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Vortex Flow Meter

Description-Vortex Flow Meter

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Vortex Flow Meter description

Principle of measurement

GVF100 vortex flowmeter is based on the Karman vortex street principle, that is, when the fluid passes through the vortex flow transmitter in the pipeline, the vortex generator of the triangular column alternately generates two rows of vortices proportional to the flow rate. The frequency can calculate the average velocity of the fluid flowing through the vortex generator, and calculate the fluid flow rate according to the pipe diameter, temperature, pressure, etc.

涡街流量计.gif

When a non-streamline vortex generator (bluff body) is installed in the fluid, two rows of regular vortices are alternately generated from both sides of the vortex generator. This vortex is called a Karman vortex street, as shown in the figure below.

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The vortex array is arranged asymmetrically downstream of the vortex generator. Suppose the frequency of the vortex is f, the average velocity of the measured medium's incoming flow is V, the width of the frontal surface of the vortex generator is d, and the diameter of the surface body is D. According to the Karman vortex street principle, the following relational formula:

f=StV/d  

F-Carman vortex frequency generated on one side of the generator, St-Strohal number (dimensionless number)

V-average flow velocity of fluid

D——The width of the vortex generator It can be seen that the instantaneous flow can be calculated by measuring the separation frequency of the Karman vortex street. Among them, the Stroghal number (St) is a dimensionless unknown number

The figure below shows the relationship between Stromhal number (St) and Reynolds number (Re).

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In the straight part of the curve table with St=0.17, the release frequency of the vortex is proportional to the flow velocity, which is the measurement range of the vortex flow sensor. As long as the frequency f is detected, the flow velocity of the fluid in the tube can be obtained, and the volume flow rate can be obtained from the flow velocity V. The ratio of the measured pulse number to the volume is called the meter constant (K)

K=N/Q(1/m³)

K=Meter constant (1/m³)

N=number of pulses

Q=Volume flow (m³)

Product structure

The basic structure of a vortex flowmeter is shown in the figure. It is mainly composed of a meter body, a shell, a vortex generator, a piezoelectric element (frequency detector), a display, and a converter.

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