according to the flow meter structure principle classification
6. Impulse Flowmeter
The flowmeter, which uses impulse theorem to measure flow, is called Impulse flowmeter, which is used to measure the flow of granular solid medium, and to measure the flow of slurry, crystalline liquid and abrasive material. Flow measurement range from several kilograms per hour to nearly tons. A typical instrument is a horizontal force-type impulse flowmeter, its measurement principle is that when the measured medium from a certain height of H-free fall to the tilt angle of the test board to produce a momentum, the momentum of the horizontal force of the horse mass flow proportional, so the measurement of this level of force can reflect the mass flow size. According to the detection mode of signal (ix), this type of flowmeter is divided into displacement detection type and direct force-measuring type.
7. Electromagnetic flowmeter
Electromagnetic flowmeter is the application of conductive body in the magnetic field to generate induction electromotive force, and the induction electromotive force and flow size is proportional, through the measurement of electromotive force to reflect the principle of pipeline flow made. Its measurement accuracy and sensitivity are high. Industrial more to measure the flow of water, pulp and other media. The maximum diameter can be measured up to 2m, and the pressure loss is very small. But the low conductivity of the medium, such as gas, steam and so can not be applied.
The high cost of the electromagnetic flowmeter, and the signal susceptible to external magnetic field interference, affect the industrial pipe flow measurement in a wide range of applications. To this end, the product continues to improve and update, to the development of micro-computer.
8. Ultrasonic flowmeter
The ultrasonic flowmeter is designed based on the geometry and principle of the average velocity of the measured medium and the velocity of the sound wave in the flowing medium. It is also measured by velocity to reflect the flow size. Although the ultrasonic flowmeter appeared in the 70 's, but because it can be made into non-contact type, and ultrasonic water level meter linkage of open flow measurement, the fluid does not produce disturbances and resistance, so very popular, is a very promising flowmeter.
The Doppler effect of ultrasonic Doppler flowmeter has been widely concerned in recent years, and is considered as an ideal instrument for non-contact measurement of dual-phase flow.
9. Fluid-oscillating flowmeter
Fluid oscillating flowmeter is designed by the principle that the flow of fluid in a specific flow path will generate oscillation and the frequency of oscillation is proportional to the velocity. When the flow section is certain, the flow rate is proportional to the flux of the guide volume. Therefore, the measurement of oscillation frequency can be measured flow. The flowmeter was developed and developed in the 70 's. Because it has the advantages of rotational parts and pulse digital output, it has a promising future. At present, typical products are vortex flowmeter, vortex flowmeter.
10. Mass flowmeter
Because the volume of the fluid is affected by the temperature and pressure, the volume flow is used to indicate the parameters of the medium. In the case of changing media parameters, it is often difficult to achieve this requirement, which results in distortion of the display value of the instrument. Therefore, mass flowmeter has been widely used and valued. The mass flowmeter is divided into two types of direct and indirect type. Direct mass flowmeter using the principle of direct related to mass flow measurement, currently commonly used in the volume of heat, angular momentum, vibratory gyroscope, Magnus effect and Coriolis type of mass flowmeter. The indirect mass flowmeter is used to obtain the mass flow by multiplying the density meter and the volume flow directly.
In modern industrial production, the temperature of flowing working medium, pressure and other operating parameters continue to improve, in the case of high temperature and pressure, due to material and structural reasons, the application of direct mass flowmeter encountered difficulties, while the indirect mass flowmeter due to the density of humidity and pressure on the scope of application limits, often also bad practical application. Therefore, widely used in industrial production is the temperature pressure compensation type mass flowmeter. It can be regarded as an indirect mass flowmeter, not a densitometer, but the use of temperature, pressure and density of the relationship between the temperature, pressure signal through the function of the operation of the density of the signal, and volume flow to obtain mass flow. At present, although the temperature and pressure compensated mass flowmeter have been applied, the correct compensation will be difficult or impossible when the parameters of the measured medium vary widely or rapidly, so it is still a problem to further study the mass flowmeter and density meter applicable in actual production.
The flowmeter of the above commonly used structure principle is much more than the flowmeter of various structures, such as the Weir flowmeter which is suitable for open channel measurement trough flow meter; The flow meter is suitable for the large caliber flow, the laminar flow flowmeter is measured, the correlation flowmeter is suitable for two-phase flow measurement, and the laser method, the NMR method flowmeter and various tracer method, the dilution method and so on. With the development of science and technology and the need of practical application, new flowmeter will continue to emerge the type of flowmeter will be more complete.