JPS6221019A - Fluidic flowmeter - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement of the flow rate regardless of large changes in the flow rate, by connecting two measuring sections each equipped with a reduced part of a pipeline, a jet nozzle and the like in series and providing a diaphragm type governor valve in a bypass passage thus formed. CONSTITUTION:A small passage 13 and a bypass passage 15 are formed with a partition 9 on the downstream in a pipe 1. A pair of first passage formation members 4a and 4b which each form a pipeline reduced part 2 and a jet nozzle 3 is arranged and a pair of control nozzles 6a and 6b and partitions 8a and 8b are provided on the downstream side of a pipeline expanded section 5 to form feedback passages 7a and 7b. At first, because of a small differential pressure P1-P2 between the upstream side pressure P1 and the downstream side pressure P2, with a governor valve C fully closed, a fluid flows to a downstream measuring section (A) from an upstream side measuring section (B). When the differential pressure P1-P2 reaches the second set value, a diaphragm 17 moves to the position of releasing the attraction of a magnet 22 to open a valve body 16 so that the differential pressure P1-P2 lowers to be maintained at the first set value. This permits a small opening measuring section to maintain the measurement of a small flow rate at a better accuracy.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is characterized in that a conduit constriction section, a jet nozzle, and a conduit enlarged section are formed in sequence in the flow direction, and the jet nozzle and the conduit enlarged section are connected in this order. a pair of control nozzles at the boundary in a direction substantially perpendicular to the jetting direction of the jetting nozzle, and
A pair of return channels 41 are formed facing each other and connect each of the control nozzles to the downstream side of the expanded pipe section.
This makes use of the Coanda effect, that is, the phenomenon in which the jet flow from the jet nozzle connected to the pipe constriction part is stabilized along one slope of the pipe enlargement part, and also makes use of the Coanda effect. Utilizing the phenomenon that the jets from the jet nozzles alternately flow along the double-sided slope of the pipe expansion section by blowing fluid out alternately, the fluid frequency change is caused by the change in the flow direction of the jet from the jet nozzles. This invention relates to a feedback type fluid flow meter configured to measure flow rate based on.

[Conventional technology]

Conventionally, only one measuring section has been provided, and the ejection nozzle of the measuring section has simply formed one ejection port (for example, Japanese Patent Laid-Open No. 57-66313).

[Problem that the invention seeks to solve]

However, if we improve the sensitivity by reducing the area of the jet nozzle and make it possible to accurately measure the flow rate at low flow rates, the pressure becomes excessive at high flow rates, which deteriorates the accuracy of flow rate measurement, and conversely,
Increasing the area of the jet nozzle allows for accurate flow measurement at large flow rates, but the flow rate measurement accuracy at small flow rates deteriorates, and there is room for improvement in terms of measurement accuracy when there is a large change in flow rate. there were.

The purpose of the present invention is to rationally modify the measurement configuration so as to be able to always measure the flow rate with high accuracy regardless of large changes in flow rate, and to make it difficult for measurement errors to occur due to the adverse effects of dust. .

[Means for solving problems]

The characteristic configuration of the present invention is that two of the measuring parts, each having a pipe constricting part, a jet nozzle, a pipe expanding part, and a pair of control nozzles and a return flow path, are connected in series. The jet nozzle on the downstream side is formed to have a smaller opening area than the jet nozzle on the upstream side, a bypass flow path that bypasses the downstream measurement section is connected to the upstream measurement section, and the bypass flow path is connected to the upstream measurement section. The diaphragm type governor valve is provided in such a manner that the differential pressure between the upstream side pressure and the downstream side pressure is maintained within the set range when the flow rate exceeds the set flow rate, and its effects are as follows.

[For production]

In other words, when the flow rate is large, the difference between the upstream pressure horn of the downstream measuring section and the downstream pressure becomes large, so the governor valve is activated to increase the downstream pressure and maintain the difference between the measured pressures within the set range. When opened, fluid is allowed to flow out of the bypass channel. When the flow rate is small, the difference between the upstream pressure and the downstream pressure of the downstream measuring section becomes small, so even when the governor valve is fully closed, the differential pressure between the upstream and downstream sides is within the set range, and the fluid is A small amount is supplied from the upstream measurement section to the downstream measurement section without passing through the bypass channel.

Therefore, if the flow rate is measured based on the information from the upstream measuring section when the flow rate is large and based on the information from the downstream measuring section when the flow rate is small, the effect of the upstream measuring section where the opening area of the ejection nozzle is large is Therefore, a large flow rate range can be measured with good accuracy at a small pressure, and a small flow rate range can be measured with high sensitivity and good accuracy due to the effect of the downstream measuring section where the opening area of the jet nozzle is small.

Furthermore, since the bypass flow path is automatically opened and closed by the diaphragm, measurement accuracy can always be maintained at a high level even if there is a large change in flow rate.

Since the differential pressure between the upstream side and the downstream side can be maintained within a set range by the action of the governor valve, the opening and closing of the bypass flow path is performed reliably and stably, and troubles such as chattering do not occur. The flow rate can be measured satisfactorily even in the fL amount range corresponding to the flow rate at which the measurement form should be switched. To explain further, for example, it is possible to automatically open and close the governor valve depending on the pressure change at - location, but the pressure for opening and closing the governor valve fluctuates greatly due to the opening and closing of the governor valve itself, and the opening and closing of the governor valve is repeated. There is a drawback that accuracy is greatly reduced, and the present invention can eliminate such an inconvenient phenomenon.

Furthermore, since the measurement section with a large opening area is placed on the upstream side and the measurement section with a small opening area is placed on the downstream side, dust in the fluid is less likely to be adversely affected by dust at the entrance of the measurement section with a large opening. This makes it difficult for the dust to accumulate on the sides and flow into the measuring section with the small opening, which is susceptible to the adverse effects of dust, and it is possible to maintain a small flow rate measurement with good accuracy using the 'α1 constant section of the small opening.

〔Effect of the invention〕

As a result, when large flow rate changes occur frequently, there is a risk of dust inflow, and accurate flow rate measurement is required, feedback type fluidics are used, for example, in city gas pipes and water supply meters for customers. We are now able to provide flow meters.

Incidentally, when maintaining the pressure drop below 15 mm) IzO, the conventional method described above can only handle a flow rate change of about 50 to 3,000 e/h, but when the measurement configuration of the present invention is used, the flow rate change is 10 to 3,000 e/h. It was able to respond to flow rate changes of about N2/h, and sufficiently achieved the performance required for a residential city gas meter.

〔Example〕

Next, an example will be shown with reference to FIGS. 1 and 2.

On the downstream side of the pipe (1), a small channel (13) with a small opening area and a noibus channel (15) with a large opening area are defined by a partition wall (9). ) is provided with a downstream measuring section (8), which will be described later, and an upstream measuring section (B), which will be described later, is provided on the upstream side of the small channel (13) and the bypass channel (15), and in the bypass channel (15). A diaphragm governor valve (C) is provided to open and close it.

The upstream and downstream measuring sections (A) and (B) have the same configuration and are formed as follows.

A pair of first flow path forming members (4a) and (4b) forming the pipe condensation portion (2) and the jet nozzle (3) are arranged symmetrically with respect to the pipe center axis (1'), Conduit reduction part (2
), the fluid is smoothly guided to the jet nozzle (3), and the fluid is jetted from the jet nozzle (3) almost parallel to the pipe center axis (T'), and the pipe enlarged part (
5), a pair of control nozzles (6a), (6b), and the downstream side of the conduit expansion part (5) and the control nozzle (6a),
A pair of return channels (7a) that communicate with each other (6b) separately.
, (7b) forming a pair of partition walls (8a), (8
b) is arranged symmetrically with respect to the pipe center axis (P), and a pair of control nozzles (6a) and (6b) are placed between the jet nozzle (3) and the pipe enlarged part (5). , a pair of second flow path forming members (12a) which are oriented substantially perpendicularly to the jetting direction of the jet nozzle (3) and are opposed to each other to form a throttled flow path on the downstream side of the expanded pipe section (5). ).

(12b) are arranged symmetrically with respect to the tube center axis (P).

That is, when fluid ejection from the ejection nozzle (3) is started, the ejected fluid flows along one partition wall (8a) due to the above-mentioned Coanda effect, and therefore the control nozzle ( 6a) is given a large amount of fluid energy from the return channel (7a), causing the ejected fluid to flow along the opposite bulkhead (8b), which in turn receives fluid energy from the opposite control nozzle (6b). This causes the ejected fluid to flow again along the partition wall (8a) along which it started, and in this way the fluid from the ejection nozzle (3) follows the partition walls (8a) and (8b) alternately. Thus, as the amount of ejected fluid increases, the flow direction of the ejected fluid changes at a shorter period and in a quantitatively correlated state.

A target (14) is provided on the downstream side of the expanded pipe section (5) to further stabilize the change in flow direction of the ejected fluid.

The opening area of the jet nozzle (3) of the downstream measuring section (A) is smaller, for example, 1728, than the opening area of the jet nozzle (3) of the upstream measuring section (B), The correlation between the flow rate and the frequency of change in flow direction of ejected fluid is configured such that the accuracy is good in the downstream measurement section (8) in the small flow rate range, and the accuracy is good in the upstream measurement section (B) in the large flow rate range. It is.

One of the upstream and downstream measuring sections (A) and (B); a sensor (10) for detecting pressure changes or meteor changes is attached to the flow path (7a), and both sensors (
A flow rate display device (11) that calculates and displays the flow rate from the frequency of pressure or flow rate change based on information from 10).
), and with that, the return type fluid, ri>A't m
This is what makes up the meter.

The governor valve (C) has a pressure difference (PI-P2) between the upstream pressure (P, ) and the downstream pressure (P2) at a flow rate higher than the set flow rate.
In order to maintain it within the set range, it is configured as follows.

A diaphragm (17) linked to a valve body (16) that opens and closes the bypass flow path (15) is connected to a pressure chamber (18a) communicating with the upstream side of the valve body (16) through a passage (19), and a valve body ( 1
A spring (20) is provided facing the pressure chamber (18b) that communicates with the downstream side of the diaphragm (17), and biases the diaphragm (17) in the valve closing direction. A magnet (22) acts to hold the valve in the closed position.
) is attached to the valve body (16), and between the diaphragm (17) and the diaphragm (23) attached to the valve body (16), the diaphragm (17) is attached to the valve body (16) and the diaphragm (17) is brought into the fully closed position by the spring (25).
) that allows movement within a certain range in the valve opening direction (
D) is provided. The locking piece (24) restricts the swinging of the iron (23).

In other words, the change in differential pressure (PI-112) due to the change in flow rate is as shown in FIG. 3, for example, and the details are as follows.

Assuming that the flow rate gradually increases from zero, initially the differential pressure (P
Since the governor valve (C) is small, the fluid flows from the upstream measuring section (B) to the downstream measuring section (A), and the differential pressure (p+-pz) is at the point (I). ) to point (II) corresponding to the first set differential pressure (ΔPI), and the differential pressure (p+-pz) rises to point (0) due to the valve closing action of the magnet (22).
) to point (c).

Then, the differential pressure (r'+-Pz) becomes the second set differential pressure (ΔP2
), the diaphragm (17) moves to the position where the adsorption of magneto (22) is released, and the differential pressure (PI-
The valve body (16) is opened so that the differential pressure (PI-PK) is maintained at the first set differential pressure (Δp+), and the differential pressure (PI-PK) decreases from point (c) to point (d). The differential pressure (PI-PK) is initially maintained constant by changing the opening degree of the governor valve (C) commensurate with the flow rate, and finally rises slightly after the governor valve (C) is fully opened. , changes from point (D) to point (N) corresponding to the maximum flow rate.

The flow rate display device (11) includes a means (lla) for determining whether the frequency in the first information from the sensor (10) of the upstream side measuring section (B) is equal to or lower than a setting, and a means for determining (11a). ), when the frequency of the first information is below the setting, the sensor (10) of the downstream measuring section (A)
means (llb) for calculating the flow rate based on the second information from the source and based on the first information when the vibration frequency of the first information exceeds a set value; and means (llb) for displaying the calculated flow rate. llc), for example 10 to 3,000
If the differential pressure is 15 m+e over a wide range of N /h
□This allows accurate measurements to be made while keeping the value below 0.

Further, the set frequency in the determination means (lla) is set to the first
The minimum frequency in the information and the frequency corresponding to the closing of the valve body (16) are set to approximately the intermediate value, and the flow rate measurement using the first information is checked to ensure that there is no error due to linearity deterioration in the correlation between flow rate and frequency. It is configured so that it can be carried out in a state where the number of measurements is extremely small, and so that measurement errors due to the opening of the valve body (16) do not occur.

That is, before the valve body (16) opens, the flow ■ is calculated based on the first information, and conversely, when the valve body (16) closes, the frequency of the valve closing and the lowest vibration of the first information are calculated. When the frequency is below the intermediate frequency of the number, the flow rate is calculated using the second information.

[Another example]

Next, another embodiment will be described.

The specific configuration of the governor valve (C) can be changed as appropriate; in short, it may be configured to open so that the differential pressure (P, -PK) is maintained within the set range when the flow rate is higher than the set flow rate.

The detection method, configuration, number of sensors, etc. of the sensor (10) can be changed freely, for example, both return channels (7a) and (7b)
A sensor (10) may be provided at. Further, the device (11) for detecting and displaying the flow rate can also be modified in various ways.

Meteor meters are mainly used for household purposes such as fuel gas and water supply, but their use is not specific.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line nn in FIG. FIG. 3 is a graph illustrating changes in differential pressure with changes in flow rate. (2)...Pipe constriction section, (3)...Ejection nozzle, (5)...Pipe enlargement section, (6a)
, (6b)・Old...control nozzle, (7a), (7
b)...Return flow path, (15)...Bypass flow path, (8)...Downstream measurement section, (B)...
・Eye: Upstream measurement section, (C)...Governor valve.

Claims (1)

[Claims] Pipe constriction section (2), jet nozzle (3) and conduit enlargement section (
5) are formed in series in the flow direction, and a pair of control nozzles (6a) and (6b) are provided at the boundary between the jet nozzle (3) and the expanded pipe section (5). ) are formed in a direction substantially perpendicular to the ejection direction of the control nozzles (6a) and (6b), and are formed opposite to each other, and connect the downstream side of the conduit enlarged portion (5) with each of the control nozzles (6a) and (6b). Measuring sections (A) and (B) forming a pair of return channels (7a) and (7b)
), the two measuring parts (A) and (B) are connected in series, and the jet nozzle (3) of the downstream measuring part (A) is connected in series. A bypass flow path (15) that is formed to have a smaller opening area than the jet nozzle (3) of the upstream side (B) and bypasses the downstream measurement section (A) is provided in the upstream measurement section (B). A diaphragm governor valve (C) is connected to the bypass flow path (15).
) is provided so that the differential pressure (P_1-P_2) between the upstream pressure (P_1) and the downstream pressure (P_2) is maintained within the set range when the flow rate is higher than the set flow rate.