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Shanghai Dianda Automation Instrument Co., Ltd
vortex flow meter
NegotiableUpdate on 05/18
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Overview
The vortex flowmeter is a fluid oscillation type flow instrument developed based on the Karman vortex principle, with high signal-to-noise ratio, high sensitivity, and strong anti vibration performance. The signal circuit uses microcontroller technology for data processing, encapsulating the CPU unit, storage unit, display unit, communication unit, and other functional modules in an amplifier circuit. It has very stable zero point and accuracy, and is widely used for measuring saturated steam, superheated steam, compressed air, and general liquids.
Product Details
vortex flow meterIt is a fluid oscillating flowmeter developed based on the principle of Karman vortex street.
vortex flow meterIf a non streamlined vortex generator (flow resistant fluid) is set up in the fluid, two columns of regular vortices are alternately generated from both sides of the vortex generator. This type of vortex is called a Karman vortex street, as shown in Figure (1).
The vortices are arranged asymmetrically downstream of the vortex generator. Assuming the frequency of vortex occurrence is f, the average velocity of the incoming flow of the measured medium is V, the width of the upstream face of the vortex generator is d, and the diameter of the body is D, according to the principle of Karman vortex street, the following relationship is obtained:
f=StV/d
In the formula:
Frequency of Karman vortex generated on one side of the f-body
St Strouhal number (dimensionless number)
The average flow velocity of V-fluid
The width of the vortex generator
From this, it can be seen that the instantaneous flow rate can be calculated by measuring the separation frequency of the Karman vortex street. Among them, Strouhal number (St) is an dimensionless unknown variable, and Figure (2) shows the relationship between Strouhal number (St) and Reynolds number (Re).
In the straight part of the curve table with St=0.17, the frequency of vortex release 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 inside the pipe can be obtained, and the volumetric flow rate can be calculated from the flow velocity V. The ratio of the measured number of pulses to the volume is called the instrument constant (K), as shown in the formula:
K = N/Q ( 1/m3)
Where:
K=Instrument constant (1/m)3）.
N=number of pulses
Q=volumetric flow rate (m3）
Special precautions
1. Installation requires cutting the pipeline, so before installation, it is necessary to ensure that the fluid in the pipeline has been emptied (except for the installation of pressure instruments), especially high-temperature and high-pressure fluids such as steam, to avoid accidents;
2. It is prohibited to install products, pressure transmitters, etc. on pipelines for welding operations;
3. When packaging or insulating high-temperature pipelines such as steam, the flowmeter body and connecting rod should be exposed;
4. When installing a pressure transmitter, the condenser equipped with the pressure sensor should be filled with water before installing the pressure sensor;
5. After each pipeline stop, the valve must be slowly opened and kept open for at least 2 minutes before resuming flow;
6. The signal line should use shielded wire, and the direction of the signal line should be far away from the interference of strong electromagnetic fields. It is never allowed to be laid together with high-voltage cables.
