JP2007121071A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance accuracy of flow measurement while reducing the size of a flowmeter. <P>SOLUTION: In a sound wave flowmeter, a fluid flows in the horizontal direction in flow paths 1a, 1b, and 1c of a measuring tube 30 as shown in Fig. (b). An ultrasonic wave is caused to propagate through the fluid along a straight line 6 inclined at an angle θ from an axis line Xa - Xa of the flow path 1a to calculate a flow speed based on forward propagation time in the same direction as a flow and reverse propagation time in the reverse direction, thereby operating a flow volume. As to the flow paths, the three flow paths 1a, 1b, and 1c are provided around the straight line 6 so as to be shifted from each other by 120° as shown in Figs. (c) and (d). Each flow path is equipped with a rectangular cross-section of height H and width W. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in an ultrasonic flowmeter having a rectangular channel.

  2. Description of the Related Art An ultrasonic flowmeter that measures the flow rate of a fluid flowing through a rectangular cross-section flow path based on the propagation time of ultrasonic waves and calculates the flow rate is known (for example, see Patent Document 1).

  1A and 1B are schematic diagrams for explaining the flow channel shape and the positional relationship between the flow channel and the ultrasonic transducer in the prior art. FIG. 1A is a longitudinal sectional view, and FIG. 1B is a transverse sectional view.

  In this prior art, as shown in FIG. 1A, a straight line 6 forming an angle θ between an angle A between an axis XX of a rectangle 2 and a diagonal line of the rectangle 2 in a cross section parallel to the flow of the flow path 1. The ultrasonic transducers 4 and 5 are disposed on the top. That is, the flow path 1 is disposed so as to be relatively inclined by the angle θ with respect to the straight line 6 connecting the vibrators 4 and 5. L is the length of the flow path 1, H is the height of the rectangular cross section perpendicular to the flow, and W is the width of the rectangular cross section (see FIG. 1B).

  FIG. 2 is a longitudinal sectional view showing the structure of the flow meter. The rectangular flow path portion 3 is attached so that the axis XX of the flow path 1 is inclined with respect to the straight line 6 connecting the vibrators 4 and 5 so as to form an angle θ.

The fluid to be measured enters the measurement chamber 10 from the inflow part 9 and enters the flow path 1 of the rectangular flow path part 3 from the left. It flows along the axis XX on the right side of the flow path 1 in the drawing, exits from the right side of the flow path 1, and further flows out of the flow meter from the outflow portion 11. Reference numeral 12 denotes a partition wall that partitions the inflow portion side and the outflow portion side, and the rectangular flow path portion 3 is fixed through the partition wall 12. Ultrasonic transducers 4 and 5 are arranged opposite to the opposing wall surfaces 13 and 14 of the measuring chamber 10, respectively.
JP 2001-201379 A

  In the flow meter, in order to suppress the pressure loss to a predetermined value or less, a flow path cross-sectional area corresponding to the maximum flow rate to be measured is required. In the prior art, the channel cross-sectional area S is represented by the product of the height H and the width W of the rectangular cross-section of the channel, and S = H · W.

  The smaller the width W, the smaller the change in the flow velocity within the width W, and the flow is a two-dimensional plane including the length direction and height direction of the flow path 1, that is, the paper surface in FIG. 1 (a) and FIG. Can be handled as a two-dimensional flow in a two-dimensional plane including In other words, the smaller the width W and the larger the aspect ratio H: W of the rectangular cross section, the more advantageous the formation of a two-dimensional flow.

  However, the channel cross-sectional area S does not change if the maximum flow rate to be measured is the same. Therefore, as the aspect ratio is increased, the height H is increased and the maximum dimension of the flow path cross section is increased. As a result, there is a problem that the outer dimension of the flow meter is increased.

  Accordingly, an object of the present invention is to provide an ultrasonic flowmeter that is advantageous for forming a two-dimensional flow and that can reduce the external dimensions of the flowmeter.

The most important feature of the present invention is that a plurality of channels each having a substantially rectangular channel cross section are provided.
Therefore, in order to achieve the above object, the invention according to claim 1 is arranged such that the axis of the flow path having a substantially rectangular cross section is relatively inclined with respect to a straight line connecting the pair of ultrasonic transducers. In the installed ultrasonic flow meter,
An ultrasonic flowmeter comprising a plurality of flow paths.

  According to a second aspect of the present invention, in the ultrasonic flowmeter according to the first aspect, a plurality of flow paths are arranged at equal angles around a straight line connecting the ultrasonic transducers. .

  According to a third aspect of the present invention, in the ultrasonic flowmeter according to the second aspect, the angle of inclination at which the axis of the flow path intersects the straight line connecting the ultrasonic transducers is the same angle in any flow path. It is characterized by this.

The invention according to claim 4 is the ultrasonic flowmeter according to claim 1, 2, or 3, wherein the rectangular shape forming the cross section of the flow path is a width on the side far from the straight line connecting the ultrasonic transducers ( By defining W ₁ ) to be larger than the width (W ₂ ) on the other side, the channel cross section is trapezoidal.

  The invention according to claim 5 is the ultrasonic flowmeter according to claim 3 or 4, characterized in that the number of flow paths is three and the cross-sectional dimensions of the respective flow paths are determined to be the same.

  Since the present invention is configured as described above, the height / width of the rectangle, which is the aspect ratio of each flow path, can be increased, and the height of the rectangle can be decreased. Therefore, an ultrasonic flowmeter which is advantageous for forming a two-dimensional flow and has a small outer dimension can be realized.

In the invention of claim 4, the width is defined as W ₁ > W ₂ as compared with the case where the width (W ₁ ) on one side is set to be equal to the width (W ₂ ) on the other side. The flow velocity on the larger side is increased, and the accuracy on the flow meter side is further improved.

  Next, the best mode for carrying out the present invention will be described based on the embodiments shown in the drawings.

  FIG. 3 is a cross-sectional view of one embodiment of the flowmeter of the present invention, and 4, 5, 6, 9, 10, 11, 13, and 14 are the same as those in FIG. In this embodiment, the channel cross section perpendicular to the flow is a rectangular shape having a height H and a width W, and the length of the channel is L. This flow path is denoted by reference numeral 1a. 3a is a flow path part provided with the flow path 1a. In this embodiment, as shown in FIGS. 4A, 4B, 4C, and 4D, the axis Xa-Xa of the flow path 1a is inclined by an angle θ with respect to the straight line 6 through which the ultrasonic waves propagate. Arranged. In addition to the flow path 1a, the flow paths 1b and 1c having the same shape as the flow path 1a and having a height H × width W having a rectangular cross section are arranged around the straight line 6 as shown in FIGS. The circumference is divided into three equal parts and arranged at intervals of 120 °. The channels 1b and 1c are inclined by an angle θ with respect to the straight line 6 through which the ultrasonic wave propagates in the same manner as the channel 1a.

  The flow path portions 3a, 3b, and 3c provided with the flow paths 1a, 1b, and 1c, respectively, extend in the shape of ridges in the L direction, which is the longitudinal direction of the flow path, and constitute the measurement tube 30 integrally. . In other words, the flow path portions 3a, 3b, and 3c are formed in the measurement tube 30, and the flow path portions 3a, 3b, and 3c are provided with flow paths 1a, 1b, and 1c having rectangular cross sections, respectively. A single straight line (that is, an ultrasonic propagation path) 6 connecting the ultrasonic transducers 4 and 5 shown in FIG. 3 is formed with respect to the axis lines Xa-Xa of these three flow paths 1a, 1b, and 1c. Cross at an angle θ. In FIG. 5, reference numeral 15 denotes a virtual center hole indicated by a virtual line having a diameter A (two-dot chain line) at a portion where the three flow paths 1a, 1b, and 1c overlap each other.

  Since the ultrasonic wave obliquely crosses the flow paths 1a, 1b, and 1c along the straight line 6, the propagation time corresponding to the cross-sectional average flow velocity of the flow path is measured, and the flow velocity is calculated based on the propagation time.

One channel 1a, 1b, each flow path cross-sectional area of 1c, is substantially H × W, the flow path cross-sectional area S _T as a flow rate meter cross-sectional area of the central bore and S _0,
S _T = (H · W−S ₀ ) × 3 + S ₀
It becomes. Therefore, the measurement capacity of the flow meter is the maximum flow velocity x _ST
It is represented by The aspect ratio can be set to 20: 5 by setting the height H and the width W of each of the flow paths 1a, 1b, and 1c to, for example, the height H = 20 mm and the width W = 5 mm.

  In FIG. 4, a flange 30 </ b> A for attaching the measurement tube 30 to the partition wall 12 of FIG. 3 is formed at the center of the measurement tube 30.

Instead of forming the channels 1a, 1b, and 1c in a rectangular cross section having a height H and a width W as described above, a cross section perpendicular to the flow may be trapezoidal. As shown in FIGS. 4C and 4D and FIG. 5, the width of the rectangular cross section of the flow path 1a may be W ₁ and W _2, and W ₁ > W _{2 so} as to have a trapezoidal cross section. Thus, by making the width W ₁ on the side where the distance from the propagation path 6 of the ultrasonic wave is larger than the width W ₂ on the side where the distance from the propagation path 6 is smaller, the end side W _{1 of the} cross section is rectangular. It is possible to reduce a decrease in flow velocity due to a decrease in the flow velocity of the fluid flowing along the wall surface due to viscosity, and to reduce errors in flow measurement. Flow path 1a of the trapezoidal cross-section, in FIG. 4 (c), the width of the illustrated upper portion of the flow path 1a is in W _1, the width of the lower end portion is W _2. Then, the width of the bottom end portion shown in FIG. 4 (d) in the flow path 1a is _{W 1,} the width of the upper portion is _{W 2.} As described above, the width of the flow path 1a is determined so as to gradually change depending on the position in the left-right direction, that is, the longitudinal direction L in FIG. In FIG. 2B, the width W of the flow path 1a in the direction perpendicular to the drawing surface of the upper edge is W _{1 at} the left end and W ₂ at the right end. In FIG. 2B, the width W in the direction perpendicular to the drawing of the lower edge of the flow path 1a is W _{2 at} the left end in the figure and W ₁ at the right end in the figure. These widths are determined so as to continuously change in a linear function from the left to the right in FIG. Therefore, in the central portion of the length L, the width of the channel cross section is (W ₁ + W ₂ ) / 2, and the cross-sectional shape is a rectangular cross section having a height of H and a width of (W ₁ + W ₂ ) / 2. That is, the shape of the cross section of the flow path changes as it moves in the flow direction.

  The shape of the cross section of the flow path is not limited to a rectangle and a trapezoid as described above, and may be other shapes as long as it is substantially rectangular.

Further, the number of flow paths is not limited to three in the above embodiment.
The ultrasonic pulse is repeatedly transmitted and received between the ultrasonic transducers 4 and 5 alternately in the forward direction and the reverse direction, and the flow rate is calculated based on the propagation time in the forward direction and the reverse direction to calculate the flow rate. .

  In the above embodiment, since the number of flow paths is three, the capacity that can be measured can be obtained if the flow path cross-sectional shape has the same aspect ratio as compared with the case of using one flow path as in the prior art. If it is the same, the height H can be reduced to 1/3 of the prior art. Further, if the same height H as in the prior art is allowed, the aspect ratio can be increased by about 3 times, which is advantageous for forming a two-dimensional flow.

  The ultrasonic flowmeter of the present invention can be applied to gas or liquid flow measurement.

It is the schematic explaining the flow path shape of a prior art, and the arrangement | positioning relationship between a flow path and an ultrasonic transducer | vibrator, (a) is a longitudinal cross-sectional view, (b) is a cross-sectional view. It is a longitudinal cross-sectional view of the ultrasonic flowmeter of a prior art. It is a longitudinal cross-sectional view of the Example of this invention. In the drawing of the measuring tube in the present invention, (a) is a plan view, (b) is a longitudinal sectional view, (c) is a left side view, and (d) is a right side view. FIG. 5 is an enlarged view corresponding to FIG.

Explanation of symbols

1a, 1b, 1c flow path 3a, 3b, 3c flow path section 4, 5 ultrasonic transducer 6 straight line connecting ultrasonic transducers (ultrasonic propagation path)
W, W ₁ , W ₂ width H height Xa-Xa axis θ angle 30 measuring tube

Claims (5)

In an ultrasonic flowmeter in which a channel cross section having a substantially rectangular cross section is inclined relative to a straight line connecting a pair of ultrasonic transducers,
An ultrasonic flowmeter comprising a plurality of flow paths.   The ultrasonic flowmeter according to claim 1, wherein a plurality of flow paths are arranged at equal angles around a straight line connecting the ultrasonic transducers.   The ultrasonic flowmeter according to claim 2, wherein an angle of inclination at which the axis of the flow path intersects with a straight line connecting the ultrasonic transducers is the same angle in any flow path. By defining the width (W ₁ ) on the side far away from the straight line connecting the ultrasonic transducers so that the rectangular shape forming the cross section of the flow path is larger than the width (W ₂ ) on the other side, 4. The ultrasonic flowmeter according to claim 1, 2 or 3, wherein the cross section is trapezoidal. The ultrasonic flowmeter according to claim 3 or 4, wherein the number of flow paths is three and the cross-sectional dimensions of the respective flow paths are determined to be the same.

Images