Vortex flowmeter: principle, characteristics and applications

　　In the vast system of industrial production, accurate measurement of fluid flow plays a crucial role in ensuring production efficiency, controlling costs, and ensuring product quality. As a widely used flow measurement instrument, vortex flowmeter has emerged in many fields due to its unique working principle and many excellent characteristics. ​

　　The core principle of vortex flowmeter is based on the Karman vortex phenomenon. When the fluid flows through the non streamlined vortex generator set in the pipeline, the fluid will alternately separate and release two columns of regular vortices on both sides of the vortex generator, which is the Karman vortex street.

　　The release frequency of vortices is closely related to the average velocity of the fluid flowing through the vortex generator and the characteristic width of the vortex generator, which can be expressed by the formula f=St × dv. Among them, f is the release frequency of the vortex (unit: Hz), v is the average velocity of the fluid flowing through the vortex generator (unit: m/s), d is the characteristic width of the vortex generator (unit: m), and St is the Strouhal number (dimensionless, numerical range: 0.14-0.27).

　　Within a certain Reynolds number range, the St value is relatively stable. By accurately measuring the vortex frequency f, the average velocity v of the fluid can be calculated. Combined with the cross-sectional area A of the fluid flowing through the vortex generator, the flow rate q can be accurately calculated using the formula q=v × A. ​

　　Common vortex generators have various shapes, such as cylinders, triangles, rectangles, etc. The cylindrical pressure loss is small, but the vortex intensity is relatively low; The rectangular vortex has a high intensity, but the pressure loss is also significant; Triangles achieve a good balance between pressure loss and vortex intensity, making them the most widely used in practical applications. ​

　　High precision measurement: The vortex flowmeter is almost unaffected by parameters such as fluid density, pressure, temperature, viscosity, etc. when measuring the volumetric flow rate under working conditions, and can provide extremely accurate measurement results. The measurement accuracy can reach 1.0 level or even higher, which makes it perform well in industrial scenarios that require strict flow accuracy. ​

　　Wide range: With a wide range ratio of 1:10 or even higher, it can adapt to measurement needs of different flow rates, and can stably and accurately measure both low and high flow conditions. ​

　　Simple and reliable structure: There are no movable mechanical parts inside, greatly reducing the risk of failure caused by mechanical wear, and the reliability is extremely high. This not only reduces maintenance workload, but also extends the service life of instruments and reduces overall maintenance costs. ​

　　Small pressure loss: The pressure loss generated during fluid flow is relatively small, which is of great significance for energy conservation and consumption reduction, especially in long-distance pipeline transportation or pressure sensitive process flows, which can effectively reduce energy consumption. ​

　　Diverse output signals: It can output analog standard signals (such as 4-20mA current signals), as well as provide digital pulse signals, which are convenient for use with various automation control systems and digital devices such as computers, achieving remote transmission, processing, and monitoring of data. ​

　　Strong environmental adaptability: The piezoelectric stress sensor used has stable performance and can work in a wide temperature range. It can generally adapt to working temperature environments ranging from -20 ℃ to+250 ℃, and some special models can even adapt to more extreme temperature conditions, meeting the measurement needs of different industrial environments. ​

　　Petrochemical industry: In the process of petroleum refining and chemical product production, it is necessary to accurately measure the flow rates of various liquids, gases, and vapors to control the reaction process, optimize production processes, and ensure product quality. For example, in crude oil pipelines, vortex flowmeters can monitor the flow rate of crude oil in real time, providing accurate data for production scheduling; Monitoring the flow rate of raw materials and products in chemical synthesis reactions helps ensure the stability and consistency of the reaction. ​

　　Power industry: used for measuring steam flow in power plants, which is crucial for combustion control of boilers and optimization of steam turbine operating efficiency. Accurate steam flow data can help power plants allocate energy reasonably, improve power generation efficiency, and reduce energy consumption. Meanwhile, in the cooling circulating water system, vortex flowmeter can also be used to monitor water flow and ensure the normal cooling of equipment. ​

　　Urban public utilities: Vortex flow meters play a crucial role in urban water and gas supply systems. By accurately measuring the flow of tap water and gas, it can not only meet the daily needs of residents and businesses, but also provide accurate measurement data for public utilities for billing, pipeline maintenance, and resource allocation. ​

　　Metallurgical industry: Flow measurement of gases such as oxygen, nitrogen, coal gas, and cooling water is crucial in the steel production process. Vortex flowmeter can monitor the flow rate of these fluids in real time, ensuring the stable operation of metallurgical processes, improving production efficiency, and reducing production costs. ​

　　Requirements for front and rear straight pipe sections: The installation of vortex flowmeter has strict requirements for the front and rear straight pipe sections. In common cases, the length of the upstream straight pipe section needs to meet 15D-50D (D is the pipeline diameter), and the length of the downstream straight pipe section needs to meet 5D. The specific value depends on the pipeline situation. For example, if there are concentric contraction pipes and fully open gate valves upstream, the upstream straight pipe section requires 15D; If there are two 90 ℃ right angled elbows on the same plane, the upstream straight pipe section needs to be 25D, etc. Appropriate front and rear straight pipe sections can ensure that the fluid flows in a stable flow state through the flowmeter, thereby ensuring measurement accuracy. ​

　　Installation location selection: The sensor can be installed on horizontal, vertical, or inclined pipelines, but it should be noted that when measuring liquid flow, if there is a small amount of gas in the liquid, the sensor should be installed at a lower part of the pipeline to avoid interference from gas on the measurement; When measuring gas flow, if the gas contains a small amount of liquid, the sensor should be installed at a higher position in the pipeline. In addition, sensors should be avoided from being installed in places with strong mechanical vibrations, strong electromagnetic field interference, small space, and inconvenient maintenance. ​

　　Pipeline connection and concentricity: During installation, the welding of dedicated flanges and straight pipe sections should not be carried out with sensors to prevent damage to the sensors. At the same time, it is necessary to ensure that the flow direction mark of the sensor is consistent with the flow direction of the fluid in the pipeline. The piping upstream and downstream of the sensor installation point should be concentric with the sensor, with a coaxial deviation of not less than 0.5DN, to ensure that the fluid passes smoothly through the flowmeter. ​

　　Daily inspection: Regularly inspect the appearance of the flowmeter to check for damage, cracks, rust, and other conditions, ensuring that there are no leaks at all connections. At the same time, check the drain valve and open it in a timely manner to remove steam condensate and prevent water accumulation from affecting measurement accuracy. ​

　　Measurement calibration: After prolonged use, the vortex flowmeter may experience abnormal readings or measurement errors. In this case, the device can be reset by resetting it to zero to ensure the accuracy of the next reading. In addition, it is necessary to regularly inspect the wear of process pipelines and components. If the wear of components and pipelines affects the accuracy of coefficients, timely correction is required. ​

　　Cleaning and maintenance: Due to the possibility of impurities in the fluid, after long-term use, the vortex generated by the vortex flowmeter will attach to the package, which will have a significant impact on the measurement accuracy. Therefore, the vortex generator should be cleaned regularly to maintain its surface cleanliness and ensure measurement accuracy. ​

　　Regular calibration: Conduct comprehensive calibration of the vortex flowmeter according to the prescribed calibration cycle (usually two years) to ensure that its various performance indicators meet the requirements. By using professional calibration equipment and methods, the measurement accuracy, linearity, and other parameters of the flowmeter are tested and adjusted to ensure its reliability and accuracy during long-term use. ​

　　Vortex flowmeter has become an indispensable tool in the field of industrial fluid flow measurement due to its unique working principle, excellent performance characteristics, and wide application range. With the continuous advancement of technology and the continuous improvement of industrial automation level, the technology of vortex flowmeter will also continue to innovate and improve, providing more reliable flow monitoring guarantee for the efficient and stable operation of industrial production.