Research On Adaptability Of Vortex Flowmeter Under Various Operating Conditions

The vortex flowmeter is a hydrodynamic instability flowmeter and is widely used in chemical industry, metallurgy, light industry, food industry due to its non-mobile components, insensitivity to media, low pressure loss, etc. However, because of the complexity of operating conditions and the flow instability, the performance of vortex flowmeters under these conditions should be investigated in detail. Based on the above considerations, the vortex flowmeters'adaptabilities to periodic pipe vibration, different medium densities and oil-water two-phase flow have been tested and discussed.In the periodic pipe vibration experiments, the accuracy of a typical stress type vortex flowmeter and the digital vortex flowmeters of Yokogawa and ABB have been studied by means of changing the pipe vibrating direction vertically and horizontally and varying the values of the vibrating accelerations. Their relative errors of meter coefficient show that they are all sensitive to vibrations and their anti-vibrating accelerations do not exceed 0.1g. Thus a novel piezoelectric detector, named three-line-common-joint, having two outputs is designed. One output is the periodic pipe vibration signal, and the other is the vortex flow rate signal superposed with these vibration noises. The frequency of the vibrating signal is obtained by the EMD method. Then the vortex frequency is extracted from the mixed signals through the adaptive notch filter. Both the simulation and experiments show that the three-line-common-joint method is able to overcome the influence of periodic pipe vibrations. Finally, an anti-periodic-vibrating vortex flowmeter is developed based on TMS320F2812 DSP and the same vibration experiments of different vibrating directions and accelerations have been carried out. The results show that the anti-vibrating acceleration is up to 0.7g with the accuracy of 1%.In the medium density experiments, the characteristics of vortex flowmeters have been studied by adjusting the pressure of the barotropic-venturi nozzles gas flow calibration facility. The results demonstrate that the medium density has no influence on the accuracy of vortex flowmeters and that the lower flow limit decreases as the density of the fluid increases.In the oil-water two-phase flow experiments, the performances of vortex flowmeters have been studied by installing it on a vertical upward pipe of the multi-phase flow facility. The results show that the accuracy of vortex flowmeters is insensitive to the components of the fluid. And the relationship between relative errors of the meter coefficient and oil volume fractions is also discussed.Above all, the anti-vibrating performance of the vortex flowmeter has been improved and the data for its using in different medium densities and oil-water two-phase flow has been supplemented, which have great practice.