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Temperature and pressure compensated vortex flowmeter

Vortex flowmeter is a kind of flow measurement equipment, which is most suitable for flow measurement with problems when moving parts are introduced.Compared with other types of flowmeters, the sensitivity to changes in process conditions is lower, and the wear of no moving parts is relatively low.Vortex flowmeters work under the principle of vortex shedding, and oscillating eddies occur when a fluid (such as water) flows through a suspension (rather than a streamline).How often the vortex falls off depends on the size and shape of the object.It is ideal for applications where low maintenance costs are important.

The meter can measure directly when we only need the volume flow figure.For example, if we have water flow in an application that does not have the conductivity required for an electromagnetic flowmeter, we can use an eddy current flowmeter.For mass flow, the vortex flowmeter must have a measuring component and a temperature sensor.In some applications, you also need a pressure transmitter.Some vendors build all of this into their eddy-meter, while others may include only a few, with the rest as add-ons.If a person needs mass flow, then you should check your vortex meter for what can do this.

The digital signal processing method is adopted to process the output signal of the vortex flowmeter, extract the flow frequency from the noise output of the vortex flow sensor, and realize the measurement of small flow.However, in applications, the power of the noise is sometimes greater than the power of the flow.These strong disturbances are mainly caused by pipe vibrations.In this case, previous digital signal processing methods will not be available.Therefore, this paper studies the anti-strong interference solution of the twin-sensor vortex flowmeter.In this solution, two piezoelectric sensors are mounted on the vortex probe.One, called a flow sensor, is used to measure both flow and vibration noise;The other, called a vibration sensor, is used to detect vibration noise and also to detect weak flow signals.An anti-interference signal processing method combining frequency domain substation algorithm and frequency variance calculation algorithm is proposed to identify the flow frequency.When the amplitude-spectrum peaks of the flow sensor are different from those of the vibration sensor, the frequency-domain subtraction algorithm is adopted.When the amplitude spectrum peak number of the flow sensor is the same as that of the vibration sensor, the frequency difference calculation algorithm is adopted.The whole algorithm is realized by MCU in real time to meet the requirements of process instrument.Experimental results show that this method can obtain the flow frequency correctly even if the power of pipeline vibration noise is greater than that of vortex street flow signal.

Communication function: the intelligent vortex flowmeter of fieldbus has the function of remote communication, which can communicate with the upper machine and other instruments.These functions perform the requirements of fieldbus communication protocols, such as HART protocols, FF protocols, etc.Conventional communication, such as RS485 communication, can also be used.

Liquid vibration is one of the unique physical phenomena of objects.Under certain conditions, according to the corresponding relationship between the frequency of fluid vibration and the velocity of flow, the flow meter which adopts the method of measuring the frequency of fluid vibration to measure the flow is called fluid vibration flowmeter.Up to now, the fluid vibration flowmeter mainly includes: vortex separation flowmeter, also known as vortex flowmeter;Vortex precession flowmeter, also known as the vortex precession flowmeter;Jet flow meter, etc.Vortex flowmeter is a universal flowmeter with rapid development and wide application.The vortex flowmeter is researched and produced based on Karman's vortex street principle. It is mainly used for flow measurement of industrial pipeline media, such as gas, liquid, vapor and other media.It is characterized by small pressure loss, large measuring range and high accuracy, and is almost unaffected by fluid density, pressure, temperature, viscosity and other parameters when measuring volume flow in working conditions.No moving mechanical parts, so high reliability, small maintenance.Instrument parameters can be stable for a long time.The vortex flowmeter adopts piezoelectric stress sensor with high reliability and can operate in the operating temperature range of -20℃ ~ +250℃.There are analog standard signals, but also digital pulse signal output, easy to use with computer and other digital systems, is a more advanced, ideal measurement instrument.

Requirements for straight section: at least 15 times pipe diameter in front of flowmeter and 5 times pipe diameter behind flowmeter.If there is elbow in front of the flowmeter, indentation, expansion and other interference sources, it is necessary to ensure that the front of the flowmeter is 30-40 times the pipe diameter, and the back of the flowmeter is 6 times the pipe diameter.The flow meter shall be installed upstream of the regulator, pressure or temperature sensor.


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