The flow measurement method and the instrument type is various, classification method is very much also.
Turbine
flowmeter is a kind of speed meter, it is mainly used for measuring the liquid flow.
It USES multi blade rotor (
Turbine)
Feel the mean velocity of fluid, thus deduced flow or instrument of the total.
It consists of two parts, sensor and intelligent display, also can make integral.
Because it has high precision, good repeatability and strong anti-jamming ability, wide measurement range, and the advantages of compact structure, not only is widely used in the source water and water supply system water flow measurement, and in the oil, organic liquid and inorganic liquid, liquefied gas, natural gas and has wide application in measuring objects, such as low temperature fluid.
1.
The working principle of turbine flowmeter turbine flowmeter principle diagram as shown in figure 1.
A turbine was laid in the center of the pipe, supported by bearings on both ends, when fluid through a pipe, the impact of vortex lun blade, on the turbine driving moment, make the turbine to overcome the friction torque and fluid resistance torque and rotation.
Within a certain flow range, for a certain amount of fluid viscosity, the rotation of the turbine angular velocity is proportional to the fluid velocity.
As a result, the fluid velocity can be obtained through the rotation of the turbine angular velocity, which can calculate the fluid flow through a pipe.
The speed of the turbine by sensing coil to detect in a casing.
When the turbine blade cutting lines of magnetic force produced by light body * magnets, it could cause sensing coil in the magnetic flux changes.
Sensing coil will detect the magnetic flux of cycle number yet into the front amplifier, the signal amplification, plastic, is proportional to the velocity of the pulse signal, send one unit conversion and flow integrating circuit and display the accumulated flow value;
At the same time also gave away the pulse signal frequency conversion circuit, current converting the pulse signal into analog electrical flow, which indicates the instantaneous flow values.
2.
The structure of the turbine flowmeter due to the amount of traffic is a dynamic, so the flow measurement is a complex technology import flow of fluid from the chassis, through support to fix a pair of bearing in the center of the pipe axis, the turbine is installed on the bearing.
On the turbine upstream and downstream of the bracket is equipped with a radiation type rectifier board, to guiding role to the fluid, in order to avoid fluid spin and change to the effect of turbine blade Angle.
Above the turbine casing external line equipped with sensor, signal receiving magnetic flux changes.
2.
1 turbine turbine by magnetic stainless steel, equipped with spiral blade.
Leaf number according to the change and different diameter, 2 ~ 24 pieces.
In order to make the turbine has a good response to the flow rate, quality requirements as small as possible.
General requirements for turbine blade structure parameters is: 10 blade Angle & deg;
~ 15 (
Gas)
,30°
~45°
(
Liquid)
;
Blade overlapping degree P for 1 ~ 1.
2;
Leaf blade and the clearance between the inner shell is 0.
5 ~ 1毫米。
2.
2 bearing of turbine bearing generally adopts sliding fit cemented carbide bearing, wear-resisting performance is good.
As the fluid passes through the turbine, a turbine to generate an axial thrust, the bearing friction torque of water, such as bearing damage, in order to eliminate the axial force, need hydraulic ping who measures taken in the junction tree, the principle of this method as shown in figure 2.
Due to the turbine diameter slightly less than before and after stent DH in diameter D8, so, in the turbine flow area expanded, velocity of flow is reduced, the delta P fluid static pressure rise, the static pressure of this delta P will have the effect of offset part of the axial thrust.
2.
Three former volume amplification preamplifier by magnetoelectric induction switch and amplifier shaping circuit two parts, as shown in diagram as shown in figure 3.
Magnetoelectric transducer domestic generally adopts magnetic resistance type, it is composed of * of magnetic steel and external dimension of wound induction line.
When fluid through the impeller rotating blades in * magnets directly reluctance ZUI small, two at the bottom of the magnetic steel blade gap reluctance ZUI, turbine trip turn, constantly changing magnetic flux, changes in the line of induction electric potential, into shaping circuit to enlarge, into the pulse signal.
Output pulse frequency is proportional to the by the flow meter, the proportion coefficient K is K = f/qv type f for turbine flowmeter output pulse frequency;
Qv for by the flow meter.
The proportional coefficient is also called the instrument coefficient of turbine flowmeter.
2.
4 signal receiving and signal receiving and displays the coefficient of the corrector, adder and frequency converter, etc, its role is to the pulse signal amplifier before sent to transform into cumulative flow and transient flow and display.
3.
The characteristics of the turbine flowmeter 3.
1 high accuracy the accuracy of the turbine flowmeter in 0.
5% ~ 0.
About 1%.
Within the scope of the linear flow, even if the flow changes, also won't reduce cumulative flow accuracy.
And in a short period of time, reproducibility of turbine flowmeter can reach 0.
05%.
3.
2 range than wide range of turbine flowmeter can reach 8 ~ 10.
Under the same caliber, turbine flowmeter ZUI flow value is greater than many other flowmeter.
3.
Nearly 3 should be closed knot 枃 sex temperature turbine flowmeter can make it, the speed signal is the contact measurement, so easy to achieve high pressure resistant design.
If the turbine flowmeter and bearing resistance to high temperature, small thermal expansion coefficient of the material, it can be used in a wider range of temperatures.
At this time, should pay attention to its instrument coefficient modification (
Mainly the change of the flow area)
:K = K0 (
1 -
(
R+2H)
(
t-
t0)
K type, K0 for use and calibration of the instrument coefficient of t, t0 for and check when using fluid temperature;
R, H of turbine and casing material expansion coefficient respectively.
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