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Introduction to the vortex flowmeter Introduction to the principle

Introduction to vortex flowmeter: Under certain active conditions, a part of fluid kinetic energy is converted into fluid oscillation, and its oscillation frequency is related to the flow rate (flow rate). The flowmeter working according to this principle is called fluid. Oscillating flow meter. There are currently three types of fluid oscillating flowmeters: vortex flowmeters, precession (vortex precession) flowmeters, and jet flowmeters. The fluid oscillating flowmeter has the following characteristics: 1) The output is a pulse frequency whose frequency is proportional to the actual volume flow of the fluid to be measured. It is not affected by fluid composition, density, pressure, temperature; 2) The measurement scale is wide, The general scale can reach more than 10:1; 3) the accuracy is the upper middle level; 4) the non-movable parts have high reliability; 5) the structure is simple and solid, the device is convenient, and the protection fee is low; 6) the use scale is wide, Suitable for liquids, gases and vapours. This article only introduces vortex flow juice (hereinafter referred to as VSF or flow meter). VSF is to place one (or more) non-streamlined bluff body in the fluid. The fluid is replaced on both sides of the bluff body to release two series of vortexes. In a certain flow scale, the vortex is proportional to the frequency. The uniform flow rate inside can be calculated by measuring the vortex frequency using various types of detecting elements. As early as 1878, Strouhal announced an article on the relationship between fluid oscillation frequency and flow velocity. The Strauhal number is a similar principle that indicates the relationship between vortex frequency and bluff body characteristic scale and flow velocity. People's previous research on vortex street is mainly the purpose of disaster prevention. For example, the natural frequency of the boiler and heat exchanger steel tube and the fluid vortex frequency will produce resonance and damage the equipment. The vortex fluid oscillation phenomenon was used for measurement and research in the 1950s, such as anemometers and ship speedometers. In the late 1960s, the development and closure of the pipeline flowmeter, the vortex flowmeter, was born, and the hot wire detection method and the thermal detection method VSF were born. In the 70s and 80s, the vortex flowmeter developed anomalous agility, and announced many types of vortex flowmeters for bluffing and detection methods, and put them into the market in large quantities. In this way, they arrived from the laboratory prototype to the batch in just a few years. The flow meter of the production process is also unique. The production of VSF in China has also been carried out at a rapid pace. There are dozens of factories in the country, and this kind of production boom has never been seen abroad. It should be noted that VSF is still a developing flowmeter, regardless of its theoretical basis or practical experience. The most basic flow equations to date often refer to the Karman vortex theory, and this theory and some quantitative relationships are derived from Kaman's gas wind tunnel (uniform flow field), which has a three-dimensional uneven flow in the closed pipeline. The law of the vortex separation is different. As for practical experience, it is necessary to accumulate after a long period of use. The general flowmeter factory calibration is carried out under the conditions of the laboratory, and it is unavoidable to violate these conditions at the site. It is still unclear how much additional error will be caused by the violation of working conditions. All of these indicate that the flow of the agile development needs to be kept up to the bottom of the discussion, otherwise it will often present some unexpected problems in the usefulness, which is why users have some doubts about the VSF, it needs to be explored. VSF has become one of the universal flow meters, regardless of whether it has been announced at home and abroad. The full range and standard complete products are also very important for standardization work. Some problems with the flowmeter are normal phenomena in development.

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