When the fluid passes through a vortex generator composed of spiral blades (see figure 1), the fluid is forced to rotate violently around the axis of the generator to form a vortex. When the fluid enters the diffusion section, the vortex is affected by the backflow and starts to rotate for the second time, forming a gyro vortex precession phenomenon. The precession frequency is proportional to the flow velocity and is not affected by the physical properties and density of the fluid. When the detecting element measures the precession frequency of the secondary rotation of the fluid, the flow rate can be known. But also can obtain good linearity in a wide flow range. The formula of flowmeter is: k = f/q.

Where: k- flowmeter coefficient l/m&; sup3

F- vortex frequency Hz

Q- volume flow m&m；; sup3/s

The instrument coefficient of the flowmeter is within certain structural parameters and specified Reynolds number range, and has nothing to do with the temperature, pressure, composition and physical properties (density and viscosity) of the fluid.

The flowmeter consists of a sensor and a conversion display.

1. The sensor includes vortex generator, detection element, rectifier and shell.

The vortex generator consists of special spiral blades, which are fixed at the front end of the contraction section of the shell, forcing the fluid to produce strong vortex.

The detection element is installed near the throat of the expansion tube, and thermal, piezoelectric, strain, capacitance or optical fiber detection elements can be used to detect the frequency signal of vortex precession.

The rectifier is fixed at the outlet of the flowmeter body, and its function is to eliminate eddy current, so as to reduce the influence of downstream flow pattern on instrument measurement.

The shell is designed as a flow channel with a certain shape, which makes eddy current form, fixes and protects the components installed inside, and is connected with the pipeline through the flange.

2, conversion display instrument

After being amplified, filtered and shaped, the weak voltage signal detected by the piezoelectric sensor becomes a pulse signal whose frequency is proportional to the flow rate, and then it is counted and displayed by the display instrument. The display instrument is equipped with an output interface which can output various signals. The measured gas medium can be compensated for temperature and pressure, converted into volume flow under standard conditions and displayed.

Main features:

1. Built-in pressure, temperature and flow sensors have high safety performance, compact structure and beautiful appearance.

2. On-site display of temperature, pressure, instantaneous flow and cumulative flow.

3. Using new signal processing amplifier and unique filtering technology, the interference signals caused by pressure fluctuation and pipeline vibration are effectively eliminated, and the anti-interference ability of the flowmeter is greatly improved, so that the small flow rate has excellent stability.

4. Unique time display and real-time data storage function can ensure that internal data will not be lost under any circumstances and can be stored permanently.

5. The power consumption of the whole machine is extremely low, and it can run with built-in battery for a long time, so it is an ideal local display instrument without external power supply.

6. Reliable anti-theft function and password protection to prevent parameter change.

7. The meter head can rotate at will 180 degrees, which is convenient for installation.