Principle of Vortex Flow Meters

Under specific flow conditions, part of the kinetic energy of the fluid is converted into fluid vibration, and its vibration frequency has a certain proportional relationship with the flow rate (flow rate). Flowmeters operating according to this principle are called fluid vibration flowmeters. Vortex flowmeter is one of them and others. So if you don't understand earthquakes, you don't understand vortex.

The vortex flow meter is researched and produced according to the Karman vortex street principle and is mainly used for the flow measurement of medium fluid in industrial pipelines. Vortex flow meters for various mediums such as gas, liquid, steam, etc. measure flow using the fluid oscillation principle. When fluid passes through a vortex flow transmitter in the pipeline, two rows of vortices proportional to the flow rate are generated alternately up and down behind the vortex generator of the triangular column, The frequency of vortex release is related to the average velocity of the fluid flowing through the vortex generator and the characteristic width of the vortex generator.

Principle Explanation

When a stable fluid flows through a straight pipe with a certain length, it impacts a nonlinear cylinder immersed in the fluid, and a vortex (i.e., Karman vortex) will be generated downstream of the fluid. When the Reynolds number (Re) of the fluid is within a certain range, the law of vortex occurrence is stable and reliable, and the frequency F of vortex occurrence is determined by the formula: F=(St * V)/d

Where V is the flow rate; D is the width of the upstream face of the cylinder; St is the Strouhal number.

Strouhal number is a dimensionless parameter. The figure below shows the relationship between the Strouhal number and the Reynolds number. Within a certain Reynolds number range, Strouhal's number is unchanged, so it can be considered that the release frequency of the Karman vortex is proportional to the fluid speed within this range of Reynolds number. Therefore, the flow velocity V can be obtained from the detected frequency F, and the volume flow can be obtained from V.

A vortex flowmeter consists of a sensor and converter, as shown in the figure. The sensor includes a vortex generator (fluid barrier), detection element, instrument body, etc; The converter includes a preamplifier, filter shaping circuit, D/A conversion circuit, output interface circuit, terminal, bracket, and protective cover. In recent years, the microprocessor, display communication, and other functional modules of intelligent flowmeter are also installed in the converter.

So the point is since the vibration has an impact on the vortex flowmeter, is there much vibration on site? So what solutions are available to solve the vibration problem?

We are sure to tell you that there are still a lot of vibrations on site. What should we pay attention to when buying a vortex flowmeter? The answer is: buy a heavier flowmeter

Our proposal is based on facts. It is very simple. Heavy objects are not easy to shake. The basis is that the heavier the object, the greater the inertia, and the better the anti-vibration performance.

The final answer to the decryption: actually, you can take a shot at the vortex flowmeter when you buy it. If there is no signal generated when you beat hard, it shows that the flowmeter has a good seismic effect. I will only tell you this tip.

So, even if a heavy vortex flowmeter is used, vibration still easy to occurs. How to solve this problem on-site? Here are two common suggestions:

1. Support both sides of the flowmeter with supports to reduce vibration.

2. Cut off small signals, and cut off the false small signals that interfere.