Investigation of the pressure probe properties as the sensor in the vortex flowmeter

Abstract

Poor anti-disturbance ability to piping vibrations is one of the most difficult problems in vortex flowmeters which have been widely used in many industrial fields. Duct-wall differential pressure method (DDPM) proposed by the author's previous work is proved to be an effective measure to reduce these interferences. In order to improve the performance of DDPM, the relationship between pressure-sampling tube's natural frequency and its geometrical parameters was derived by theoretical modeling, and the influences of different pressure-sampling positions, pressure-sampling tubes, duct diameters and bluff body shapes on the performance of DDPM-based vortex flowmeter were compared and discussed experimentally. One important feature found is that the pressure-sampling system hardly affects the measurment of signal frequencies in DDPM but it has great impact on the signal amplitudes. Measures to reduce the distortion of signal amplitudes include increasing the natural frequency of pressure-sampling system, choosing symmetric sampling tubes and selecting their parameters according to specific measurement conditions, etc. It is also found that despite of duct diameter and bluff body shape, the amplitudes of duct-wall differential pressures in DDPM fall and keep nearly a finite constant after they reach the peak values, which may reduce the requirement of signal amplifiers. These properties of the pressure sensor are useful to improve the design of DDPM-based vortex flowmeters in flow measurement and at the same time give an in-depth understanding about the measurement of differential pressures.