Frequency variance calculation and amplitude value operation combined vortex shedding flowmeter pipeline vibration resisting method and system

Abstract

The invention relates to the field of flow detection, in particular to a single-sensing structure-oriented frequency variance calculation and amplitude value operation combined vortex shedding flowmeter pipeline vibration resisting method and system. In output signals of vortex shedding flow sensors, the frequency variances of flow signals are relatively large and the frequency variances of pipeline vibration are relatively small. When signal to noise ratios are bad, vibration harmonic waves, frequency variances of which are greater than frequency variances of flows, occur. When flow signals are same as the pipeline vibration frequencies, amplitude values of signals are suddenly increased or decreased in an intermittent manner, so as to cause measurement errors. According to the method andsystem, spectral analysis is carried out on output signals of vortex shedding flow sensors, frequency variances of spectral peak values are calculated, and amplitude values of the spectral peak values are calculated, so that vibration harmonic wave interferences are eliminated and the problem of same-frequency signal measurement errors is solved, namely, a frequency variance calculation and spectral amplitude value operation combined method is adopted to extract vortex shedding flow frequencies so that the pipeline vibration resisting performance of vortex shedding flowmeters is effectively improved.

Description

technical field [0001] The invention relates to the field of flow detection, and relates to a signal processing method and system of a vortex flowmeter, in particular to a method and system for anti-pipeline vibration of a vortex flowmeter combining frequency variance calculation and amplitude calculation. Background technique [0002] The vortex flowmeter is suitable for the flow measurement of various media such as liquid, gas and saturated steam. At the same time, it has been widely used because of its advantages of no mechanical moving parts, simple and reliable structure and long service life. Since the vortex flowmeter is a flowmeter based on the principle of fluid vibration, it is particularly susceptible to the influence of pipeline vibration interference. However, motors, pumps, valves and other equipment are commonly found in industrial sites, and their work will cause vibrations in pipelines. Especially when the pipeline vibration interference energy in the outpu...

AI Technical Summary

Problems solved by technology

However, the digital vortex flowmeter based on the dual-sensor structure and anti-strong interference has the following disadvantages: (1) the requirements for the electromechanical characteristics and packaging process of the two vortex flow sensors are extremely high, otherwise, when the cut-off frequency and Harmonic interference that cannot be removed by the cut-off amplitude will lead to misjudgment of on-site conditions, resulting in measurement errors

(2) There are high requirements for the sensitivity difference of the two vortex sensors to feel the vortex flow signal and vibration noise, and it is difficult to meet the design requirements of the sensitivity difference required by this method in actual implementation

However, this vortex flowmeter digital signal processing system based on a single sensor with strong anti-interference also has shortcomings: (1) The amount of autocorrelation calculation is large. In practical applications, in order to meet the requirements of low power consumption of the vortex flowmeter, can only reduce the number of autocorrelation points

(2) For autocorrelation calculations with fewer points, the attenuation curve of the autocorrelation function of the vortex signal fluctuates and is not completely unidirectional. Therefore, it is difficult to accurately obtain the ratio of the required autocorrelation function amplitude, which is likely to cause the result to be wrong. Misjudgment

[0006] However, the proposer of this method did not explain the specific method of calculating the frequency variance, and at the same time, did not explain how to judge whether the peak value in the spectrum has jumped, because when the peak value jumps, it is necessary to update the actual peak value used to calculate the frequency variance Otherwise, it will cause the calculation error of the frequency variance

[0007] In practical applications, due to the vibration harmonic interference whose frequency variance is greater than the flow frequency variance in the output signal of the vortex flow sensor, it is wrong to extract the flow frequency based on the frequency variance

In addition, when the frequency of flow and vibration are the same, because the two phases are not completely synchronized, the amplitude of the output signal of the vortex flow sensor will intermittently increase or decrease suddenly, and the signal amplitude suddenly decays In the data segment, the actual number of peaks in the spectrum is 0, and the direct output of 0Hz is the flow frequency, which will cause measurement errors

[0008] Therefore, to apply this method to vortex flowmeter products, the following problems need to be solved: (1) How to calculate the frequency variance quickly and accurately; (2) How to judge whether the frequency of each peak in the spectrum has jumped ;(3) How to eliminate the influence of vibration and harmonic interference; (4) How to solve the measurement error caused by the decrease of signal amplitude when the flow and vibration are at the same frequency

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