How to interpret the principle of the volumetric flow meter

The volumetric flow meter uses an accurate standard container to continuously measure the measured fluid, so there are few factors affecting the measurement accuracy;

It will not be affected by fluid viscosity, the influence of density, flow state and Reynolds number, the measurement accuracy is also high.

Especially in recent years, with the great improvement of material selection, structural design, processing technology, etc., the performance is also constantly improving.

Gear flow meter accuracy can reach ±0.3%; screw flow meter accuracy can reach ±0.1%; the precision of the squeegee flowmeter can even reach ±0.05%, and its repeatability is also very good.

Principle of volumetric flowmeter

1. Structure and classification of volumetric flowmeter

Volumetric Flowmeter is also calledvolumetric flow meter.

It is mainly composed of a metering body and a metering part.The metering body is composed of a casing and a moving body (rotameter rotor).

The central component is the moving body, which is the moving part of the measurement process.

Each measurement cavity formed by the mobile body and the shell is a standard volume unit, which is used to measure the volume of the measured fluid.

The measurement part is in fact a rotation or counting speed sensor, and the pinion of one of the threaded rods of the screw flow meter is embedded in a magnetic material;

When the screw rotates, the sensor can identify the rotating speed of the screw through the magnetic effect and convert it into a standard pulse signal or a current signal.

In this way, the flow can be directly displayed by the secondary instrument or collected and analyzed by the computer.

It isThere are many types of volumetric flowmeters, which can be classified according to different principles.

Generally acAccording to the structure of the measuring element, it is divided into rotor type, scraper type, rotary piston type, reciprocating piston type and diaphragm type, etc. ;

Among them, the rotor type is the most commonly used, and the sales of rotor flowmeters account for about 90% of the total sales of volumetric flowmeters.

Common gear-type, screw-type, waist-wheel, and egg-wheel type flowmeters are all rotor type.

2. The principle of volumetric flow meter

There are many kinds of volumetric flow meters, all of which adopt the fixed displacement measurement method, but The details There is still a big difference.

Rotameters are common in the hydraulic field and their operating principle consists of using elements of mymechanical ure to continuously divide the incoming flow into one or more parts of known volume. The number of times the cavity is filled with liquid per unit time is measured to measure the volume of fluid flowing through it.

RotorAmong them, gear type and screw type are more commonly used.

3. Advantages and disadvantages of volumetric flow meter

Volumetric flow meter has been widely used in industrial production process flow measurement for a long time, and Rapidly expanded to the measurement of medicine, precision chemistry, food industry and other fields.

It shows that the volumetric flow meter has many excellent characteristics:

(1) High measurement accuracy, good repeatability and influence on the accuracy of measure Degree factors are relatively small. The viscosity of the liquid, the change in the velocity field of the fluid et other factors have little influence on its measurement accuracy.

(2) Since the swirling flow and distortion of the velocity field have no effect on the degree, installation is simple and does not require a device for stabilizing the flow and a long straight pipe in front, so it is of great practical significance for practical use.

(3) The viscosity range used is very wide, especially for high viscosity liquids.

(4) The flow rate range that can be measured is relatively wide. Compared to the 10:1 and 5:1 measurement ratio of general flow meters, some container flow meters can reach 30:1. even bigger.

(5) Positive displacement flowmeters can have direct-reading instruments, without other external power sources, and the operation is simple and clear.

(6) Since the volume flow meter is directly calculated byvolume, compared with other bypass volume flow meters such as speed type, it is less affected by factors.

Of course, due to the influence of materials, processing technology and its own structure, current volumetric flow meters also have some shortcomings:

(1) Since it is directly connected and installed with the pipe to be tested, when the gauge is large, the instrument is relatively bulky, and it is troublesome to transport and install.

(2) Since the mechanical material becomes brittle at low temperature and expands and deforms at high temperature, the temperature range and pressure level used by the volumetric flow meter are boundaries.

(3) Because there are moving parts, it is not suitable for the measured liquid which is dirty and contains solid impurities, and the filtration precision should be high.

Furthermore, the flFluid should also be used to drive the moving parts to make the flowmeter work normally, so the pressure drop is relatively large.

Tag: volumetric flow meter