EMD and Spectrum-Centrobaric-Correction-Based Analysis of Vortex Street Characteristics in Mist Annular Flow of Wet Gas

To improve the accuracy of vortex flowmeter in mist annular flow of wet gas, the characteristics of two-phase vortex street were investigated and the influence of discrete droplets on the meter over-reading was analyzed. For calibrating experiments, a mist annular flow loop was developed where the discrete droplets smaller than 50 micrometer were generated by high-pressure microsprayer nozzles. The accurate gas and the liquid flowrates were calibrated by the sonic nozzle standard facility and metering pump system, respectively. Then, the amplitude and the signal quality of the vortex street signal were investigated to analyze the effect of liquid phase on the signals. Due to the poor vortex street signal in two-phase flow, a new signal processing algorithm based on empirical mode decomposition (EMD) and the spectrum centrobaric correction method (SCCM) was proposed and validated by the experiments. Finally, the key parameter, the over-reading was analyzed by the proposed method and found that the mass loading of dispersed micrometer droplets can be as a main factor, which affects the gas flowrate overreading of vortex flowmeter in mist annular flow directly.