What is a vortex flow meter
Vortex flowmeter is the only flowmeter that can measure all three-phase fluids (liquid, gas and steam). It is an ideal choice for measuring saturated steam and superheated steam in large facilities, which can improve steam production efficiency.
Vortex flowmeter is a new type of volumetric flowmeter developed based on the Karman vortex principle, which belongs to fluid vibration flowmeter. Using vortex sensor and single-chip microcomputer technology, both mass flow and volume flow can be calculated.
Therefore, vortex flowmeter is widely used in flow measurement of steam, gas, liquid, etc. It is used in industries such as petroleum, chemical, metallurgy, thermal power, textile, papermaking, electricity, environmental protection and municipal construction.
Vortex flow meter working principle
Von Kármán Effect
In fluid dynamics, a Kármán vortex (or a von Kármán vortex ) is a repeating pattern of swirling vortices, caused by a process known as vortex shedding, which is responsible for the unsteady separation of flow of a fluid around blunt bodies.
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.
In a Vortex flow meter, an obstruction in the flow path, often referred to as a shedder bar, serves as the bluff body. The shedder bar causes process fluid to separate and form areas of alternating differential pressure known as vortices around the back side of the shedder bar.
How does a Vortex Flow Meter Work?
Vortex flowmeters use the principle of vortex shedding, where vortexes (or vortices) are alternately formed downstream of an object. The frequency of vortex shedding is proportional to the velocity of the liquid flowing through the flowmeter. And the Karman vortex principle, where a blunt body in a pipe creates vortices. The number of vortices is proportional to the volume flow in the pipe.
The vortex flowmeter measures volume flow based on the Karman vortex principle. The vortex flowmeter is composed of a vortex generator, a detection probe and corresponding electronic circuits.
A non-streamlined vortex generating body (blocking member) is provided in the fluid. Then two rows of regular vortices are alternately generated from both sides of the vortex generator, and this vortex becomes the Karman vortex . As shown below:
The vortex rows are arranged asymmetrically downstream of the vortex generator. Suppose the frequency of vortex generation is f, the average velocity of the incoming flow of the measured medium is V, the width of the flow-facing surface of the generating body is d, and the diameter of the surface body is D.
According to the Karman vortex principle, there is the following relationship:
f=StV/d
In the formula:
F – Karman vortex frequency generated on one side of the generating body.
St-Strohal number (dimensionless number) .
V-average flow velocity of fluid .
d-width of vortex generator
It can be seen that the instantaneous flow rate can be calculated by measuring the Karman vortex separation frequency. Among them, Strohal number (St) is a dimensionless unknown number. The following figure shows the relationship between Strohal number (St) and Reynolds number (Re).
In the curve table, the straight part of St=0.17. The release frequency of vortex is proportional to the flow speed, which is the measurement range of the vortex flow sensor. As long as the frequency f is detected, the flow rate of the fluid in the tube can be found. The volumetric flow rate is determined from the flow velocity V. The ratio of the measured pulse number to the volume flow rate is called the instrument constant K.
K=N/Q(1/m³)
In the formula:
K=instrument constant (1/m³)
N=Number of pulses
Q=volume flow
Vortex flow meter advantages and disadvantages
Advantages
Vortex flowmeter has a wide measurement range, the adjustment ratio can generally reach 1:10, stable performance and long life.
Vortex flowmeter has no moving parts, simple and sturdy structure, high reliability, and very reliable long-term operation.
Vortex flowmeter can be installed at any angle, simple installation, convenient maintenance, and the pressure loss caused is very small.
Common signals of the vortex flowmeter are pulse or analog signals, the signal is stable, and the anti-interference ability is strong.
High precision and low maintenance.
The new appearance design, the body adopts precision casting technology, beautiful appearance, high temperature resistance and strong corrosion resistance.
Medium temperature | Normal temperature: -40~100℃ |
Material | Clamping type: 304 stainless steel, 316L, matching flange bolts and nuts: carbon steel, stainless steel; |
Disadvantages
Thas poor anti-vibration performance. External vibrations can cause measurement errors in the vortex flowmeter and may not even work properly.
The high flow velocity shock of the fluid causes vibrations in the vortex body, which reduces the measurement accuracy.
Cannot measure dirty media
Straight pipe requirements are high when mounting the vortex flow meter
Not suitable for low Reynolds number fluids measurements;
Low meter factor (compared to turbine flow meter);
It is not suitable for the pulsating flow.
Vortex flowmeter is mainly used for flow measurement of industrial pipeline medium fluid, such as gas, liquid, steam and other media. It is a relatively advanced and ideal flow meter.
We, Sino-Inst, supply a full range of vortex flowmeters. Including flange installation, clamp installation, insertion type, thread installation, etc.
If you need to purchase a vortex flowmeter or have any questions about the installation of the vortex flowmeter, please contact our engineers!
