JP4007652B2 - Flowmeter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow meter, and more particularly to a flow meter suitable for gas flow measurement.
[0002]
[Prior art]
Since the characteristics of the speculative flow meter are usually greatly affected by the piping conditions of the upstream and downstream parts, a straight pipe part with an appropriate length as a rectifying part is required in the upstream part and the downstream part. Is determined to be at least 10 times the diameter D of the flow meter.
[0003]
Moreover, in the conventional speculative flow meter, the flow rate is measured based on the signal of a single sensor provided in the flow path.
[0004]
[Problems to be solved by the invention]
Since the flow rate of the flow meter is determined by (flow velocity × channel cross-sectional area), the conventional technology requires a large-capacity flow meter because it is necessary to install a rectification unit corresponding to the cross-sectional area of the measurement unit in the upstream and downstream portions. There was a problem with downsizing.
[0005]
In addition, the conventional flow meter using a single sensor has a problem in that the range of flow measurement is limited by the characteristics of the sensor, so that the expansion of the rangeability of the flow meter is limited.
[0006]
Accordingly, a first object of the present invention is to provide a flow meter that can solve the problems of the prior art and can be downsized even with a large capacity.
A second object is to further expand the rangeability.
[0007]
[Means for Solving the Problems]
In order to achieve the first object, the invention of claim 1 provides:
The measurement flow path (3) includes a first cylindrical surface (4) and an axis Y having an axis Y-Y perpendicular to the axis XX of the inlet flange (1) and the outlet flange (2) constituting the pipe connection portion. A cross-section sandwiched between second cylindrical surfaces (5) having an axis parallel to -Y is a donut-shaped channel, and the first cylindrical surface (4) and the second cylindrical surface are eccentric to each other. Arranged,
The diameter (Ф ₁ ) of the first cylindrical surface (4) is smaller than the diameter (Ф ₂ ) of the second cylindrical surface (5) , and the first cylindrical surface (4) is the second cylindrical surface ( 5) The amount of eccentricity (B) is determined so as to fit inside,
Of measurement flow path sandwiched between the two cylindrical faces (3), the flow rate of at least a gap narrow flow path portion (H ₁ parts) sensor installed in, measures the flow rate based on the signal of the sensor It is a total .
[0008]
In order to achieve the first object, the invention of claim 2 is the flow meter of claim 1,
Of measurement flow path (3), is characterized in that it has installed a sensor for detecting the flow rate in the gap wide flow path portion (H ₂ parts).
[0010]
The invention of claim 3 is characterized in that, in the invention of claim 2 , one sensor is a thermal flow sensor and the other sensor is an ultrasonic sensor.
[0011]
The invention of claim 4 is the flowmeter of claim 2 ,
Both sensors are characterized by being thermal flow sensors.
The invention of claim 5 is the flow meter of claim 2 ,
Both sensors are ultrasonic sensors.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, preferred embodiments of the present invention will be described based on examples of the drawings.
FIGS. 1A and 1B are flow measurement principle diagrams of the first embodiment, and an inlet flange 1 and an outlet flange 2 having an axis XX constitute a pipe connecting portion.
[0013]
The measurement flow path 3 is installed orthogonally to the flanges 1 and 2 as shown in FIG. 1A, and the cross section of the flow path is formed in a donut shape as shown in FIG. The measurement channel 3 has a cross section sandwiched between a first cylindrical surface 4 having an axis YY orthogonal to the axis XX and a second cylindrical surface 5 having an axis parallel to the axis YY. Since the cylindrical surfaces 4 and 5 are eccentrically arranged in the donut-shaped flow path, the gap between the cylindrical surfaces is continuously changed from a narrow portion to a gradually wide portion.
[0014]
In FIG. 4B, reference numeral H ₁ indicates the narrowest gap, and H ₂ indicates the widest gap. Reference B is the amount of eccentricity of the cylindrical surfaces 4 and 5. 4a indicates the center through which the axis YY of the first cylindrical surface 4 passes, and 5a indicates the center through which the axis of the second cylindrical surface 5 passes.
[0015]
Diameter [Phi ₁ of the first cylindrical surface 4 is smaller than the diameter [Phi ₂ of the second cylindrical surface, and a first cylindrical surface 4 is the eccentricity B are determined to fit inside the second cylindrical surface 5 Thus, a flow rate measuring unit is installed inside the dual structure, and the flow rate is detected by the flow sensors 6 and 7.
[0016]
The flow sensors 6 and 7 are so-called flow rate detection sensors, which are thermal flow rate detection elements using a platinum thin film resistor, which are used for measuring a small flow rate range of a home gas meter, and the mass obtained from the flow sensors 6 and 7. The volume flow rate is obtained by performing arithmetic processing based on the output corresponding to the flow rate.
[0017]
In general, when the flow path cross section is not a circular cross section, the pressure difference (pressure loss) ΔP between the inlet and outlet of the flow rate measuring unit is H corresponding to the diameter D of the circular cross section, V is the flow velocity, f is the pipe friction coefficient, Where ρ is the density, μ is the viscosity, L is the length of the flow rate measuring unit, and g is the gravity conversion coefficient.
ΔP = (4fρLV ² ) / ( ² gH)
It is expressed.
[0018]
Accordingly, as shown in FIGS. 1 (a) and 1 (b), pressure is applied to both the gaps H ₁ and H _{2 in} the measurement flow path 3 having the gaps H ₁ and H ₂ sandwiched between the eccentric cylindrical surfaces 4 and 5. Since the difference (pressure loss) ΔP is the same, assuming that the flow velocities at the gaps H ₁ and H ₂ are V ₁ and V ₂ , respectively, the gas velocity ratio V ₁ / V ₂ is
_{V 1 / V 2 = (H} 2 / H 1) 1/2
It becomes.
[0019]
When the dimensions of H ₁ and H ₂ are selected as H ₁ = 3 mm and H ₂ = 27 mm, the wide flow path portion with H ₂ = 27 mm has a flow velocity three times that of the narrow flow path portion with H ₁ = 3 mm.
Single range catcher Stability and measuring the flow rate of the flow sensor 1: 1000 and 0.008~8m / s and assuming, H ₂ parts becomes measurable flow rate range of 8m / s at 24m / s at H ₁ parts small If the flow rate range is measured by the flow sensor 7 of the H ₂ part and the large flow rate range is measured by the flow sensor 6 of the H ₁ part, the cross-sectional average flow velocity of the entire flow rate is between about 0.008 to 24 m / s. 1: 3000 measurement is possible, and the flow rate can be measured with a rangeability that is three times the flow sensor performance.
[0020]
The flow rate measurement part of length L is installed independently in the inside made into the double structure, and it is set as the stable flow. Then, the measuring unit in place of the normally required 10D for stable growth of the velocity distribution, are used 10H ₁ or 10H _2.
[0021]
In the embodiment, since 10H ₁ = 10 × 3 = 30 mm, 10H ₂ = 10 × 27 = 270 mm, the measurement flow path of L = 270 mm is installed at a position orthogonal to the connecting piping portion, and upstream and downstream Prevents adverse effects of flow.
[0022]
In FIG. 1A, reference numeral 8 denotes a partition wall between the upstream side and the downstream side.
Further, 10 represents a flow velocity distribution, and 3 times 3V ₁ is with H ₂ parts based on V ₁ of the H ₁ parts.
[0023]
In the first embodiment shown in FIGS. 1A and 1B, sensors 6 and 7 for detecting a flow rate are respectively installed in a narrow channel portion (H ₁ portion) and a wide channel portion (H ₂ portion). but was, among the measurement flow path sandwiched between the two cylindrical surfaces 4 and 5 with each other, the sensor was placed in H ₁ part of at least the gap narrow flow path portion, measuring the flow rate on the basis of the signal of the sensor You may make it do.
[0024]
FIGS. 2A and 2B differ from the first embodiment only in that an ultrasonic sensor 9 is provided on the large flow rate measurement side and used instead of the flow sensor 6. By doing so, an ultrasonic sensor excellent in long-term stability is used for a large flow rate measurement value, and the reliability as a flow meter is improved. In general, since the measurement range of an ultrasonic sensor is 0.02 to 20 m / s on the high speed side, the combination with a flow sensor is more effective.
[0025]
For example, the measurement range of the flow sensor 7 is 0.008 to 8 m / s, its rangeability is 1: 1000, the measurement range of the ultrasonic sensor 9 is 0.02 to 20 m / s, and its rangeability is 1: 1000. Then, since H ₁ : H ₂ = 1: 9 and V ₁ : V ₂ = 1: 3, the overall ratio is 1: 7500 of 0.008 to 60 m / s. In this case, 60 m / s of 0.008 to 60 m / s is obtained from 20 m / s × 3.
[0026]
In the embodiment shown in FIGS. 2A and 2B, a thermal flow sensor is used for one sensor and an ultrasonic sensor is used for the other sensor. However, both sensors may be thermal flow sensors.
Also, both sensors can be ultrasonic sensors.
[0027]
【The invention's effect】
Since the flowmeter of the present invention is configured as described above, the dimension (overall length) between the pipe connecting portions (flange) can be reduced, and the flowmeter can be downsized for its capacity.
[0028]
In addition, rangeability can be expanded.
In the invention of claim 3 , rangeability can be expanded more effectively by taking advantage of the features of each sensor.
[Brief description of the drawings]
FIG. 1 is a principle view of a first embodiment of the present invention, where (a) is a longitudinal sectional view and (b) is a transverse sectional view.
FIG. 2 is a principle view of a second embodiment of the present invention, where (a) is a longitudinal sectional view and (b) is a transverse sectional view.
[Explanation of symbols]
1, 2 Flange (Piping connection)
3 Measurement channel 4, 5 Cylindrical surface 6, 7 Flow sensor 9 Ultrasonic sensor

Claims (5)

The measurement flow path (3) includes a first cylindrical surface (4) and an axis Y having an axis Y-Y perpendicular to the axis XX of the inlet flange (1) and the outlet flange (2) constituting the pipe connection portion. A cross-section sandwiched between second cylindrical surfaces (5) having an axis parallel to -Y is a donut-shaped channel, and the first cylindrical surface (4) and the second cylindrical surface are eccentric to each other. Arranged,
The diameter (Ф ₁ ) of the first cylindrical surface (4) is smaller than the diameter (Ф ₂ ) of the second cylindrical surface (5) , and the first cylindrical surface (4) is the second cylindrical surface ( 5) The amount of eccentricity (B) is determined so as to fit inside,
Of measurement flow path sandwiched between the two cylindrical faces (3), that at least the gap narrow flow path portion (H ₁ parts) sensor installed in, measures the flow rate based on the signal of the sensor A flow meter characterized by _{2. The} flowmeter according to claim 1, wherein a sensor for detecting a flow rate is also installed in a flow channel portion (H2 portion) having a wide gap in the measurement flow channel (3) . 3. The flowmeter according to claim 2 , wherein one sensor is a thermal flow sensor and the other sensor is an ultrasonic sensor. 3. A flow meter according to claim 2, wherein both sensors are thermal flow sensors. 3. A flow meter according to claim 2, wherein both sensors are ultrasonic sensors.

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