Ultrasonic flowmeter

Abstract

An ultrasonic flowmeter according to the present invention is provided with: a measurement flow path formation section that forms a measurement flow path through which a fluid under measurement flows from an upstream side to a downstream side along a prescribed flow direction and that extends in a prescribed extending direction; a first ultrasonic transducer that is disposed on one side in an intersecting direction intersecting the extending direction of the measurement flow path formation section and that has a first ultrasonic transmission / reception wavefront for transmitting and receiving ultrasonic waves; and a second ultrasonic transducer that is disposed on the other side in the intersecting direction of the measurement flow path formation section and that has a second ultrasonic transmission / reception wavefront for transmitting and receiving ultrasonic waves. A first intersection of a first virtual line and an inner surface on the proximal side with respect to the first ultrasonic transmission / reception wavefront among the inner surfaces of the measurement flow path formation section, the first virtual line passing through the downstream end of the first ultrasonic transmission / reception wavefront and being parallel to the propagation path of an ultrasonic wave transmitted from the first ultrasonic transducer, is disposed downstream of a second intersection of a second virtual line and an inner surface on the proximal side with respect to the second ultrasonic transmission / reception wavefront among the inner surfaces of the measurement flow path formation section, the second virtual line passing through the upstream end of the second ultrasonic transmission / reception wavefront and being parallel to the propagation path of an ultrasonic wave transmitted from the second ultrasonic transducer.

Description

ultrasonic flow meter

[0001] The present disclosure relates to ultrasonic flow meters.

[0002] Conventionally, there has been known an ultrasonic flowmeter having a flow rate measuring section (measurement flow path) having a rectangular cross section and arranged so that the long side of the rectangular cross section is horizontal, and a pair of ultrasonic vibrators arranged horizontally opposite each other with the flow rate measuring section sandwiched between them (see Patent Document 1). In this ultrasonic flowmeter, the other ultrasonic vibrator is arranged downstream of one ultrasonic vibrator.

[0003] Japanese Unexamined Patent Publication No. 10-19618

[0004] However, the above document does not clearly state the width of the measurement flow path, the dimensions of the ultrasonic wave transmitting and receiving surface of the ultrasonic transducer, and the positional relationship between the measurement flow path and the ultrasonic wave transmitting and receiving surface, so there is a risk that the ultrasonic waves may not pass through the area related to the entire flow velocity distribution. Therefore, there is room for improvement in the accuracy of flow rate measurement.

[0005] Therefore, an object of the present disclosure is to provide an ultrasonic flowmeter that is capable of measuring flow rates using ultrasonic waves with high accuracy.

[0006] The ultrasonic flowmeter of the present disclosure forms a measurement flow path in which a fluid to be measured flows from an upstream side to a downstream side along a predetermined flow direction, and includes: a measurement flow path forming section extending in a predetermined extension direction; a first ultrasonic transmitter / receiver arranged on one side of a cross direction intersecting the extension direction of the measurement flow path forming section, the first ultrasonic transmitter / receiver having a first ultrasonic transmitting / receiving surface for transmitting and receiving ultrasonic waves; and a second ultrasonic transmitter / receiver arranged on the other side of the cross direction of the measurement flow path forming section, the second ultrasonic transmitter / receiver having a second ultrasonic transmitter / receiver surface for transmitting and receiving ultrasonic waves, wherein an outer surface of the one side of the measurement flow path forming section is provided with a first opening through which ultrasonic waves transmitted by the first ultrasonic transmitter / receiver to the second ultrasonic transmitter / receiver pass and through which ultrasonic waves transmitted by the second ultrasonic transmitter / receiver to the first ultrasonic transmitter / receiver pass, The outer surface of the other side of the forming portion is provided with a second opening through which ultrasonic waves transmitted by the first ultrasonic transmitter-receiver toward the second ultrasonic transmitter-receiver pass and through which ultrasonic waves transmitted by the second ultrasonic transmitter-receiver toward the first ultrasonic transmitter-receiver pass, and a first intersection between a first virtual line passing through the downstream end of the first ultrasonic transmitter-receiver surface and parallel to the propagation path of the ultrasonic waves transmitted from the first ultrasonic transmitter-receiver and the inner surface of the measurement flow path forming portion that is proximal with respect to the first ultrasonic transmitter-receiver surface is located downstream of a second intersection between a second virtual line passing through the upstream end of the second ultrasonic transmitter-receiver surface and parallel to the propagation path of the ultrasonic waves transmitted from the second ultrasonic transmitter-receiver and the inner surface of the measurement flow path forming portion that is proximal with respect to the second ultrasonic transmitter-receiver surface.

[0007] According to the present disclosure, because the first intersection is located downstream of the second intersection, ultrasonic waves can more easily pass through the region related to the entire flow velocity distribution than in an embodiment in which the first intersection is located upstream of the second intersection. This makes it possible to calculate the flow velocity with high accuracy based on the ultrasonic waves passing through the region related to the entire flow velocity distribution, and to calculate the flow rate with high accuracy based on the flow velocity and the cross-sectional area of ​​the measurement flow path. As a result, high accuracy in flow rate measurement can be achieved.

[0008] In the above disclosure, when the distance between the first intersection and the second intersection in the extension direction is X, the width of the first ultrasonic transmitting and receiving surface and the second ultrasonic transmitting and receiving surface is S, the width of the measurement flow path is W, and the angle of the propagation direction of the ultrasonic waves with respect to the flow direction is θ, X = (S / sin θ) - (W / tan θ) may be established.

[0009] According to the above configuration, by establishing the above calculation formula, it is possible to realize an embodiment in which the first downstream end is disposed downstream of the second upstream end.

[0010] In the above disclosure, X may be greater than 0 and less than S.

[0011] According to the above configuration, by setting the distance X to be greater than 0 and less than the width S, it is possible to design with variations in the distance X, while assuming that a configuration in which the first downstream end is positioned downstream of the second upstream end is realized.

[0012] In the above disclosure, the first opening and the second opening may each be provided with a mesh member.

[0013] According to the above configuration, the mesh member can suppress the generation of turbulent flow, which occurs when the velocity of the fluid to be measured is relatively high, and laminar flow, which occurs when the velocity of the fluid to be measured is relatively low, near each ultrasonic transmitter / receiver, thereby suppressing interference of the ultrasonic waves transmitted from each ultrasonic transmitter / receiver with the turbulent flow and laminar flow.

[0014] In the above disclosure, the ultrasonic flowmeter may further include a partition plate provided in the measurement flow path forming portion, dividing the measurement flow path into a plurality of divided flow paths, and having a surface along the flow direction.

[0015] According to the above configuration, the measurement target fluid that has flowed into the measurement flow path is divided into the plurality of divided flow paths and rectified, thereby making it possible to suppress a decrease in measurement accuracy due to turbulence in the measurement target fluid.

[0016] The ultrasonic flowmeter of the present disclosure forms a measurement flow path through which a fluid to be measured flows from an upstream side to a downstream side along a predetermined flow direction, and includes: a measurement flow path forming section extending in a predetermined extension direction; a first ultrasonic transmitter / receiver disposed on one side of the measurement flow path forming section in a cross direction intersecting the extension direction, the first ultrasonic transmitter / receiver having a first ultrasonic transmitting / receiving surface for transmitting and receiving ultrasonic waves; and a second ultrasonic transmitter / receiver disposed on one side of the cross direction of the measurement flow path forming section and downstream of the first ultrasonic transmitter / receiver in the extension direction, the second ultrasonic transmitter / receiver having a second ultrasonic transmitter / receiver surface for transmitting and receiving ultrasonic waves, wherein an outer surface of the one side of the measurement flow path forming section is provided with a first opening through which ultrasonic waves transmitted by the first ultrasonic transmitter / receiver toward the second ultrasonic transmitter / receiver and ultrasonic waves transmitted by the second ultrasonic transmitter / receiver toward the first ultrasonic transmitter / receiver and reflected by a reflecting section on an inner surface of the measurement flow path forming section pass. The outer surface of one of the measurement flow path forming portions further has a second opening, which is positioned downstream of the first opening in the extension direction and through which ultrasonic waves transmitted by the second ultrasonic transmitter-receiver toward the first ultrasonic transmitter-receiver and ultrasonic waves transmitted by the first ultrasonic transmitter-receiver toward the second ultrasonic transmitter-receiver and reflected by the reflecting portion pass, and a first intersection between a first virtual line passing through the downstream end of the first ultrasonic transmitter-receiver surface and parallel to the propagation path of the ultrasonic waves transmitted from the first ultrasonic transmitter-receiver and the inner surface of the measurement flow path forming portion that is proximal with respect to the first ultrasonic transmitter-receiver surface is positioned downstream of a second intersection between a second virtual line passing through the upstream end of the second ultrasonic transmitter-receiver surface and parallel to the propagation path of the ultrasonic waves transmitted from the second ultrasonic transmitter-receiver and the inner surface of the measurement flow path forming portion that is distal with respect to the second ultrasonic transmitter-receiver surface.

[0017] According to the present disclosure, because the first intersection is located downstream of the second intersection, ultrasonic waves can more easily pass through the region related to the entire flow velocity distribution than in an embodiment in which the first intersection is located upstream of the second intersection. This makes it possible to calculate the flow velocity with high accuracy based on the ultrasonic waves passing through the region related to the entire flow velocity distribution, and to calculate the flow rate with high accuracy based on the flow velocity and the cross-sectional area of ​​the measurement flow path. As a result, high accuracy in flow rate measurement can be achieved.

[0018] In the above disclosure, the ultrasonic flowmeter may further include a partition plate provided in the measurement flow path forming portion, dividing the measurement flow path into a plurality of divided flow paths, and having a surface along the flow direction.

[0019] According to the above configuration, the measurement target fluid that has flowed into the measurement flow path is divided into the plurality of divided flow paths and rectified, thereby making it possible to suppress a decrease in measurement accuracy due to turbulence in the measurement target fluid.

[0020] According to the present disclosure, it is possible to provide an ultrasonic flowmeter that is capable of measuring flow rates using ultrasonic waves with high accuracy.

[0021] FIG. 5 is a diagram showing the configuration of an ultrasonic flowmeter in one embodiment. FIG. 6 is a diagram for explaining the principle of flow velocity measurement. FIG. 3A is a diagram showing ultrasonic waves passing through a region of the flow velocity distribution in the ultrasonic flowmeter of FIG. 1, and FIG. 3B is a diagram showing ultrasonic waves passing through a region of the flow velocity distribution in an ultrasonic flowmeter according to a comparative example. FIG. 6 is a diagram showing a partition plate in the measurement flow path of the ultrasonic flowmeter of FIG. 1. FIG. 7 is a diagram showing the configuration of an ultrasonic flowmeter in one embodiment. FIG. 8 is a diagram showing a partition plate in the measurement flow path of the ultrasonic flowmeter of FIG.

[0022] An ultrasonic flowmeter according to an embodiment of the present disclosure will be described below with reference to the drawings. The ultrasonic flowmeter described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiment, and additions, deletions, and modifications are possible within the scope of the present disclosure.

[0023] (First embodiment) Fig. 1 is a diagram showing the configuration of an ultrasonic flowmeter 50 according to one embodiment. Fig. 2 is a diagram for explaining the principle of measuring flow velocity.

[0024] 1 , the ultrasonic flowmeter 50 includes a measurement flow path forming unit 20, a first ultrasonic transmitter / receiver 4, and a second ultrasonic transmitter / receiver 5. The first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are each capable of transmitting and receiving ultrasonic waves. The second ultrasonic transmitter / receiver 5 can receive ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4, and the first ultrasonic transmitter / receiver 4 can receive ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 5.

[0025] The measurement flow path forming portion 20 is formed in a tubular shape. The measurement flow path forming portion 20 forms a measurement flow path 1 through which the fluid to be measured flows from the upstream side (left side in FIG. 1) to the downstream side (right side in FIG. 1) along a predetermined direction D1. The measurement flow path forming portion 20 has a predetermined cross section, for example, a rectangular cross section (transverse cross section of the measurement flow path forming portion 20) or a circular cross section. The measurement flow path forming portion 20 extends in the direction D1. As a result, the measurement flow path 1 extends in the direction D1. The measurement flow path 1 has an inlet 1a and an outlet 1b. The fluid to be measured flows in from the inlet 1a of the measurement flow path 1 and then flows out from the outlet 1b. In this embodiment, the direction D1 corresponds to the flow direction and the extension direction. The fluid to be measured may be, for example, a liquid such as water or a gas such as air.

[0026] The first ultrasonic transmitter / receiver 4 is disposed on one side (upper side in FIG. 1 ) of the measurement flow path forming portion 20 in a cross direction D3 that crosses the direction D1. The first ultrasonic transmitter / receiver 4 has a first ultrasonic transmitting / receiving surface 4a that transmits and receives ultrasonic waves. The ultrasonic waves transmitted from the first ultrasonic transmitting / receiving surface 4a propagate through a propagation path PP1. The first ultrasonic transmitter / receiver 4 is disposed so that the propagation direction D2 of the ultrasonic waves transmitted from the first ultrasonic transmitting / receiving surface 4a forms an angle θ with respect to the direction D1.

[0027] The second ultrasonic transmitter / receiver 5 has basically the same configuration as the first ultrasonic transmitter / receiver 4 described above. The second ultrasonic transmitter / receiver 5 is arranged at a distance from the first ultrasonic transmitter / receiver 4. The second ultrasonic transmitter / receiver 5 is arranged on the other side (lower side in FIG. 1 ) of the measurement flow path forming section 20 in the intersecting direction D3. The second ultrasonic transmitter / receiver 5 has a second ultrasonic transmitter / receiver surface 5a that transmits and receives ultrasonic waves. The ultrasonic waves transmitted from the second ultrasonic transmitter / receiver surface 5a propagate through the propagation path PP2. The width S of the second ultrasonic transmitter / receiver surface 5a is the same as the width S of the first ultrasonic transmitter / receiver surface 4a. The second ultrasonic transmitter / receiver 5 is arranged so that the propagation direction D2 of the ultrasonic waves transmitted from the second ultrasonic transmitter / receiver surface 5a forms an angle θ with respect to the direction D1.

[0028] The first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are each electrically connected to a signal processing unit (not shown). The signal processing unit receives ultrasonic signals from the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 and calculates the flow velocity of the fluid to be measured and a flow rate based on the flow velocity. Below, a method for calculating the flow velocity and flow rate of the fluid to be measured in an ultrasonic flowmeter 150 with a general configuration will be described. Note that the method for calculating the flow velocity and flow rate of the fluid to be measured in the ultrasonic flowmeter 150 can also be applied to the ultrasonic flowmeter 50 of this embodiment.

[0029] 2, the ultrasonic propagation distance within measurement flow path forming portion 20, i.e., the ultrasonic propagation distance in measurement flow path 1, is denoted as M, the angle formed by ultrasonic propagation direction D2 with respect to direction D1 as described above is denoted as θ, the sound speed is denoted as C, and the propagation times of ultrasonic waves in the section of ultrasonic propagation distance M are denoted as T1 and T2. Propagation time T1 corresponds to the ultrasonic waves transmitted from first ultrasonic transmitter / receiver 4, and propagation time T2 corresponds to the ultrasonic waves transmitted from second ultrasonic transmitter / receiver 5. Also, the flow velocity of the fluid to be measured is denoted as U. In this case, propagation time T1 is calculated using the following equation 1, and propagation time T2 is calculated using the following equation 2.

[0030] (Math. 1) T1=M / (C+Ucosθ)

[0031] (Math. 2) T2=M / (C-Ucosθ)

[0032] By eliminating the sound velocity C from the above formulas 1 and 2, the following formula 3 is obtained: Therefore, the flow velocity U of the fluid to be measured is calculated from formula 3.

[0033] (Equation 3) U = (M / 2 cos θ) × {(1 / T1) - (1 / T2)}

[0034] Here, a first opening 2 is provided on the outer surface of measurement flow path forming portion 20 on one side in intersecting direction D3. The first opening 2 allows ultrasonic waves transmitted by first ultrasonic transmitter / receiver 4 toward second ultrasonic transmitter / receiver 5 to pass through, and allows ultrasonic waves transmitted by second ultrasonic transmitter / receiver 5 toward first ultrasonic transmitter / receiver 4 to pass through. First opening 2 has a first upstream end 2u and a first downstream end 2d located downstream of first upstream end 2u in direction D1. This prevents interference between ultrasonic waves transmitted by first ultrasonic transmitter / receiver 4 and ultrasonic waves received by first ultrasonic transmitter / receiver 4.

[0035] 1, a mesh member 6 is provided at the first opening 2. The mesh member 6 is provided so as to cover the first opening 2 from the inside of the measurement flow path forming portion 20. An example of the mesh member 6 is a wire mesh. Note that the mesh member 6 is not limited to a wire mesh, and for example, a woven fabric having a mesh pattern may be used.

[0036] Without this mesh member 6 and the mesh member 7 described below, fluid from the measurement flow path 1 would flow into the cavity (spatial region) in front of the first ultrasonic transmitter / receiver 4 and the cavity in front of the second ultrasonic transmitter / receiver 5, or vortices would be generated by the flow of fluid in the measurement flow path 1. The ultrasonic waves propagating between the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 would also measure the flow in the cavity generated as described above, resulting in errors. On the other hand, providing the mesh members 6 and 7 can prevent the generation of flow in the cavity. This creates a state where there is almost no flow velocity in the cavity, preventing errors due to unwanted flow.

[0037] However, if the propagation time for ultrasonic waves to pass through the cavity is t, an error of 2t occurs corresponding to the cavity in front of the first ultrasonic transmitter / receiver 4 and the cavity in front of the second ultrasonic transmitter / receiver 5. Therefore, it is necessary to correct the propagation time used in the flow velocity calculation. In this case, if the propagation times of ultrasonic waves between the first ultrasonic transmitter / receiver 4 and the second ultrasonic transmitter / receiver 5 are T1' and T2', respectively, and the propagation time for ultrasonic waves to pass through the cavity as described above is t, then T1 = T1' - 2t and T2 = T2' - 2t hold. This T1 is used as T1 in the above-mentioned Equation 1, and T2 is used as T2 in the above-mentioned Equation 2.

[0038] However, even if mesh members 6 and 7 are not provided and a flow occurs in the cavity, if the error in the propagation time due to the flow velocity of the fluid occurring in the cavity can be determined, it is possible to calculate the flow velocity taking that error into account. Therefore, mesh members 6 and 7 are not essential components.

[0039] A second opening 3 is provided on the outer surface of the measurement flow path forming section 20 on the other side in the intersecting direction D3. The second opening 3 allows ultrasonic waves transmitted by the first ultrasonic transmitter / receiver 4 toward the second ultrasonic transmitter / receiver 5 to pass through, and allows ultrasonic waves transmitted by the second ultrasonic transmitter / receiver 5 toward the first ultrasonic transmitter / receiver 4 to pass through. The second opening 3 has a second upstream end 3u and a second downstream end 3d located downstream of the second upstream end 3u in the direction D1. This prevents interference between the ultrasonic waves transmitted by the second ultrasonic transmitter / receiver 5 and the ultrasonic waves received by the second ultrasonic transmitter / receiver 5.

[0040] Similar to the first opening 2, a mesh member 7 is provided at the second opening 3. The mesh member 7 is provided so as to cover the second opening 3 from the inside of the measurement flow-path forming portion 20. As with the mesh member 6 at the first opening 2, an example of the mesh member 7 at the second opening 3 is a wire mesh.

[0041] 1 , a first virtual line Lv1 is defined as a virtual line that passes through the downstream end of the first ultrasonic transmitting / receiving surface 4a and is parallel to the propagation path PP1 of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4. A second virtual line Lv2 is defined as a virtual line that passes through the upstream end of the second ultrasonic transmitting / receiving surface 5a and is parallel to the propagation path PP2 of the ultrasonic waves transmitted from the second ultrasonic transmitter / receiver 5. A first intersection P1 between the first virtual line Lv1 and a proximal inner surface of the inner surface of the measurement flow-channel forming unit 20 with respect to the first ultrasonic transmitting / receiving surface 4a is located downstream of a second intersection P2 between the second virtual line Lv2 and a proximal inner surface of the inner surface of the measurement flow-channel forming unit 20 with respect to the second ultrasonic transmitting / receiving surface 5a. A method for calculating the distance X in the direction D1 between the first intersection P1 and the second intersection P2 will be described below with reference to FIG. 1 . The intersection of an imaginary line passing through the upstream end of the first ultrasonic transmitting and receiving surface 4a and parallel to the propagation path PP1 with the inner surface of the measurement flow path forming unit 20 that is closer to the first ultrasonic transmitting and receiving surface 4a is defined as upstream intersection point P5. The intersection of an imaginary line passing through the downstream end of the second ultrasonic transmitting and receiving surface 5a and parallel to the propagation path PP2 with the inner surface of the measurement flow path forming unit 20 that is closer to the second ultrasonic transmitting and receiving surface 5a is defined as downstream intersection point P6.

[0042] In FIG. 1, when the distance between the second intersection point P2 and the downstream intersection point P6 is L and the distance in the direction D1 between the first intersection point P1 and the downstream intersection point P6 is A, the distance X is calculated by the following equation 4.

[0043] (Math. 4) X=LA

[0044] 1, distance A can be calculated by the following equation 5. In equation 5, B is the distance in the propagation direction D2 between the first intersection point P1 and the downstream intersection point P6, but it does not need to be known.

[0045] (Equation 5) A = B cos θ

[0046] 1, the distance B can be calculated by the following formula 6. In formula 6, W is the width of the measurement flow path 1.

[0047] (Equation 6) B = W / sin θ

[0048] From the above equations 5 and 6, the distance X can be calculated by the following equation 7.

[0049] (Math. 7) X=L-(W / tanθ)

[0050] 1, the distance L can be calculated by the following formula 8. In formula 8, S is the width of the first ultrasonic transmitting and receiving surface 4a and the second ultrasonic transmitting and receiving surface 5a.

[0051] (Equation 8) L = S / sin θ

[0052] Therefore, from the above equations 7 and 8, the distance X can be calculated by the following equation 9.

[0053] (Math. 9) X=(S / sinθ)−(W / tanθ)

[0054] Next, FIG. 3A is a diagram showing ultrasonic waves passing through the region of flow velocity distribution FD in the ultrasonic flowmeter 50 of FIG. 1, and FIG. 3B is a diagram showing ultrasonic waves passing through the region of flow velocity distribution FD in an ultrasonic flowmeter 150 according to a comparative example.

[0055] In the above formula 9, the width S of the first ultrasonic transmitting and receiving surface 4a and the second ultrasonic transmitting and receiving surface 5a, the width W of the measurement flow path 1, and the angle θ are determined so that the distance X is greater than 0 and less than the width S. This makes it easier for ultrasonic waves to pass through a region related to the entire flow velocity distribution in the ultrasonic flowmeter 50. In this case, as shown in FIG. 3A, the ultrasonic waves pass through the entire range of the region showing the flow velocity distribution FD in the measurement flow path 1. For ease of understanding, the entire range is indicated by an arrow in FIG. 3A.

[0056] In contrast, in the ultrasonic flowmeter 150 shown in Fig. 3B, the first downstream end 2d is disposed upstream of the second upstream end 3u in the direction D1, and therefore 0 < X ​​< S is not satisfied. Therefore, as shown in Fig. 3B, in the ultrasonic flowmeter 150, ultrasonic waves pass through only a part of the region showing the flow velocity distribution FD in the measurement flow path 1. For ease of understanding, the part of the region is indicated by an arrow in Fig. 3B.

[0057] Fig. 4 is a diagram showing a partition plate 30 in the measurement flow path 1 of the ultrasonic flowmeter 50. As shown in Fig. 4, the ultrasonic flowmeter 50 may further include a plurality of partition plates 30 that are provided in the measurement flow path forming portion 20, divide the measurement flow path 1 into a plurality of divided flow paths 31, and have surfaces along the direction D1. Note that the direction D4 in Fig. 4 is a direction perpendicular to both the direction D1 and the intersecting direction D3.

[0058] The partition plate 30 is formed, for example, in a flat plate shape and is provided so as to extend in direction D1. The partition plate 30 is arranged in the measurement flow path 1 so that the thickness direction of the partition plate 30 is parallel to direction D4. The distance between one partition plate 30 and the other partition plate 30 adjacent to each other in direction D4 may be, for example, the same. In this configuration, the fluid to be measured that has flowed into the measurement flow path 1 is diverted into the divided flow paths 31 formed by the partition plate 30 and rectified. This makes it possible to suppress a decrease in measurement accuracy caused by turbulence in the fluid to be measured.

[0059] As described above, according to the ultrasonic flowmeter 50 of this embodiment, since the first intersection P1 is located downstream of the second intersection P2, ultrasonic waves can more easily pass through the region related to the entire flow velocity distribution than in an embodiment in which the first intersection P1 is located upstream of the second intersection P2. This makes it possible to calculate the flow velocity with high accuracy based on the ultrasonic waves passing through the region related to the entire flow velocity distribution, and to calculate the flow rate with high accuracy based on the flow velocity and the cross-sectional area of ​​the measurement flow path. As a result, high accuracy in flow rate measurement can be achieved.

[0060] 5 is a diagram showing the configuration of an ultrasonic flowmeter 50A in one embodiment. In this embodiment, elements that are the same as or correspond to those in the first embodiment are given the same reference numerals throughout the drawings, and duplicated descriptions will be omitted unless otherwise noted.

[0061] In this embodiment, the first ultrasonic transmitter / receiver 4 is disposed on one side (upper side in FIG. 5 ) of the measurement flow path forming section 20 in the intersecting direction D3. The second ultrasonic transmitter / receiver 5 is disposed on one side (upper side in FIG. 5 ) of the measurement flow path forming section 20 in the intersecting direction D3, and is disposed downstream of the first ultrasonic transmitter / receiver 4 in the direction D1.

[0062] A first opening 2 and a second opening 3 are provided on the outer surface of measurement flow path forming section 20 on one side in intersecting direction D3. Second opening 3 is disposed spaced apart from first opening 2 in direction D1 and is provided downstream of first opening 2. First opening 2 allows passage of ultrasonic waves transmitted by first ultrasonic transmitter / receiver 4 toward second ultrasonic transmitter / receiver 5, and ultrasonic waves transmitted by second ultrasonic transmitter / receiver 5 toward first ultrasonic transmitter / receiver 4 and reflected by reflecting section 21 on the inner surface of measurement flow path forming section 10. Second opening 3 allows passage of ultrasonic waves transmitted by second ultrasonic transmitter / receiver 5 toward first ultrasonic transmitter / receiver 4, and ultrasonic waves transmitted by first ultrasonic transmitter / receiver 4 toward second ultrasonic transmitter / receiver 5 and reflected by reflecting section 21.

[0063] In addition, the second ultrasonic transmitter / receiver 5 is arranged in a manner that makes the first ultrasonic transmitter / receiver 4 linearly symmetrical with respect to the virtual line Ts, which is a virtual line parallel to the intersecting direction D3 and passes through the intersection P7 between the propagation path PP1 of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver 4 and the bottom surface on the inner surface of the measurement flow path forming section 10.

[0064] 5 , a first virtual line Lv1 is defined as a virtual line that passes through the downstream end of the first ultrasonic transmitting and receiving surface 4a and is parallel to the propagation path PP1 of the ultrasonic waves transmitted from the first ultrasonic transmitter and receiver 4. A second virtual line Lv2 is defined as a virtual line that passes through the upstream end of the second ultrasonic transmitting and receiving surface 5a and is parallel to the propagation path PP2 of the ultrasonic waves transmitted from the second ultrasonic transmitter and receiver 5. In this case, a first intersection P1 between the first virtual line Lv1 and the inner surface of the measurement flow-channel forming unit 20 that is closer to the proximal side with respect to the first ultrasonic transmitting and receiving surface 4a is located downstream of a second intersection P2 between the second virtual line Lv2 and the inner surface of the measurement flow-channel forming unit 20 that is closer to the distal side with respect to the second ultrasonic transmitting and receiving surface 5a.

[0065] A method for calculating the distance X in the direction D1 between the first intersection point P1 and the second intersection point P2 will be described below with reference to FIG.

[0066] 5, when the distance in direction D1 between the second intersection P2 and the fourth intersection P4 is L and the distance in direction D1 between the first intersection P1 and the fourth intersection P4 is A, the distance X is calculated by the following formula 10. Note that the fourth intersection P4 is the intersection between the first virtual line Lv1 and the inner surface of the measurement flow-channel forming portion 20 that is distal to the first ultrasonic transmitting / receiving surface 4a.

[0067] (Math. 10) X=LA

[0068] 5, distance A can be calculated by the following formula 11. In formula 11, B is the distance between the first intersection point P1 and the fourth intersection point P4 in the direction parallel to the propagation path PP1, but it does not need to be known.

[0069] (Equation 11) A = B cos θ

[0070] 5, the distance B can be calculated by the following formula 12. In formula 12, W is the width of the measurement flow path 1.

[0071] (Equation 12) B = W / sinθ

[0072] From the above formulas 11 and 12, the distance X can be calculated by the following formula 13.

[0073] (Math. 13) X=L-(W / tanθ)

[0074] 5, the distance L can be calculated by the following formula 14. In formula 14, S is the width of the first ultrasonic transmitting and receiving surface 4a and the second ultrasonic transmitting and receiving surface 5a.

[0075] (Equation 14) L = S / sin θ

[0076] Therefore, from the above formulas 13 and 14, the distance X can be calculated by the following formula 15. Note that the distance X is equal to or greater than 0.

[0077] (Math. 15) X=(S / sinθ)−(W / tanθ)

[0078] As described above, according to the ultrasonic flowmeter 50A of this embodiment, since the first intersection P1 is located downstream of the second intersection P2, ultrasonic waves can more easily pass through the region related to the entire flow velocity distribution than in an embodiment in which the first intersection P1 is located upstream of the second intersection P2. In this case, as shown in FIG. 5 , ultrasonic waves pass through the entire range of the region showing the flow velocity distribution FD in the measurement flow path 1. This makes it possible to calculate the flow velocity with high accuracy based on the ultrasonic waves passing through the region related to the entire flow velocity distribution, and to calculate the flow rate with high accuracy based on the flow velocity and the cross-sectional area of ​​the measurement flow path. As a result, high accuracy in flow rate measurement can be achieved.

[0079] In addition, the third intersection P3 between the second virtual line Lv2 and the inner surface of the measurement flow path forming portion 20 that is proximal to the second ultrasonic transmitting / receiving surface 5a may be located upstream of the above-mentioned fourth intersection P4.

[0080] Fig. 6 is a diagram showing a partition plate 30 in the measurement flow path 1 of an ultrasonic flowmeter 50A. As shown in Fig. 6, the above-described ultrasonic flowmeter 50A may further include a plurality of partition plates 30 that are provided in the measurement flow path forming section 20, divide the measurement flow path 1 into a plurality of divided flow paths 31, and have surfaces along direction D1. Note that the configuration and function of the partition plate 30 in Fig. 6 are the same as the configuration and function of the partition plate 30 in Fig. 4 described above, and therefore a description thereof will be omitted.

[0081] 1 Measurement flow path 1a Inlet of measurement flow path 1b Outlet of measurement flow path 2 First opening 2u First upstream end 2d First downstream end 3 Second opening 3u Second upstream end 3d Second downstream end 4 First ultrasonic transmitter / receiver 4a First ultrasonic transmitting / receiving surface 5 Second ultrasonic transmitter / receiver 5a Second ultrasonic transmitting / receiving surface 6 Mesh member 7 Mesh member 20 Measurement flow path forming section 21 Reflecting section 30 Partition plate 31 Divided flow path 50, 50A Ultrasonic flow meter D1 Direction D2 Propagation direction of ultrasonic waves Lv1 First virtual line Lv2 Second virtual line P1 First intersection P2 Second intersection PP1, PP2 Propagation path of ultrasonic waves

Claims

1. A measurement flow path forming section that forms a measurement flow path through which a fluid to be measured flows from upstream to downstream along a predetermined flow direction and that extends in a predetermined extension direction; a first ultrasonic transmitter / receiver that is arranged on one side of the measurement flow path forming section in a cross direction that crosses the extension direction and has a first ultrasonic transmitting / receiving surface for transmitting and receiving ultrasonic waves; and a second ultrasonic transmitter / receiver that is arranged on the other side of the cross direction of the measurement flow path forming section and has a second ultrasonic transmitting / receiving surface for transmitting and receiving ultrasonic waves, wherein an outer surface of the one side of the measurement flow path forming section is provided with a first opening through which ultrasonic waves transmitted by the first ultrasonic transmitter / receiver to the second ultrasonic transmitter / receiver pass and through which ultrasonic waves transmitted by the second ultrasonic transmitter / receiver to the first ultrasonic transmitter / receiver pass; and a second opening that is arranged on the other side of the measurement flow path forming section is provided with a second opening through which ultrasonic waves transmitted by the first ultrasonic transmitter / receiver to the second ultrasonic transmitter / receiver pass and through which ultrasonic waves transmitted by the second ultrasonic transmitter / receiver to the first ultrasonic transmitter / receiver pass. an ultrasonic flow meter, wherein a first intersection point between a first imaginary line that passes through the downstream end of the first ultrasonic transmitting / receiving surface and is parallel to the propagation path of the ultrasonic waves transmitted from the first ultrasonic transmitter / receiver and an inner surface of the measurement flow path forming portion that is proximal with respect to the first ultrasonic transmitting / receiving surface, is located downstream of a second intersection point between a second imaginary line that passes through the upstream end of the second ultrasonic transmitting / receiving surface and is parallel to the propagation path of the ultrasonic waves transmitted from the second ultrasonic transmitter / receiver and an inner surface of the measurement flow path forming portion that is proximal with respect to the second ultrasonic transmitting / receiving surface.

2. The ultrasonic flowmeter according to claim 1, wherein X = (S / sin θ) - (W / tan θ) holds, where X is the distance between the first intersection and the second intersection in the extension direction, S is the width of the first ultrasonic transmitting and receiving surface and the second ultrasonic transmitting and receiving surface, W is the width of the measurement flow path, and θ is the angle of the propagation direction of the ultrasonic waves with respect to the flow direction.

3. The ultrasonic flow meter of claim 2, wherein X is greater than 0 and less than S.

4. An ultrasonic flowmeter according to any one of claims 1 to 3, wherein the first opening and the second opening are each provided with a mesh member.

5. The ultrasonic flowmeter according to claim 1, further comprising a partition plate provided in the measurement flow path forming section, dividing the measurement flow path into a plurality of divided flow paths, and having a surface along the flow direction.

6. A measurement flow path forming section that forms a measurement flow path through which a fluid to be measured flows from upstream to downstream along a predetermined flow direction and that extends in a predetermined extension direction; a first ultrasonic transmitter / receiver that is arranged on one side of the measurement flow path forming section in a cross direction that crosses the extension direction and has a first ultrasonic transmitting / receiving surface for transmitting and receiving ultrasonic waves; and a second ultrasonic transmitter / receiver that is arranged on one side of the cross direction of the measurement flow path forming section and is arranged downstream of the first ultrasonic transmitter / receiver in the extension direction and has a second ultrasonic transmitting / receiving surface for transmitting and receiving ultrasonic waves, wherein a first opening is provided on the outer surface of the one side of the measurement flow path forming section through which ultrasonic waves transmitted by the first ultrasonic transmitter / receiver toward the second ultrasonic transmitter / receiver and ultrasonic waves transmitted by the second ultrasonic transmitter / receiver toward the first ultrasonic transmitter / receiver and reflected by a reflecting portion on the inner surface of the measurement flow path forming section pass, The outer surface of one of the measurement flow path forming portions further has a second opening, which is positioned downstream of the first opening in the extension direction and through which ultrasonic waves transmitted by the second ultrasonic transmitter-receiver toward the first ultrasonic transmitter-receiver and ultrasonic waves transmitted by the first ultrasonic transmitter-receiver toward the second ultrasonic transmitter-receiver and reflected by the reflecting portion pass, and a first intersection of a first imaginary line passing through the downstream end of the first ultrasonic transmitter-receiver surface and parallel to the propagation path of the ultrasonic waves transmitted from the first ultrasonic transmitter-receiver and an inner surface of the measurement flow path forming portion that is proximal with respect to the first ultrasonic transmitter-receiver surface is positioned downstream of a second intersection of a second imaginary line passing through the upstream end of the second ultrasonic transmitter-receiver surface and parallel to the propagation path of the ultrasonic waves transmitted from the second ultrasonic transmitter-receiver and an inner surface of the measurement flow path forming portion that is distal with respect to the second ultrasonic transmitter-receiver surface.

7. The ultrasonic flowmeter according to claim 6, further comprising a partition plate provided in the measurement flow path forming section, dividing the measurement flow path into a plurality of divided flow paths, and having a surface along the flow direction.

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