2 Measurement of the U-shaped mass flowmeter
As shown in Figure 8, U-shaped tube as a single, double measurement of the two structures, single-tube-type measuring principle
Figure 8 a single U-shaped structure of
Figure 8 b double of the U-shaped structure
As shown in Figure 9, electromagnetic drive system to drive U-shaped fixed frequency of vibration measurement, when the fluid tubes were forced to accept the vertical movement, the first half of vibration cycle, the tubes upward movement of the driver measuring Guanzhong Liu Before produce a downward pressure of the tubes impede the upward movement in the driver points after the upward force, to accelerate the tubes upward movement. The two of the synthesis, making measurements of the distortions occur in the other semi-cycle of vibration, while the opposite direction of distortion.
Figure 9 U-tube principle
Measuring the extent of the distortion, and the fluid flow through the measurement of value is directly proportional to the quality of traffic, driving point in the measurement of both sides on the installation of electromagnetic sensors to measure their movement phase, the phase difference directly proportional to the The quality of traffic flow.
In the measurement of double-U-shaped structure, two measuring the vibration of the opposite direction, making measurement of the difference between 180 degrees phase distortion, as shown in Figure 10. Measuring the relative single-, twin-tube-type signal to enlarge, circulation capacity has been upgraded.
Figure 10 measurements of deformation diagram
3 Double J-tube mass flowmeter
Figure 11 shows, two J-shaped pipe to pipe as the center, symmetrical distribution; installed in the J-shaped part of the drive allows the tubes to a fixed frequency of vibration.
Figure 11 J-shaped structure of the mass flowmeter
Its working principles as shown in Figure 12, when the measurement of the fluid flow in a certain speed, due to the presence of vibration measurements made in the fluid produced a Coriolis force effect. The Coriolis force in the measurement, but from top to bottom on two of the Coriolis force in the direction different from the direct control of different parts of the additional movement, that is, produce a relative displacement of the phase difference.
Figure 12 J-tube principle
In double-J-tube measuring system, two of the vibration at the same time the opposite direction, increased its upper and the lower part of two straight between the relative displacement of the phase difference. Figure 13 shows, the fluid does not flow from the A, B two sensor measured the displacement signals in the zero phase difference.
Figure 13 free flow measurement of vibration
When the measurement of the fluid flow, its vibration in the drive up the party, the Coriolis force of the reaction force in the measurement of the impact on the results shown in Figure 14, of a separate and the two near, the top 1 Speed up the movement, the lower part of the slow-down of two in the opposite direction on the same top speed up, slow down the bottom; results in the upper and lower installation of sensors detected the presence of a phase difference between the signal, as shown in Figure 15. This signals a direct reflection of the size of the mass flow.
Figure 14 when a mobile measurement of vibration
Figure 15 sensor output signal
4 B-tube mass flowmeter
Figure 16 shows, flow measurement system parallel to each other by the two B-tube components. After the measured fluid shunt was evenly into two B-shaped measuring tube, drives installed in two between the centre, to a certain stability in the measurement of the harmonic vibration frequency drive. Measurement of field generated in the campaign, as shown in Figure 17 a straight part of the push to leave each other, in the role of the drive circuit L1 'and L1''around each other, the same circuit L2' and L2''around each other. As each circuit are fixed at one end of the main flow meter, the rotating movement in the end zone was inhibited thus concentrated in the vicinity of nodes.
Figure 16 B-shaped structure of the mass flowmeter
The circuit of fluid in the Coriolis force of the show circuit L1 'and L1''slow down the speed of each other around, and the other end of L2' and L2''the two-loop increasing at a rate of close to each other.
Figure 17 B-tube work force of the state
In a measure of inward movement, as shown in Figure 17 b, the opposite happens. Direct control of part of the role of the driving forces under and around each other, and both of the two sections on each other to leave the circuit in the direction of movement. The fluid within the pipeline Coriolis force superimposed on this basic movements will L1 'and L1''the two-loop faster the separation due to L2' and L2''the two-loop separation speed decreases.
Through the end of the two loop between reasonable install sensors, the Coriolis force by the introduction of the movement of fluid can be used for precise determination of the mass flow.
5 Single straight tube-shaped mass flowmeter
This flowmeter the structure shown in Figure 18, the measurement system at both ends by a fixed (flange) on the straight and the vibration drive components.
Figure 18-straight mass flowmeter structure
Guanzhong Liu does not flow in the body, the drive lets pipe vibration, Guanzhong Liu body does not produce Coriolis force, A, B force equal to two points, the same rate of change, as shown in Figure 19 b.
Figure 19-straight principle of mass flowmeter
When measuring Guanzhong Liu body in order to speed the flow V, C, vibration due to the impact of (this is the vibration of the upward), fluid particles from Point A to Point C campaign was accelerated particles generated reaction force F1, the upward movement slowed down the tubes, while in C point to point B, and fluid particles being slow down, the upward movement so that the tubes faster. C results in these two points on both sides of the opposite direction of the tubes to produce a deformed, the deformation of the phase difference Guanzhong Liu and measurement of the quality of traffic flow in direct proportion.
6 Two-straight tube-shaped mass flowmeter
Figure 20 pair of straight pipe structure of mass flowmeter
Figure 20 pair of straight pipe structure of mass flowmeter
Relatively straight-straight-run double to reduce pressure loss and increase feelings of sensor signals, the actual structure of Figure 20 shows, drive and placed center, only two photoelectric sensor on both sides of symmetrical position with the Centre , Including the structure shown in Figure 20 a measurement of the impact of the axial force small. Two-straight tube-shaped mass flowmeter the working principle as shown in Figure 21, when the fluid does not flow, photoelectric sensor tubes are generated by the displacement of the phase is the same as when the fluid flow through two medium vibration measurement of time , It produced a Coriolis force, this force so that the measurement of vibration in the opposite point of displacement on both sides, before the test-point Guanzhong Liu medium so that the tubes oscillation decay, that is, slowed down the tubes displacement;-point after the test Guanzhong Liu medium to strengthen the oscillation, or displacement of the tubes faster. Through the photoelectric sensor, measured at both ends of the phase, the phase difference in the oscillation frequency at a certain proportional and in the measurement of the mass flow.
Figure 21 pair of straight pipe measuring principle
7 shape measurement of mass flow meter
This flowmeter the structure shown in Figure 22, drive straight on the part of the middle, when the Guanzhong Liu in a certain rate of flow, due to drive the vibration, so that the tubes separately or near.
Figure 22 shape measurement of mass flow meter structure
Figure 23 a, when the tubes separate, in-points before the fluid in the Coriolis force and vibration in the opposite direction, slowing down the tubes in velocity, and in point-after Guanzhong Liu of the Coriolis force and Vibration the same direction, speed up the tube velocity. When the driver allows the tubes around, Figure 23 b, then have the opposite result. In A, B two points of the sensor can be measured in two words of the campaign phase, which can be measured Guanzhong Liu flow of the mass flow.
Figure 23 -tube mass flowmeter measurement principle
8 Double ring measurement of mass flow meter
This flow meter is a parallel with short and straight composition of the spiral pipe, as shown in Figure 24. In the middle of the tube with D drive, so that the two measurements are cyclical opposite vibration, in elliptical spiral pipe at both ends, D and the mid-point equidistant locations, set up two sensors, these two points of measurement The tubes between the relative velocity, the two relative velocity of phase with the measurement of the flow of fluid is proportional to mass flow.
Figure 24 pairs of ring mass flowmeter
Its working principles outlined as follows: When the body does not flow measurement Guanzhong Liu, the vibration of the tubes so that the deformation, in the mid-point is the same on both sides, the two sensors measuring point, measured the vibration displacement of the zero phase difference When measured in mobile Guanzhong Liu, in the amplitude of the largest point before the fluid particles due to the Coriolis force and vibration have a role in the opposite direction of the force, in this point and produce a vibration direction of the same force, because At the same time measuring two by the force of the same size, the opposite direction, reflected in the two sensors measuring points on the tube velocity be increased or decreased, measuring these two points of the phase difference can be measured by the The quality of fluid flow.
Third, the structure of mass flowmeter
In a measurement system, the role of fluid particles in the measurement of the Coriolis force is very small, to the accurate measurement very difficult. To enable measurement of a strong enough signal, it should increase the Coriolis force on the measurement of the role or in the same Coriolis force under increasing role in the measurement of deformation.
From the principle of speaking Fc = 2 VM, measured in a certain fluid, or only increase V, to increase Fc. in the actual increase in the instrument on the need to increase the frequency and amplitude of vibration. The frequency increased, seriously affecting the measure of life expectancy, and the amplitude of the increase on the need for greater impetus. V is to increase the flow rate of increase, such an increase on the measurement of pressure, flow meter also increase the pressure on the system as a whole loss. These flowmeter itself and the whole system are disadvantaged.
On the other hand from the structural design, we should consider raising the Coriolis force of the vibration and improve the efficiency of the sensor detection capabilities, to improve the performance of the latter will not discuss. To improve the Coriolis force on the measurement of the efficiency of the need to improve the measurement of the shape of the overall system flexibility, reduce steel, flexible choice of good, stable performance of materials and accurately select the oscillation frequency. To achieve the same Coriolis force, measuring deformation of the increase. Generally speaking, the measurement of the thin wall, the longer the length, shape the structure of the system flexibility as possible, in the role of the Coriolis force on the more obvious. This will enable the measurement of the deformation increased, signal to noise ratio increased, but also reduce the external interference. On the measurement of the stress suffered not to be too concentrated in the point, so as to avoid mechanical fatigue. The role of different forms of stress, fatigue on the tube and measuring the impact of sensitivity to a certain extent. For a different structure, because of their different design ideas, each with characteristics, but there are also a number of problems, each have a form of perfection can not be achieved. In light of these problems, manufacturers are constantly upgrading their products to enhance the performance of their products, enhance its competitiveness. Below the concrete structure on the performance of a simple analysis.
1 Measuring the shape of
Increase the flexibility of the measurement system, increasing the role of vibration control systems in the Coriolis force of effect, but also increase the mechanical noise outside interference and instrument size. Measurement should minimize the sharp bend, the greatest possible measure of the diameter of the increase, this will reduce the pressure loss. Measurement of the double-to-noise ratio be increased, circulation has increased capacity, not commonly used.
2 Wall
Pipe wall thickness increased to more rigid, but also increase the flow of the tubes when the fixed quality and reduce the fluid inclusions in the gas, because of its uneven distribution of the tubes caused the change in pattern of the impact of vibration, and improve the measurement of pressure, resistance Mill, but will reduce system flexibility, impact measurement sensitivity.
3 Manufacture and installation
Measuring the shape of the production process should ensure that its symmetry, the structure of the double-measure of the two should be guaranteed the consistency and accuracy to the positioning sensors to measure reduction in the density or viscosity change due to the impact of the measurement results. The quality of the distribution of flow instability to the accuracy of the measurement results affected.
From the principle of speaking, the measurement of the Coriolis force suffered only with the size of the mass flow of the fluid, and fluid density and viscosity has nothing to do. However, the changes in density will bring additional inertia force, and measuring changes in the viscosity of the different layers of the wall attachment, the boundary layer produce different effects. The results from measuring the quality of the distribution of instability, the measurement accuracy of the results of the impact.
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