Online Measurement of Wet Gas by Modeling Frequency and Amplitude Characteristics of a Vortex Flowmeter

Abstract

In this article, an accurate online measurement of gas flowrate in wet gas was developed by modeling the frequency and amplitude characteristics of a vortex flowmeter in annular mist flow. The low-frequency modulation behaviors of the vortex signals were analyzed by the ridge method based on continuous wavelet transform (CWT). It indicates that the instability of frequency and amplitude of the signals both enhance with the increase of liquid loading; and therefore, a feature extraction method based on ridge-averaged was proposed and validated by the tests. A film extraction device was developed to measure the flowrate of the liquid film and further obtain the droplet mass loading. Then, a uniform linear equation for the overreading was obtained experimentally on the basis of the scaling parameter analysis in particle-laden flow. A uniform exponential equation for the dimensionless signal amplitude of the sensor output was developed with droplet mass loading. Finally, a wet gas measurement model with the simultaneous equations from these two correlations was established and the iterative solution algorithm was given. In the present cases, the percentage errors (PEs) of the gas flowrate predicted by the modeling are within ±1.5% and the mean absolute PE is 0.37%. The method proposed in this article can achieve accurate measurement of gas flowrate by using only one vortex flowmeter and, hence, creates a simple inexpensive metering system for wet gas flow.