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Analysis of the Working Principle and Characteristics of Different Types of Flowmeters

Flowmeters are the eyes of industrial production and are closely related to national economy, national defense construction, and scientific research. They occupy an important position and function in the national economy and can be used to measure the flow of gas, liquid, steam and other media. In order to better demonstrate the flowmeter measurement principle, let us introduce the working principle and characteristics of different flowmeters.

Ⅰ. Orifice flowmeter

1. Working principle

When the fluid fills the pipeline and flows through the throttling device in the pipeline, the flow beam will shrink locally, so that the flow velocity increases and the static pressure is low, so a pressure drop occurs before and after the throttling piece, that is, the pressure difference, the more the flow rate of the medium flows. The larger the pressure difference, the greater the pressure difference generated before and after the throttle, so the orifice flowmeter can measure the fluid flow by measuring the pressure difference. This measurement method is based on the law of conservation of energy and the law of continuity of flow.

2. Working characteristics

① The throttling device has a simple and firm structure, stable and reliable performance, long service life and low price;

② Wide range of applications, all single-phase flows can be measured, and some mixed-phase flows can also be applied;

③The standard throttling device can be put into use without actual flow calibration;

④The installation of the integrated orifice plate is simpler, no pressure pipe is needed, and it can be directly connected to the differential pressure transmitter and the pressure transmitter.

Ⅱ. Electromagnetic flowmeter

1. Working principle

Based on Faraday's law of electromagnetic induction. In the electromagnetic flowmeter, the conductive medium in the measuring tube is equivalent to the conductive metal rod in the Faraday test, and the two electromagnetic coils at the upper and lower ends generate a constant magnetic constant. When a conductive medium flows, an induced voltage will be generated. Two electrodes inside the pipe measure the induced voltage generated. The measuring tube is electromagnetically isolated from the fluid and the measuring electrode by means of a non-conductive lining (rubber, Teflon, etc.).

2. Working characteristics

①Have a two-way measurement system;

②The straight pipe section required by the sensor is short, and the length is 5 times the pipe diameter;

③ Small pressure loss;

④The measurement is not affected by changes in fluid density, viscosity, temperature, pressure and conductivity;

⑤ Mainly used in sewage treatment.

Ⅲ. Turbine flowmeter

1. Working principle

Within a certain flow range, the rotational speed of the turbine is proportional to the flow rate of the fluid. The fluid flow drives the turbine to rotate, and the rotational speed of the turbine is converted into electrical pulses, and the data is displayed by the secondary table, which reflects the fluid flow rate.

2. Working characteristics

①Strong resistance to impurities;

② Strong anti-electromagnetic interference and anti-seismic ability;

③ Its structure and principle are simple and easy to maintain;

④Almost no pressure loss, saving power consumption.

Ⅳ. Volumetric flowmeter

1. Working principle

When the fluid passes through the flowmeter, a certain pressure difference will be created between the inlet and outlet of the flowmeter. The rotating part of the flowmeter (referred to as the rotor) rotates under the action of this pressure difference and discharges the fluid from the inlet to the outlet. During this process, the fluid fills the "metering space" of the flowmeter again and again, and is then continuously sent to the outlet. Under the conditions of a given flowmeter, the volume of the metering space is determined, and as long as the number of rotations of the rotor is measured, the cumulative value of the fluid volume passing through the flowmeter can be obtained.

2. Working characteristics

①High measurement accuracy;

②The installation pipeline conditions have no influence on the measurement accuracy;

③ It can be used for the measurement of high viscosity liquids;

④ wide range;

⑤ The direct-reading instrument can directly obtain the accumulation without external energy, the total amount is clear and easy to operate;

⑥ The structure is complex and the volume is huge;

⑦Not suitable for high and low temperature occasions;

⑧Most instruments are only suitable for clean single-phase fluids;

⑨ Noise and vibration are large.