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Turbine flowmeter Posted by : admin / Posted on : Jul 01, 2021

A flow meter that uses a turbine for measurement. It first converts the flow rate into the rotational speed of the turbine, and then converts the rotational speed into an electrical signal proportional to the flow rate. This kind of flowmeter is used to detect instantaneous flow and total integrated flow, and its output signal is frequency, which is easy to digitize. The induction coil and the permanent magnet are fixed on the housing together. When the ferromagnetic turbine blade passes the magnet, the reluctance of the magnetic circuit changes, thereby generating an induction signal. The signal is amplified and shaped by the amplifier, and sent to the counter or frequency meter to display the total accumulated flow. At the same time, the pulse frequency undergoes frequency-voltage conversion to indicate instantaneous flow. The speed of the impeller is proportional to the flow, and the number of revolutions of the impeller is proportional to the total amount of flow. The output of the turbine flowmeter is a frequency modulated signal, which not only improves the anti-interference of the detection circuit, but also simplifies the flow detection system. Its turndown ratio can reach 10:1, and the accuracy is within ±0.2%. The time constant of the turbine flowmeter with small inertia and small size can reach 0.01 second.

In Europe and the United States, the turbine flowmeter is the second statutory natural gas flowmeter after the orifice plate flowmeter. It has developed into a multi-variety, full-series, multi-specification, and mass-production scale natural gas flowmeter. The standard specifications are also very complete, but there are also shortcomings: the cleanliness of the measurement medium is relatively high, and the service life is limited. However, according to the foreign use department, 240 flowmeters that have been used for 8 to 15 years have been periodically verified, and it is found that the deviation of the meter's accuracy is still within the specified range. In addition, a high-efficiency rectifier and turbine flow sensor are used to couple a gas turbine flowmeter with an integrated structure. When the upstream baffle is an elbow or a half-open shut-off valve, only 2D straight pipe length is required. It is a very prominent feature for the narrow installation space for urban use.

Turbine flowmeter is the main type of velocity flowmeter. When the measured fluid flows through the turbine flowmeter sensor, under the action of the fluid, the impeller is rotated by force, and its speed is proportional to the average flow velocity of the pipe. At the same time, the blades are periodic Ground cutting of the magnetic field lines generated by the electromagnet changes the magnetic flux of the coil. According to the principle of electromagnetic induction, a pulsating electric potential signal, that is, an electric pulse signal, is induced in the coil. The frequency of the electric pulse signal is proportional to the flow rate of the fluid to be measured.

Among the various flow meters, turbine flow meters, positive displacement flow meters and Coriolis mass flow meters are the three types of products with the best repeatability and accuracy. Turbine flow meters have their own characteristics, such as simple structure and few processing parts. , Light weight, convenient maintenance, large flow capacity (large flow through the same caliber) and adaptable to high parameters (high temperature, high pressure and low temperature), etc. So far, this type of flowmeter products can reach technical parameters: caliber 4-750mm, pressure up to 250MPa, temperature -240-700℃, technical parameters like this are difficult to reach the other two types of flowmeters.

Turbine flowmeters are widely used in the following measurement objects: petroleum, organic liquids, inorganic liquids, liquefied gas, natural gas, coal gas, and cryogenic fluids. It is widely used in the transfer and gathering stations of foreign liquefied petroleum gas, refined oil and light crude oil, and the first and last stations of large crude oil pipelines for trade settlement. In Europe and the United States, turbine flow meters are second only to orifice plate flow meters for natural gas measurement. In the Netherlands alone, more than 2,600 gas turbine flow meters of various sizes and pressures ranging from 0.8 MPa to 6.5 MPa are used in natural gas pipelines. They Has become an excellent natural gas flow meter. Although the excellent metering characteristics of turbine flowmeters are favored by people, it gives people the impression that they are made of movable parts and have a short service life. They can't help but hesitate when choosing them. After people's unremitting efforts, it should be said that the situation has changed a lot. Turbine flowmeter is the most versatile flowmeter, and its products have developed into a multi-variety, full-series, and multi-specification mass production scale.

It should be pointed out that, in addition to the large number of applications in the aforementioned industrial sectors, turbine flowmeters are also widely used in some special sectors, such as scientific research experiments, national defense technology, and measurement departments. The use of these fields just avoids its weaknesses (not suitable for long-term continuous use) , Give full play to its characteristics (high precision, good repeatability, can be used in high pressure, high temperature, low temperature and micro flow conditions). In these fields, most of them carry out special structural design according to the special requirements of the tested object, they are special instruments and do not carry out mass production.