Several characteristics of vortex flowmeter
vortex flowmeter has a short history and is currently in the process of research and development. Therefore, it is still difficult to discuss its characteristics in a very specific and complete way. Therefore, here, only a certain type of vortex flowmeter is taken as an example to discuss its error characteristics, pressure loss characteristics and frequency characteristics
the error characteristics of vortex flowmeter can be seen in Figure 3-13. This is the error calibration test of vortex flowmeter with the same caliber with air, water and light oil. Because the viscosity of these three fluid media is different, their error characteristics are also different. However, it can be seen from the figure that except that the Reynolds number Re is less than 2 × The error of oil within the range of L04 will increase greatly, except that the re number is 2 × l. 5 × Within the range of l05, the error characteristics of any medium are within ± 1%. This indicates that the vortex flowmeter has a wide range of application, and the accuracy is little affected by the medium.
error characteristics of vortex flowmeter
the pressure characteristics of vortex flowmeter are shown in Figure 3-14. It can be seen from the figure that although the vibration energy of the fluid is only a part of the kinetic energy of the fluid, the pressure loss is inevitable. The greater the flow rate, the greater the pressure loss
figure 3-14 pressure loss characteristics of vortex flowmeter figure 3-15 frequency characteristics of vortex flowmeter in recent two years
the frequency characteristics of vortex flowmeter are shown in Figure 3-15. From equation (3-29), it can be seen that the vortex frequency is inversely proportional to the diameter (width) of vortex generator and is directly proportional to the incoming flow velocity in the pipe. Therefore, it can be seen that it is fixed on the shaft rack 9 with limit block 8. Generally speaking, the larger the diameter of flowmeter is, The generated vortices can save a lot of intermediate procurement links, and the lower the frequency; The smaller the diameter is, the higher the vortex frequency will be.
the above characteristics are obtained when the front straight pipe section is 20 times D and the rear straight pipe section is 10 times d. This is also the length of the straight pipe section generally required by the vortex flowmeter
the upper and lower limits of the flow measured by the vortex flowmeter are determined according to the range of Reynolds number re that produces a stable vortex, and the lower limit flow value also depends on the lowest flow value whose output linearity decreases and the accuracy does not meet the requirements. (end)