Measurement principle of vortex flowmeter | Will there be data fluctuations when measuring liquid flow and purging with vortex flowmeter

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The principle of vortex flowmeter is based on the Karman vortex phenomenon in fluid dynamics, and its core is to achieve flow measurement by detecting vortex frequency. Here are the specific principles and key points.

1. The core working principle is to set up non streamlined vortex generators (such as triangular columns and cylinders) in the early silver body. When the fluid flows through the generator, regular vortex columns will be alternately generated on both sides.

. These vortices are asymmetrically arranged downstream of the generator, forming Karman vortex streets. The shedding frequency of a vortex is directly proportional to the fluid flow velocity, and the flow velocity can be calculated by measuring the frequency. The mathematical relationship between frequency and flow velocity is described by the formula (f=frac {St cdot v} {(1-1.27d/D) cdot d}), where (St) is the Strouhal number (a dimensionless constant that depends on the shape and Reynolds number of the vortex generator); (d) is the frontal width of the object; (D) is the nominal diameter of the pipeline. This formula indicates that under specific conditions (such as Reynolds number stability), frequency (f) is linearly related to flow velocity (v)

3. Signal output characteristics have strong anti-interference ability: the output signal (frequency) is only related to the shape, size, and Reynolds number of the vortex generator, and is not affected by changes in fluid density, pressure, temperature, viscosity, and other physical properties. Instrument coefficient stability: The instrument coefficient (K) (the number of pulses corresponding to a unit flow rate) is only determined by the geometric parameters of the generating body, and

does not require recalibration for long-term use. Advantages and disadvantages analysis Advantages: simple structure, no mechanical movable parts, high reliability, and low maintenance cost for wide fibers; Widely applicable, capable of measuring liquids, gases, vapors, and some mixed phase fluids; High accuracy (± 1% R), wide range ratio (up to 10:1 to 20:1); Small head loss, no zero drift, and relatively low price. Disadvantages: Not suitable for low Reynolds number (Re<20000) scenarios, with significant limitations on high viscosity, low flow rate, and small-diameter fluids; High requirements for installation environment, need to avoid vibration interference, and a long straight pipe section should be carefully installed upstream (usually 15-20 times the pipe diameter); The instrument coefficient decreases with the increase of diameter, and the signal strength of large-diameter equipment is weak. 5. Typical application areas are widely used in industries such as steel, coking, petrochemicals, heating, medical, thermal power plants, and environmental protection, especially suitable for measuring volumetric flow rate under working conditions. Its advantages include: strong temperature adaptability (-20 ℃ to+250 ℃); Strong compatibility of output signals (supporting analog standard signals and digital pulse signals); Long term stability is high, suitable for automation control system integration. Summary: The vortex flowmeter achieves flow measurement by detecting the shedding frequency of the Karman vortex street. It has the characteristics of simple structure, strong applicability, and high accuracy, but attention should be paid to its requirements for flow field conditions and installation environment. In the field of

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