JP4936856B2 - Flowmeter - Google Patents

Description

  The present invention relates to a flow meter that measures the flow rate of a fluid such as LP gas, city gas, and water.

  2. Description of the Related Art Conventionally, an ultrasonic flowmeter that measures flow velocity using ultrasonic waves is known as a flow measurement device that measures the flow rate of a fluid such as LP gas, city gas, and water. In such an ultrasonic flowmeter, for example, an ultrasonic wave is oscillated toward the upper side or the lower side of the fluid flow direction on the wall portion (mounting wall surface) of the measurement channel for allowing the fluid to pass, and then the flow direction. A pair of transmission / reception transducers (ultrasonic sensors) that receive ultrasonic waves coming from the upper side or the lower side are attached. In order to asymmetric the flow velocity distribution on the inlet side of the measurement flow path and bias the position where the maximum value of the flow velocity is generated to one side from the center of the measurement flow path, an asymmetry consisting of a bent portion, a stepped portion, an irregularly shaped portion, etc. It is disclosed that a flow promoting means is provided (see Patent Document 1).

Japanese Patent No. 3436247

  According to Patent Document 1, by providing an asymmetric flow promoting means, the difference in the correction coefficient between the laminar flow area and the turbulent flow area is reduced, and even if the viscosity coefficient changes depending on the type of fluid, the change in the correction coefficient is reduced. Is possible. However, in many flowmeters including ultrasonic flowmeters, the transmitter / receiver transducer (measurement unit) usually has a measurement line that is higher than the measurement channel (straight channel for measurement) in the vertical direction because of the arrangement space. It is arranged so that it is located in the center. Therefore, by providing the asymmetric flow promoting means as in Patent Document 1, the flow velocity distribution in the height direction tends to be asymmetric (uneven). Therefore, it is necessary to arrange a rectifying means for symmetrizing (equalizing) the flow velocity distribution like a rectifying element on the front side (the upper side in the flow direction) of the measuring unit.

  The problem of the present invention is to devise the cross-sectional shape of the flow path from the introduction-side flow path to the measurement linear flow path, thereby to obtain the flow velocity distribution of the fluid in the direction perpendicular to the flow direction without arranging a rectifying means. It is an object of the present invention to provide a flow meter that can be easily equalized and symmetrized.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the flow meter according to the present invention is:
An introductory side channel having a predetermined channel cross-sectional area for allowing fluid to pass therethrough, and is formed in a straight line so as to intersect the introductory side channel and from the introductory side channel to measure the flow rate of the fluid A flow meter including a measurement linear channel having a small channel cross-sectional area,
In the common cross section passing along the flow direction of the fluid flowing through the introduction side flow path and the measurement straight flow path and passing through the center of both flow paths,
A curved direction changing portion that changes the flow of the fluid in a form following the outlet side end portion of the introduction side flow path;
A flow path cross-sectional reduction part that is connected and formed so as to include the outlet side end part of the direction change part, and whose flow cross-sectional area decreases toward the lower side in the flow direction on the curved outer peripheral side and / or curved inner peripheral side of the direction change part. When,
The flow passage cross-section is connected and formed so as to follow the flow passage cross-sectional reduced portion, and the flow passage cross section on the curved outer peripheral side continuously expands gradually toward the lower side in the flow direction or rapidly expands and changes in a staircase fashion. Including an outer peripheral enlarged portion connectable to a road,
The flow velocity distribution of the fluid that is relatively faster on the curved outer circumferential side than the curved inner circumferential side while flowing through the direction changing portion and the flow path cross-sectional reduced portion is the flow direction while passing through the outer circumferential enlarged portion. It is characterized by being equalized and / or symmetrized in an orthogonal direction.

Further, in order to solve the above problems, when an ultrasonic flowmeter is used for the flowmeter according to the present invention,
An introductory side channel having a predetermined channel cross-sectional area for allowing fluid to pass therethrough, and is formed in a straight line so as to intersect the introductory side channel and from the introductory side channel to measure the flow rate of the fluid Has a small channel cross-sectional area and oscillates ultrasonic waves toward the upper or lower side of the fluid flow direction on the mounting wall of the wall, and / or ultrasonic waves coming from the upper or lower side of the flow direction A flowmeter including a measurement linear flow channel to which a transmission / reception transducer for receiving
In the common cross-section along the flow direction of the fluid flowing through the introduction-side flow path and the measurement linear flow path and through the center of both flow paths and parallel to the mounting wall surface to which the transmission / reception vibrator is mounted,
A curved direction changing portion that changes the flow of the fluid in a form following the outlet side end portion of the introduction side flow path;
A flow path cross-sectional reduction part that is connected and formed so as to include the outlet side end part of the direction change part, and whose flow cross-sectional area decreases toward the lower side in the flow direction on the curved outer peripheral side and / or curved inner peripheral side of the direction change part. When,
The flow passage cross-section is connected and formed so as to follow the flow passage cross-sectional reduced portion, and the flow passage cross section on the curved outer peripheral side continuously expands gradually toward the lower side in the flow direction or rapidly expands and changes in a staircase fashion. Including an outer peripheral enlarged portion connectable to a road,
The flow velocity distribution of the fluid that is relatively faster on the curved outer circumferential side than the curved inner circumferential side while flowing through the direction changing portion and the flow path cross-sectional reduced portion is the flow direction while passing through the outer circumferential enlarged portion. It is characterized by being equalized and / or symmetrized in an orthogonal direction.

  According to these flow meters, while the fluid to be measured (for example, LP gas) flows through the direction changing portion and the flow path cross-sectional reduction portion located on the upper side in the flow direction of the measurement linear flow channel, the flow velocity distribution is curved on the inner circumference. It tends to be relatively faster on the curved outer peripheral side than on the side. However, the flow velocity distribution is even in the direction orthogonal to the flow direction while the flow path cross section on the curved outer peripheral side passes through the outer peripheral enlarged part where the lower side in the flow direction continuously expands gradually or changes stepwise. And / or symmetrized. In other words, the drift (flow where the center of the flow is biased toward the curved outer periphery) generated in the direction change section or the flow path cross-section reduction section is corrected at the outer peripheral expansion section (the center of the flow is at the center of the measurement linear flow path). The flow velocity distribution is adjusted symmetrically so that Therefore, the measurement line (for example, a pair of transmission / reception transducers) is placed at the center of the flow velocity distribution to stably measure the central (average) flow velocity of the fluid to be measured flowing through the measurement straight flow path. Therefore, the flow rate can be measured with high accuracy over a wide range from the laminar flow region to the turbulent flow region. The outer periphery enlargement part has a curved or linear gradient (inclination) toward the lower side in the flow direction, and is formed in a shape that gradually and gradually expands in a stepwise manner, or abruptly expands and changes in a staircase shape. Or can be formed into a shape to be formed.

  And in the flow path cross-section reduction part, the flow path cross-sectional area is reduced toward the lower side in the flow direction, and there is no need to arrange a rectifying means such as a rectifying element in the flow path. The flow rate of the fluid flowing through the measurement linear flow path can be increased, and the measurement range in the flow rate measurement unit can be expanded. Moreover, since the rectifying means is not provided, the cost of the flow meter can be reduced. When the radius of curvature on the curved outer peripheral side of the direction changing portion (or the subsequent flow path cross-sectional reduced portion) is set to be larger than the radius of curvature on the curved inner peripheral side, Therefore, the pressure loss can be further suppressed and the measurement range can be expanded.

  As described above, in the ultrasonic flowmeter, the measurement line of the transmission / reception vibrator is arranged at the center position of the flow velocity distribution of the measurement linear flow path. Similarly, the present invention can also be applied to a type of flow meter in which the measurement line of the measurement unit is arranged at the center position of the flow velocity distribution of the measurement linear flow path. Examples of such a type of flow meter include a Pitot tube flow meter (measurement unit: Pitot tube) and a vortex flow meter (measurement unit: vortex generator).

  The flow path cross-sectional reduction part is smoothly connected in the tangential direction from the end position of the direction changing part on the curved outer peripheral side, and is connected to the outer peripheral enlarged part including the outer peripheral straight part for stabilizing the flow direction. It is desirable that the curved inner peripheral side includes an inner peripheral curved portion that is smoothly connected in a curved shape from the terminal position of the direction changing portion.

  Since the fluid that has flowed into the direction changing section is in the process of changing the direction from the introduction-side flow path (for example, downward) to the measurement linear flow path (for example, horizontal direction), the velocity component in the intermediate direction (for example, diagonally downward) is large. . Since the fluid having such a velocity component moves to the downstream side in the flow direction along the curved outer peripheral side of the direction changing portion, the flow direction is still uneven and unstable even when reaching the end position of the direction changing portion. It is in a state. In addition, the flow velocity distribution in the direction orthogonal to the flow direction at the end position of the direction changing portion has a non-uniform (asymmetric) state in which the flow velocity increases toward the curved outer peripheral side. As described above, a flow (corresponding to the above-described drift) is generated in the direction changing portion (and the inlet side of the flow path cross-sectional reduction portion) in which the flow direction is unstable and the flow velocity is uneven (asymmetric).

  Therefore, first, the flow path cross-sectional reduced portion is formed with an outer peripheral straight line portion smoothly connected in a tangential direction from the end position of the direction changing portion on the curved outer peripheral side, thereby eliminating irregularities and instabilities in the flow direction. That is, the outer peripheral straight portion functions as a stabilizing section in the flow direction. Next, the outer peripheral straight line portion is connected to the outer peripheral enlarged portion, so that the flow path on the curved outer peripheral side widens and the uneven flow velocity is reduced (corresponding to the correction described above). That is, the outer peripheral enlarged portion functions as a flow velocity relaxation section (flow velocity distribution equalization / symmetrization section). In other words, the drift that occurs on the inlet side of the direction changing section and the flow path cross-section reduction section is stabilized in the flow direction at the outer peripheral straight section formed on the curved outer circumference side of the flow path cross-section reduction section, and further connected to the tip. The flow velocity distribution is equalized and symmetrized at the outer peripheral enlarged portion.

As a first specific example, the flow path cross-sectional reduction portion is configured to include an inner peripheral straight portion smoothly connected in the tangential direction from the end position of the inner peripheral curved portion, and the inner peripheral straight portion is a flow of the outer peripheral straight portion. which may be arranged in Oite parallel shape to the end portion and the flow direction of the direction downstream side. In this way, the flow direction can be further stabilized by the parallel arrangement of the inner peripheral linear portion and the outer peripheral linear portion.

  At this time, the outer peripheral straight line portion and the inner peripheral straight line portion of the flow path cross-sectional reduction portion can be arranged in parallel with the measurement straight flow path. Accordingly, the flow direction can be easily stabilized without using a rectifying means (for example, a rectifying element).

  On the other hand, as a second specific example, the flow path cross-sectional reduction part is configured to include an inner peripheral straight part smoothly connected in the tangential direction from the end position of the inner peripheral curved part, while the outer peripheral straight part is superior in the flow direction. A first straight portion located on the side and a second straight portion located on the lower side and reducing the cross-sectional area of the flow path. The first straight portion is an inner circumferential curved portion, and the second straight portion is an inner portion. There may be cases where they are arranged opposite to the circumferential straight portion. By reducing the cross section of the outer peripheral straight section in two stages, the flow direction stabilization section is formed relatively long, so that the flow direction can be stabilized over a wide range regardless of the laminar flow region or the turbulent flow region.

  At this time, the first straight line portion, the second straight line portion, and the inner peripheral straight line portion of the flow path cross-sectional reduction portion can be arranged in parallel with the measurement straight flow path. Accordingly, the flow direction can be easily stabilized without using a rectifying means (for example, a rectifying element).

  If the inlet flow channel and the measurement straight flow channel are arranged orthogonally and the cross-sectional area of the measurement straight flow channel is constant with respect to the flow direction, the flow meter can have a compact box shape. Can be formed. Moreover, since the flow velocity distribution equalized (symmetrized) at the outer peripheral enlarged portion is stably maintained even in the measurement straight flow path, the accuracy of flow rate measurement is improved.

Example 1
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an overall perspective view of an embodiment of an ultrasonic flow meter used as a general residential gas meter or the like. The ultrasonic flow meter 100 (flow meter) includes a main body unit 10, an intermediate flow path forming unit 20, and a shut-off valve 30, and the main body unit 10 includes a main body portion 11 and a lid portion 17.

  FIG. 2 is a front sectional view of the ultrasonic flowmeter 100, and the AA sectional view of FIG. 2 is shown in FIG. As shown in FIG. 2, the main body 11 has a rectangular parallelepiped shape as a whole, and an inlet 12 connected to the upstream gas pipe and an outlet 13 connected to the downstream gas pipe are formed on the upper surface thereof. Each is open. In addition, a main body flow path 14 for allowing a gas (fluid) to pass between the inflow port 12 and the outflow port 13 is formed therein. A main body flow path cutting portion 15 is formed in the lower part of the main body portion 11 from the back side in FIG. 2 toward the front side (fitting direction). The main body flow path cutting portion 15 is provided with a packing 17a (seal material). It is covered from the outside by the cover part 17 (refer FIG. 3). A pair of window holes 16, 16 (see FIG. 1) communicating with the main body flow path cutting portion 15 are opened on the outer surface of the main body portion 11 on the front side in the fitting direction (front side in FIG. 2).

  As shown in FIG. 3, when the intermediate flow path forming unit 20 is fitted into the main body flow path cutting section 15 of the main body section 11 from a direction (fitting direction) perpendicular to the gas flow direction, An intermediate flow path 21 connected to the path 14 is formed through. The intermediate flow path 21 is connected to the main body flow path 14 in a vertically continuous inlet-side connection flow path 21b (introduction-side flow path) and outlet-side connection flow path 21c (outflow-side flow path). Consists of a horizontal linear intermediate flow channel 21a (measurement linear flow channel) that is continuous with the flow channels 21b and 21c and is disposed along the lower surface of the main body 11 in a form substantially orthogonal to the main body flow channel 14. (See FIG. 2). Further, the intermediate flow path forming unit 20 is integrally formed with a pair of projecting portions 22 and 22 on the front side in the fitting direction corresponding to the pair of window holes 16 and 16 opened in the main body portion 11. Further, the pair of projecting portions 22 and 22 of the intermediate flow path forming unit 20 has a pair of transmission / reception vibrators 23a and 23b of the ultrasonic sensor 23 in order to measure the flow rate of the gas passing through the linear intermediate flow path 21a. Are detachably attached. The axial orthogonal cross-sectional area (flow-path cross-sectional area) of the straight intermediate flow path 21a is made smaller (throttle) than the axial-perpendicular cross-sectional area (flow-path cross-sectional area) of the main body flow path 14 and the inlet-side connecting flow path 21b. Are formed in a certain size. As a result, the flow rate of the gas flowing through the linear intermediate flow path 21a is increased and kept constant, and the measurement accuracy of the flow rate (flow rate) by the ultrasonic sensor 23 is increased. The main body flow path 14 between the inlet 12 and the intermediate flow path 21 is provided with a shut-off valve 30 that blocks the gas flow in the main body flow path 14 (see FIG. 2).

  Therefore, in FIG. 3, when the intermediate flow path forming unit 20 is fitted to the main body flow path cutting portion 15 of the main body portion 11 so that the intermediate flow path 21 communicates with the main body flow path 14, the protrusions 22, 22 become the main body. Projecting from the window holes 16 and 16 of the portion 11 to the outside. And each protrusion part 22 and 22 seals each window hole 16 and 16 via packing 16a (sealing material), respectively. Further, the transmission / reception transducers 23a and 23b of the ultrasonic sensor 23 are inserted from the outside into the receiving holes 22a and 22b of the protrusions 22 and 22, respectively, and are attached to a mounting screw (a mounting member; not shown) or a pressing plate (pressing). It is detachably fixed by a member (not shown).

  As shown in FIG. 3, the linear intermediate flow path 21a (intermediate flow path 21) has a long side L in the fitting direction to the main body flow path cutting portion 15 and a short side S in the vertical direction (see FIG. 2). It is formed in a rectangular shape. The ultrasonic sensor 23 is configured in the following reflective V-shaped arrangement. That is, the transmitting / receiving vibrators 23a and 23b on the mounting wall surface 21d (wall portion) forming the short side on the front side in the fitting direction in the cross section orthogonal to the flow direction of the straight intermediate flow path 21a are separated by a predetermined distance W in the flow direction. A wall surface (wall portion) that is attached and forms a short side on the rear side in the fitting direction is defined as a reflecting surface 21e.

  Returning to FIG. 1, the output signals obtained by the transmission / reception transducers 23 a and 23 b (sensor elements) of the ultrasonic sensor 23 are transmitted to the flow rate calculation processing circuit 24 via the lead wires 25 and 25 to calculate the gas flow rate. The notification is made using a flow rate display unit (not shown) or the like. The transmission / reception vibrators 23a and 23b, the flow rate calculation processing circuit 24, the lead wires 25 and 25, the flow rate display unit, and the like constitute a flow rate measurement unit M. Since the lead wires 25 and 25 are drawn out from the ultrasonic sensor 23 (transmission / reception transducers 23a and 23b) provided to project outside from the window holes 16 and 16, the measurement gas leaks to the outside through the core wire portion and is airtight. Therefore, there is no insufficiency and measurement accuracy is not lowered. Thus, the airtightness of the three parts of the main body part 11, the lid part 17, and the intermediate flow path forming unit 20 is ensured, and the lead wires 25 and 25 are located outside the flow path. There will be no fire caused by sparks. Note that a rectifying element (rectifying member) is provided between the inlet-side connecting flow path 21b and the straight intermediate flow path 21a to suppress the disturbance of the measurement gas flow in the flow path and make the speed distribution uniform. (See FIGS. 2 and 3).

  Next, FIG. 4 is an enlarged explanatory view of main parts showing an embodiment of the flow path configuration of the intermediate flow path in FIG. In the intermediate flow path 21 shown in FIG. 4, there are a direction changing portion 211, a cross section of the flow path between the inlet-side connection flow path 21 b (main flow path 14) and the straight intermediate flow path 21 a that are arranged substantially orthogonally. The reduced portion 212 and the outer peripheral enlarged portion 213 are connected and formed in this order from the upper side toward the lower side in the flow direction.

  The direction changing portion 211 is formed in a curved shape for changing the direction of gas flow by about 90 °, following the outlet side end portion of the inlet side connecting channel 21b arranged substantially downward. The curved shape of the direction changing portion 211 is formed in an arc shape on both the inner side and the outer side, and the radius R1 on the curved outer peripheral side is set to be larger than the radius R2 on the curved inner peripheral side (for example, R1 = 2 × R2). As a result, the reduction ratio of the flow passage cross-sectional area in the flow direction in the flow passage cross-section reduction section 212 described later can be increased, so that the flow rate measurement section M (FIG. 1) is increased by increasing the flow velocity in the linear intermediate flow path 21a. In addition, it is possible to improve the measurement accuracy in the reference) and to suppress pressure loss.

  The channel cross-section reducing portion 212 is connected and formed so as to partially overlap the outlet-side end portion of the direction changing portion 211. Therefore, the flow path cross-sectional reduction part 212 and the direction change part 211 have a form in which the flow path cross-sectional area is reduced toward the lower side in the flow direction on the curved outer peripheral side and the curved inner peripheral side. On the other hand, the outer peripheral enlarged portion 213 formed to be connected to the flow passage cross-section reducing portion 212 is formed such that the flow passage cross section on the curved outer peripheral side is enlarged toward the lower side in the flow direction and connected to the linear intermediate flow passage 21a.

  Specifically, on the curved outer peripheral side of the flow path cross-sectional reduction part 212, the outer straight line part 212a is smoothly connected in the tangential direction (horizontal direction) from the terminal position of the direction changing part 211, and the flow direction is horizontal from the oblique direction. Aligned in the direction and stabilized, and further connected to the outer peripheral enlarged portion 213. The outer peripheral enlarged portion 213 has a gradient (inclination) that is curved or linear (arc shape in FIG. 4) toward the lower side in the flow direction, and gradually expands and changes gradually or stepwise (continuously in FIG. 4). And is connected to the linear intermediate flow path 21a. In addition, the outer periphery enlarged part 213 may be formed in the shape which expands and changes rapidly in step shape.

  On the other hand, on the curved inner peripheral side of the flow path cross-section reducing portion 212, the inner peripheral curved portion 212b is formed so as to be smoothly connected in a curved shape from the end position of the direction changing portion 211. Furthermore, the inner peripheral straight portion 212c is smoothly connected in the tangential direction (horizontal direction) from the end position of the inner peripheral curved portion 212b, and is connected to the linear intermediate flow path 21a.

Then, the inner peripheral straight portion 212c of the channel cross-section shrinking section 212 is arranged in Oite parallel shape (horizontally) to the end and the flow direction of the flow direction downstream side of the outer peripheral straight portion 212a. As a result, the outer peripheral straight part 212a and the inner peripheral straight part 212c of the flow path cross-sectional reduction part 212 are arranged in parallel (horizontal) with the straight intermediate flow path 21a, respectively.

  Since the flow path is configured as described above, the gas flow in the flow path is as follows.

  Since the gas that has flowed into the direction changing section 211 is in the process of turning from the downward (vertical direction) inlet-side connecting flow path 21b to the horizontal (horizontal direction) linear intermediate flow path 21a, the gas is inclined downward (intermediate direction). The speed component of is large. Since the gas having such a velocity component moves to the downstream side in the flow direction along the curved outer peripheral side of the direction changing portion 211, the flow direction is still uneven even when reaching the end position of the direction changing portion 211. It is in an unstable state. Further, the flow velocity distribution in the direction orthogonal to the flow direction at the end position of the direction changing portion 211 is in a non-uniform (asymmetric) state with the flow velocity increasing toward the curved outer peripheral side. Thus, in the direction changing part 211 (and the inlet side of the flow path cross-section reducing part 212), a flow (uneven flow) in which the flow direction is unstable and the flow velocity is uneven (asymmetric) is generated.

  Therefore, first, the flow path cross-sectional reduction part 212 is formed with an outer peripheral straight part 212a that smoothly connects in a tangential direction from the end position of the direction changing part 211 on the curved outer peripheral side, thereby eliminating irregularities and instabilities in the flow direction. Is done. That is, the outer peripheral straight portion 212a functions as a stabilizing section in the flow direction. Next, by connecting the outer peripheral straight part 212a to the outer peripheral enlarged part 213, the flow path on the curved outer peripheral side is expanded, and the deviation of the flow velocity is alleviated (corrected). That is, the outer periphery enlargement part 213 functions as a flow velocity relaxation section (equalization / symmetrization section of flow velocity distribution). That is, the flow direction of the drift generated on the inlet side of the direction changing portion 211 and the flow path cross-sectional reduction portion 212 is stabilized by the outer peripheral straight portion 212a formed on the curved outer peripheral side of the flow passage cross-section reduction portion 212. The flow velocity distribution is equalized and symmetrized by the outer peripheral enlarged portion 213 connected first.

Moreover, since the inner peripheral straight portion 212c of the channel cross-section shrinking section 212 are arranged in Oite parallel shape (horizontally) to the end and the flow direction of the flow direction downstream side of the outer peripheral straight portion 212a, the flow direction is more Stabilize. Furthermore, since the outer peripheral straight line portion 212a and the inner peripheral straight line portion 212c of the flow path cross-sectional reduction section 212 are arranged in parallel (horizontal) with the straight intermediate flow path 21a, a rectifying means (for example, a rectifying element) is provided. Even if it is not used, the flow direction can be easily stabilized.

  Therefore, if the measurement lines of the pair of transmission / reception vibrators 23a and 23b are arranged at the center position of the flow velocity distribution in the straight intermediate flow path 21a, the central (average) flow velocity of the gas flowing through the straight intermediate flow path 21a. Therefore, the flow rate can be measured with high accuracy over a wide range from the laminar flow region to the turbulent flow region.

(Example 2)
FIG. 5 is an enlarged explanatory view of a main part showing another embodiment of the flow path configuration of the intermediate flow path in FIG. 2 instead of FIG. Also in the intermediate flow path 21 shown in FIG. 5, similarly to FIG. 4, the inlet-side connection flow path 21 b (introduction-side flow path) and the straight intermediate flow path 21 a (measurement straight flow path) are arranged almost orthogonally. Between them, the direction changing part 211, the flow path cross-section reducing part 212, and the outer peripheral enlarged part 213 are connected and formed in this order from the upper side toward the lower side in the flow direction.

  In this embodiment, the outer straight portion 212a of the flow path cross-section reducing portion 212 is a first straight portion 212a1 located on the upper side in the flow direction and a second straight portion 212a2 located on the lower side and reducing the cross-sectional area of the flow passage. And is connected to the outer peripheral enlarged portion 213 on the lower side in the flow direction. In addition, the first straight line portion 212a1 and the second straight line portion 212a2 are connected via an outer peripheral reduction portion 212d. The outer periphery reducing portion 212d has a curved or linear (arc shape in FIG. 5) gradient (inclination) toward the lower side in the flow direction, and continuously or stepwise (continuously in FIG. 5). Is formed.

  The first straight portion 212a1 and the second straight portion 212a2 of the flow path cross-sectional reduction portion 212 are opposed to the inner curved portion 212b and the inner straight portion 212c, respectively. As a result, the first straight portion 212a1, the second straight portion 212a2, and the inner peripheral straight portion 212c of the flow path cross-sectional reduction part 212 are arranged in parallel (horizontal) with the straight intermediate flow path 21a.

  In this embodiment, the outer peripheral straight line portion 212a of the flow path cross section reducing portion 212 is reduced in cross section in two stages of the first straight portion 212a1 and the second straight portion 212a2, so that the flow direction stabilization section is formed relatively long. Therefore, the flow direction can be stabilized over a wide range regardless of the laminar flow region or the turbulent flow region. Further, the first straight portion 212a1, the second straight portion 212a2, and the inner peripheral straight portion 212c of the flow path cross-sectional reduction portion 212 are arranged in parallel (horizontal) with the straight intermediate flow path 21a, so that the rectifying means The flow direction can be easily stabilized without using (for example, a rectifying element). In addition, in Example 2 (FIG. 5), the part which has a function common to Example 1 (FIG. 4) is provided with the same code | symbol, and description is abbreviate | omitted.

(Modification)
In the above embodiment, the case where the reflection type V-shaped arrangement is adopted as the arrangement of the ultrasonic sensor (transmission / reception unit) and the path through which the ultrasonic wave passes (referred to as a survey line) has been described. In the reflective V-shaped arrangement, the pair of transmission / reception units can be concentrated on the same side along the flow direction, so that there is an advantage that the transmission / reception units can be attached and detached from the same direction. In addition to the reflective V-shaped array, many types are known for the line measuring method of the ultrasonic sensor (transmission / reception unit) in the ultrasonic flowmeter. Examples of application of the present invention to other line survey methods will be described below.

(1) Transmission type Z arrangement (FIG. 6A)
In this method, ultrasonic waves emitted from one transmission / reception unit 123a are received by the other transmission / reception unit 123b arranged at a predetermined distance in the flow direction. In this method, one transmission / reception unit 123a and the other transmission / reception unit 123b are arranged separately on both sides in the flow direction.

(2) Transmission type V-shaped array (FIG. 6B)
In this method, ultrasonic waves emitted from one transmitter 223a are received by a pair of receivers 223b and 223b arranged at a predetermined distance in the flow direction. In this method, the transmission unit 223a and the reception units 223b and 223b are arranged separately on both sides in the flow direction.

(3) Crossed X array (FIG. 6 (c))
The ultrasonic waves emitted from the pair of transmitters 323a and 323a arranged at a predetermined distance along the flow direction are received by the pair of receivers 323b and 323b arranged at a predetermined distance along the flow direction. It is a method. This method corresponds to the method of FIG. 6 (b) described above in which one transmission unit is added as a pair.

  In the above examples and modifications, the main unit 10 has been described only in the case where the main unit 10 includes the main body 11 having the main body flow path 14 and the lid 17 that covers the main body 11 from the outside. The main unit 10 may have the following configuration. In other words, the main body unit may be configured such that the first main body portion and the second main body portion each having a half-shaped main body flow path are combined. However, in this case, the window hole is provided in at least one of the first main body and the second main body, and the lid may or may not be provided.

1 is an overall perspective view of an embodiment of an ultrasonic flowmeter according to the present invention. FIG. 2 is a front sectional view of FIG. 1. AA sectional drawing of FIG. The principal part expansion explanatory drawing which shows one Example of the flow-path structure of the intermediate flow path in FIG. The principal part expansion explanatory drawing which shows the other Example of the flow-path structure of the intermediate flow path in FIG. Explanatory drawing which shows the arrangement | positioning modification of an ultrasonic sensor.

Explanation of symbols

21 Intermediate channel 21a Linear intermediate channel (Straight channel for measurement)
21b Inlet side connection flow path (introduction side flow path)
21c Outlet side connecting channel (outlet side channel)
21d Mounting wall (wall)
211 Direction change part 212 Flow path cross-sectional reduction part 212a Outer periphery straight part 212a1 First straight part 212a2 Second straight part 212b Inner circumference curved part 212c Inner circumference straight part 212d Outer circumference reduction part 213 Outer circumference enlargement part 23 Ultrasonic sensor 23a, 23b Transmission / reception vibration Child (sensor element)
100 Ultrasonic flow meter (flow meter)

Claims (8)

An introductory side channel having a predetermined channel cross-sectional area for allowing fluid to pass therethrough, and is formed in a straight line so as to intersect the introductory side channel and from the introductory side channel to measure the flow rate of the fluid A flow meter including a measurement linear channel having a small channel cross-sectional area,
In the common cross section passing along the flow direction of the fluid flowing through the introduction side flow path and the measurement straight flow path and passing through the center of both flow paths,
A curved direction changing portion that changes the flow of the fluid in a form following the outlet side end portion of the introduction side flow path;
A flow path cross-sectional reduction part that is connected and formed so as to include the outlet side end part of the direction change part, and whose flow cross-sectional area decreases toward the lower side in the flow direction on the curved outer peripheral side and / or curved inner peripheral side of the direction change part. When,
The flow passage cross-section is connected and formed so as to follow the flow passage cross-sectional reduced portion, and the flow passage cross section on the curved outer peripheral side continuously expands gradually toward the lower side in the flow direction or rapidly expands and changes in a staircase fashion. Including an outer peripheral enlarged portion connectable to a road,
The flow velocity distribution of the fluid that is relatively faster on the curved outer circumferential side than the curved inner circumferential side while flowing through the direction changing portion and the flow path cross-sectional reduced portion is the flow direction while passing through the outer circumferential enlarged portion. A flowmeter characterized by being equalized and / or symmetrized in an orthogonal direction. An introductory side channel having a predetermined channel cross-sectional area for allowing fluid to pass therethrough, and is formed in a straight line so as to intersect the introductory side channel and from the introductory side channel to measure the flow rate of the fluid Has a small channel cross-sectional area and oscillates ultrasonic waves toward the upper or lower side of the fluid flow direction on the mounting wall of the wall, and / or ultrasonic waves coming from the upper or lower side of the flow direction A flowmeter including a measurement linear flow channel to which a transmission / reception transducer for receiving
In the common cross-section along the flow direction of the fluid flowing through the introduction-side flow path and the measurement linear flow path and through the center of both flow paths and parallel to the mounting wall surface to which the transmission / reception vibrator is mounted,
A curved direction changing portion that changes the flow of the fluid in a form following the outlet side end portion of the introduction side flow path;
A flow path cross-sectional reduction part that is connected and formed so as to include the outlet side end part of the direction change part, and whose flow cross-sectional area decreases toward the lower side in the flow direction on the curved outer peripheral side and / or curved inner peripheral side of the direction change part. When,
The flow passage cross-section is connected and formed so as to follow the flow passage cross-sectional reduced portion, and the flow passage cross section on the curved outer peripheral side continuously expands gradually toward the lower side in the flow direction or rapidly expands and changes in a staircase fashion. Including an outer peripheral enlarged portion connectable to a road,
The flow velocity distribution of the fluid that is relatively faster on the curved outer circumferential side than the curved inner circumferential side while flowing through the direction changing portion and the flow path cross-sectional reduced portion is the flow direction while passing through the outer circumferential enlarged portion. A flowmeter characterized by being equalized and / or symmetrized in an orthogonal direction. The flow path cross-sectional reduction portion includes an outer peripheral straight portion that is smoothly connected in a tangential direction from an end position of the direction changing portion on the curved outer peripheral side, and includes an outer peripheral straight portion for stabilizing the flow direction. While connected
The flowmeter according to claim 1 or 2, comprising an inner peripheral curved portion that is smoothly connected in a curved shape from an end position of the direction changing portion on the curved inner peripheral side. The flow path cross-sectional reduction part is configured to include an inner peripheral linear part smoothly connected in a tangential direction from a terminal position of the inner peripheral curved part,
The inner peripheral straight portion flowmeter of claim 3 disposed Oite parallel shape to the end portion and the flow direction of the flow direction downstream side of the outer peripheral straight portion.   The flowmeter according to claim 4, wherein an outer peripheral straight line portion and an inner peripheral straight line portion of the flow path cross-sectional reduction portion are arranged in parallel with the measurement straight flow path. While the flow path cross-sectional reduction part is configured to include an inner peripheral linear part smoothly connected in a tangential direction from the terminal position of the inner peripheral curved part,
The outer peripheral straight part includes a first straight part located on the upper side in the flow direction and a second straight part located on the lower side and reducing the cross-sectional area of the flow path,
The flow meter according to claim 3, wherein the first straight portion is disposed opposite to the inner circumferential curved portion, and the second straight portion is disposed opposite to the inner circumferential straight portion.   The flowmeter according to claim 6, wherein the first straight line portion, the second straight line portion, and the inner peripheral straight line portion of the flow path cross-sectional reduction portion are arranged in parallel with the measurement straight flow path. The introduction side channel and the measurement linear channel are arranged orthogonally,
The flow meter according to any one of claims 1 to 7, wherein a channel cross-sectional area of the measurement linear channel is formed to be constant with respect to a flow direction.

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