Otherwise, set the high-level flag, increment the interval counter, and return to S1.

[0015] Preferably, in step S2, it is determined whether both the high and low level flags are set. If both flags are set, a validity check is performed on the pulse segment, and the interval counter is set to 0 to count the number of valid pulses, including:

[0016] If both the high and low level flags are set, the pulse segment is determined to be a potentially valid pulse, and the frequency of the pulse segment is calculated based on the actual sampling rate and the number of valid points of the pulse segment.

[0017] Determine whether the frequency of the pulse segment is within a reasonable range. If the frequency of the pulse segment is within a reasonable range, increment the pulse counter and return to S1; otherwise, return directly to S1.

[0018] Preferably, the calculation of the pulsating flow rate based on the effective pulse count includes:

[0019] Record the effective pulse counts P1, P2, ..., P obtained from m statistical analyses. m If the sampling rate and the number of sampling points remain constant at f each time... s If N, then the average flow rate Q for the m cycles is calculated using the following formula:

[0020]

[0021] Among them, P i Let i = 1, 2, ..., m, and K be the instrument coefficient of the vortex flowmeter.

[0022] Preferably, setting the high-level threshold and the low-level threshold includes:

[0023] Define a threshold level V that can be adjusted by a parameter. th V ref +V th V ref -V th These are respectively used as the high-level threshold and the low-level threshold. When the signal amplitude is greater than the high-level threshold V... ref +V th When the signal amplitude is less than the low-level threshold V, a valid high level is considered to have occurred. ref -V th When this occurs, a valid low level is considered to have occurred;

[0024] Among them, V ref This is the reference voltage.

[0025] Preferably, the step of scanning the acquired vortex shear digital signal point by point according to a high-level threshold and a low-level threshold, and counting the number of effective pulses during the point-by-point scanning process, includes:

[0026] The ping-pong dual buffering method is adopted. After the ping group data acquisition is completed, the acquired vortex digital signal is scanned point by point according to the high level threshold and the low level threshold, and the number of effective pulses in the point-by-point scanning process is counted. At the same time, the pong group performs data sampling.

[0027] (III) Beneficial Effects

[0028] Compared with the prior art, the flow calculation method for measuring pulsating flow using a vortex flowmeter provided by this invention has more flexible threshold selection than a hardware counter, and adds pulse validity checking, which greatly improves anti-interference ability. The technical solution of this application is simple and reliable, and can accurately measure sparsely varying pulsating flow, ensuring that the measurement error is within 3%. In contrast, traditional digital signal processing methods cannot accurately measure sparsely varying pulsating flow. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0030] Figure 1 This is a schematic diagram illustrating the counting of effective pulses during point-by-point scanning in this invention;

[0031] Figure 2 A schematic diagram of a typical sparsely varying pulsating flow signal generated by a Dürer pump;

[0032] Figure 3 A schematic diagram of a pulsating flow signal with high-frequency spikes;

[0033] Figure 4 This is a schematic diagram of the time-domain waveform of the pulsating flow signal of the superimposed interference signal detected on site.

[0034] Figure 5 for Figure 4 A schematic diagram of the frequency domain waveform obtained after Fourier transform;

[0035] Figure 6 This is a graph comparing the errors of various algorithms. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] A method for calculating the flow rate of pulsating flow using a vortex flowmeter involves setting a high-level threshold and a low-level threshold, scanning the acquired vortex digital signal point by point based on the high-level threshold and the low-level threshold, counting the number of effective pulses during the point-by-point scanning process, and calculating the flow rate of the pulsating flow based on the number of effective pulses.

[0038] ① Set high-level threshold and low-level threshold, including:

[0039] Define a threshold level V that can be adjusted by a parameter. th V ref +V th V ref -V thThese are respectively used as the high-level threshold and the low-level threshold. When the signal amplitude is greater than the high-level threshold V... ref +V th When the signal amplitude is less than the low-level threshold V, a valid high level is considered to have occurred. ref -V th When this occurs, a valid low level is considered to have occurred;

[0040] Among them, V ref This is the reference voltage.

[0041] ②For example Figure 1 As shown, the acquired vortex shear digital signal is scanned point by point according to high-level and low-level thresholds, and the number of effective pulses during the point-by-point scanning process is counted, including:

[0042] S1. Determine whether the signal voltage value is less than the low-level threshold. If the signal voltage value is less than the low-level threshold, proceed to S2; otherwise, proceed to S3.

[0043] S2. Determine whether both high and low level flags are set. If both high and low level flags are set, check the validity of the pulse segment, set the interval counter to 0, count the number of valid pulses, and return to S1. Otherwise, set the low level flag if it is not set, increment the interval counter, and return to S1.

[0044] S3. Determine if the signal voltage value is greater than the high-level threshold. If the signal voltage value is greater than the high-level threshold, proceed to S4; otherwise, increment the interval counter and return to S1.

[0045] S4. Determine if the high-level flag is set. If the high-level flag is set, increment the interval counter and return to S1. Otherwise, set the high-level flag, increment the interval counter, and return to S1.

[0046] Specifically, it checks whether both the high and low level flags are set. If both are set, it checks the validity of the pulse segment, sets the interval counter to 0, and counts the number of valid pulses, including:

[0047] If both the high and low level flags are set, the pulse segment is determined to be a potentially valid pulse, and the frequency of the pulse segment is calculated based on the actual sampling rate and the number of valid points of the pulse segment.

[0048] Determine whether the frequency of the pulse segment is within a reasonable range. If the frequency of the pulse segment is within a reasonable range, increment the pulse counter and return to S1; otherwise, return directly to S1.

[0049] Meanwhile, in the process of scanning the acquired vortex street digital signal point by point according to the high-level threshold and the low-level threshold and counting the number of valid pulses, the technical solution of this application adopts the ping-pong dual buffering method. After the ping group data acquisition is completed, the acquired vortex street digital signal is scanned point by point according to the high-level threshold and the low-level threshold, and the number of valid pulses in the point-by-point scanning process is counted. At the same time, the pong group performs data sampling.

[0050] ③ Calculate the flow rate of pulsating flow based on the effective pulse count, including:

[0051] Record the effective pulse counts P1, P2, ..., P obtained from m statistical analyses. m If the sampling rate and the number of sampling points remain constant at f each time... s If N, then the average flow rate Q for the m cycles is calculated using the following formula:

[0052]

[0053] Among them, P i The number of valid pulses saved each time, i = 1, 2, ..., m, and K is the instrument coefficient of the vortex flowmeter, in units of P / m. 3 .

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the flow rate of pulsating flow measured by a vortex flowmeter, characterized in that: Set high-level and low-level thresholds, scan the acquired vortex shear digital signal point by point according to the high-level and low-level thresholds, count the number of effective pulses in the point-by-point scanning process, and calculate the flow rate of the pulsating flow based on the number of effective pulses; The step of scanning the acquired vortex shear digital signal point by point based on high-level and low-level thresholds, and counting the number of effective pulses during the point-by-point scanning process, includes: S1. Determine whether the signal voltage value is less than the low-level threshold. If the signal voltage value is less than the low-level threshold, proceed to S2; otherwise, proceed to S3. S2. Determine whether both high and low level flags are set. If both high and low level flags are set, check the validity of the pulse segment, set the interval counter to 0, count the number of valid pulses, and return to S1. Otherwise, set the low level flag if it is not set, increment the interval counter, and return to S1. S3. Determine if the signal voltage value is greater than the high-level threshold. If the signal voltage value is greater than the high-level threshold, proceed to S4; otherwise, increment the interval counter and return to S1. S4. Determine whether the high-level flag is set. If the high-level flag is set, increment the interval counter and return to S1. Otherwise, set the high-level flag, increment the interval counter, and return to S1. In S2, it is determined whether both the high and low level flags are set. If both flags are set, a validity check is performed on the pulse segment, and the interval counter is set to 0. The number of valid pulses is then counted, including: If both the high and low level flags are set, the pulse segment is determined to be a potentially valid pulse, and the frequency of the pulse segment is calculated based on the actual sampling rate and the number of valid points of the pulse segment. Determine whether the frequency of the pulse segment is within a reasonable range. If the frequency of the pulse segment is within a reasonable range, increment the pulse counter and return to S1; otherwise, return directly to S1.

2. The method for calculating the flow rate of pulsating flow using a vortex flowmeter according to claim 1, characterized in that: The calculation of pulsating flow rate based on the effective pulse count includes: Record the effective pulse counts P1, P2, ..., P obtained from m statistical analyses. m If the sampling rate and the number of sampling points remain constant each time... If N, then the average flow rate Q for the m cycles is calculated using the following formula: ； Among them, P i The number of valid pulses saved each time. K is the instrument coefficient of the vortex flow meter.

3. The method for calculating the flow rate of pulsating flow using a vortex flowmeter according to claim 1, characterized in that: Setting the high-level threshold and low-level threshold includes: Define a threshold level V that can be adjusted by a parameter. th ,Will , These are used as the high-level threshold and low-level threshold, respectively. When the signal amplitude is greater than the high-level threshold... When the signal amplitude is less than the low-level threshold, a valid high level is considered to have occurred. When this occurs, a valid low level is considered to have occurred; Among them, V ref This is the reference voltage.

4. The method for calculating the flow rate of pulsating flow using a vortex flowmeter according to claim 1, characterized in that: The step of scanning the acquired vortex shear digital signal point by point based on high-level and low-level thresholds, and counting the number of effective pulses during the point-by-point scanning process, includes: The ping-pong dual buffering method is adopted. After the ping group data acquisition is completed, the acquired vortex digital signal is scanned point by point according to the high level threshold and the low level threshold, and the number of effective pulses in the point-by-point scanning process is counted. At the same time, the pong group performs data sampling.

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