Coriolis mass flowmeter Situation and Future
Published on：2014-12-24 9:28:50 Hits：
Coriolis mass flowmeter Situation and Future
In order to adapt to the production of the flow measurement in various different media and different operating conditions require, produce a variety of different types of positive displacement flowmeter. The more common type of gear, scraper-type and rotary piston type, three types, respectively, are presented below.
1. Gear type volumetric flowmeter
This flow meter installed in the housing with two rotors mesh with each other, directly or indirectly, to produce rotation in the pressure differential between the inlet and outlet flow meter. By rotating gears, continue to be filled between the gear and the housing "measurement space" fluid discharge. By measuring the number of gears, obtainable by the amount of fluid flowmeter.
Figure 2-1 shows the oval gear type positive displacement flow meter (also known as volumetric flowmeter Aubard) schematic diagram
2-1 oval gear flow meter schematic diagram
The figure shows the two oval gear meter by working with each other, their work are summarized as follows: The figure represents the meter inlet fluid pressure P1; expressed outlet fluid pressure is clearly greater than the pressure P1 P2. Figure 2-1 (a) in, below the rotor despite the pressure difference of the fluid, but does not generate the rotational torque, while the gear is rotated above the rotational torque generated in the two cases of a differential pressure effect. Since the two gears meshing with each other, so each side O1, O2 as the axis direction of the arrow while rotating the gear O1 fluid meniscus to the discharge outlet of the metering space. In Figure 2-1 (a) status, the gear for the driving wheel, the next gear is driven wheel. In Figure 2-1 (b) position, the two gears are rotating torque generated at a fluid differential pressure action, and the rotation direction of the arrow at the moment action, the transition to Fig. 2-1 (c) position shown. In this case the gear position and FIG. 2-1 (a) On the contrary, the lower gear of the driving wheel, the gear of the driven wheel. Under the Import and Export lower gear differential effect of rotating fluid, and again it will be half-moon shape of the housing between the "measurement space" fluid discharge. So continuous movement, oval gear each rotation is discharged four "measurement space" fluid volume. Therefore, as long as the number of revolutions of the gear readout, you can calculate the amount of the discharged liquid. Refer to Figure 2-2, calculate the total amount of fluid is discharged
V = 4nv
＝2 n（R 2 －ab） （2－4
Where the number of rotations n-- gear;
a, long-sleeve b-- oval gear, short half-uranium;
------ Thickness oval gear.
Another gear type positive displacement flow meter is volumetric flowmeter round the waist, also known as Roots-type positive displacement flowmeter. This meter works and the work process is basically the same with the oval gear type, is also relying on the inlet and outlet fluid pressure differential to produce movement, every revolution discharged four "measurement space" volume of fluid. Except that no teeth in the back wheel, they are not directly engaged with each other is rotated, but the transmission is accomplished by means external to the housing by a transmission gear set.
The two rotor type volumetric flowmeter, can be used to measure a variety of liquid flow, in particular for the accurate measurement of oil flow. In the high-pressure gas flow measurement, the flow of such flowmeters are also applied. Due to the volume of oval gear flow meter measuring wheel engages directly depend, therefore, require the cleaning media is higher, does not allow any solid particles of impurities through the meter.
2. Scraper volumetric flowmeter
Scraper flowmeter is a relatively common volumetric flowmeter. This meter on the rotor can be equipped with two pairs of inner and outer radial sliding blade, rotor flowmeter inlet and outlet differential effect of rotation, the discharge of four per revolution "measurement space" fluid volume. The same as the former flow meter, so long as the measured number of rotations, can calculate the volume of discharge of fluid.
The more common type scraper flowmeter cam structure shown in Figure 2-4. FIG bore of the housing is a circular cylinder space, the rotor is a hollow cylindrical body, radially with a width, in the radial direction is 90 ° open position of the four slots, slot blade can freely slide . Four blade by two-link connection, mutually perpendicular, intersecting in space. At one end of each blade is provided with a small ball, four balls are on a secondary fixed cam rolling the blade when retracted. When two adjacent blades are extended to the housing wall to form - a standard volumetric space. In measuring the movement of the blade segment, only with the rotor to rotate without slippage, in order to ensure its standard volume constant. When leaving the metering section, blade retracted into the tank, the fluid discharged from the outlet. At the same time, but after a scraper blade adjacent thereto to form another second "measurement space", the same action. Rotor week, discharged four "measurement space" fluid volume.
In the scraper volumetric flowmeter, there are so-called rotary valve scraper flowmeter, it works similar to the cam, but a different structure, not described in detail here.
3. Rotary piston positive displacement flowmeter
Rotary piston (also called swing piston type) structure and working principle of volumetric flowmeter seen in Figure 2-5.
As shown, the rotary piston is positioned between the inner and outer rings 3 and 4 fixed, the axis of the piston 6 against the guide rollers 5 rolling, the intermediate plate 1 the metering space into two portions, the piston and the partition plate 2, a notched engaging, when piston movement in the direction of the arrow and separator 1 into linear motion. In Importers piston fluid pressure difference, always in close contact with the inner and outer walls of the rotating drum, alternatively the piston and continuously fluid is discharged between the inner and outer cylinder, the piston frequency and the amount of rotation available computational fluid flow therethrough.
Rotary piston positive displacement flowmeter has a greater flow capacity advantages. It's not enough there will be some leakage in the work process
Drain, so accuracy is low.
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