The working principle of a turbine flowmeter is mainly based on the principles of fluid dynamics, indirectly measuring the flow rate of the fluid by measuring the rotational speed generated by the impact of the fluid on the turbine blades. Specifically, its working principle can be summarized as follows:

　　1. The relationship between turbine rotation and fluid velocity

　　When the measured fluid passes through the turbine flowmeter, the fluid impacts the turbine blades, generating a driving torque on the turbine and causing it to rotate.

　　Within a certain flow range, the rotational angular velocity of the turbine is directly proportional to the fluid flow velocity. This means that the faster the fluid flow rate, the faster the rotation speed of the turbine.

　　2. Speed detection and signal conversion

　　The speed of the turbine is detected by a sensing coil installed outside the casing. When the turbine blades cut the magnetic field lines generated by the permanent magnet inside the shell, it will cause changes in the magnetic flux in the sensing coil.

　　The sensing coil sends the detected magnetic flux periodic change signal to the preamplifier, amplifies and shapes the signal, and generates a pulse signal proportional to the flow rate.

　　3. Traffic calculation and display

　　The pulse signal is sent to the unit conversion and flow accumulation circuit, and after calculation, the accumulated flow value is obtained and displayed.

　　At the same time, the pulse signal is also sent to the frequency current conversion circuit, which converts it into an analog current quantity and indicates the instantaneous flow rate value.

　　4. Structural composition of turbine flowmeter

　　The turbine flowmeter is mainly composed of a housing, a guide body (diffuser), an impeller, a shaft, bearings, and a signal detector.

　　A turbine flowmeter is placed at the center of the pipeline, supported at both ends by bearings. When the fluid enters the flowmeter, it first passes through the special structure of the leading fluid inside the turbine flowmeter and accelerates, and then impacts the turbine blades to rotate.

　　5. Flow characteristics and measurement range

　　The flow characteristic curve of the turbine flowmeter shows that when the flowmeter increases from zero, the impeller needs to overcome the static friction torque generated between the shaft and the bearing before starting to rotate.

　　When the flow rate exceeds a certain minimum value, the turbine begins to rotate steadily, and the speed is linearly related to the flow rate. However, due to constraints such as bearing life, impeller strength, and pressure loss, the turbine cannot rotate too fast, so there are upper and lower limits for the measurement of turbine flow meters.

　　6. Application Fields and Characteristics

　　Turbine flowmeters are widely used in fields such as petroleum, chemical, power, gas pipelines, and urban gas. They are highly favored due to their high measurement accuracy, good repeatability and stability, wide range, rapid response to flow changes, and strong anti-interference ability.

　　Turbine flow meters are not only suitable for measuring liquid flow rates, but also for measuring gas flow rates, but it should be noted that gas turbine flow meters are easily affected by density.

　　In summary, the turbine flowmeter indirectly measures the flow rate of the fluid by measuring the rotational speed generated by the impact of the fluid on the turbine blades. Its working principle is based on the principles of fluid dynamics and combines techniques such as electromagnetic induction, signal amplification, and conversion.