JPH02262017A - Mass flowmeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mass flow meter, and more particularly to a mass flow meter configured to directly measure the total flow rate of a fluid to be measured.

Conventional technology The flow rate of the fluid to be measured depends on the type of fluid and its physical properties (density, viscosity, etc.)
, it is desirable to express it as a mass that is not influenced by the process conditions (temperature, pressure)1. Conventionally, the quality of the fluid to be measured is expressed as a mass that is not influenced by the flow rate. The so-called indirect mass flowmeter measures 131fa and converts this 131fa into mass, and the so-called direct mass flow meter directly measures the mass flow rate of the measured fluid, and the indirect mass flow has a smaller error than a meter. There is. Among this type of mass flowmeter, various types of flowmeters are being proposed, each based on a different principle, particularly as a direct-type hanging flowmeter that can measure flow rate with higher accuracy. Also, one of them is an outflow M that directly measures the mass flow rate by utilizing the Coriolis force that occurs when fluid flows inside a vibrating sensor tube.

Further, as a mass flow (bit) using this Coriolica, for example, the one shown in FIG. 10 is considered.

In FIG. 10, the mass flowmeter 1 has a pair of center ribs 2 and 3 attached to the side 1 main body 1a.

One sensor tube 2 has a straight pipe part 2a communicating with an inlet (not shown), a straight pipe part 2b communicating with an outlet 5, and a bent part bent back at the tips of the straight pipe parts 2a and 2b. 2c, 2d, and curved portion 2c.

2d and a U-shaped connecting portion 2e.

Further, the other Senrib 1-B3 is formed in the same shape as the Senrib 1-P2 described above, and has straight pipe portions 2a, 2b.

3a and 3b are parallel to the sensor tube 2 and above,
are arranged asymmetrically.

One ends of the straight pipe portions 2a, 2b, 3a, and 3b pass through the fixing plate 6, and are connected and fixed to the main body 1a at predetermined intervals.

Further, the sensor tube 2.3 is supported at a predetermined spaced position by a support member 7 interposed between the connecting portions 2e and 3eLj.

Between the a pipe parts 2a and 3a on the inflow side and the straight pipe part 2 on the outflow side
A pickup 9.10 is disposed between b and 3b. In the pickup 9.104, the coil portion is fixed to the lower straight tube portions 3a, 3b, and the magnet portions facing the upper and lower surfaces of the coil portion are fixed to the upper straight tube portions 2a, 2b. 11° and 12 are vibration exciters, located between the tips of the straight pipe parts 2a and 2b.

It is provided between the tips of the straight pipe portions 3a and 3b.

During flow measurement, sensor tube 2.3t and exciter 11.1
2, and vibrates at a natural frequency determined by the spring constant of the center rib q-72°3 and the flow rate flowing through the center ribs 2 and 3.

Therefore, when fluid passes through the vibrating sensor tube 2.3, a Coriolis force is generated and the M tube portions 2a, 2b, 3a
, 3b are displaced by Coriolika. The pair of sensor tubes 2.3 are each excited with a phase difference of 180°, for example, the straight tube portion 2a of the upper sensor rib 1-12.
, 2bHfi are separated, the lower Senrib 1-B3
The straight pipe portions 3a and 3bll are close to each other.

Pickups 9 and 10 each vibrate sensor tube 2.
．． Detect the relative displacement of 3. Then, based on the output signals of the pickups 9 and 10, the mass flow distortion of the fluid flowing inside the sensor pipe 2.3 is determined.

Problems to be Solved by the Invention With the above mass F I Kl, for example, when measuring the flow rate of a liquid mixed with gas, the gas in the liquid is
-12.3 may remain. In this case, the mass of the fluid flowing through the sensor tube 2.3 changes due to the retention of gas, and thus the natural frequency of the sensor tubes 2, 3 changes.

In particular, when measuring a minute flow rate M1, the flow rate of the liquid is low, so gas tends to stagnate. More specifically, in the mass flowmeter 1 in which sensor tubes 2.3 are vertically symmetrically arranged as shown in FIG.
In the song part 2G.

2d and an arcuate connecting portion 2e connecting the curved portions 2c and 2d.
Gas in the liquid tends to stay in the lower Senrib 1-1.
3, gas tends to stay in the straight pipe portions 3a and 3b.

In this way, the upper sensor tube 2 and the lower sensor tube 3 have different gas retention positions, and even if the retained gas is in the receiving part, the UIA of the sensor tubes 2 and 3 is different.
The right frequency is off. However, b1 trade m shown in Figure 10
In the flow ffi 841, the pair of sensor tubes 2.3 are each vibrated in a resonance state with a large amplitude, but (if the ilR frequency deviates due to gas retention,
It becomes impossible to vibrate the Senrib 1-B 2.3 in a resonant state. As a result, the amplitude of the sensor tube 2°3 becomes small, making it impossible to obtain a sufficient amount of Coriolis.

Therefore, in the above-mentioned quality m flowmeter, Senrib 1-12
．． Sensor tube 2.3 due to the difference in gas retention location in 3.
The balance of is relatively upset, and hard s! Since fte+a also varies, the output signal of the pickup 9.10 that detects the displacement of the sensor tube 2.3 is also disturbed, causing a problem that it is difficult to measure the flow m stably.

Therefore, an object of the present invention is to provide a quality backflow process 1 that solves the above problems.

Y! Means for solving m The present invention provides a pair of sensors 1 in the quality j outflow 81.
- Each of the straight pipe portions of the ribs extends in the horizontal direction, and the first... A pair of sensor tubes are arranged so that the second curved portion and the connecting portion are symmetrical with respect to a vertical plane that stands vertically.

When measuring the outflow of a liquid mixed with a working gas, if the gas remains in the pair of sensors 1-1, the pair of sensors 1-1 arranged symmetrically across the vertical plane are approximately the same. Is there gas in one place? The phase n of the pair of sensor tubes is
The balance is maintained, and there is no variation in the number of natural frequencies 1113.

ACTUAL EXAMPLE FIGS. 1 to 5 show an embodiment of the mass flow rate according to the present invention.

In each figure, the quality ω outflow δ121 is connected to a pair of sensor tubes 22° between the inflow side flange 21a where the inflow port 21a1 opens at the center and the outflow side flange 21b where the outflow port (not shown) opens. 23 (shown in FIG. 2) is connected to the manifold 24, and a box-shaped cover 21G that houses and protects the sensor tubes 22 and 23. The tR function of the cover 21c is to protect the sensor tube 1-122, 23 from external force, and also to protect the sensor tube 2.3 from dust and foreign matter adhering to the sensor tube 22.23. Prevents mass changes, and changes in wind pressure, temperature, etc.
, 3, and has the role of increasing the performance.

Arrows 21d and 21e indicating the flow direction of the fluid to be measured are provided on the upper surface 21C1 and the upper surface 21C2 (not visible in FIG. 1) of the cover 21G. Furthermore, this arrow 2
1d and 21e may be formed by pasting with adhesive Arp or the like, or may be formed by printing or press processing@6°. Therefore, when installing the quality a flow ω meter 21, it is necessary to follow the arrows 21d or 21e. Connect the inflow side 7 flange 21a to the upstream side rotation (f not shown) with the 7 outflow side flange 21 facing up.
Connect b to the upstream piping (not shown).

1j The sensors l-722 and 23 of the 3-volume flowmeter 21 are covered by the cover 21c and cannot be seen, but the arrow 2 on the cover 210
By attaching using 1d or 21e as a mark, the Senrib 1-722, 23 can be attached in a predetermined direction.

As shown in FIG. 4, what are the pair of sensor tubes 22 and 23? It is assembled to the second hold 24, and the manifold 2
4 is provided between the inflow pipe 25 and the outflow @26, and has an inflow path 24a connected to the inflow pipe 25 and an outflow path 24t connected to the outflow pipe 26. Further, the inflow passage 24a communicates with connection ports 24a+ and 24a2 that branch to the left and right.

Note that, like the inflow path 24a, the outflow path 24b also communicates with branched connection ports 24b+ and 24b2.

Also, there is a mass flow on the top surface of the manifold 24! - A connector 24c is provided for taking out a total of 21 output signals.

As shown in FIG. 2, the pair of sensor tabs 1 and 22 and 23 extend horizontally from the manifold 24 and are arranged laterally symmetrically with respect to a vertical plane that stands up in the vertical direction. be done.

One Senzab 1-722 has its jlm connected to the inflow path 24.
A first straight pipe part 22a is connected and fixed to the connection port 24a1 of the outlet passage 24a by snow and extends in the piping direction, and a first straight pipe part 22a whose base end is connected and fixed to the connection port 24b of the outflow path 24b is fixed. a second straight pipe section 22b extending parallel to the pipe section 22a;
．． It consists of curved parts 22c and 22d bent back toward the proximal end from the tips of the second straight pipe parts 22a and 22b, and a 0-shaped connecting part 22e that connects the curved parts 22c and 22d.

In addition, the other sensor tube 1-723 is connected to the sensor tube 2.
2, and is formed in the same shape as the straight pipe part 23a.

23b is arranged symmetrically with the sensor tube 22 so that it is parallel to the outflow pipe 26 and the straight pipe parts 22a, 22b. In addition, the connection parts 22e and 2 of the sensor tubes 22 and 23
3e1m are connected and mutually held by a holding member 28.

Note that this holding member 28 is not in contact with the outflow pipe 26, so that piping vibrations of the outflow pipe 6 are not directly transmitted to the Senrib 1-722°23.

The pair of sensor probes 22 and 23 extend horizontally so that they are symmetrically oriented with respect to a vertical plane that stands in the upward direction.
For example, when measuring the flow rate of a liquid containing gas, a pair of sensor tubes 22.
It becomes easier to accumulate in the straight pipe portions 22b and 23b above the tube 23, respectively. Therefore, since the gas retention position of the pair of sensor tubes 22 and 23 is between the paths, the balance will not be lost due to gas retention, and as a result, the respective natural frequencies will not deviate.

In the pair of Senribs 1-722 and 23, a big ring 729.30 is arranged between the straight pipe parts 22a and 23a on the inflow side and between the straight pipe parts 22b and 23b on the outflow side. .

Note that since the pickups 29 and 30 have the same configuration, only the pickup 29 of -h will be explained.

In FIGS. 6 and 7, the pickup 29 is a bracket 3 that protrudes from the middle of the straight pipe portion 22a of the sensor tube 22.
1, and magnets 29b and 29c provided on a mouth-shaped bracket 32 to face the coil part 29a on the left and right sides. In addition,
The bracket 32 extends laterally and connects the Senrib 1-123.
It is connected to the i-tube section 23a.

Therefore, when Senrib 1-122.23 vibrates, the coil part 29a provided in the straight pipe part 23a moves to the magnet 29.
b and 29e relative to each other in the direction of arrow X. Therefore, an electromotive force is generated in the coil portion 298 according to the relative displacement of the straight tube portions 22a and 23a, and the pickup 29 detects the displacement of the straight tube portion 23a from the voltage of the coil portion 29a.

33 and 34 are vibration exciters, which are provided between the ends of the straight pipe parts 22a and 22b and between the ends of the straight pipe parts 23a and 23b.

The vibrator 33 has substantially the same configuration as @magnetic solenoid,
A coil part 33a attached to the straight pipe part 22a on the inflow side and a coil part 3a attached to the straight pipe part 22b on the outflow side.
It consists of a magnet part 33b that is absorbed inside. Therefore,
When the coil portion 33a of the vibrator 33 is energized, the straight pipe portion 2
: 2a, 22b are vibrated 1° in the direction of arrow X (upward, downward direction) Note that the vibrator 34 has the same configuration as the vibrator 33 described above, so a description thereof will be omitted. 1 Above quality! In fiifHt21, since the pair of center ribs 1-122 and 23 are housed in the cover 21C, the mounting direction of the pair of center ribs 1-22 and 23 cannot be recognized from the outside. However, the upper surface 21C+ and the lower surface 21C2 of the cover 21C are provided with arrows 21d and 21e indicating the direction of fluid flow, and the quality ω flowmeter 21 is installed in the middle of the piping so that the arrows 21d or 21e face upward.

As a result, the pair of Senridupes 2 inside the cover 21C
2.23 are positioned symmetrically across the vertical plane as shown in FIG.

Next, the operation on the 51 side of the mass flow rate δ121 having the above configuration will be explained.

When measuring the flow rate, the pair of sensor tubes 22 and 23 are vibrated with fluid flowing inside them by the operation of the vibrator 33 and 34. The fluid to be measured that has flowed into the inflow path 24a of the manifold 24 from the inflow pipe 25 is branched and flows into the straight pipe portions 22a and 23a above the centripetal valves 22 and 23, and then flows into the curved portion 22c.

23C1 connection parts 22e, 23e, curved part 22d.

23d and reach the upper straight pipe parts 22b and 23b,
The manifold 24 merges with the outflow passage 24b and forms the outflow pipe 26.
More leakage. In addition, Senrib 1-B 22.23 is the excitation 1
33 and 34, it vibrates in the direction of arrow X (vertical direction) at a natural frequency determined by the spring constant of the Senrib 1-bu 22, 23 and the flow rate flowing through the Senrib 1-722, 33.

Senrib 1-722° vibrating as above
3. Gas tends to stay inside.

However, since the pair of sensor tubes 22 and 23 are provided so as to extend symmetrically in the horizontal direction with a vertical plane that stands up in the vertical direction interposed therebetween, as shown in FIG.
Even if gas is mixed in the liquid, the upper straight pipe portions 22b, 2
Gas tends to stay in 3b. Therefore, since the pair of sensor ribs 1-722゜23 have the direction in which the gas is retained between the paths, it is possible to prevent the natural frequency from shifting due to the difference in the gas retention position, and the gas source 11i (Ω 2. First, the operation of one sensor rib 1-72 of the pair of sensor tubes 22, 23 will be explained.

Note that the straight pipe portions 22a, 22b, and 23a.

When 23b vibrates, the straight pipe portions 22a, 22b, and 23a are elastically deformed in a direction 1 m apart from each other.

Due to the elastic restoring force of 23b itself, it deforms in a direction approaching n.

As shown in FIG. 8, since the straight pipe portions 22a and 22b are fixed to the support plate 7 by brazing or the like, they vibrate more strongly in the direction of the arrow X toward the tip using the penetrating portion of the support plate 27 as a fulcrum. Therefore, deformation of the angular velocity ω occurs in the straight pipe portions 22a and 22b due to the vibration. Also, songs ¥B22c,
22d and the connecting portion 228 are bent in a 0-shape, so even if the vibrator 33 performs an excitation operation in the direction of the arrow X, the bent portion 22
d and 22e are bent in the direction of rotation, and the straight pipe portion 22a.

Displacement of the tip end side of 22b is allowed.

As mentioned above, when fluid flows inside the vibrating sensor tube 22, the amplitude increases as it approaches the tip of the straight pipe section 22a on the inflow side, so the velocity of the fluid in the direction of the arrow X increases. Therefore, acceleration in the vibration direction is applied to the fluid. Further, in the straight pipe portion 22b on the outflow side, the velocity in the direction of arrow X gradually decreases as it returns to the manifold 24 side, so that negative acceleration is applied to the fluid. In this way, when the fluid is accelerated due to the vibration of the sensor tube 22, Coriolis <Fc) in the direction opposite to the direction of the acceleration
occurs.

As shown in FIGS. 8(A) and 8(B), the straight pipe section 22 on the inflow side
Suppose that a is displaced in the direction of arrow X1 at an angular velocity of -ω, and the straight pipe portion 22b on the outflow side is displaced in the direction of arrow x2 at an angular velocity of 0ω. In this way, the straight pipe portion 22a.

In a single row culm in which the culms 22b are displaced in one direction with a distance of 111 from each other, Coriolika Fc is generated in the straight pipe portions 22a and 22b in the direction of the arrow X27I, as shown in Figures 9 (A) and (B). Therefore, the straight pipe portions 22a and 22b are 1 δ,
δ changes.

Next, as shown in FIGS. 8(C) and 8(D), the straight pipe R22a on the inflow side is displaced in the direction of the arrow ×2 at an angular velocity of 10ω, and the straight pipe portion 22b on the outflow side is displaced in the direction of the arrow ×1 at an angular velocity of ω. Suppose that it is displaced in the direction. In this way, in the single-row culm that is displaced in the direction approaching the 6-line parts 22a and 22b, as shown in Fig. 9 (C
), (as shown in D>, the straight pipe portions 22a and 22b are
Coriolika FC in the 7'J direction occurs. Therefore, the straight pipe portion 22a.

22b is shifted by -δ and 10δ by 6° from the two-point stop 9 (original displacement position) to the position l shown by the solid line.In addition, the pair of center ribs 1-22 and 23 are each added by 6 with a phase difference of 180°. For example, the straight pipe portion 22a of one of the center ribs 1-b 22 is swung.

When 22b is spaced apart, the straight pipe portions 23a and 23b of the other sending tubes 23 are close to each other.

That is, the Senrib 1-B 22 is shown in FIG. 8 (△).

When the sensor tube 23 is displaced as shown in (B),
is displaced as shown in FIGS. 8(C) and (D). Therefore, as shown in FIGS. 9(A) and 9(B), Coriolica occurs in the straight pipe portions 22a and 22b of one Senrib 1-bu 22, and in the straight pipe portions 23a and 23b of the other Senrib 1-bu 23.
Coriolis as shown in FIGS. 9(C) and 9(D) is produced. .

In the Coriolis Fc, the straight pipe portions 22a and 22b are displaced -δ by the pickup 29°30.

It is determined by detecting the magnitude of +δ or the phase angle difference between the straight pipe portions 22a and 22b. Also Coriolika Fc
is expressed as Fc = 2ωmv, and the mass flow ffi (mV>) is obtained by determining the angular velocity ω and FC.

The pickups 29 and 30 are straight pipe portions 22a.

The displacements -δ and +δ of 22b are detected as time difference signals. Therefore, the time 31 required for the voltage obtained at the coil portion of the pickup 29, 30 to change from a certain reference voltage to a certain voltage A is measured, and this time is proportional to the flow rate.

Note that the output signals of the pickups 29 and 30 are shaped and amplified, and then converted into voltage signals proportional to the interrogation flow rate by rIIO integration. Furthermore, this voltage signal is converted into a frequency signal, and outputted as a voltage pulse signal and an analog signal from an output circuit (f, not shown). In the low-quality flowmeter 21, the straight pipe portion 22a is caused by Coriolika occurring in the sensor sub 1-722°23.

The displacements of 23a, 22b, and 23b can be detected twice, and the outflow can be measured with high accuracy. In addition, when detecting the phase difference of the sensor sub 1-722゜23 due to the occurrence of Coriolis, even if external vibration (vibration noise) is input, it is canceled out and the flow can be measured stably without being affected by external vibration. can.

Effects of the Invention As described above, the quality W flowmeter according to the present invention includes a pair of Senribs 1 so that the curved portions and connecting portions of the Senribs 1 are symmetrical with respect to a vertical plane that stands vertically. - When measuring the outflow of liquid mixed with gas, even if gas remains in sensor sub 1-1, the stagnant position will occur at the same location on the pair of sensor tubes. As a result, it is possible to prevent the natural frequencies of the pair of sensor tubes from shifting, thereby obtaining a stable Roliori force, and preventing disturbance of the output signal due to the difference in gas retention position at 29 ffi it 3!11. This is a feature of snow that eliminates the problem of snow and allows stable outflow Kl a!l.

[Brief explanation of drawings]

Fig. 1 is an external perspective view of an embodiment of the mass flow m-ray according to the present invention, Fig. 2 is a perspective view with the cover removed to show the main parts of the present invention, and Fig. 3 is a partially cutaway view. A bottom view, FIG. 4 is a front view of the mass flowmeter, FIG. 5 is a sectional view taken along line V-V in FIG. 3, FIG. 6 is a longitudinal sectional view taken along line Vl-Vl in FIG. 4, FIG. 7 is an enlarged view of the pickup, FIGS. 8 and 9 are side views for explaining the operation of the sensor sub 1 during flow rate measurement,
FIG. 10 is a perspective view for explaining a conventional mass flow ω meter. 21-...Mass flow ff1Ht, 21c...Cover, 21d. 21e...Arrow, 22.23...Cenridge 1-pu,
24... Manifold, 25... Inflow pipe, 26...
- Outflow pipe, 27... Support plate, 28... Holding member, 2
9.30... Pickup, 33.34... Vibrator. Figure 7 Figure 8 Figure 9 Patent applicant Toki] Co., Ltd.

Claims (1)

[Scope of Claims] A first straight pipe portion extending in a straight line with one end communicating with an inlet into which the fluid to be measured flows, and a first straight pipe portion having one end communicating with an outflow port and extending in parallel with the first straight pipe portion. an extending second straight pipe part; a first bent part bent from the other end of the first straight pipe part toward one end side of the first straight pipe part; and a first bent part of the second straight pipe part. A pair of sensor tubes formed by a second bent part bent toward one end of the second straight pipe part from the other end, and a connecting part connecting both ends of the first and second bent parts are connected in the same direction. vibrates the first straight pipe part and the second straight pipe part of the pair of sensor tubes in the direction of approaching and separating, and vibrates the first straight pipe part and the second straight pipe part of the pair of sensor tubes. In a mass flowmeter that measures the flow rate flowing through the pair of sensor tubes by detecting a relative displacement between straight tube sections, each straight tube section of the pair of sensor tubes extends horizontally, and the pair of sensors A mass flow meter comprising a pair of sensor tubes arranged such that the first and second curved portions and connection portions of the tubes are symmetrical with respect to a vertical plane that stands vertically.