Vortex flowmeter application, practical! Convenience! Save money! Posted by : admin / Posted on : Oct 12， 2019

Under certain flow conditions, a part of the fluid kinetic energy will be converted into fluid vibration, and its vibration frequency has a certain proportional relationship with the flow rate (flow rate). This is the principle of the vortex flowmeter.
The vortex flowmeter has the following characteristics:
1 The output is pulse frequency, and its frequency is proportional to the actual volume flow of the fluid to be measured, and is not affected by fluid composition, density, pressure and temperature;
2 The measuring range is wide, and the general range can reach more than 10:1;
3 accuracy is the upper middle level;
4 no moving parts, high reliability;
5 The structure is simple and firm, the installation is convenient, and the maintenance cost is low;
6 Wide range of applications for liquids, gases and steam.
Application in the field
Vortex flowmeters are suitable for a wide range of fluids, but are not suitable for low Reynolds number (Re D ≤ 2 × 10 4 ) fluids. Because at low Reynolds numbers, the Strauhal number changes with the Reynolds number, and the meter linearity deteriorates.
At the same time, the fluid containing solid particles will generate noise to the vortex generator, and the short fibers contained therein will change the meter factor if they are wound around the vortex generator.
The application of vortex flowmeters in mixed-phase fluids is as follows:
1 It can be used for gas and liquid two-phase flow with dispersed and uniform micro-bubble, but the volumetric gas content should be less than 7%~10%. If the volume gas content exceeds 2%, the meter factor should be corrected.
2 It can be used for gas-solid and liquid-solid two-phase flow containing dispersed and uniform solid particles with a content of not more than 2%.
3 can be used for two-component flow of liquid and liquid (such as oil and water) which are insoluble in each other. Pulsating and swirling flow can have a severe impact on the vortex flowmeter. If the pulsation frequency coincides with the vortex frequency band, it may cause resonance, destroy normal operation and equipment, and cause the vortex signal to produce a "Lock-in" phenomenon, at which time the signal will be fixed at a certain frequency. "Locking" is related to the pulsation amplitude, the shape of the vortex generator, and the clogging ratio.
The accuracy of the vortex flowmeter is generally between ± 0.5% R and ± 2% R for liquids and between 0.2% and 0.5% for gases ranging from ± l% R to ± 2% R. Because the meter coefficient of the vortex flowmeter is low, the frequency resolution is low, the larger the diameter, the lower the accuracy, so the gauge diameter should not be too large (below DN300).
Range width is a feature of vortex flowmeters, but the important point is the flow rate at the lower end of the range. Generally, the average liquid flow rate lower limit is 0.5 m/s, and the gas is 4 to 5 m / s. The normal flow rate of the vortex flowmeter is preferably 1/2 to 2/3 of the normal measurement range.
The biggest advantage of the vortex flowmeter is that the meter factor is not affected by the physical properties of the measured medium and can be extended to other media by a typical medium. However, due to the wide range of flow rates of liquid and gas, the frequency range is also very different. In the amplifier circuit that processes the vortex signal, the passband of the filter is different and the circuit parameters are different. Therefore, the same circuit parameter cannot be used to measure different media. In addition, the density of gas and liquid varies greatly, and the signal intensity generated during vortex separation is proportional to the density, so the signal intensity is also very different. The gain and trigger sensitivity of the liquid and gas amplifier circuits are different, the piezoelectric charge difference is large, and the parameters of the charge amplifier are also different. Even if the gas (or liquid, steam) is the same, the flow range is different, the signal intensity is different, and the circuit parameters are also changed as the medium pressure, temperature, and density are different. Therefore, a vortex flowmeter is not modified by hardware or software, and it is not feasible to change the medium or change the gauge.
Orifice plate flowmeter