JPH04160321A - Flowmeter of fluid vibrating type - Google Patents

Abstract

PURPOSE:To enlarge the measuring range of the flow rate and to measure the flow rate with reduced errors in the whole measuring area by widening an expanded wall part of an inner wall face of an expanded flow passage more towards downstream to a position corresponding to the position of a target in the flowing direction. CONSTITUTION:At the projecting side of a nozzle 10 having a projecting face 11 orthogonal to the direction of a flow passage, there is provided a flow passage expanded part 12 which has an inner wall face 14 of an expanded flow passage symmetric to the axis of the nozzle 10. A target 20 is provided at the central part of the expanded part 12, and a narrowed part 13 is formed at the downstream part of the part 12. At this time, the inner wall face 14 is in touch with the projecting face 11 at a principal circular part 15, then defines an expanded wall part 16 expanding the flow passage to the position of the target 20, and is connected to the narrowed part 13 at a sub circular part 17. Accordingly, a feedback current diverging from the gushing main stream at the target 20 starts to be fed back in a smooth circular streamline to the projecting face 11 depending on the cross section of the expanded wall part 16 without being excessively decelerated. The main circular part 15 helps this smooth feedback. In this manner, the change of the flow rate can be absorbed in a stable manner.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fluid vibrating flowmeter that measures the flow rate of various fluids (gas, liquid), including gas meters, and more specifically, to A nozzle having orthogonal nozzle ejection surfaces is disposed in the flow path, a flow path enlarged portion having an enlarged flow path inner wall surface symmetrical with respect to the axis of the nozzle is provided on the ejection side of the nozzle, and the flow path A target is provided at the center of the channel in the enlarged section to prevent the jet flow ejected from the nozzle from moving straight, and further, a throttle channel section having a channel width narrower than that of the enlarged channel section is provided on the downstream side of the enlarged channel section. The present invention relates to a fluid vibrating flowmeter equipped with a fluid vibration type flowmeter.

[Conventional technology]

Conventionally, this type of fluid vibrating flowmeter has been used as shown in Fig. 11 (
A structure as shown in b) has been proposed. To briefly explain the operating principle of this fluid vibration type flowmeter, the jet jet ejected from the nozzle jetting surface (11) is directed to the target (20
) The main jet stream flows out from the throttle channel by bypassing the side of ( ).
Ll), and a return flow (L) that collides with the branch L from the main jet main stream (Ll), the rear part of the enlarged flow path section, or the reduced cross section forming the throttled flow path section, and flows backward through the flow path.
2). In this type of flowmeter, when fluid is ejected from the nozzle, the jet flow is directed to one side wall (50, 5) along the flow direction due to the Coanda effect.
It will flow because it is attracted to 1). That is, the jet stream does not travel straight, but is distorted toward either side wall portion (50, 51). At this time, a return flow (L2) as described above is generated, and this flow imparts fluid energy in a direction perpendicular to the straight direction of the jet flow near the nozzle jetting surface, and in the subsequent step, the jet flow is reversed. The water flows along the side wall portions (50, 51). In other words, this return flow (L2) plays a role as a control flow for the main jet flow near the nozzle outlet, and a phenomenon occurs in which the jet flow ejected from the nozzle flows alternately on both sides of the target (depending on the presence of the target). (This effectively induces vibrations on the low flow rate side.) Furthermore, in a flowmeter having a configuration in which only a target is disposed in the enlarged flow path section, the state of the vortex formed in the wake formed downstream of the target also affects this vibration phenomenon. This period of oscillation is generally proportional to the fluid flow rate through the flow meter. Therefore, we try to use this phenomenon to measure the flow rate of fluid flowing through this flow path.

In other words, in the flowmeter shown in FIG. 11(A) in which the flow passage enlarged portion is formed in a box-like shape, a pair of measurement positions (55, 55) sandwiching the jet stream are located near the downstream side of the nozzle ejection surface. A mechanism for detecting pressure or flow rate is provided in L, and changes in the pressure or flow rate caused by the phenomenon in which the jet stream flows alternately on both sides of the target are detected.The flow rate is detected by measuring the frequency of this vibration. It is.

[Invention or problem to be solved]

Now, generally speaking, for example, in the case of a gas meter, the allowable measurement tolerance (the error between the actual flow rate and the value detected by the meter) is the flow rate of 0 to 0.6 m.
”/h range of ±2.5%, flow rate 0.6 to 3 m3
/h (shown by the broken line in FIG. 11(b)). If the flow meter shown in Fig. 11 (a) is formed in the shape of a hollow box, the error will be as shown by the solid line in Fig. 11 (b). Become.

FIG. 11(b) shows the error (%) of the measured value from the proper detection value when the flow rate is changed (0 to 5 m''/h) (hereinafter referred to as flow rate-instrumental error characteristic). ), and in this measurement, the micro flow rate range (0.15 to 0.3 m3/h)
The error is ±4, which far exceeds the measurement tolerance standard.
It takes a value of 4%, and only measured values that fall within the measurement acceptance standards are obtained within the range of 0.3 to 2.1 m'/h. The numerical value shown as ΔE in the figure is E in the characteristic curve.
This is a value indicating max (maximum value on the plus side) - Emin (maximum value on the minus side), and is a numerical value by which the stability of measurement can be determined. (In the examples and experiments shown below, all of the tests for the flow rate-instrumental error characteristics of flowmeters are performed using air as the target gas, as in the case shown in the example above.
Test up to the flow rate range of h. The reason for this is that the change in the Reynolds number when measuring another type of gas such as L or methane was taken into consideration with respect to the upper limit flow rate of 3 m'/h of the allowable standard. ) Now, according to the acceptance standards, this value is 5% in the small flow area.
, it is 3% in the large flow area. That is, such a conventional structure cannot be adopted as a measurement device, and the above-mentioned conventional technology has room for improvement in terms of measurement accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain a fluid vibratory flowmeter that has a sufficiently wide range of flow rates to be measured and that has small errors over the entire measurement range.

[Means to solve the problem]

The characteristic structure of the fluid vibrating flowmeter according to the present invention for achieving this purpose is as follows: The inner wall surface of the enlarged flow path includes a main circular arc portion that contacts the ejection surface, an enlarged wall portion that smoothly connects to the main circular arc portion, and Smoothly connects to the enlarged wall part L, consists of a sub-arc part L that connects to the throttle flow path part on the downstream side, and connects the enlarged wall part to the position corresponding to the target position in the flow path direction toward the downstream side. The structure is such that it can be expanded, and its functions and effects are as follows.

[For production]

In other words, in the fluid vibrating flowmeter of the present application, compared to a conventional box-shaped flowmeter, the inner wall surface of the enlarged channel is gradually enlarged by the main circular arc portion from the nozzle jetting surface toward the downstream side. Furthermore, this expanding tendency continues up to the position corresponding to the target position.In such vibrating flowmeters, there is a problem in whether the return flow smoothly returns to the control position (near the nozzle outlet). First, the return flow that branches from the main jet stream begins to return by drawing a smooth arc-shaped streamline at the sub-arc section, and is subject to excessive deceleration depending on the cross-sectional shape of the expanded flow path section. The return flow returns to the nozzle ejection surface without causing the return flow to occur.Furthermore, the fact that the outer wall portion of the main arc portion has a circular arc shape helps the return flow return smoothly.

〔Effect of the invention〕

Therefore, the flow range that falls within the measurement acceptance criteria that defines the applicable limits of the vibratory flowmeter is expanded (the fluid flow within the flowmeter will be formed as a reasonably smooth flow, In response to changes in the flow rate to be measured, it is possible to absorb changes in the flow rate in a stable state without significantly changing the flow pattern. It has now become possible to represent Japan.

Therefore, it has become possible to make a fluid vibrating flowmeter that has only a target in the flow path and forms a return flow only by the shape of the outer wall of the pipe, which was almost impossible to use as a flow rate measurement device in the past, possible. I was able to do that.

In addition, this type of flowmeter has a simpler structure, is easier to manufacture, and is less expensive than the fluid vibrating flowmeter that has been used in practical use in the past and is equipped with a member that actively forms a return flow. As a result, it was possible to reduce the

〔Example〕

Flow rate measuring device incorporating the fluid vibration flowmeter of the present application (1)
will be explained based on FIGS. 1 and 2. Fig. 1 shows a plan view of the flow rate measuring device (1), and Fig. 2 shows the fluid vibration flow meter (2) incorporated in this flow rate measuring device (1).
Details of the main parts are shown. First, the schematic configuration of this flow rate measuring device (1) will be explained. This device (1)
, the fluid to be measured (f) is flowing in its inflow direction (
A) is configured to be 180 degrees opposite to the outflow direction (B). That is, fluid (f) such as gas or water flowing in from the device inlet (3) is sent to the cutoff valve part (5) through the first bent path (4) in the shape of an abbreviation. After passing through this shutoff valve section (5), it flows into the storage section (6). Further, from this storage part (6), a nozzle (1
0). This fluid (f) is measured by a fluid vibration flowmeter (
2) is configured so that it flows out from the device outlet (24) via the flow passage expansion part (12) and the constriction flow passage part (13) provided on the downstream side of the nozzle ejection surface (11). be.

The configuration of the fluid vibration flow meter (2), which is the main part of the present application, will be explained below based on FIG. 2.

This fluid vibration flowmeter (2) includes the aforementioned nozzle (10),
It is configured to include a channel enlarged section (12) and a throttle channel section (13) smoothly connected to the channel enlarged section (12). Here, the nozzle (lO) is formed with the inner side wall of the nozzle as a straight flow path parallel to the flow path (F), and exists with the nozzle ejection surface (11) perpendicular to the flow path direction. are doing. Next, the enlarged channel part (12) is explained. The enlarged channel part (12) is provided with an enlarged channel inner wall surface (I4) that is symmetrical with respect to the axis of the nozzle that coincides with the flow channel direction. This inner wall surface (14) is the nozzle ejection surface (11)
It is composed of a main arc part (15) in contact with the main arc part (15), a straight wall part (16) connected to this, and a sub-arc part (]I7 further connected to this straight wall part (16). The rear end of the section (17) is similarly connected to the aforementioned throttle channel section (13) by an arc-shaped discharge arc section (18). A target (20) is provided in the center to prevent the jet flow ejected from the jet surface from moving straight.This target (20) allows the flow direction of the jet flow to be stably switched in a small flow rate region. has an effect. Here,
- The width of the nozzle (10) is w, the radius of the main arc part (15) is R1, the distance in the flow path direction from the jetting surface of the center of the sub arc part (17) is L, the center of the sub arc part (17) is The distance from the nozzle axis in the flow path transverse direction is x, the radius of the sub-arc portion (17) is r, the width of the target (20) is Tw, the target (
20) The separation distance in the flow path direction from the jetting surface at the tip position is T
1. If the width of the throttle channel section (13) is P, the above w and R
, LSx, rSTw, TI, P are R/w=4.38, L/R=1.5, x/R=0.78, r/R=0.5, Tw/w=1.75 TI /R=1, P/R=1.18.

Furthermore, the radius r1 of the discharge arc portion (18) described above is approximately equal to r, and the maximum transverse dimension of the enlarged channel portion (12) (corresponds to the width of the box-shaped portion in the transverse direction of the channel in FIG. 11(A)). ) is 2
(x0r)/R=2.56, and furthermore, the distance from the nozzle ejection surface (11) to the throttle flow path section (13) (first
The distance in the flow path direction of the box-shaped portion in FIG. The distance Z from the nozzle ejection surface (11) to the rear end (19) of the fluid vibration flow meter (2) is approximately Z=2.67R.

Here, the actual dimension of W is 3.2 mrn, and that of R is 14 mm.

Here, flowmeter related dimensions R, L, x, r, TI.

In making P dimensionless, L, x, r, T I, P
The reason why R is selected as the standard is that the angle (θ) of the bending part of the main jet flow and the angle (θ) of the main return part of the return flow
′) are almost parallel to each other.

Below, the measurement results of this fluid vibration flow meter (2) will be explained. FIG. 3(b) shows the flow rate-instrumental error characteristics. As can be seen from this figure, it has high accuracy with an error of ±1.0% or less at large flow rates of 0.6 m''/h or more, and 0.1 to 0.
．． Even at a low flow rate of 6, the fluid vibration type has an error of ±1.5% or less and is well within the tolerance specified by the measurement method (±2.5% or less), and is highly accurate and can withstand practical use. A flow meter has been obtained. Here, the transmission lower limit flow rate is about 651/h, and it is possible to measure up to a Reynolds number of about 50, which is an extremely good result.

[Experiment example]

Below, the results of experiments conducted by the inventors regarding the present application will be explained.

Experimental example 1 Examination of changes in flow rate-instrumental error characteristics when the radius R of the main arc part is changed, with the radius R of the main arc part being the same as the nozzle width W and other parameters as in the example. The results are shown in Figure 3 (a).
Shown in (b) and (c). Here, (a), (b), (
Regarding c), R was set to 11, 14, and 17 mm, respectively. To explain the results below, when the radius R of the main circular arc is small as shown in Figure 3 (a), the error in the small flow area shifts to the positive side, and the measured value in the large flow area increases. The displacement towards the positive side is increasing. As the radius R of the main arc portion increases from this region, the third
Shown in Figure (b).

In this way, a state in which accurate and good measurement is possible from a small flow rate area to a large flow rate area will be realized. Furthermore, as shown in FIG. 3(c), when the radius R of the main circular arc portion is increased, the error swings to the negative side in both the small flow rate region and the large flow rate region.

Experimental Example 2 Regarding the change in flow rate-instrumental error characteristics when the radius r of the secondary arc part is changed with the radius r of the secondary arc part and the nozzle width W and other parameters the same as in the example. , Figure 4 (a), (b), (c)
It was shown to. Here, r was set to 5° and 7.9 mm for each of (a), (b), and (c). To explain the results below, if the radius of the secondary arc is small as shown in Fig. 4 (a), it will not cause any major problems regarding errors in the small flow range, but in the large flow range. The tendency of the measured values to shift toward the positive side is increasing. However, L and ΔE are relatively small. As the radius r of the secondary arc increases from this region, a good condition with low error within the tolerance is achieved from the small flow area to the large flow area, as shown in Figure 4 (b). It becomes like this.

Furthermore, as shown in Fig. 4 (c), when the radius r of the main circular arc section is increased, the error swings significantly toward the negative side in the small flow rate region, and once swings toward the negative side in the medium flow rate region. After that, the error swings to the positive side in the large flow area. The ΔE value increased significantly to 4.8.

Experimental example 3 Connection relationship between the main arc part and the sub-arc part In the examples described above, the main arc part and the sub-arc part were connected by straight walls circumscribing each arc part, but these main arc parts and An example in which the sub-arc portions are connected to each other by a protrusion (30) as shown in FIG. 5(a) while remaining in an arc shape will be shown below.

FIG. 5(b) shows the flow rate-instrumental error characteristic in this example. ΔE is 3.5, which is a great improvement compared to the box-shaped one, but compared to the straight wall part shown in Figure 2 (b), the error is on the positive side in the large flow part. Displacement to or large. This is considered to be due to the fact that the return flow is not returned well when the flow rate becomes large.

Experimental example 4 Target width Tw Flow rate - when the target width Tw is changed with the nozzle width W and other parameters being the same as in the example.
Changes in the instrumental error characteristics are shown in Figures 6 (a), (b), and (c). Here, Fig. 6 (a) shows the ones with Tw of 5.0 and 5.2 mm, Fig. 6 (b) shows the ones with Tw of 5.6 mm, and Fig. 6 (c) shows the ones with Tw of 5.8 and 5.2 mm. The flow rate-instrument difference characteristics of the 6.0 mm one are shown. The results will be explained below. When the width of the target is small as shown in FIG. 6(a), the error in the small flow rate range swings to the positive side, and the tendency of the measured value to shift to the negative side in the large flow rate area becomes large.

However, L and ΔE are 3.6 or less, which is relatively small for a range of this extent. As the width Tw of the target increases from this region, as shown in FIG. 6(b), the range from the small flow rate area to the large flow rate area falls within the allowable error, and a state with small errors is realized. Furthermore, as shown in Fig. 6(c), when the width Tw of the target is increased, the error swings greatly toward the plus side in the small flow rate region, and after once swinging to the minus side in the medium flow rate region,
In the large flow range, the error becomes even more positive. The ΔE value increases as the target width Tw increases.

Experimental example 5 Target position TI With the nozzle width W and other parameters being the same as in the example, the flow path direction from the ejection surface at the tip position of the target.
Figure 7 (
A), (B), and (C) are shown in Figure 8. FIG. 8 shows the target distance (non-dimensionalized) on the horizontal axis and the ΔE value on the vertical axis. Specific points in Figure 8 (
The flow rate-instrumental error characteristics of points 3) are shown in FIGS. 7(a), (b), and (c).

Figure 7 (a) shows the TI or 11.5mm one.
(b) - is Tl or 15mm, and Fig. 7 (c) is TI is 1.
The flow rate-instrumental error characteristics of the 6 mm one are shown. The results will be explained below. When the target distance is small as shown in FIG. 7(A), the error in the small flow rate range is quite large and swings to the positive side, and in the large flow rate area, the measured value tends to shift to the negative side. Furthermore, △E is 6
．． It has a very large value of 4. As the target distance T1 is increased from this region, a state within the permissible error is realized from the small flow region to the large flow region, as shown in FIG. 7(b). Furthermore, Fig. 7 (
As shown in c), when the target distance T1 is increased, the error tends to decrease as the flow rate increases in the small flow rate region, gradually increases in the medium flow rate region, and then The error will further increase in the large flow area. In this state, the measurement condition is extremely unstable, and the ΔE value is 5.3%, which is a poor value.

ΔE when increasing target distance T1 like this
The change in ΔE is shown in FIG. 8, and the region where ΔE is 4 or less is the region where TI/R is 0.94 to 1.1.

Experimental Example 6 Width P of Throttle Outflow Channel The change in flow rate-instrumental error characteristic when the width P of the throttle flow path is changed with the nozzle width W and other parameters being the same as in the example, Figures (a), (b), (c)
, shown in Figure 1O. In FIG. 10, the horizontal axis shows the width of the throttle channel section (which is dimensionless), and the vertical axis shows the ΔE value. Flow rate at specific points (3 points) in Figure 10 -
The instrumental error characteristics are shown in FIGS. 9(a), (b), and (c).

Here, Fig. 9 (A) shows the one with P of 14 mm, Fig. 9 (B) shows the one with P of 29 mm, and Fig. 9 (C) shows the one with P of 23 mm.
The flow rate-instrumental error characteristics of m are shown.

The results will be explained below. The width of the throttle channel is 9th.
If it is small as shown in Figure (a), the error in the lower limit value in the small flow rate range is quite large and swings to the negative side, but the change in the measured value is stable in the large flow rate area. Here, Δ
E is a fairly large value of 5.6. As the width P of the constricted flow path increases from this region, a state within the permissible error is realized from the small flow rate region to the large flow rate region, as shown in FIG. 9(b). Furthermore, as shown in FIG. 9(C), when the width P of the throttle channel section is increased, the error increases as the flow rate increases in the small flow rate region.
The error starts to show a decreasing tendency, gradually transitions to an increasing tendency in the medium flow rate region, and becomes almost stable in the large flow rate region. Here, the ΔE value is 4.7%, which is a poor value.

The change in ΔE when the width P of the discharge section is increased is shown in Figure 1O, and the region where 8E or less is 4 is the region where P/R is 1.14 to 1.52. It is.

[Another example]

In the above-mentioned embodiment, the main arc part (15) and the sub-arc part (17) were connected by a straight wall part (16) formed in a straight line, which was connected to the target (20) in the flow path direction. It is only necessary that the flow path has a tendency to expand at a position corresponding to a certain position, and it is possible to connect with any shape curve.

Furthermore, almost the same results can be obtained even if the center position of the Kaida arc portion (17) is displaced to some extent compared to that of the embodiment.

It should be noted that the present invention is not limited to the structure of the attached drawings by adding numerals in the claims for convenient comparison with the drawings.

[Brief explanation of drawings]

The drawings show examples of conventional and inventive fluid vibrating flowmeters, FIG. 1 is a plan view of a flow rate measuring device incorporating the fluid vibrating flowmeter of the present invention, and FIG. 2 is a fluid vibrating flow meter of the present invention. The plan view of the flowmeter, Figures 3 (A), (B), and (C) are diagrams showing the relationship between the radius of the main circular arc portion and the flow rate-instrumental error characteristic, and Figures 4 (A), (B), (C) is a diagram showing the relationship between the radius of the Kaida arc and the flow rate-instrumental error characteristics. Figures 5 (A) and (B) are for the case where the main arc and the Kaida arc are connected via a protrusion. A plan view of the flowmeter and a diagram showing the relationship between flow rate and instrumental error characteristics, Figure 6 (a), (b), (c)
is a diagram showing the relationship between target width and flow rate-instrumental error characteristics; Figures 7 (a), (b), and (c) are diagrams showing the relationship between target distance and flow rate-instrument error characteristics; , a diagram showing the relationship between the target distance and 8E, Figures 9 (a), (b), and (c) are diagrams showing the relationship between the width of the throttle channel and the flow rate-instrumental error characteristic, and Figure 1O is , a diagram showing the relationship between target distance and △E, and Figures 11 (a) and 11 (b) are diagrams showing a plan view of a box-shaped flowmeter with a conventional configuration and the relationship between its flow rate and instrumental error characteristics. be. (lO)... Nozzle, (11)... Nozzle ejection surface, (12)... Channel expansion part, (13
)... Restricted channel section, (14)... Enlarged channel inner wall surface, (15)... Main circular arc section, (16)
......Enlarged wall part, (17)...Kaida arc part, (20)...Target.

Claims (1)

[Claims] 1. A nozzle (10) having a nozzle ejection surface (11) perpendicular to the flow path is arranged in the flow path, and an axis of the nozzle (10) is provided on the ejection side of the nozzle (10). A channel enlarged portion (12) having an enlarged channel inner wall surface (14) symmetrical to A target (20) that obstructs straight movement is provided, and the flow path enlarged portion (
12) is provided with a constricted flow path section (13) having a narrower flow path width than the rear end of the expanded flow path section (12) on the downstream side of the expanded flow path section (12), the inner wall surface of the expanded flow path. (14), a main circular arc part (15) in contact with the nozzle ejection surface (11), and an enlarged wall part (1) smoothly connected to the main circular arc part (15).
6), and a sub-arc portion (17) that smoothly connects to the enlarged wall portion (16) and connects to the throttle channel portion (13) on the downstream side.
and the enlarged wall portion (16) is arranged in the direction of the flow path toward the target (
20) A fluid vibratory flowmeter configured to expand the flow path toward the downstream side to a position corresponding to position 20). 2. The enlarged wall portion (16) is a linear wall portion (
16) The fluid vibratory flowmeter according to claim 1, wherein the fluid vibratory flowmeter is formed by: 3. The width of the nozzle (10) is w, the main arc portion (15
) is the radius R, the distance in the flow path direction from the nozzle ejection surface (11) to the center of the sub-arc part (17) is L, and the flow path from the nozzle axis to the center of the sub-arc part (17). The distance in the transverse direction is x, the radius of the sub-arc portion (17) is r, the width of the target (20) is T_w, and the target (2
0), the distance in the flow path direction from the nozzle ejection surface (11) is T1, and the width of the throttle flow path portion (13) is P.
Then, the above w, R, L, x, r, T_w, T1, P
However, R/w=3.5~5.3, L/R=1.5, x/R=0.78, r/R=0.35~0.56, T_w/w=1.56~ 1.81, T1/R=0.94 to 1.1, and P/R=1.14 to 1.52.