JPH05180677A - Ultrasonic flow meter - Google Patents

Abstract

PURPOSE:To enable an accuracy for measuring flow rate to be improved by providing a branch pipe at a main pipe for circulating a fluid and then placing a pair of ultrasonic transmitter/receiver oppositely on a pipe wall of the branch pipe. CONSTITUTION:In an ultrasonic flow meter 10, a branch pipe 12 is provided at a main pipe 11 for circulating fluid and a pair of ultrasonic transmitter/ receiver 13 are placed oppositely on a pipe wall of the branch pipe 12. In this case, an introduction pipe 14 is branched at right angle for a pipe axis in the branch pipe 12, a flow-dividing part 15 is in parallel to the pipe axis of the main pipe 11, and a reflex part 16 is formed to be at right angle for the pipe axis of the main pipe 11. Also, the ultrasonic transmitter/receiver 13 is mounted so that an ultrasonic propagation path at a specified angle theta for the pipe axis. An inner diameter (d) of the flow-dividing part 15 is set so that 2320>Re=V0.d/nu, where R3: Reynolds number, V0: face average flow rate of pipe, nu: kinetic viscosity coefficient), thus resulting in measurement in laminar flow and enabling the flow rate to be measured highly accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flowmeter for measuring the flow rate of a fluid by measuring the flow velocity in a pipe using ultrasonic waves.

[0002]

2. Description of the Related Art Normally, the flow rate of a fluid in a pipe is obtained by multiplying the surface average flow velocity V ₀ of the pipe by a pipe cross-sectional area or the like.
As one of the flow rate measuring means, for example, as shown in FIG. 9, an ultrasonic flow meter 1 has a pair of ultrasonic wave transmitters / receivers 2 mounted on a tube wall 3 so as to face each other and alternately generate ultrasonic pulses. It is a flow velocity measurement type flow meter that is made to propagate and measure the flow velocity. The measured flow velocity is the line average flow velocity V ₁ of the ultrasonic propagation path (measurement line). The surface average flow velocity distribution of the fluid in the pipe is obtained by Re = V ₀ · D / ν (1) (where Re: Reynolds number, D: pipe inner diameter, ν: kinematic viscosity coefficient). Here, the flow of Re <2320 is a laminar flow, and the flow of Re≈4000 or more is called turbulent flow. An example of the distribution is shown in FIG. In the laminar flow, if the ratio of the linear average flow velocity V ₁ to the surface average flow velocity V ₀ is κ, κ = V ₁ / V ₀ (2) In this case, κ = 4/3, which is constant. In turbulence,
There are several reports, but here, the one by Ge i Birgel is applied. Reynolds number Re and κ
FIG. 11 shows the relationship of the above.

[0003] In the actual flow rate measurement, usually, it becomes a measure of the turbulent basin, the flow rate Q in the turbulent _{basin, Q = V 0 · S ·} 3600 = V 1 / κ · πD 2/4 · 3600 ( m ³ / H) (3) (where, V ₀ : surface average flow velocity, S: cross-sectional area, V ₁ : linear average flow velocity, κ: flow velocity correction coefficient according to Reynolds number).

[0004]

However, in the turbulent flow range, κ in the equation (3) varies depending on the Reynolds number Re, that is, the surface average flow velocity V ₀ , as shown in FIG. It is difficult to obtain a highly accurate value. The present invention has been made in view of the above problems, and an object thereof is to improve the accuracy of the measured value of the flow rate by configuring the ultrasonic flow meter so that it can be measured in the laminar flow region where κ is constant. To do.

[0005]

In order to solve the above-mentioned problems, the present invention provides a branch pipe in a main pipe through which a fluid circulates, and a pair of ultrasonic transducers are provided on the pipe wall of the branch pipe. It is characterized by being arranged. Further, the present invention is characterized in that a branch pipe is provided in a main pipe through which a fluid flows, and in this branch pipe, a pair of ultrasonic transducers is arranged so as to match the pipe axis of the branch pipe. Further, in the above-mentioned branch pipe, a fluid introduction portion is projected to an intermediate portion of the main pipe. Further, the present invention is characterized in that the upstream side of the branch pipe is diametrically extended in the main pipe, and a fluid introduction hole is formed in the upstream surface of the branch pipe. Further, a laminar flow pipe separated in a honeycomb shape is arranged in the main pipe.

[0006]

[Function] From the relation of Re = V ₀ · D / ν, the inner diameter D of the main pipe
If the ultrasonic wave transmitter / receiver is arranged in a branch pipe having a small inner diameter provided in the main pipe without increasing the value, the flow rate can be measured in the laminar flow region in which the value of Re is less than 2320. Since the value of κ is constant in the laminar flow region, it is possible to obtain a highly accurate flow rate.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an ultrasonic flowmeter according to the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 10 indicates an ultrasonic flowmeter 10 according to a first embodiment. The ultrasonic flowmeter 10 includes a branch pipe 12 in a main pipe 11 through which a fluid flows, and a pipe of the branch pipe 12 is provided. This is a configuration in which a pair of ultrasonic wave transmitters / receivers 13 are arranged to face each other on a wall. In this case, in the branch pipe 12, the introduction part 1
4 is branched and formed at a right angle to the pipe axis of the main pipe 11, the flow dividing portion 15 is parallel to the pipe axis of the main pipe 11, and the reflux portion 16 is formed at a right angle to the pipe axis of the main pipe 11. The ultrasonic wave transmitter / receiver 13 is attached so that the ultrasonic wave propagation path forms a predetermined angle θ with respect to the tube axis. The inner diameter d of the flow dividing portion 15 is set so as to satisfy 2320> Re = V ₀ · d / ν.

In such an ultrasonic flowmeter 10, the flow velocity of the fluid introduced into the branch pipe 12 and flowing through the flow dividing portion 15 is
It is almost the same as the flow velocity in the main pipe 11. Moreover, if the inner diameter d of the flow dividing portion 15 is set so as to satisfy 2320> Re = V ₀ · d / ν, the measurement becomes a laminar flow, and κ is substantially constant, so that the flow rate can be measured with high accuracy. it can.

Next, FIG. 2 shows a second embodiment. In the ultrasonic flowmeter 20 in this case, the ultrasonic wave transmitter / receiver 13 is arranged at both ends of the flow dividing portion 15 of the branch pipe 12 so that the ultrasonic wave propagation path is aligned with the pipe axis direction so as to face each other. It is a thing. The ultrasonic wave propagation path formed between the ultrasonic wave transmitters / receivers 13 has a distance corresponding to the length L of the flow dividing unit 15.

According to such an ultrasonic flowmeter 20, by adopting a large ultrasonic wave propagation path, the resolution of time measurement can be improved and highly accurate measurement can be performed.

Further, FIG. 3 shows a third embodiment. In this case, in the ultrasonic flowmeter 30, the fluid introduction portion 14 of the branch pipe 12 is provided so that the tip portion thereof is located at the middle portion of the main pipe 11 (see FIG. 4). The ultrasonic wave transmitter / receiver 13 is provided at the same position as in the first embodiment.

According to the ultrasonic flowmeter 30, since the main pipe 11 having a large flow velocity is introduced into the branch pipe 12, the degree of stability of the diversion ratio is increased.

Next, FIG. 5 shows a fourth embodiment. In the ultrasonic flowmeter 40 in this case, the introduction portion 14 of the branch pipe 12 is made to extend in the diametrical direction in the main pipe 11, and the introduction holes 41 for the fluid are provided at a constant interval on the upstream surface of the introduction portion 14. It is designed so that multiple holes are drilled.
(See Figure 6). The ultrasonic wave transmitter / receiver 13 is provided at the same position as in the first embodiment.

According to such an ultrasonic flowmeter 40, the main pipe 1
By introducing the fluid from the introduction holes 41 at regular intervals within 1, the flow velocity distribution of the main pipe 11 is averaged and the degree of stability of the diversion ratio is increased.

Further, FIGS. 7 and 8 show a fifth embodiment. In this case, in the ultrasonic flow meter 50, in the main pipe 11,
This is a configuration in which the laminar flow pipe 51 that is divided and formed into a pipe having a honeycomb-shaped cross section is arranged.

According to the ultrasonic flowmeter 50, the flow velocities flowing through the respective honeycomb tubes can be equalized, and the diversion ratio can be stabilized.

As described above, according to the present invention, the flow rate can be measured in the laminar flow region by using the branch pipe. Therefore, since the ratio of the linear average flow velocity to the surface average flow velocity in the laminar flow region is constant, the flow rate measurement accuracy can be improved.

[0018]

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an ultrasonic flowmeter according to the present invention.

FIG. 2 is a schematic explanatory view of a second embodiment of the ultrasonic flowmeter according to the present invention.

FIG. 3 is a schematic explanatory view of a third embodiment of the ultrasonic flowmeter according to the present invention.

FIG. 4 is a schematic cross-sectional explanatory view of the ultrasonic flow meter shown in FIG.

FIG. 5 is a schematic explanatory view of a fourth embodiment of the ultrasonic flowmeter according to the present invention.

6 is a schematic cross-sectional explanatory view of the ultrasonic flowmeter shown in FIG.

FIG. 7 is a schematic explanatory view of a fifth embodiment of the ultrasonic flowmeter according to the present invention.

8 is a schematic cross-sectional explanatory view of the ultrasonic flow meter shown in FIG.

FIG. 9 is a schematic explanatory view of a conventional ultrasonic flow meter.

FIG. 10 is a graph showing a flow velocity distribution in a circular pipe.

FIG. 11 is a graph showing a relationship between a flow velocity in a circular pipe and a flow velocity correction coefficient.

[Explanation of symbols]

 10, 20, 30, 40, 50 Ultrasonic flowmeter 11 Main pipe 12 Branch pipe 13 Ultrasonic wave transmitter / receiver 14 Introducing part 15 Flow dividing part 16 Refluxing part 41 Introducing hole 51 Laminar flow pipe

Claims (5)

[Claims] 1. An ultrasonic flowmeter, characterized in that a main pipe through which a fluid flows is provided with a branch pipe, and a pair of ultrasonic transducers are arranged opposite to each other on the pipe wall of the branch pipe. 2. An ultrasonic wave, characterized in that a branch pipe is provided in a main pipe through which a fluid flows, and in this branch pipe, a pair of ultrasonic transducers are arranged so as to coincide with the pipe axis of the branch pipe. Flowmeter. 3. The ultrasonic flowmeter according to claim 1, wherein the fluid introduction part is projected to the middle part of the main pipe. 4. An ultrasonic flow rate characterized in that the upstream side of the branch pipe according to claim 1 is diametrically extended in the main pipe, and a fluid introduction hole is formed in the upstream surface of the branch pipe. Total. 5. An ultrasonic flowmeter characterized in that a laminar flow pipe divided into a honeycomb shape is arranged on the main pipe according to claim 1.