The vortex flowmeter is a volume flowmeter that is researched and produced according to the Karman vortex principle to measure the volume flow of gas, steam, or liquid, the volume flow of the standard condition, or the mass flow.
It is mainly used for flow measurement of industrial pipeline medium fluid, such as gas, liquid, steam, and other media.
It is characterized by small pressure loss, a large measuring range, and high accuracy.
It is hardly affected by fluid density, pressure, temperature, viscosity, and other parameters when measuring volume flow under working conditions.
There are no movable mechanical parts, so the reliability is high and the maintenance is small. The instrument parameters can be stable for a long time. The vortex flowmeter adopts a piezoelectric stress sensor, which has high reliability and can work in the working temperature range of -20℃～+250℃. It has an analog standard signal and digital pulse signal output.
It is easy to use with digital systems such as computers. It is a relatively advanced and ideal measuring instrument.
Vortex flow meters measure fluid velocity using a principle of operation referred to as the von Kármán effect, which states that when flow passes by a bluff body, a repeating pattern of swirling vortices is generated.
The vortex flowmeter uses the principle of fluid oscillation to measure flow. When the fluid passes through the vortex flow transmitter in the pipeline, two rows of vortices proportional to the flow velocity are alternately generated up and down after the vortex generator of the triangular column. The release frequency of the vortex is proportional to the flow rate. The average velocity of the fluid flowing through the vortex generator is related to the characteristic width of the vortex generator, and can be expressed by the following formula:
where: f is the release frequency of the vortex, unit in Hz; v is the average velocity of the fluid flowing through the vortex generator, unit in m/s, d is the characteristic width of the vortex generator, the unit is m; St is the Strouhal number, dimensionless, and its numerical range is 0.14-0.27.
St is a function of Reynolds number
When the Reynolds number Re is within the range, the value of St is about 0.2. In the measurement, try to satisfy the Reynolds number of the fluid at
and the vortex frequency at this time is
Thus, by measuring the frequency of the vortex, the average velocity “v “of the fluid flowing through the vortex generator can be calculated, q=vA, and then the flow rate “q” can be calculated from the formula, where “A “is the cross-sectional area of the fluid flowing through the vortex generator