JP4604520B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow measuring device that measures the flow velocity and flow rate of a fluid such as a gas.

Conventionally, as shown in FIG. 7, this type of flow measuring device includes transmitters / receivers 2 a, 2 b in a part of a rectangular fluid pipe 1, measures the propagation time from the transmitter / receiver 2 a to 2 b, The flow velocity and flow rate are calculated based on the propagation time. As shown in FIG. 8, the cross section of the fluid conduit 1 was partitioned into a plurality of flow paths by partition plates 3a, 3b, 3c, 3d, 3e, and 3f (see, for example, Patent Document 1).
JP-A-9-43015

  However, in the conventional configuration, the flow velocity distribution in the fluid pipe line 1 varies depending on the flow rate flowing in the pipe, and a plurality of flow paths partitioned by the partition plates 3a, 3b, 3c, 3d, 3e, and 3f under the influence thereof. The flow rate ratio was not uniform, resulting in an error in the measured flow rate.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a flow rate and flow rate measurement device that maintains a uniform flow rate ratio of a plurality of flow paths and performs highly accurate flow rate measurement.

In order to solve the above-described conventional problems, the flow measuring device of the present invention includes a flow path dividing unit that equally divides a fluid flowing in a section in which sound waves between transmitters and receivers propagate, and a section in which sound waves between the transmitter and receiver propagates. The flow path dividing means divides the fluid flowing through the channel at the upstream end of the flow path dividing means, and the flow path dividing means propagates the sound wave between the transmitter and the receiver in order to make the flow velocity distribution of the laminar flow uniform. In the section, the central portion of the cross section at the end portion on the upstream side is formed so as to be divided more densely than the peripheral portion, and the center is formed in a convex shape from the periphery in the planar direction .

  In the flow measuring device of the present invention, the ratio of the flow rates of the central part and the peripheral part of the divided flow path becomes equal regardless of the magnitude of the flow rate or the type of fluid, and the flow rate can be detected with high accuracy over a wide flow rate range.

  According to a first aspect of the present invention, there is provided a fluid calculation means for calculating a flow velocity or a flow rate of a fluid according to a sound wave propagation time of a transmitter / receiver that transmits or receives sound waves arranged upstream and downstream of a flow path, and a sound wave between the transmitter / receiver. A flow path dividing means for dividing the flow path into two upstream or downstream of the flow path dividing means for dividing the flow path during propagation, and the center of the transceiver is arranged at the position of the flow path dividing means. Even when the flow rate changes, the flow rate ratio between the divided flow paths becomes substantially equal, and high-precision flow rate measurement can be performed.

  According to a second aspect of the present invention, there is provided a fluid calculation means for calculating a flow velocity or a flow rate of a fluid in accordance with a sound wave propagation time between a transmitter and a receiver that transmits or receives a sound wave disposed upstream and downstream of a flow path, and a sound wave between the transmitter and the receiver. Since the flow path dividing means for dividing the flow path height H during the propagation of the flow path is provided upstream or downstream of the flow path dividing means with a length equal to or less than the length of the flow path height H, the flow from a small flow rate to a large flow rate is provided. Stable and highly accurate flow rate measurement can be performed.

  In the third invention, in particular, the flow path dividing means of the first invention is such that a part of the flow path dividing means is extended, and the number of parts is reduced to improve the dimensional accuracy. Can be measured.

  In the fourth invention, in particular, the flow path dividing means of the first invention is divided more densely in the central part than in the peripheral part, the uniformity of the flow velocity in the central part and the peripheral part becomes higher, and the high Accurate flow measurement is possible.

  In the fifth aspect of the invention, in particular, the flow path dividing means of the first aspect of the invention is configured to divide the flow path evenly, and the uniformity of the flow velocity of each divided flow path is further increased, and the flow rate with high accuracy is obtained. Can measure.

  The sixth aspect of the invention has a run-up flow path portion that has substantially the same shape as the flow path through which sound waves pass, and has no dividing means, particularly the flow path of the first aspect of the invention. In addition, accurate flow measurement can be performed.

  In the seventh invention, the split extension means, the flow channel dividing means, or the run-up flow channel section of the first invention is particularly configured as viewed from the transmitter / receiver, and the same effect as in the normal flow can be obtained at the back flow. Therefore, accurate flow rate measurement can be performed even during pulsation in which forward and reverse flow alternately.

  In the eighth invention, in particular, the flow path partitioning means of the first invention is formed such that the center is convex from the periphery in the plane direction, and the flow velocity in the center and the periphery is uniform in the plane direction. Therefore, the flow accuracy is higher.

  In the ninth aspect of the invention, the portion of the flow path of the first aspect of the invention that is in contact with the fluid in the flow path that is transmitted and received by the transceiver is made of the same material, and high-precision measurement is possible even with respect to temperature changes. Yes.

(Embodiment 1)
Hereinafter, a flow measuring apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. In FIG. 1, a transmitter / receiver 5 a that transmits an ultrasonic wave and a transmitter / receiver 5 b that receives an ultrasonic wave are disposed in the flow path 4 in the fluid flow direction. Reference numeral 6 denotes transmission means to the transceiver 5a, and reference numeral 7 denotes reception means for signals received by the transceiver 5b. The switching means 8 changes the transmission / reception direction of the transceivers 5a and 5b, and the fluid calculation means 9 calculates the flow velocity value and the flow rate value from the time difference from transmission to reception. In the present embodiment, the case where the fluid calculation means 9 calculates the flow velocity value and the flow rate value will be described. However, when the flow rate value is not required, the flow velocity value may only be calculated, and the change in the flow velocity value may be changed. By detecting, leakage of fluids such as gas and tap water can be detected.

  Next, the operation will be described. First, a signal is sent from the transmitting means 6 to the transceiver 5a, and the sound wave reaches the transceiver 5b, is received by the receiving means 7, and the propagation time of the sound wave is measured by the fluid computing means 9. Next, the transmission / reception of the transmitter / receiver 5a and the transmitter / receiver 5b is switched by the switching means 8, a sound wave signal is transmitted from the transmitter / receiver 4b to the transmitter / receiver 4a, and this transmission is timed as described above. From the time difference, the flow rate and the flow rate value are obtained by the fluid calculation means 10 in consideration of the size of the pipeline and the flow state.

  FIG. 2 is a cross-sectional view of the above-described flow measuring device, and the inside of the fluid pipe 4 is divided into four divided flow paths by three flow path dividing means 10, 11, and 12. The respective flow path dividing means 10, 11, and 12 are arranged at equal intervals, and their passage areas are made equal. The flow path dividing means 11 in the center is configured to be longer than the other flow path dividing means 10 and 12, and is formed by extending the upstream end of the flow path dividing means 11 substantially parallel to the fluid flow. It has a channel partitioning means 11a and a channel partitioning means 11b formed by extending the downstream end of the channel splitting means 11 substantially parallel to the fluid flow. In the present embodiment, the case where the flow path dividing means 11 and the flow path dividing means 11a and 11b are integrally formed has been described. However, the flow path dividing means 11 and the flow path dividing means 11a and 11b are different from each other. It may be formed on the body.

  Furthermore, on the upstream and downstream sides, there are running flow channel portions 13a and 13b in which the flow channel dividing means 10, 11, and 12 are not provided.

  The fluid flows in from the left side of the figure and removes the turbulence of the flow at the run-up flow channel portion 13a, and is divided into two by the flow channel dividing means 11a, and then divided into four by the flow channel dividing means 10, 11, and 12. Flowing. The transmitter / receiver 5a (5b is not shown) has the center of the sound wave transmission surface at the same height as the attachment position of the flow path dividing means 11a, and the transmitter / receiver 5a The sound wave is scanned and the propagation time is measured to calculate the flow velocity and flow rate. Here, the height direction means a direction substantially parallel to the side wall of the flow path 4 to which the transceivers 5a and 5b are attached.

  FIG. 3 shows the flow velocity distribution in the flow path, each normalized by the average flow rate. FIG. 3A shows the flow velocity distribution when there is no flow dividing means, FIG. 3A shows the flow velocity distribution when the flow velocity is small (laminar flow region), and FIG. 3A shows the flow velocity distribution. It is the flow velocity distribution when it is large (turbulent flow region). In this way, it is a well-known fact that the flow velocity distribution is bullet-shaped in the laminar flow region, but the transmitters / receivers 5a and 5b travel through different portions of the flow velocity, so the influence on the propagation time differs depending on the location. It is extremely difficult for the transmitter / receiver 5a to transmit a uniform sound wave from the transmission surface, and normally the sound wave also has an intensity distribution. Therefore, the flow velocity of the non-uniform flow velocity distribution is measured with the non-uniform sound wave distribution, and a large error occurs. Further, since the pattern shown in FIG. 3A is obtained at a large flow rate, some correction is required at a low flow rate and a high flow rate. Furthermore, even if the flow rate is the same, the Reynolds number is different if the type and nature of the fluid are different, so correction is necessary.

  FIG. 3 (B) has the flow path dividing means 10, 11, 12 but no flow path dividing means 11a, 11b, that is, the lengths of the flow path dividing means 10, 11, 12 are equal. It is the flow velocity distribution at the time. When the flow velocity is small, the distributions are c, d, e, and f in FIG. 3B, respectively, and when the flow velocity is large, the flow distributions are as shown in FIGS. 3B, g, h, i, and j, respectively. When the flow velocity is high, the four flow velocity distributions are almost uniform, but when the flow velocity is low, the flow velocity in the central portion is slightly increased due to the influence of the laminar flow (line k) in the upstream portion.

  When the flow path dividing means 11a is provided at the center, the flow velocity distribution becomes uniform as shown in FIG. 3 (C) l, m, n, o. That is, even if the flow velocity distribution of the laminar flow is upstream, it can be transformed into the flow velocity distribution as shown in FIGS. 3C and 3C by the flow path dividing means 11a, and the influence of the velocity distribution can be reduced. A velocity distribution close to is obtained. If the distribution shapes of the small flow velocity and the large flow velocity are similar, correction by the flow velocity is not necessary, so the flow velocity and flow rate can be measured with high accuracy.

  The flow path dividing means 11a and 11b are longer than the flow path dividing means 10, 11, and 12 by a distance of a length L in the flow direction, respectively. Is also set to a small distance. If this distance L is long, the flow is disturbed at a large flow rate, which not only adversely affects the ultrasonic waves, but also increases the pressure loss.

  The run-up channel portions 13a and 13b and the channel partitioning means 11a and 11b are symmetrically arranged as viewed from the transmitters / receivers 5a and 5b, respectively, and the flow flows in the reverse direction (from right to left in FIG. 2). Also, the flow velocity distribution is configured to maintain uniformity.

  When the flow is disturbed and flows in at a large flow velocity, the run-up flow channel portion 13a is for reducing the disturbance and requires an appropriate length according to the maximum flow velocity.

(Embodiment 2)
FIG. 4 shows a further improvement in the uniformity of the flow velocity distribution by reducing the interval at the center of the flow path dividing means, and the flow path dividing means 14, 15 and 16 have a small interval at the center and the periphery. The portion is configured to be large, and the center is for uniformizing the flow velocity distribution of the laminar flow having a large flow velocity, and can be made even more uniform.

(Embodiment 3)
FIG. 5 is a plan view of the flow path dividing means, and the flow path dividing means is extended to form the flow path dividing means. As shown in FIG. 5, the end portion 17a of the flow path dividing means 17 is shown. Is configured so that the center part is convex. In this way, the flow velocity in the central portion and the peripheral portion can be made uniform even in a plan view.

  FIG. 6 shows a flow channel upper surface means 18 on the inner wall upper surface of the flow channel 4 and a flow channel bottom surface means 19 on the inner wall bottom surface of the flow channel 4, respectively. The material having the same friction coefficient as the material of the flow path dividing means 20 and 21 is used, and the shape of the flow velocity distribution caused by the friction is the same. Further, if the same material is used, there is little error with respect to expansion and contraction due to thermal changes.

  Since the flow measuring device of the present invention can accurately measure a wide range of flow velocities and flow rates, it can also be applied to measuring meters such as metering meters such as gas and water, and flow meters in industrial plants and experimental facilities.

1 is a block diagram of a flow measuring device according to a first embodiment of the present invention. Flow path sectional view of a flow measuring device in Example 1 of the present invention (A) A characteristic diagram showing the flow velocity distribution in the flow channel when there is no flow channel dividing means (B) A characteristic diagram showing the flow velocity distribution in the flow channel when there is a flow channel dividing means (C) Characteristic diagram showing flow velocity distribution in flow path in form 1 Flow path sectional view of a flow measuring device in Embodiment 2 of the present invention The top view of the flow-path division means of the flow measurement apparatus in Embodiment 3 of this invention Flow path sectional view of a flow measuring device in Embodiment 4 of the present invention Flow path configuration diagram of a flow measurement device as a conventional flow measurement device Cross-sectional view of a conventional flow measurement device

Explanation of symbols

4 Flow path 5a, 5b Transmitter / receiver 9 Fluid calculating means 10, 11, 12 Flow path dividing means 11a, 11b Flow path dividing means 13a, 13b Running flow path section

Claims (2)

A transceiver for transmitting or receiving sound waves disposed on the upstream side and the downstream side of the flow path;
Fluid calculating means for calculating the flow velocity and / or flow rate of the fluid according to the sound wave propagation time between the transceivers;
A flow path dividing means for equally dividing a fluid flowing through a section in which sound waves propagate between the transceivers;
The fluid flowing through a section waves between the transceiver is propagated, and a flow path partition means for dividing the upstream end of the flow path dividing means,
In order to make the flow velocity distribution of the laminar flow uniform, the flow path dividing means divides the central part of the cross section at the upstream end of the section in which the sound wave between the transmitter and the receiver propagates more densely than the peripheral part. And a flow measuring device having a center formed in a convex shape from the periphery in the planar direction . A channel upper surface means and a channel bottom surface means provided in parallel with the channel dividing means and provided on the inner wall surface of the channel,
Wherein the channel bottom surface means the flow path surface means passage, the flow path dividing means and the friction coefficient of the flow measuring device according to claim 1 which is made of the same material.

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