Development history of flow meters:
The development of flow measurement can be traced back to ancient water conservancy projects and urban water supply systems. In the era of Caesar in ancient Rome, orifice plates were used to measure the amount of drinking water consumed by residents.
Around 1000 BC, ancient Egypt used the weir method to measure the flow of the Nile River. The famous Dujiangyan Irrigation Project water conservancy project in China uses the water level at Baopingkou to observe the water volume and so on.
In the 20th century, Torricelli laid the theoretical foundation for differential pressure flow meters, which was a milestone in flow measurement.
Since then, many types of flow measurement instruments have taken shape in the 18th and 19th centuries, such as weirs, tracer methods, pitot tubes, venturi tubes, volumetric, turbine, and target flow meters.
Due to the rapid growth in demand for flow measurement in the process industry, energy metering, and urban utilities in the 20th century, the rapid development of instruments has been promoted. The rapid development of microelectronics and computer technology has greatly promoted the upgrading of instruments, and new types of flow meters have mushroomed. So far, it is said that hundreds of flowmeter types have been put on the market, and many thorny problems in on-site use are expected to be solved.
The work of developing modern flow measurement technology in China is relatively late, and the flow instruments required in the early stage are all imported from abroad.
Flow measurement is the science of studying mass change, and the law of mass reciprocity is the basic law of the development of things. Therefore, its measurement object is no longer limited to the traditional sense of pipeline liquid, and wherever it is necessary to master quantitative change, there is a problem of flow measurement. Flow, pressure, and temperature are listed as three major detection parameters. For a given fluid, the energy it has can be calculated by knowing these three parameters, which must be detected in the measurement of energy conversion. Energy conversion is the foundation of all production processes and scientific experiments, so flow, pressure, and temperature instruments are the most widely used.
The application of flow measurement technology and instruments can be broadly divided into the following areas
1、 Industrial production process
Flow meters are one of the major categories of process automation instruments and devices. They are widely used in various fields of the national economy, such as metallurgy, electricity, coal, chemical industry, petroleum, transportation, construction, light textile, food, medicine, agriculture, environmental protection, and people’s daily life. They are used to develop industrial and agricultural production, save energy, and improve product quality, An important tool for improving economic efficiency and management level occupies an important position in the national economy. In process automation instruments and devices, flow meters have two main functions: as a detection instrument for process automation control systems and as a total quantity meter for measuring material quantities.
2、 Energy metering
Energy is divided into primary energy (coal, crude oil, coalbed methane, petroleum gas, and natural gas), secondary energy (electricity, coke, artificial gas, product oil, liquefied petroleum gas, and steam), and energy carrying working fluids (compressed air, oxygen, nitrogen, hydrogen, and water). Energy metering is an important means of scientifically managing energy, achieving energy conservation and consumption reduction, and improving economic efficiency. Flow meters are an important component of energy metering instruments. Water, artificial gas, natural gas, steam, and oil, which are commonly used in energy, use an extremely large number of flow meters. They are indispensable tools for energy management and economic accounting.
3、 Environmental protection engineering
The discharge of flue gas, waste liquid, sewage, etc. seriously pollutes the atmosphere and water resources, seriously threatening the human survival environment. The country has listed sustainable development as its national policy, and environmental protection will be the biggest issue in the 21st century. To control air and water pollution, it is necessary to strengthen management, which is based on quantitative control of the amount of pollution.
China is a country with coal as its main energy source, with millions of chimneys continuously emitting smoke into the atmosphere. Flue gas emission control is an important project to eradicate pollution. Each chimney must be equipped with flue gas analysis instruments and flow meters to form a continuous emission monitoring system. The flow rate of flue gas varies greatly due to its large size and irregular shape, variable gas composition, large flow rate range, dirt, dust, corrosion, high temperature, and lack of straight pipe sections.
4、 Transportation
There are five modes of transportation: railway, highway, air, water, and pipeline. Although pipeline transportation has long existed, its application is not widespread. With the prominent environmental protection issues, the characteristics of pipeline transportation have attracted people’s attention. Pipeline transportation must be equipped with a flowmeter, which is the eye for control, distribution, and scheduling, as well as a necessary tool for safety monitoring and economic accounting.
5、 Biotechnology
The 21st century will usher in the century of life science, with the rapid development of industries characterized by biotechnology. There are many substances that need to be monitored and measured in biotechnology, such as blood, urine, and so on. The development of instruments is extremely difficult and diverse.
6、 Scientific experiments
Scientific experiments require not only a large number of flowmeters, but also an extremely complex variety. According to statistics, a large proportion of the more than 100 types of flow meters are used for scientific research purposes. They are not produced in batches and are sold on the market. Many scientific research institutions and large enterprises have set up specialized teams to develop dedicated flow meters.
7、 Marine meteorology, Rivers and Lakes
These areas are open flow channels, and it is generally necessary to detect the flow rate and then calculate the flow rate. The physical principles and fluid mechanics foundations on which flowmeters and flowmeters are based are common, but the principles, structures, and operating conditions of the meters differ greatly.
The digital sampling rotary piston flowmeter is a type of volumetric flowmeter, which can measure the consumption flow of light oil in engines and other power equipment. It has been tested and certified by the Beijing Institute of Metrology and Testing Science, with an accuracy of 1.0. As a high-precision measurement sensor, it can achieve wireless communication through docking with enterprise user data and information transmission equipment, providing hardware support for connecting to the Internet.
working principle
The rotary piston flowmeter is a volumetric flowmeter based on the tangentially sealed state that the piston and the metering chamber have always maintained. There is also a fixed eccentric measuring element piston, which, under the action of differential pressure, generates a rotational torque to the piston, causing the piston to perform eccentric rotational motion. The number of revolutions of the piston is proportional to the flow rate of the fluid. The total flow rate of the fluid can be measured by recording the number of revolutions of the piston through a counting mechanism.
The inlet and outlet of the rotary piston flowmeter are separated by partitions. When the measured fluid enters the metering chamber from the inlet, a pressure difference is formed between the inlet and outlet, forcing the piston to rotate counterclockwise, as shown in Figure a. The fluid continuously flows in, forcing the piston to rotate as shown in Figure b, forming a two-and-a-half crescent cavity. Under the action of pressure difference, the piston is forced to rotate as shown in Figure c, and V2 fluid is discharged from the outlet, causing the piston to rotate as shown in Figure d. Under the action of pressure difference, the fluid emitted by the piston every revolution is equal to the sum of V1+V2.
Post time: 31-03-23