JP3109719B2 - Fluid vibration type flow meter element, method of manufacturing the same, and method of determining flow rate measurable range thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention constitutes a flow rate measuring unit of a fluid vibration type flow meter for measuring a flow rate of a Newtonian fluid such as water, oil, etc. in addition to gases such as city gas, propane gas and air. The present invention relates to an element of a fluid vibration type flow meter.

[0002]

2. Description of the Related Art Fluid vibration type flowmeters have no mechanical moving parts, so they have few failures, have a long life, can be miniaturized, have a small number of parts, have a wide rangeability, and have a linearity between flow rate and fluid vibration frequency. Due to its advantages such as goodness, research on its application to various uses such as application to gas meters is being actively conducted. FIG. 8 shows an example of an element of the fluid vibration type flow meter.

In FIG. 8, gas introduced from the inlet 10 into the element of the fluid vibration type flow meter passes through the nozzle 2 from the upstream passage 1 and is introduced into the downstream passage 5, but the nozzle outlet The jet stream (jet stream) jetted from 2b travels substantially straight, and collides with the target 3 indicated by the reference numeral 3 to periodically vibrate the fluid. That is, at some point, the jet flows along the wall 3a on one side of the target 3,
After colliding with the bottom of the side wall, a part thereof rises along one wall surface (side wall) 6a of the downstream flow path 5 and returns to the nozzle outlet 2b, and the other flows out of the element system through the outlet port 11. . At the next point, the jet flow is
It flows as if sucked in b.

[0004] Fluid vibration of such a jet stream is periodically generated in the downstream passage 5. Since a proportional relationship is established between the fluid oscillation frequency of the ejected fluid and the flow rate of the ejected fluid, the fluid oscillation frequency is determined by detecting the static pressure of the jet flow with a pressure sensor (not shown). , The flow rate of the fluid can be measured.

In such a fluid vibration type flow meter element, the flow rate and the fluid vibration frequency have a proportional relationship in a certain range, but this proportional relationship cannot be obtained in a high or low flow rate region outside the range. Here, when the fluid vibration type flow meter element is applied to a flow meter, if the proportional relationship area is wide, the flow rate measurable area is widened, indicating that the rangeability is large, so that the shape of the element, the pressure detection position, Various improvements have been attempted in the past regarding the pressure detection method, the shape of the nozzle, the shape of the upstream portion of the nozzle, the gas supply path, and the like.

[0006] Among them, in the technique described in Japanese Patent Application Laid-Open No. 63-191920, a pair of partition walls is provided in the downstream flow path,
By making the shape of the partition wall specific,
It is intended to expand the measurable area. However, the provision of the partition walls has the disadvantage of complicating the design of production and complicating the manufacturing process, resulting in high cost of the product.

[0007] JP-A-4-160321 and JP-A-4-160321
The techniques described in JP-A-278421 and JP-A-4-278422 disclose a technique in which the shape of the side wall constituting the downstream flow path is specified, and the technique disclosed in JP-A-4-2039.
The technique described in Japanese Patent Publication No. 36 aims to achieve the same object by specifying the dimensions of the nozzle and the shape of the wall surface forming the nozzle entrance, but these require precise processing. It has the disadvantage that it is necessary and the production cost is high.

Further, in the above-mentioned prior art, the measurable range of the flow rate of the fluid vibration type flow meter element is unclear,
In addition, it was probably empirical, and no criterion for clarifying the boundary of the flow rate measurable range that can be actually used was not recognized. Therefore, the user of the fluid vibration type flow meter element, when selecting the element, actually measured the performance of the element,
There is a drawback in that it is necessary to select a measurement value after confirming that the measurement value is within an acceptable range.

[0009]

DISCLOSURE OF THE INVENTION The present invention differs from the prior art in that the shape of the side wall in the downstream flow path or the shape of the downstream flow path itself is not improved, and an easier method is used. It is an object of the present invention to provide an element of a fluid vibration type flow meter in which a proportional relationship between a flow rate and a fluid vibration frequency is expanded.

[0010]

SUMMARY OF THE INVENTION A fluid-oscillating flow rate according to the present invention.
The element of the meter is inside the body of the element as claimed in claim 1.
Element of Fluid Vibration Type Flow Meter with Nozzle and Target
The straw obtained by changing the flow rate
Curve St showing the relationship between Hull number St and Reynolds number Re
= F (Re), the Strouhal number is substantially constant
Region II where Reynolds number is Re^* ₁Is the low flow side
The end point P1 and the Reynolds number are Re.^* _TwoHigh flow end point
P2 and the above Re.^* ₁Is the curve St = f
Corresponds to the area near the low flow rate end of region II in (Re)
1 of the amount of change in the differential curve dSt / dRe = f '(Re)
/ 2 is the Reynolds number at the point P1 '.
e ^* _TwoIs the differential curve corresponding to the vicinity of the high-flow-side end of region II.
The Reynolds number at a point P2 'where the amount of change in the line is 1/2
When Re^* ₁And Re^* _TwoTo the position where the difference between
It has a get.

According to a third aspect of the present invention, there is provided an element of a fluid vibration type flow meter having a nozzle and a target inside a main body of the element.
Curve St = f (Re) showing the relationship between the Strouhal number St and the Reynolds number Re obtained when changing the flow rate
In the region where the Strouhal number is substantially constant in
Is the low flow-side end point P1 whose Reynolds number is Re ^* ₁ ,
This is a region between the high flow rate end point P2 where the Reynolds number is Re ^* ₂ , and the above Re ^* ₁ is the differential curve d corresponding to the vicinity of the low flow rate end of the area II in the curve St = f (Re).
Point P at 1/2 of the amount of change at St / dRe = f '(Re)
1 ′, and Re ^* ₂ is the Reynolds number at a point P2 ′ of 変 化 of the amount of change in the differential curve corresponding to the vicinity of the high flow rate end of the region II. In this region II, the slope dSt / of the curve St = f (Re)
The target is located at a position where the Strouhal number St ^* when dRe becomes 0 becomes maximum.

[0012]

【Example】

[Embodiment 1] The element of the fluid vibration type flow meter shown in FIG. 1A has a distance (L) between the target 3 and the nozzle outlet 2b.
In order to allow j) to be changed, the target mounting table 7 was configured to be detachable from the target mounting groove 8, and this was used below.

The target 3 is formed on a target setting table 7 as shown in FIG. 1B, and the target setting table 7 is provided on a floor in the downstream side flow path 5 for setting a target. It is housed in the groove 8 detachably, and only the target 3 projects into the downstream flow path 5. Since the target installation groove 8 is cut to a size in which the target installation table 7 can be appropriately stored, the target installation table 7 can be accurately installed. Here, a target-equipped target mounting table having targets installed at various positions was prepared so that the distance Lj could be adjusted.

The dependence of the Strouhal number St on the Reynolds number Re when the air was introduced from the inlet 10 and the flow rate was changed was examined using the above-described element of the fluid vibration type flow meter. As an example of the measurement result, Lj is 1.32 ×
FIG. 2 shows the result when the thickness was 10 ⁻² m. Here, the Reynolds number Re and the Strouhal number St are obtained by the following equations, respectively: Re = ρUD / μ (Equation 1) St = FD / U (Equation 2)

In the above equations 1 and 2, D is the equivalent diameter of the nozzle, and is obtained by the following equation: D = 4WH / 2 (W + H) (Equation 3) Here, U: gas flow rate (m / s), F:
Fluid vibration frequency (Hz), W: nozzle width (m), H: nozzle height (m), ρ: gas density (kg / m ³ ), μ: gas viscosity (Pa · s). In the fluid vibration type flow meter element, the nozzle width W is 2.5 × 10 ⁻³ m, the nozzle height H is 5 × 10 ⁻³ m, and the nozzle length Ln is 2.0 × 1
0 ^-2 m.

In FIG. 2, there is a region where the Strouhal number St shows a substantially constant value. In order to clarify the tendency of the plot of FIG. 2, the data was interpolated with a curve by plotting. The result is shown in FIG. As shown in FIG. 3A, a region where the Strouhal number St shows a substantially constant value is a region II,
Assuming that a region having a lower flow rate than the region is a region I and a region having a high flow rate is a region III, as the range of the region II is wider, the fluid vibration frequency and the flow rate obtained by the element of the fluid vibration type flow meter are larger. It can be seen that the proportional relationship region of is wide, and the rangeability of flow measurement becomes large.

Therefore, in the element of the fluid vibration type flow meter, the distance from the nozzle outlet 2b to the target 3 (FIG. 1)
In this example, elements of a fluid vibration type flow meter with variously changed distances indicated by reference symbol Lj) were manufactured, and the relationship between the Strouhal number St and the Reynolds number Re was examined. As an example,
FIG. 4 shows the result when Lj is 1.44 × 10 ⁻² m.
FIG. 5 shows the results when Lj was 1.37 × 10 ⁻² m.

In comparing the range of the region II, the range was defined by the following method. The value of the slope dSt / dRe of the curve St = f (Re) showing the relationship between the Strouhal number St and the Reynolds number Re shown in FIG. 3A was obtained, and is shown in FIG. 3B. This curve is represented by the curve St =
The differential curve of f (Re) is dSt / dRe = f '(Re).

In this differential curve, as enlarged in FIG. 3 (c-1), a differential curve dSt / d corresponding to the vicinity of the low flow rate end of the region II in the curve St = f (Re).
A point P1 'of 1/2 of the amount of change at Re = f' (Re) is determined, the Reynolds number Re ^* ₁ of the point P1 'is obtained, and St =
A point P1 corresponding to Re ^* ₁ on the f (Re) curve was defined as a boundary point between the region I and the region II.

On the other hand, a boundary point P2 between the region II and the region III
Similarly, as shown in FIG. 3 (c-2), the curve St = f
(Re) The differential curve dSt / dRe = f ′ (Re) corresponding to the vicinity of the high flow rate end of the region II in the (II) of 1
/ 2 point P2 ′, and the Reynolds number R of the point P2 ′
It is determined as a point on the St = f (Re) curve having e ^* ₂ .

The influence of the distance Lj on the Reynolds numbers Re ^* ₁ and Re ^* _{2 at} the boundary points P1 and P2 was examined by changing the distance Lj from the nozzle outlet 2b to the target 3. FIG. 6 shows the result.

FIG. 6 shows that the difference between the Reynolds number Re ^* ₁ and the Reynolds number Re ^* ₂ , that is, the linear relationship region II between the flow rate and the fluid vibration frequency in the fluid vibration type flow meter element is specifically enlarged. It has been found that there is an optimum position, that is, a position optimal for the installation of the target 3 (the distance from the nozzle outlet 2b to the target at that time is Lj ^* ).

That is, in this embodiment, the Reynolds number is about 7 by installing the target 3 at a distance of 1.38 × 10 ^-2 m from the nozzle outlet 2b.
It was found that an excellent linear relationship between the flow rate and the fluid vibration frequency was obtained in the range of × 10 ^{2 to} 1.2 × 10 ⁴ .

[Embodiment 2] Next, in the element of the fluid vibration type flow meter used in Embodiment 1, the boundary point P1 and the boundary point P2 when the distance Lj from the nozzle outlet 2b to the target 3 is changed. The dependence of the constant value St ^* of the Strouhal number on the distance Lj in the divided area II was examined.
FIG. 7 shows the results.

FIG. 7 shows that the constant value of the Strouhal number St ^*
Shows two tendencies depending on the distance Lj from the nozzle outlet 2b to the target 3. That is, a certain distance Lj
^{At the} borderline ^* , when Lj is smaller than Lj ^* , St ^* increases with Lj, and when Lj is larger than Lj ^*, S
t ^* shows a tendency to be substantially constant or to decrease somewhat. This Lj ^*
Is 1.37 × 10 ⁻² m, and this value corresponds to the optimum position of the target installation position shown in FIG.

Therefore, the optimum installation position of the target is obtained as the intersection Lj ^* obtained by plotting the relationship between the constant value St ^* of the Strouhal number and the distance Lj from the nozzle outlet 2b to the target 3. From this, if the dependence of the distance Lj from the nozzle outlet 2b to the target 3 on St ^* is examined, the optimum distance Lj ^* between the nozzle outlet 2b and the target 3 can be determined from a minimum of four experimental data. Therefore, design and development are facilitated, and as a result, the product cost is reduced.

[0027]

According to the present invention, there is no need for a side wall, a return wall, a second target, or the like in the downstream flow path, and it is difficult to design and process the flow path, and the cost of the downstream flow path wall is reduced. Without change, the distance between the nozzle outlet and the target is optimized, resulting in a fluid vibratory flow meter element with a wide linear relationship between flow rate and fluid vibration frequency.

[Brief description of the drawings]

FIG. 1 is a view showing a fluid vibration type flow meter element used in an embodiment. (A) Inside the element body (b) Target and target mounting table

FIG. 2 is a diagram showing the relationship between the Strouhal number and the Reynolds number when Lj = 1.32 × 10 ⁻² m;

FIG. 3A is a diagram illustrating a relationship between the Strouhal number and the Reynolds number when Lj = 1.32 × 10 ⁻² m; (B) It is a figure which shows the differential curve of the curve which shows the relationship between the Strouhal number and Reynolds number shown in (a). (C-1) A partially enlarged view of the differential curve. (C-2) A partially enlarged view of the differential curve.

FIG. 4 is a diagram showing the relationship between the Strouhal number and the Reynolds number when Lj = 1.44 × 10 ⁻² m;

FIG. 5 is a diagram showing the relationship between the Strouhal number and the Reynolds number when Lj = 1.37 × 10 ⁻² m;

FIG. 6 shows a distance L from a nozzle outlet 2b to a target 3.
It is a figure which shows the influence on Reynolds numbers Re ^* ₁ and Re ^* ₂ in boundary points P1 and P2 when j is changed, respectively.

FIG. 7 shows a distance L from a nozzle outlet 2b to a target 3.
FIG. 9 is a diagram illustrating the dependence of a constant value St ^* of the Strouhal number in a region II on a distance Lj when j is changed.

FIG. 8 is a view showing an example of a conventional fluid vibration type flow meter element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upstream flow path 2 Nozzle 2a Nozzle inlet 2b Nozzle outlet 3 Target 4 Pressure outlet 5 Downstream flow path 6a Side wall 6b Side wall 7 Target installation stand 8 Target installation groove 10 Inflow 11 Outflow

Claims (5)

(57) [Claims] 1. A fluid vibration type flow meter element having a nozzle and a target inside the element, a curve St = f (Re) showing a relationship between a Strouhal number St and a Reynolds number Re obtained by changing a flow rate. The region II in which the Strouhal number is substantially constant includes a low flow-side end point P1 in which the Reynolds number is Re ^* ₁ , and a region in which the Reynolds number is Re.
^* ₂ is a region between the high flow rate side end point P2 which is
e ^* ₁ is a differential curve dSt / dRe = f 'corresponding to the vicinity of the low flow rate end of the region II in the curve St = f (Re).
(Re) is the Reynolds number at a point P1 'which is 1/2 of the amount of change, and Re ^* ₂ is 1 of the amount of change in the differential curve corresponding to the vicinity of the high flow rate end of the region II. / 2 point P
A fluid vibration type flow meter element having a target at a position where the difference between Re ^* ₁ and Re ^* ₂ is maximum when the Reynolds number is 2 '. 2. A method for manufacturing a fluid vibration type flow meter element having a nozzle and a target inside the element, wherein a curve St = f () representing the relationship between the Strouhal number St and the Reynolds number Re obtained by changing the flow rate. in Re), region II where Strouhal number is substantially constant, the Reynolds number and the low flow end point P1 which is the Re ^* _1, the Reynolds number is between the high flow rate end point P2 which is the Re ^* ₂ a region, the Re ^* ₁ a, corresponds to the vicinity of the low flow rate side end of the region II in the curve St = f (Re) differential curve dSt / d
Re = Reynolds number at a point P1 'which is 1/2 of the amount of change at f' (Re), and Re ^* ₂ is the change in the differential curve corresponding to the vicinity of the high flow rate end of the region II. 1/2 of the amount
When is the Reynolds number at the point P2 ', Re ^* ₁ and Re
^{* A} method for manufacturing a fluid vibration type flow meter element, wherein a target is placed at a position where the difference from the maximum is ₂ . 3. A device has a nozzle and a target inside.
Fluid vibration type flow meter element, when changing the flow rate
The relationship between the obtained Strouhal number St and Reynolds number Re
In the curve St = f (Re) indicating the relationship,
The region II where the number is substantially constant is where the Reynolds number is Re.
^* ₁, And the Reynolds number is Re.^* _Twoso
This is a region between a certain high flow rate end point P2 and the above Re.^* ₁
Is the low flow rate end of region II in the curve St = f (Re)
The differential curve dSt / dRe = f ′ (R
e) the Reynolds number at a point P1 'of 1/2 of the variation in
Yes, and the above Re^* _TwoIs near the high flow rate end of area II
At a point P2 'of 1/2 of the amount of change in the differential curve corresponding to
In this region II, the curve S
When the slope dSt / dRe of t = f (Re) becomes 0
Strouhal number St ^*Target at the position where
A fluid vibration type flow meter element characterized by having: 4. A method for manufacturing a fluid vibration type flow meter element having a nozzle and a target inside the element, wherein a curve St = f showing the relationship between the Strouhal number St and the Reynolds number Re obtained when the flow rate is changed. in (Re), during the region II where Strouhal number is substantially constant, a low-flow end point P1 that Reynolds number is Re ^* _1, a high-flow end point P2 of the Reynolds number is Re ^* ₂ Area of the
The above Re ^* ₁ is obtained by calculating the differential curve dSt / dRe = corresponding to the vicinity of the low flow rate end of the region II in the curve St = f (Re).
f ′ (Re) is the Reynolds number at a point P 1 ′ which is の of the change amount, and Re ^* ₂ is the change amount of the differential curve in the differential curve corresponding to the vicinity of the high flow rate end of the region II. 1/2 point P
Where the Reynolds number is 2 ', a target is provided at a position where the Strouhal number St ^* when the slope dSt / dRe becomes 0 in this region II is maximized. Device manufacturing method. 5. A method for determining a flow rate measurable range of a fluid vibration type flow meter element having a nozzle and a target inside the element, the method comprising:
Curve St = f (R showing the relationship between t and Reynolds number Re
In e), the region II where the Strouhal number is substantially constant is the low flow rate end point P1 where the Reynolds number is Re ^* _1.
And the high flow rate end point P2 whose Reynolds number is Re ^* ₂ , and the above Re ^* ₁ is a curve St = f (Re)
A Reynolds number in the low flow rate side corresponding to the near end differential curve dSt / dRe = f '1/2 of a point of variation at (Re) P1' region II in, also, the Re ^* ₂ is,
When the Reynolds number at a point P2 ′ of 変 化 of the amount of change in the differential curve corresponding to the vicinity of the high flow rate end of the region II,
A method for determining a flow rate measurable range, wherein the area II is a flow measurable range of a fluid vibration type flow meter element.