JPH04278422A - Fluid vibrating type flowmeter - Google Patents

Abstract

PURPOSE:To sufficiently widen the flow rate region and to reduce measuring errors of the flow rate in the whole area, by narrowing the flow path between a target where the jetting flow is hindered from going straight and a discharging arch part, and setting the shortest distance between the target and the discharging arc part to be equal to the distance from the jetting surface of a nozzle to the front face of the target. CONSTITUTION:An inner wall face 15 of an enlarged flow path of a flowmeter is constituted of a main arc part 16 connected with a jetting face 11 of a nozzle, an enlarged wall part 17 communicating smoothly with the arc part 16 and a sub arc part 18 which is smoothly connected with the wall part 17, narrowed at the side of the downstream and connected to a narrowed flow part 13. The arc part 18 and the flow part 13 are connected by an arc-shaped discharging part 19 projecting to the side of the flow path. The flow path is made narrow between a target 20 and the arc part 19 at the side lower than the target 20. The shortest distance P1 between the target 20 and the arc part 19 is set to be approximately equal to the distance T1 from the jetting face of the nozzle to the front face of the target. Accordingly, the flow can be formed and discharged smoothly and, a fluid signal can be excited well.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] 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, the present invention relates to a fluid vibrating flowmeter that measures the flow rate of various fluids (gas, liquid), and more specifically, the present invention relates to a fluid vibrating flowmeter that measures the flow rate of various fluids (gas, liquid), and more specifically, A channel enlarged section is disposed in the channel and has an enlarged channel inner wall surface symmetrical with respect to the axis of the nozzle on the ejection side of the nozzle, and the channel enlarged section is provided at the center of the channel in the channel enlarged section. Relating to a fluid vibrating flowmeter that is provided with a target that obstructs straight forward movement of a jet stream ejected from a nozzle, and further provided with a constricted flow path portion downstream of the flow path enlarged portion and having a narrower flow path width than the flow path enlarged portion. .

0002

2. Description of the Related Art Conventionally, as this type of fluid vibrating flowmeter, a structure as shown in FIG. 7 has been proposed. To briefly explain the operating principle of this fluid vibration type flowmeter, a jet jet ejected from the nozzle jetting surface 11 is divided into a main jet flow L1 that bypasses the side of the target 20 and flows out from the throttle channel section, and a main jet flow L1. It is composed of a return flow L2 that branches off from the flow path, collides with a portion on the rear side of the enlarged flow path portion or the reduced cross-section portion forming the throttle flow path portion, and flows backward through the flow path. In this type of flowmeter, when fluid is ejected from the nozzle, the jet is drawn toward one side wall portion 50, 51 along the flow direction due to the Coanda effect and flows. That is, the jet stream does not travel straight, but is distorted toward either side wall portion 50 or 51. At this time, the return flow L2 as described above is generated, and this flow imparts fluid energy in the direction perpendicular to the straight direction of the jet in the vicinity of the nozzle ejection surface, and in the subsequent step, the jet flows toward the opposite side. The water flows along the side walls 50 and 51. That is, this return flow L2 plays a role as a control flow for the main stream of the jet 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 (the presence of the target (This effectively induces vibrations on the low flow rate side.) moreover,
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 on the downstream side 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.

That is, in the flowmeter shown in FIG. 7, in which the enlarged flow path section is formed in a substantially box shape, pressure or flow rate is measured at a pair of measurement positions 55, 55 that sandwich the jet flow near the downstream side of the nozzle jetting surface. A mechanism is provided to detect the change in pressure or flow rate caused by the above-mentioned phenomenon in which the jet flows alternately on both sides of the target, and the flow rate is detected by measuring the frequency of this vibration.

0004

[Problems to be Solved by the Invention] Now, generally speaking, for example, in the case of a gas meter, the permissible measurement tolerance (the error between the actual flow rate and the value detected by the measuring instrument) is a flow rate of 0. It is ±2.5% in the range of 15 to 0.6 m3/h, and ±2.5% in the range of flow rate 0.6 to 3 m3/h.
It is 1.5% (indicated by the broken line in FIG. 8). Here, when measurement is performed using a flow meter in which the enlarged channel portion shown in FIG. 7 is formed in a substantially box shape, the error will be as shown by the solid line in FIG. 8. Figure 8 shows the error (%) of the measured value from the proper detection value when the flow rate is varied (0.1 to 5 m3/h) (hereinafter referred to as flow rate-instrumental error characteristics). , in this measurement, the micro flow rate range (0.15 to 0.4 m3/h)
The error in the measurement is ±4.0, far exceeding the measurement acceptance standard.
It takes a value of 4%, and only measured values within the range of 0.4 to 2.1 m3/h are within the measurement acceptance standards. The numerical value indicated by ΔE in the figure is a value indicating Emax (maximum value on the positive side) - Emin (maximum value on the negative side) in the flow rate-instrumental error characteristic, and is a numerical value by which the stability of measurement can be determined. (In the examples and experimental examples shown below, air is used as the target gas, as in the case shown in the above example, when testing the flow rate-instrumental error characteristics of the flowmeter.
Tests are conducted up to a flow rate range of 5 m3/h. The reason for this is that the upper flow rate value of the allowable standard is 3 m3/h, and a change in the Reynolds number when measuring a different type of gas such as methane is taken into consideration. )

According to the acceptance criteria, this value is 5% in the small flow area and 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.

Furthermore, in such a fluid vibratory flowmeter, the position of the target plays an important role in the measurement accuracy. Conventionally, the position of this target has been determined by placing the most importance on the distance from the nozzle ejection surface to the front of the target in order to excite the oscillating flow well, and it is not necessarily the case that the distance between the nozzle jet surface and the front surface of the target is the most important. It has not been determined based on location. That is, in the past, although the conditions on the upstream side of the target were relatively well satisfied, the conditions on the discharge side of the oscillating flow formed here were not considered to be optimal.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain a fluid vibrating flowmeter that has a sufficiently wide flow rate range to be measured and has small errors over the entire measurement area, and to An object of the present invention is to obtain a fluid vibratory flowmeter in which the target position can also be in a favorable condition on the vibrating flow discharge side.

[0008]

[Means for Solving the Problems] The characteristic structure of the fluid vibrating flowmeter according to the present invention to achieve this object is that the inner wall surface of the enlarged flow path is a main circular arc portion with a first radius R that is in contact with the nozzle ejection surface. , an enlarged wall part that smoothly connects to the main arc part, and a sub-arc part that smoothly connects to the enlarged wall part on the upstream side and connects to the throttle channel part on the downstream side. , the secondary circular arc portion and the throttle flow path portion are connected by an arc-shaped discharge circular portion extending toward the flow path side, and the flow path is configured to be narrowed between the target and the discharge circular portion on the downstream side of the target; The shortest separation distance Pl from the discharge arc portion is set to be approximately equal to the separation distance Tl between the nozzle ejection surface and the front surface of the target, and its functions and effects are as follows.

[0009]

[Function] In other words, in the fluid vibrating flowmeter of the present application, the inner wall surface of the enlarged flow path is composed of a main circular arc portion, an enlarged wall portion connected to the main arc portion, and a sub circular arc portion, and the sub circular arc portion and the throttle flow path Since the sections are connected by the discharge arc section, the flow is naturally formed as an ejected main stream and a return flow branching from the ejected main stream at the flow path enlarged section, contributing to stabilization of the flow rate-instrumental error characteristics. Furthermore, since the shortest separation distance Pl between the target and the discharge arc section is substantially equal to the separation distance Tl between the nozzle ejection surface and the front surface of the target, the main flow of the jet flow is between the target and the discharge arc section. The fluid is easily discharged from the downstream part of the flow path formed in the flow path, and as a result, fluid vibrations are favorably excited. As a result, the flow rate-instrumental error characteristics also fall within acceptable standards.

0010

[Effects of the Invention] Therefore, in the fluid vibrating flowmeter of the present application, the flow rate range to be measured is sufficiently wide and the error is small over the entire measurement area. In the vibratory flowmeter, we were able to obtain a fluid vibratory flowmeter with a good target position on the vibrating flow discharge side.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A flow rate measuring device 1 incorporating a fluid vibrating flowmeter of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 shows a plan view of a flow rate measuring device 1, and FIG. 2 shows details of the main parts of a fluid vibration type flow meter 2 incorporated in this flow rate measuring device 1.

First, the general configuration of this flow rate measuring device 1 will be explained. This device 1 is configured such that the inflow direction A of the fluid f to be measured is 180 degrees opposite to the outflow direction B. That is, the fluid flowing from the device inlet 3 flows into the storage section 6 via the cutoff valve section 5. After being subjected to a rectifying action by a rectifier 7 disposed in this storage section 6, it flows into the nozzle. The jet flow flowing out from the ejection surface 11 of the nozzle becomes a vibrating flow in the flow passage enlarged part 12 of the fluid vibrating flowmeter 2 and flows out from the throttle flow passage part 13 provided on the downstream side thereof.

[0013] The structure and function of each operating section will be explained in more detail below. First, the flow up to the nozzle 8 will be explained. Fluid f such as gas or water flowing from the device inlet 3 passes through the approximately L-shaped first bending path 4 and passes through the cutoff valve section 5.
sent to. After passing through the shutoff valve section 5, it flows into the storage section 6. A rectifier 7 is provided in this storage section 6 . This rectifier 7 has a semicircular arc shape,
It is disposed opposite to the nozzle inlet 8i of the fluid vibrating flowmeter 2 described above. Here, the inlet 8i of this nozzle is formed by a pair of protrusions 9, which protrude into the storage section 6 described above.

[0014] Due to the arrangement relationship between the rectifier 7 and the pair of protrusions 9, the pair of end edges 10 of the rectifier 7 are located downstream in the flow path direction with respect to the pair of inlet side ends 9t of the protrusions 9. It is supposed to be located. Therefore, a pair of detours F1 are formed between the pair of end edges 10 and the pair of inlet side ends 9t.

[0015]Furthermore, the pair of detour paths F1 are formed so that fluids flow in opposite directions and merge at the upper portion of a central flow path F3 that connects to an internal nozzle flow path F2 formed within the nozzle. has been done. Here, a pair of detour channels F
1 and the aforementioned pair of inlet side ends 9t, a pair of vortex regions v are formed. Furthermore, this fluid flows through the nozzle 10
The fluid flows into the vibrating flowmeter 2 from the oscillating flowmeter 2.

The fluid f flows out from the device outlet 14 through the enlarged flow path section 12 and the restricted flow path section 13 provided on the downstream side of the nozzle ejection surface 11 of the fluid vibrating flowmeter 2. It is being done.

Now, to explain the positional relationship between the rectifier 7 and the protrusion 9 in terms of actual values, the widths a and b defining each detour and the maximum distance c between the inlet end 9t and the rectifier 7 are as follows. , wo is the width of the nozzle ejection part, then it is as follows. a/(a+b) = 0.36 to 0.54 (0.47 in the case shown in Figures 5 and 6) c/wo = 3.0 to 4.5 (Figure 5
, in the case shown in Figure 6, 3.7)

Next, the structure of the nozzle 8 will be explained. The nozzle 8 has a suction part width wi, an ejection part width wo, and a pair of linear inner walls 8w having a linear shape between their end edges.
It is configured to have a constant rectification length Nl. In order to obtain this rectification length Nl, a pair of protrusions 9 are formed to protrude from the reservoir 6 as described above. The pair of protrusions 9 are formed from rectangular members having a protrusion width NW and a protrusion length Nl (which is approximately equal to the above-mentioned rectification length), and have left and right storage areas on both sides thereof. 6L, 6R are formed, and the width of these left and right side storage areas 6L, 6R is formed to be approximately equal to or larger than the above-mentioned rectification length Nl. The suction side end 9R of the nozzle 8 in the protrusion 9 has an arc shape, and the nozzle inlet arc diameter rn is used as the radius of this arc. Speaking of the actual numbers, lol
o=3.2mm wi/wo=0.9 to 1.2 (1.0 as shown in FIGS. 5 and 6) rn/wo=0.25 to 0.62 (as shown in FIGS. 5 and 6) Nl/wo=5.00 to 6.88 (6.25 in the case shown in FIGS. 5 and 6) NW/wo=2.30 to 2.94 (in the case shown in FIGS. 5 and 6) In the case shown in , it is 2.63).

Next, the configuration of the fluid vibration type flow meter 2 will be explained based on FIG. 2. The fluid vibratory flowmeter 2 includes the aforementioned nozzle 8, an enlarged channel section 12, and a throttle channel section 13 that smoothly connects to the enlarged channel section 12. Here, in this nozzle 8,
The nozzle ejection surface 11 is perpendicular to the flow path direction. Next, the channel enlarged section 12 will be explained. This channel enlarged section 12 is provided with an enlarged channel inner wall surface 15 that is symmetrical with respect to the channel axis that coincides with the flow channel direction. It is composed of a main arc portion 16 in contact with the nozzle ejection surface 11, a linearly enlarged wall portion 17 connected to this, and a sub-arc portion 18 further connected to this linearly enlarged wall portion 17. The rear end portion of this sub-arc portion 18 is connected to the aforementioned throttle channel portion 13 by a similarly arc-shaped discharge arc portion 19. Furthermore, a target 20 is provided at the center of the flow path in the flow path enlarged portion 12 to prevent the jet flow ejected from the jet surface from moving straight.

FIG. 4 shows the detailed structure of this target. As shown in the figure, this target is formed symmetrically with respect to the axis of the flow path, and has an upstream recess 20b between the left and right upstream circular arc portions 20a, and further has a protruding portion 20c on the downstream side. are doing. This projecting portion 20c is
It includes a first arcuate portion 20d having its center on the upstream recess 20b, and a second arcuate portion 20e having the same center position as the upstream arcuate portion 20a in the flow path transverse direction. This target 20 has the effect of stably switching the flow direction of the jet flow in a microflow range.

Here, the first radius of the main circular arc portion 16 is R, the separation distance from the jetting surface of the center of the secondary circular arc portion 18 in the flow path direction is L, and the flow rate at the center of the secondary circular arc portion 18 in the flow path transverse direction is L. The distance from the axis of the road is x, the second radius of the sub-arc portion 18 is r, the width of the target 20 is Tw, and the target 20
When the vertical width of is TL and the width of the throttle channel section 13 is P, the above-mentioned wo, R, L, x, r, Tw, TL, and P are R/wo=
3.0 to 4.7 (3.9 in the case shown in Figures 5 and 6) L/R=1.5, x/R=(√3)/2 r/R=0.5 Tw/wo = 1.56 to 2.00 (1.75 in the case shown in Figs. 5 and 6) TL/wo = 1.0 to 1.5 P/R = 1.24 to 1.62 (in the case shown in Figs. In the case shown in 6, the relationship is 1.36).

FIG. 3 shows the above-mentioned main arc portion 16 and sub arc portion 18.
, an illustration of the geometry of the linearly expanding wall 17 is shown.

Furthermore, the radius r1 of the discharge arc portion 19 described above is equal to the second radius r (ie, R/2), and the maximum transverse dimension of the flow path enlarged portion 12 is 2(x+r)/R=2.73. . Further, the distance between the tip of the target 20 and the nozzle ejection surface in the flow path direction is Tl, and the distance Pl between the target 20 and the discharge arc portion 19 is Tl/P.
The relationship that l is 0.94 to 1.05 (1 in the figure) is maintained. If the distance between the center of the discharge arc portion 19 and the rear end of the fluid vibration type flowmeter 2 is ΔL, then ΔL
/R is set to 0.15 to 0.7 (the one shown is 0.3), and the distance Z from the nozzle ejection surface 11 to the rear end of the fluid vibration type flowmeter 2 is Z= 2.59-3.1
It is 4R. Here, the actual dimension of R is 13.0 mm, and the height (width in the direction perpendicular to the plane of the paper in FIG. 2) of this fluid vibration type flowmeter is 23 mm, but is not limited to this.

Furthermore, here, the flowmeter related dimensions R, L, x
, r, Tl, P to dimensionless, L, x, r, Tl
, P are selected based on R, because the configuration is such that the angle (θ) of the bending part of the main jet flow and the angle (θ') of the main return ring part of the return flow in Fig. 1 are almost parallel. Depends on what is being done.

The measurement results of this fluid vibration type flowmeter 2 will be explained below. FIG. 6(b) shows the flow rate-instrumental error characteristics. As you can see from this figure, 0.6m3/h
High accuracy with an error of less than ±0.8% at large flow rates of 0.
．． Even at a low flow rate of 1 to 0.6, the error is within +0.5 to -1.5%, well within the tolerance stipulated by the Measurement Act (±2.5% or less), and the accuracy is sufficient. A fluid vibration type flowmeter that can withstand practical use has been obtained. Here, the lower limit flow rate for oscillation is about 65 liters/h, and the Reynolds number is 5
It is possible to oscillate down to about 0, which is an extremely good result.

[Experimental Example] Below, the results of experiments conducted by the inventors regarding the present application will be explained. Experimental Example 1 In this experiment, the other conditions were the same as in the previous example, and the distance between the nozzle jetting surface and the front surface of the target was T.
1. The change in characteristics of the flowmeter was investigated when Pl/Tl was changed, where Pl is the shortest distance between the target and the discharge arc portion.

FIG. 5 shows changes in the maximum error ΔE with respect to Pl/Tl, and FIG. 6 shows flow rate-instrument difference characteristics under typical conditions in FIG.

First, to explain from FIG. 5, the horizontal axis of FIG.
l/Tl is shown, and the vertical axis shows the maximum error ΔE. Further, in the figure, the solid line indicates the first radius R of 13.0 mm, and the broken line indicates the first radius R of 11 mm. As is clear from the figure, as Pl/Tl increases monotonically, ΔE decreases at one point, and then tends to increase after Pl/Tl reaches 1. The area where the maximum error characteristic ΔE is 3 or less, which is a general standard for general fluid vibrating flowmeters, is Pl/T
l is in the range of about 0.94 to 1.05.

Next, FIG. 6 will be explained. Figure 6(a),
(b) and (c) show the flow rate-instrument difference characteristics when Pl/Tl in FIG. 5 is 0.9, 1.0, and 1.12, respectively. As can be seen from the figure, when this value is small, the error on the large flow rate side swings to the positive side, showing good results when Pl/Tl is close to 1, and when this value becomes large, the error width in the small flow rate range increases. As the value increases, the entire error swings toward the positive side on the small flow rate side.

[Another Embodiment] Another embodiment of the present application will be described below. (A) In the above embodiment, the linearly expanding wall portion 17 was formed in a straight line, but it may have any shape as long as it expands toward the downstream side. Therefore, this part is simply called an enlarged wall part.

(b) In the above embodiment, the first radius R, the second radius r, and the sub-circular portion 1 in the flow path transverse direction
Regarding the second separation distance x from the axis of the flow path at the center of No. 8,
These satisfy the relationship r/R=0.5, x/R=(√3)/2 (a flowmeter with this numerical relationship is
The main numerical values of the main arc and sub-arc parts have a simple relationship. Figure 3
is shown. ), but this may be related to the following: r/R=0.45 to 0.56 x/R=0.7 to 1.0 In this case, it is also possible to configure the fluid vibratory flowmeter vertically.

[0032]Although reference numerals are written in the claims for convenience of comparison with the drawings, the present invention is not limited to the structure of the accompanying drawings by such entry.

[Brief explanation of the drawing]

[Fig. 1] Plan view of a flow rate measuring device incorporating the fluid vibration type flowmeter of the present application.

[Figure 2] Plan view of the fluid vibration type flowmeter of the present application

[Fig. 3] An explanatory diagram showing the geometrical relationship of the main dimensions of the fluid vibratory flowmeter of the present application.

[Figure 4] Diagram showing the configuration of the target

[Figure 5] Diagram showing the relationship between Pl/Tl and maximum error

[Figure 6]
(a), (b), and (c) are diagrams showing flow rate-instrument difference characteristics when changing Pl/Tl.

[Figure 7] Diagram showing the structure of a conventional fluid vibrating flowmeter

[Figure 8
] Diagram showing the flow rate-instrument difference characteristics of a conventional fluid vibrating flowmeter

[Explanation of symbols]

6 Storage part 8 Nozzle 8w Straight inner wall 9t Nozzle inlet end face 11 Nozzle ejection surface 12 Enlarged flow path section 13 Throttle flow path section 15 Expanded channel inner wall surface 16 Main arc part 17 Enlarged wall section 18 Sub-arc part 19 Discharge arc part 20 Target

Claims (2)

[Claims] [Claim 1] A nozzle ejection surface (11) perpendicular to the flow path.
A nozzle (8) having a
8) is provided with a passage enlarged part (12) having an enlarged passage inner wall surface (15) symmetrical with respect to the axis of the nozzle on the ejection side of the nozzle, and a passage enlarged part (12) is provided in the central part of the passage of the passage enlarged part (12). A target (20) is provided to prevent the jet flow ejected from the nozzle (8) from moving straight, and the flow path enlargement portion (1
2) 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), wherein the inner wall surface of the expanded flow path (15) is the main circular arc portion (16) of the first radius R that is in contact with the nozzle ejection surface.
an enlarged wall part (17) smoothly connected to the main arc part (16); and further, an enlarged wall part (17) smoothly connected to the enlarged wall part (17) on the upstream side and the throttle flow passage part on the downstream side. (13
) and a sub-arc portion (18) connected to the
The secondary circular arc part (18) and the throttle flow passage part (13) are connected by an arc-shaped discharge circular part (19) extending toward the flow passage side, and the target (20) is connected to the target (20) on the downstream side of the target (20). The flow path is narrowed between the target and the discharge arc part (19), and the flow path is narrowed between the target and the discharge arc part (19).
) is set to be approximately equal to the separation distance Tl between the nozzle ejection surface and the front surface of the target. 2. The width of the ejection part (11) of the nozzle is w
o, the horizontal width of the target (20) is Tw, the vertical width of the target (20) is TL, the nozzle ejection surface (11)
and the separation distance to the front of the target (20) is Tl
, Pl is the shortest distance between the target (20) and the discharge arc portion (19), r is the second radius of the sub-arc portion (18), and is the center of the sub-arc portion (18) in the flow path direction. The distance from the nozzle ejection surface (11) is L, the distance from the axis of the flow path to the center of the sub-arc portion (18) in the flow path cross direction is x, and the radius of the discharge arc portion (19) is rl.
, where the width of the throttle channel section (13) is P, the wo, Tw, TL, T1, Pl, r, R, L, x, P,
Between r1, Tw/wo=1.56~2.00 TL/wo=1.0~1.5 Pl/T1=0.94~1.05 R/wo=3.0~4.7 According to claim 1, there is the following relationship: r/R=0.5 L/R=1.5 x/R=(√3)/2 r1/R=0.5 P/R=1.24 to 1.62 Fluid vibrating flowmeter.