The significance of flow measurement

Measurement is the eye of industrial production. Flow measurement is one of the components of measurement science and technology. It is closely related to the national economy, national defense construction, and scientific research. Doing this work well plays an important role in ensuring product quality, improving production efficiency, and promoting the development of science and technology. Especially in today's era of energy crisis and increasing automation of industrial production, the status and role of flow meters in the national economy are more obvious.

Flow measurement has a wide range of applications .

Flow measurement is widely used in industrial and agricultural production, national defense construction, scientific research, foreign trade, and all areas of people's lives. In the production of the petroleum industry, from oil extraction, transportation, refining and processing to trade sales, flow measurement runs through the whole process, and any link cannot be separated from flow measurement. Otherwise, the normal production and trade exchanges of the petroleum industry cannot be guaranteed. In the chemical industry, inaccurate flow measurement will cause imbalance in the distribution ratio of chemical components, and product quality cannot be guaranteed. In serious cases, production safety accidents will occur. In the production of the power industry, the measurement and regulation of the flow of liquids, gases, steam and other media occupy an important position. The accuracy of flow measurement is not only of great economic significance to ensure that the power plant operates under the optimal parameters, but also with the development of high-temperature, high-pressure and large-capacity units, flow measurement has become an important link to ensure the safe operation of power plants. For example, the interruption or reduction of the instantaneous feed water flow of large-capacity boilers may cause serious dry pot or pipe burst accidents. This requires that the flow measurement device should not only accurately measure, but also send out alarm signals in a timely manner. In the production of the steel industry, the flow measurement of circulating water and oxygen (or air) in the steelmaking process is one of the important parameters to ensure product quality. In light industry, food, textile and other industries, flow measurement is also indispensable. In

agriculture, such as farmland water conservancy, meteorological wind speed, and even some agricultural machinery, such as motorized sprayers and water pumps, characteristic testing, also requires flow measurement.

In national defense construction, with the development of space technology, flow measurement has been put forward quite high requirements. For example, the nuclear power control of spacecraft and nuclear submarines cannot be separated from flow meters; a large amount of liquefied fuel is consumed in a rocket engine test. If the flow rate is inaccurate, not only will the economic loss be huge, but the range will also deviate by thousands of kilometers; flow meters are also indispensable for chemical defense equipment; some military projects are even equipped with thousands of flow meters.

In scientific research and foreign trade, flow measurement also occupies an important position and role. Tap water, gas, natural gas, oil, etc., which are closely related to people's daily life, are measured by flow meters in large quantities.

Flow meters are important parameters in industrial production processes and scientific experiments

. Flow, like temperature, pressure, and level, is an important parameter in general thermal and chemical production processes. People rely on these parameters to monitor and control the production process and realize the automation of the production process. This will be of great significance to improving product quality and output, ensuring production safety, improving operating processes, improving production conditions and scientific experiments. At the same time, flow measurement is an important basis for enterprise economic accounting. Accurate and reliable flow measurement is one of the important means to ensure high efficiency of enterprise production and ensure the best economic benefits.

Flow measurement is an important part of energy measurement

. Energy is an important material basis for the development of the people's economy. At present, energy issues have become a prominent issue in China's national economy. Energy conservation has been identified as an important policy by the central government. We must do a good job in energy conservation. First of all, we must manage energy scientifically. Energy measurement and testing is an important technical basis for scientific management of energy. If this work is not done well, the effect of energy conservation will be difficult to determine. Water, oil, gas and other fluid media in production all belong to the category of flow measurement. Doing this work well is of great significance to energy conservation. China is not only a country with a large amount of energy consumption, but also has a low energy utilization rate, which is about 20% lower than that of developed countries. Therefore, China has great potential for energy conservation. If the energy utilization rate is increased by 1%, its economic benefits will be very considerable. In energy conservation work, metering instruments are the basis, and flow measurement will play an extremely important role.

The content of flow measurement

is that flow is a dynamic quantity, and flow measurement is a complex technology. From the perspective of the measured fluid, there are three types of fluids with different physical properties, including gas, liquid and mixed fluid; from the perspective of the conditions for measuring fluid flow, there are also many kinds, such as the temperature during measurement can be from high temperature to extremely low temperature, the pressure during measurement can be from high pressure to low pressure; the size of the measured flow can be from small flow to large flow; the flow state of the measured fluid can be laminar flow, turbulent flow, etc. In addition, for liquids, there are also situations such as different viscosity. Therefore, in order to accurately measure the flow, it is necessary to study the flow measurement methods of different fluids under different conditions and provide corresponding measuring instruments. This is one of the main tasks of flow measurement. Due to the complex characteristics of the measured fluid and the different measurement conditions, various different measurement methods and measuring instruments have been produced.

Obviously, if there is no unified method for calibrating the accuracy of flow measurement instruments, it is impossible to ensure the process requirements of large-scale production and to ensure equal exchange of trade. In addition, there must be a set of flow unit reproduction methods and calibration systems for standard methods for the transmission of small flow meters. Another main content of flow metrology is to study the discovery method and calibration system of flow units, and establish basic and standard devices for flow measurement to ensure the accuracy of value transmission and flow measurement.

Before the flowmeter leaves the factory or is used, its metering performance must be tested or verified to ensure product quality and accuracy of use. To this end, it is necessary to establish a standard device that reproduces the unit value of flow. The so-called flow standard device refers to a measuring device that can provide a flow value with certain accuracy. As for the structure, principle, technical requirements and verification methods of various flow standard devices, this site will provide detailed information for explanation. A

brief history and prospect of flow measurement

Since ancient times, flow measurement has been a symbol of human civilization. The Egyptians used the Nile flowmeter to predict the good or bad harvest. The ancient Romans built canals to divert water and used orifice plates to measure flow. However, due to economic production, until the 1950s, the main flowmeters used in industry were only orifice plates, pitot tubes, and float flowmeters. The range of the measured medium is also narrow, and the measurement accuracy only meets the low-level production needs. After the Second World War, with the rapid development of international economy and science and technology, flow measurement has received increasing attention, and flow meters have developed rapidly. In order to meet the flow measurement problems under different fluid characteristics and flow states, dozens of new flow meters have been developed and put into use in the past 30 years, including velocity flow meters, volume flow meters, momentum flow meters, electromagnetic flow meters, ultrasonic flow meters, etc.

At present, there are more than 100 flow meters in use abroad, and nearly 20 types have been finalized and put into production in China. With the development of automation and pipeline in industrial production, flow meters account for an increasingly large proportion in the entire instrument production. According to domestic and foreign data, the flow meters used in different industrial sectors account for 15-30% of the total number of instruments. With the rapid development of flow meters, flow standard devices have also developed rapidly, and a flow value transmission network has been formed. At present, high-precision flow standard devices for water, oil, gas, and steam have been established in national, provincial and municipal metrology institutions to ensure the
accuracy and consistency of their flow value transmission.

Despite this, due to the complexity of flow measurement technology and the rapid development of science and technology, newer and higher requirements have been put forward for flow measurement. The current situation of flow measurement is far from meeting the needs of production, and there are still a large number of flow measurement technology problems to be further studied and solved. The main problems are as follows:

· The variety, specification, accuracy and reliability of flow meters cannot meet the production requirements. Especially for corrosive fluids, dirty fluids, high viscosity fluids, multiphase fluids, large flows, small flows, etc., effective measurement methods need to be developed.

· The flow standard device cannot meet the flow meter calibration requirements, especially the standard device for on-site real liquid calibration of flow meters, which is an urgent problem to be solved in China's current situation.

· The level of flow measurement technology needs to be further improved.

· The large gap in the configuration of flow meters directly affects industrial cost accounting and economic management.

The existence of the above problems directly affects the development of flow measurement, which has attracted the attention of various countries and is exploring its solution.

The current development trend of flow measurement can be summarized as follows.

Adopt new technologies and develop new flow meters. With the development of science and technology, new technologies such as ultrasonic, laser, electromagnetic, nuclear technology and microcomputers have been introduced into the field of flow measurement, which has greatly developed indirect technology without contact and moving parts, and flow sensors tend to be electronic and digital, opening up new areas for flow measurement. New flow meters require concise non-contact flow digital models; wide range ratio, linearization, and digitization; high linearity, low price, and easy maintenance.

Develop special flow measurement research, increase flow, high viscosity fluid, extremely low temperature flow, multiphase flow, high pressure and low pressure gas flow measurement, etc.

Research on standard devices for online calibration and verification of flow meters. At present, the verification of flow meters mostly adopts the offline verification method.

Although the flow meter verified by this method has been corrected for error, the verification conditions are very different from the flow meter use conditions, resulting in additional use errors and reducing the measurement accuracy. The online real liquid calibration method is the fundamental way to solve this problem. The main problem of online real liquid calibration method is the reasonable design of standard device. At present, mobile standard device and standard flow meter are the standard devices that people pay more attention to. But there is still a certain distance from practical use.

With the rapid development of science and technology and the hard work of the vast number of flow measurement scientists, it is believed that in the near future, flow measurement technology will be raised to a new level. (end)