JP2009019879A - Ultrasonic flowmeter and flow measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter capable of estimating a pattern of a flow velocity distribution state, even if the flow velocity distribution is changed in a flow rate area, without interposing a partition member or the like inside a channel, and calculating the flow rate of fluid to be measured based on the flow velocity distribution pattern. <P>SOLUTION: The ultrasonic flowmeter includes a flow rate calculation part 13 for calculating the flow rate of the fluid to be measured based on a propagation time of an ultrasonic wave transmitted from/received by a pair of ultrasonic elements 10, 20. The pair of ultrasonic elements 10, 20 transmits/receives two or more ultrasonic beam patterns having each mutually-different directivity in correspondence with two or more different frequencies (an upper limit and a lower limit or the like) included in a frequency band of the pair of ultrasonic elements 10, 20, and thereby divides the channel width direction into a plurality of detection areas. The flow rate calculation part 13 estimates the flow velocity distribution of the fluid to be measured based on a propagation time of the two or more ultrasonic beam patterns having each mutually-different directivity, and calculates the flow rate of the fluid to be measured from the estimated flow velocity distribution. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic flowmeter and a flow rate measuring method, and more particularly to an ultrasonic flowmeter that mainly measures the flow velocity and flow rate of a fluid such as a gas, and a flow rate measuring method using the ultrasonic flowmeter.

  Conventionally, it is generally known hydrodynamically that when a flow velocity of a fluid flowing through a flow path is measured, the flow velocity distribution of the fluid flowing through the flow path varies depending on the flow rate. That is, when the flow is slow, a parabolic flow velocity distribution called laminar flow is shown in the channel width direction, and the peak flow velocity and the average flow velocity are different from each other. On the other hand, when the flow becomes faster, the distribution gradually collapses and becomes a basin called a turbulent flow area. The distribution is uniformly equal in the road width direction.

  Further, in the laminar flow region, a slight difference occurs in the parabolic flow velocity distribution shape, and the flow velocity difference in the width direction is not constant. Furthermore, it is generally known that in the laminar flow region, the flow velocity distribution varies depending on the gas type, the flow channel geometry, and the like.

  Thus, if there is a difference in the flow velocity distribution in the flow channel width direction due to the flow rate range, fluid type, flow channel geometry, etc., the ultrasonic transducer transmits and receives ultrasonic waves across the flow velocity distribution by the ultrasonic transducer, When measuring the flowing fluid, the measured average flow velocity is affected by the distribution depending on the flow rate region. Since an error is included in the value measured due to the influence of this distribution, an accurate flow rate cannot be calculated.

  Even if the influence of this error is corrected, it is extremely difficult to correct the flow velocity distribution in the flow region as the average flow velocity because the measured flow velocity distribution itself cannot be grasped.

To deal with such a problem, for example, Patent Document 1 discloses that the influence of this distribution is reduced, and the flow direction inside the flow path is divided into a plurality of areas so as to obtain an averaged flow velocity distribution in any flow rate region. The structure which arrange | positions a partition member inside a flow path is described so that it may divide | segment into 2 and may smooth the parabolic flow velocity distribution which generate | occur | produces especially in a laminar flow area. According to this, since the averaged flow velocity distribution can be measured and handled in the laminar flow region as in the turbulent flow region, an accurate flow velocity can be calculated, and the flow rate can be calculated with high accuracy.
JP 2005-257363 A

  However, in the case of the invention described in Patent Document 1, by inserting the partition member into the flow path, resistance is generated with respect to the flow, and there is a problem that pressure loss becomes significant. Furthermore, there is a limit to the number of partition members, and it is difficult to average the flow velocity distribution in the laminar flow region close to the turbulent flow region with only this finite number of partition members. Even if this pressure loss can be suppressed to a certain level, the stability of the product, yield, etc. may be affected by taking into account the effects of individual differences in the product, assembly accuracy of the partitioning members, variation, temperature factors, etc. There is sex. Furthermore, there is a problem that the number of parts increases due to the addition of the partition member, and the cost increases accordingly.

  The present invention has been made in view of the circumstances as described above, and even if the flow velocity distribution changes in the flow rate region without interposing a partition member or the like inside the flow path, the flow velocity distribution state pattern is estimated, An object of the present invention is to provide an ultrasonic flowmeter capable of calculating the flow rate of the fluid to be measured based on the flow velocity distribution pattern and a flow rate measurement method using the ultrasonic flowmeter.

  In order to solve the above-mentioned problems, the invention of claim 1 is directed to a flow path through which a fluid to be measured flows, a pair of ultrasonic elements disposed at opposite positions across the flow path, and the pair of ultrasonic elements An ultrasonic flowmeter comprising flow rate calculation means for calculating a flow rate of the fluid to be measured based on a propagation time of ultrasonic waves transmitted and received by the pair of ultrasonic elements, wherein the pair of ultrasonic elements is the pair of ultrasonic elements In response to two or more different frequencies included in the frequency band, two or more ultrasonic beam patterns having different directivities are transmitted and received to divide the width direction of the flow path into a plurality of detection areas, The flow rate calculation means estimates a flow velocity distribution of the fluid to be measured based on a propagation time of the two or more ultrasonic beam patterns transmitted and received between the pair of ultrasonic elements or a flow velocity calculated from the propagation time. The estimated Is obtained by the calculating means calculates the flow rate of the fluid to be measured from the speed distribution.

  According to a second aspect of the present invention, in the first aspect, the two or more ultrasonic beam patterns have a beam width that is narrower than a width of the flow path corresponding to an upper limit frequency of the pair of ultrasonic elements. 1 ultrasonic beam pattern, and a second ultrasonic beam pattern having a beam width substantially the same as the width of the flow path corresponding to the lower limit frequency of the pair of ultrasonic elements. is there.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the flow rate calculation means is a value of a ratio of propagation times by the two or more ultrasonic beam patterns or a value of a ratio of flow rates calculated from the propagation times. The flow velocity distribution in the width direction of the flow path is estimated based on the above, and the flow rate of the fluid to be measured is calculated from the estimated flow velocity distribution.

  According to a fourth aspect of the present invention, in the third aspect of the invention, the flow rate calculation means is configured to determine a flow velocity in the width direction of the flow path based on a ratio value of the propagation times or a flow velocity ratio calculated from the propagation times. The distribution is estimated, an optimum correction coefficient corresponding to the estimated flow velocity distribution is applied, and the flow rate of the fluid to be measured is calculated.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, the flow rate calculation unit assigns another correction coefficient different from the correction coefficient based on at least one of a fluid type, a flow path dimension, and a flow rate range. It is characterized by doing.

  The invention of claim 6 is the invention according to any one of claims 2 to 5, wherein the pair of ultrasonic elements is calculated from a propagation time obtained from the two or more ultrasonic beam patterns or from the propagation time. When the flow rate region of the fluid to be measured is determined to be a turbulent flow region based on the flow velocity, a center frequency that is substantially in the middle of the upper and lower limit frequencies in addition to the first ultrasonic beam pattern and the second ultrasonic beam pattern. A third ultrasonic beam pattern corresponding to a band is transmitted and received, and the flow rate calculation means is configured to transmit the third ultrasonic beam pattern based on a propagation time of the third ultrasonic beam pattern or a flow velocity calculated from the propagation time. The flow velocity distribution is estimated, and the flow rate of the fluid to be measured is calculated from the estimated flow velocity distribution.

  According to a seventh aspect of the present invention, there is provided a flow path through which a fluid to be measured flows, a pair of ultrasonic elements disposed at positions facing each other across the flow path, and propagation of ultrasonic waves transmitted and received by the pair of ultrasonic elements. A flow rate measurement method using an ultrasonic flowmeter comprising flow rate calculation means for calculating a flow rate of the fluid to be measured based on time, wherein two or more different frequencies included in a frequency band of the pair of ultrasonic elements. Correspondingly, by transmitting and receiving two or more ultrasonic beam patterns having different directivities, the width direction of the flow path is divided into a plurality of detection areas, and transmitted and received between the pair of ultrasonic elements. Estimating the flow velocity distribution of the fluid under measurement based on the propagation time of the ultrasonic beam pattern or the flow velocity calculated from the propagation time, and calculating the flow rate of the fluid under measurement from the estimated flow velocity distribution. Special It is obtained by the.

  According to the present invention, even if the flow velocity distribution changes in the flow rate region without interposing a partition member or the like inside the flow channel, the flow velocity distribution state pattern is estimated, and the measured fluid is measured based on the flow velocity distribution pattern. Since the flow rate can be calculated, highly accurate flow rate detection can be performed.

  FIG. 1 is a diagram illustrating an arrangement example of ultrasonic elements included in the ultrasonic flowmeter of the present invention. 1A and 1B show examples of arrangement when a pair of ultrasonic elements is viewed from the side. The ultrasonic flowmeter of the present invention includes a flow path 30 through which a fluid to be measured flows, a pair of ultrasonic transducers 10 and 20 disposed at positions facing each other with the flow path 30 therebetween, and a pair of ultrasonic transducers 10 and 20. And a flow rate calculation unit 13 that calculates the flow rate of the fluid to be measured flowing through the flow path 30 based on the propagation time of the ultrasonic waves transmitted and received by.

  The ultrasonic transducer 10 includes an acoustic matching layer 11 and a piezoelectric element 12. Similarly, the ultrasonic transducer 20 that is paired with the ultrasonic transducer 10 includes an acoustic matching layer 21 and a piezoelectric element 22. The pair of ultrasonic transducers 10 and 20 is installed at an angle θ with respect to the flow direction, and the distance between both radiation surfaces is L (propagation length). In the case of this example, it is assumed that the fluid to be measured flows in the flow path 30 at the flow velocity V in the direction of the arrow in the figure.

  As illustrated in FIGS. 1A and 1B, the ultrasonic transducers 10 and 20 having a piezoelectric element structure are located upstream and downstream of the flow path 30 with respect to the width direction of the flow path 30. These are disposed at positions that are diagonally opposed to the flow direction of the flow path.

  FIG. 2 is a diagram illustrating an example of ultrasonic beam patterns having different frequency bands. Here, the description of the upstream ultrasonic transducer 10 is omitted. As shown in FIG. 1, a pair of ultrasonic transducers 10 and 20 are arranged opposite to each other so as to cross the flow on the upstream side and downstream side of the flow path 30 through which the fluid to be measured flows, and the upstream ultrasonic transducer. The ultrasonic beam is propagated from the ultrasonic transducer 20 to the downstream ultrasonic transducer 20 (forward direct propagation) and from the downstream ultrasonic transducer 20 to the upstream ultrasonic transducer 10 (direct propagation in the reverse direction).

Corresponding to the upper limit frequency of the frequency band of the ultrasonic transducer, the beam pattern has a beam width narrower than the channel width and has directivity X (= θ ^1/2 ) that propagates through the substantially central portion in the channel width direction. Is an ultrasonic beam pattern 1 (corresponding to the first ultrasonic beam pattern of the present invention). An ultrasonic beam pattern 1 with this upper limit frequency is shown in FIG. In addition, a beam pattern having a beam width extending over the entire flow path width and having directivity Y (= θ ^1/2 ) corresponding to the lower limit frequency of the frequency band of the ultrasonic transducer is referred to as the ultrasonic beam pattern 2 (the present invention). Equivalent to the second ultrasonic beam pattern. An ultrasonic beam pattern 2 with this lower limit frequency is shown in FIG. Then, in correspondence with the center frequency band (± 50 kHz) which is substantially in the middle of the upper and lower limit frequencies, the beam pattern having directivity in the middle of the upper and lower limits is changed to the ultrasonic beam pattern 3 (the third ultrasonic beam of the present invention). Equivalent to the pattern). An ultrasonic beam pattern 3 based on this center frequency is shown in FIG.

In this way, ultrasonic beam patterns having different directivities can be generated with two or more different frequencies within the frequency band, and the flow velocity distribution generated in the width direction can be divided into almost two detection areas and measured. . Thereby, it is possible to grasp a flow velocity distribution pattern that is a difference in flow velocity distribution depending on a flow rate, calculate a flow velocity, and perform a flow rate calculation. The flow rate calculation unit 13 performs these flow rate measurements.
In addition, the calculation results (right side in the figure) shown in FIGS. 2A, 2B, and 2C show that the diameter of the radiation surface of the ultrasonic transducer is about 10 mm, and the city gas (13A) is propagated. The calculation results at the upper frequency band limit (600 KHz), the lower limit (400 KHz), and the center frequency (500 KHz) are illustrated. The directivity at the upper limit frequency is about 3.4 °, the directivity at the lower limit frequency is 6.0 °, and the directivity at the center frequency is 4.0 °. , Grasp the flow velocity distribution and calculate the flow velocity.

  The fluid to be measured flowing through the flow path can have a difference in flow velocity distribution in the width direction depending on the flow rate. In particular, it is generally known that the flow velocity distribution in the width direction has a parabolic shape in a range where the flow velocity is slow, and a bathtub shape in a region where the flow velocity is fast. Therefore, as described above, the flow velocity distribution generated in the flow path width direction is obtained by using two different directivities so that at least two types of ultrasonic beams propagating through the entire area in the width direction and the central area can be obtained. Be prepared. That is, an ultrasonic beam emitted from a broadband ultrasonic transducer spreads when the frequency is low, and conversely narrows when the frequency is high. As an ultrasonic beam with the upper limit frequency of this ultrasonic transducer, the beam width is A beam pattern having a directivity that becomes narrower than the flow path width is propagated. Conversely, a beam pattern having a directivity that spreads the beam width uniformly in the flow path width direction is propagated as an ultrasonic beam having a lower limit frequency. Further, if necessary, it is possible to propagate a substantially intermediate ultrasonic beam pattern at the center frequency. By adopting a configuration in which ultrasonic waves can be transmitted and received independently by at least two types of ultrasonic patterns having different areas, subtle differences due to the flow velocity distribution pattern generated in the width direction can be identified. Measurement errors due to distribution differences can be significantly reduced.

In addition, since the same accuracy can be ensured without using an additional member such as a partition plate or a rectifying plate for controlling the flow velocity distribution inside the flow path, the manufacturing cost can be reduced.
In addition, since the flow velocity distribution state can be directly grasped from the difference in propagation time due to the patterns of ultrasonic beams divided in multiple width directions, the influence of individual differences such as flow path dimensions, partition plate placement accuracy, dimensional accuracy, etc. It is not affected, and furthermore, it is less affected by temperature, so it is possible to realize highly stable flow rate measurement with good stability.

  FIG. 3 is a diagram showing the flow velocity distribution state of the ultrasonic beam pattern 1 near the upper limit frequency within the frequency band of the ultrasonic transducer. FIG. 4 is a diagram showing the flow velocity distribution state of the ultrasonic beam pattern 2 near the lower limit frequency within the frequency band of the ultrasonic transducer.

As shown in FIG. 4, the ultrasonic beam pattern 2 in the vicinity of the lower limit frequency in the frequency band of the ultrasonic transducer has a directivity Y (= θ ^1/2 ) spreading almost in the entire channel width direction. As shown in FIG. 3, the ultrasonic beam pattern 1 near the upper limit frequency has a directivity X (= θ ^1/2 ) narrower than the channel width. The directivities at two different frequencies satisfy the relationship X <Y, and the propagation time of the ultrasonic beam pattern 1 at a frequency near the upper limit frequency is measured using these two types of ultrasonic beam patterns. That is, the time measurement value (forward direct propagation time) by direct propagation until the ultrasonic wave radiated from the ultrasonic transducer 10 is received by the ultrasonic transducer 20 on the downstream side is set to “Tj1”, which is the reverse of this. In addition, a time measurement value (reverse direct propagation time) by direct propagation until the ultrasonic wave radiated from the downstream ultrasonic transducer 20 is received by the upstream ultrasonic transducer 10 is defined as “Tg1”.

  Furthermore, the propagation time by the ultrasonic beam pattern 2 at a frequency near the lower limit frequency is measured. That is, the time measurement value (forward direct propagation time) by direct propagation until the ultrasonic wave radiated from the ultrasonic transducer 10 is received by the ultrasonic transducer 20 on the downstream side is set to “Tj2”, which is the reverse of this. In addition, the time measurement value (reverse direct propagation time) by direct propagation until the ultrasonic wave radiated from the downstream ultrasonic transducer 20 is received by the upstream ultrasonic transducer 10 is defined as “Tg2”. Based on these two types of propagation time measurement results and the flow velocity results calculated from the propagation times, subtle differences in the flow velocity distribution due to the flow velocity distribution pattern generated in the channel width direction are identified, the flow velocity due to the flow rate is calculated, and the flow rate Is calculated.

  FIG. 5 is a diagram showing the state of the ultrasonic beam near the upper and lower limit frequencies in the frequency band of the ultrasonic transducer and the detection area by the ultrasonic beam. As shown in FIG. 5A, the directivity ratio of the upper and lower limit frequencies is in a range that differs by about twice, and the flow path width direction is divided into two areas by the ultrasonic beam pattern with two relatively different frequencies. To divide. In the figure, 14 indicates an ultrasonic beam with a frequency on the low frequency side within the frequency band, 15 indicates an ultrasonic beam with a frequency on the high frequency side within the frequency band, and 16 indicates the directivity of the ultrasonic beam with an upper and lower limit frequency.

  FIG. 5B shows a state of a detection area by a low-frequency ultrasonic beam having directivity spreading substantially in the entire width direction, and FIG. 5C shows a directivity narrower than the width in the flow path width direction. The state of the detection area by the high frequency ultrasonic beam which it has is shown.

  As shown in FIG. 5, the ultrasonic beam at two frequencies that are different in frequency near the upper and lower limit frequencies in the frequency band of the ultrasonic transducer, or relatively different in the frequency band, that is, on the low frequency side. An ultrasonic beam pattern (ultrasonic beam pattern 2) whose directivity is close to the channel width and an ultrasonic beam pattern (ultrasonic beam pattern 1) whose directivity on the high frequency side is narrower than the channel width are used. . The channel width direction is divided into two areas by two different ultrasonic beams, and the propagation time is measured in each area.

  As described above, the propagation time measurement by the ultrasonic beam pattern 1 at the upper limit frequency is based on the direct propagation until the ultrasonic wave radiated from the upstream ultrasonic transducer 10 is received by the downstream ultrasonic transducer 20. In contrast to the forward direct propagation time Tj1, the reverse direct propagation time by the direct propagation until the ultrasonic wave radiated from the downstream ultrasonic transducer 20 is received by the upstream ultrasonic transducer 10 is reversed. Tg1 is measured.

  Further, as the propagation time measurement by the ultrasonic beam pattern 2 at the lower limit frequency, the forward direct direct propagation until the ultrasonic wave radiated from the upstream ultrasonic transducer 10 is received by the downstream ultrasonic transducer 20 is performed. On the contrary, the propagation time Tj2 and the reverse direct propagation time Tg2 due to the direct propagation until the ultrasonic wave radiated from the ultrasonic transducer 20 on the downstream side is received by the ultrasonic transducer 10 on the upstream side are obtained. measure. Based on these two types of propagation time measurement results and the flow velocity results calculated from the propagation times, subtle differences in the flow velocity distribution due to the flow velocity distribution pattern generated in the channel width direction are identified, the flow velocity due to the flow rate is calculated, and the flow rate is calculated. Can be calculated.

  Thus, within the ultrasonic transducer frequency band, the directivity due to high frequency is narrower than the channel width, the pattern of the ultrasonic beam propagating through the central area of the channel, and the directivity due to low frequency is the channel width. The pattern of the ultrasonic beam which diffuses and propagates to the area of the whole direction is utilized. That is, by using an ultrasonic beam having different directivities according to at least two different frequencies, a subtle difference in average flow velocity due to a flow velocity distribution pattern generated in the flow channel width direction can be identified. Measurement errors due to differences in flow velocity distribution can be significantly reduced.

  Also, the flow path width direction is divided into at least two from the propagation time measurement result measured by the pattern of ultrasonic beams having two different directivities or the flow velocity result calculated from the propagation time measurement result. In addition, since the flow velocity by each area can be calculated, it is possible to calculate and calculate the flow rate from the flow velocity calculated from at least two types of areas by each ultrasonic pattern.

In addition, since it is possible to relatively change and use two different frequencies within the band of the ultrasonic transducer, even if there is a change in the medium to some extent or a change in flow velocity distribution due to the flow path dimensions, Even if there is a difference in the directivity area in the width direction, two different frequencies in the reference medium can be selected and measured as arbitrary frequencies other than the upper and lower limits. For this reason, the adaptation range is wide and versatility is high. In addition, when the measurement accuracy is not so necessary, the applicable range can be further expanded.
Furthermore, since two different types of frequencies other than the upper and lower limit frequencies can be selected and the two different types of directivity can be used in the same transducer, it is possible to cope with subtle differences in directivity characteristics due to temperature.

FIG. 6 is a diagram for explaining an example of a flow rate measuring method using the ultrasonic flowmeter of the present invention. 6A shows the state of the beam area by the ultrasonic beam pattern 1 having directivity X, and FIG. 6B shows the state of the beam area by the ultrasonic beam pattern 2 having directivity Y.
In this way, the channel width direction is divided into two areas by two different ultrasonic beams, and in each area, the forward direct propagation time Tj1, the backward direct propagation time Tg1, the forward direct propagation time Tj2, The reverse direct propagation time Tg2 is measured.

Due to the directivity X (= θ ^1/2 ) by the ultrasonic beam pattern 1 and the directivity Y (= θ ^1/2 ) by the ultrasonic beam pattern 2, the ratio of the propagation times in the beam patterns is
Tj1 / Tj2 = α, Tg1 / Tg2 = β Equation (1)
It becomes. It is possible to compare the values of the ratios α and β, estimate the flow velocity distribution pattern in the channel width direction based on the magnitude relationship, predict an appropriate flow rate range, and calculate the flow rate of the fluid to be measured. .

Further, when two kinds of flow velocity values calculated from measurement results of propagation times in two kinds of ultrasonic beam patterns are V1 and V2,
V1 = {L / (2 · COSθ)} · (1 / Tj1-1 / Tg1) (2)
V2 = {L / (2 · COSθ)} · (1 / Tj2-1 / Tg2) (3)
It is calculated from. Here, L is the distance between the radiation surfaces of the ultrasonic transducers 10 and 20, and θ is the angle formed with the flow direction. From these flow velocity results, the ratio of flow velocity ratios of the two types of ultrasonic beam patterns is compared, and based on the magnitude relationship, the flow velocity distribution pattern in the channel width direction is estimated, and an appropriate flow area is predicted. The flow rate of the fluid to be measured can be calculated.

  6C shows the difference in flow velocity distribution depending on the flow rate region of the ultrasonic beam pattern 1 shown in FIG. 6A, and FIG. 6D shows the flow rate region of the ultrasonic beam pattern 2 shown in FIG. 6B. The difference in flow velocity distribution due to. In the figure, the flow velocity pattern (1) is a laminar flow region, α and β by the laminar flow region (1) are α1 and β1, and the flow velocity pattern (2) is a laminar flow region, and α and β by the laminar flow region (2) β is α2 and β2, and the flow velocity pattern (3) is a turbulent region, and α and β by the turbulent region (3) are α3 and β3.

In this case, the magnitude relationship is
α1 (β1)> α2 (β2)> α3 (β3) ≈1 (4)
Thus, an appropriate flow velocity distribution pattern depending on the flow rate region can be estimated from the ratio values, and the flow rate of the fluid to be measured can be calculated from the estimated flow velocity distribution.

Needless to say, the flow rate range may be grasped as a flow velocity value calculated from the propagation times measured from the two types of beam patterns, or the flow rate range may be predicted from the magnitude relationship between the flow rates.
That is, in each flow velocity distribution pattern shown in FIG. 6C, that is, in the laminar flow regions (1) and (2) and the turbulent flow region (3), the flow velocity by the ultrasonic beam pattern 1 shown in FIG. If the flow velocity by the ultrasonic beam pattern 2 shown in FIG. 6 (B) is Vw, the flow rate region may be predicted based on the magnitude relationship, and an appropriate flow velocity may be determined.

Here, in the case of Vc> Vw, it is estimated that the region is a laminar flow region, and an appropriate flow velocity is determined by the value of the ratio (Vc / Vw) at that time. Further, in the case of Vc / Vw≈1, it is estimated that the region is a turbulent flow region, thereby determining an appropriate flow velocity. The flow velocity ratio in the distribution pattern of the laminar flow region (1) is Vc1 / Vw1, the flow velocity ratio in the distribution pattern of the laminar flow region (2) is Vc2 / Vw2, and the flow velocity ratio in the distribution pattern of the turbulent flow region (3) is Vc3 / Vw3. To do. in this case,
(Vc1 / Vw1)> (Vc2 / Vw2)> (Vc3 / Vw3) ≈1 (5)
Therefore, the current flow rate region can be estimated from the order of the flow rate ratio, and the current flow rate can be calculated. The estimation of the flow rate range is compared with the data stored in advance, the flow rate range is determined according to the value suitable for the range of the data, and a reasonable coefficient is assigned in the flow rate range to calculate the flow velocity and calculate the flow rate. Calculate. FIG. 7 shows the relationship between the flow rate Q and the flow velocity distribution ratio ζ (= Vc / Vw) when the medium is city gas (13A).

In this way, two types of ultrasonic beam patterns having different directivities can be transmitted and received within the frequency band of the ultrasonic transducer, and the flow path width direction can be divided into at least two different areas. Propagation time results corresponding to the flow velocity distribution are obtained. From the results of the propagation times, the ratio of the propagation times of the two types of ultrasonic beams is compared, and an appropriate flow rate range is predicted based on the magnitude relationship. The flow rate of the fluid to be measured can be calculated.
Also, from the flow velocity result calculated and calculated from the time measurement information, the ratio value of the flow velocity ratio of the two ultrasonic beams is compared, and based on the magnitude relationship, the flow velocity distribution pattern in the channel width direction is estimated, A reasonable flow rate region can be predicted and the flow rate of the fluid to be measured can be calculated.
As a result, subtle differences due to the flow velocity distribution pattern generated in the flow path width direction can be identified, so even if there is a difference in flow velocity distribution due to the flow rate range, measurement errors can be significantly reduced and highly accurate flow measurement can be realized. .

As described above, within the frequency band of the ultrasonic transducer, the propagation time by the ultrasonic beam pattern with two different frequencies is measured, and the flow rate range is grasped according to the value of the flow rate ratio calculated from each propagation time, An appropriate correction coefficient may be assigned according to the value of the flow rate ratio, the average flow rate may be calculated, and the flow rate may be calculated. When two different types of frequencies are frequencies apart from each other except for the upper and lower limits, if the flow width direction is divided into two types by each ultrasonic beam and the measured flow velocity is Vc and Vw, the flow velocity Vc is ultrasonic. Corresponding to the beam pattern 1 (measurement of propagation time by a high frequency with a narrow beam width), the flow velocity Vw corresponds to the ultrasonic beam pattern 2 (measurement of propagation time by a low frequency in which the beam width extends over the entire channel width). These flow velocities Vc, Vw are
Vc = {L / (2 · COSθ)} · (1 / Tj1-1 / Tg1) (6)
Vw = {L / (2 · COSθ)} · (1 / Tj2-1 / Tg2) (7)
Can be written. Here, L is the distance between the radiation surfaces of the transmitting and receiving transducers 10 and 20, and θ is the angle formed with the flow direction.

Thus, the flow rate region is predicted based on the magnitude relationship between the flow velocities Vc and Vw calculated from each propagation time and the value of the flow velocity ratio (Vc / Vw), and an appropriate flow velocity is determined.
That is, in the case of Vc> Vw, it is estimated as a laminar flow region, and the flow rate of the fluid to be measured can be calculated by determining an appropriate flow velocity coefficient based on the value of Vc / Vw and calculating the average flow velocity. In addition, when Vc≈Vw, since it can be estimated that the region is a turbulent flow region, the average flow velocity can be determined without a coefficient. The velocity distribution related to turbulent flow does not use the correction factor basically because the peak velocity is the average velocity, but by assigning a reasonable correction factor until switching to the turbulent flow region according to the ratio value, Regardless, the average flow velocity can be calculated and the flow rate can be calculated and calculated.

FIG. 8 is a diagram for explaining the state of the flow velocity distribution pattern (laminar flow region) in the flow channel width direction.
As shown in FIG. 8 (A), according to the flow velocity distribution in the width direction, for example, the velocity distribution pattern (1) in the laminar basin where the center as shown by the solid line is the largest and symmetrical from the center. In this case, the ratio (Vc) between the flow velocity Vc calculated by the ultrasonic beam pattern 1 whose directivity X is narrower than the flow path width and the flow velocity Vw calculated by the ultrasonic beam pattern 2 whose directivity Y is substantially equal to the flow path width. The value of / Vw) is “ζ1”.

Further, as shown in FIG. 8B, in the case of the flow velocity distribution pattern as shown by the dotted line, that is, the flow velocity distribution pattern (2) in the laminar basin, the value of the ratio (Vc / Vw) between the flow velocity Vc and Vw is “ In the case of ζ2 ″, if the correction coefficients proportional to the ratio values ζ1 and ζ2 are φ1 and φ2, respectively, the average flow velocity V1 (solid line) in each flow velocity pattern shown in FIGS. , V2 (dotted line) is
V1 = φ1 · (Vc + Vw) / 2 Formula (8)
V2 = φ2 · (Vc + Vw) / 2 Formula (9)
Can be calculated as

Or
V1 = φ1 ′ · Vc Formula (10)
V2 = φ2 ′ · Vc Formula (11)
Can also be calculated as However, φ1 ′ and φ2 ′ are other correction coefficients proportional to ζ1 and ζ2. Of course, the flow velocity may be calculated as a correction for Vw using another correction coefficient.
In this way, the distribution pattern is estimated according to the flow rate ratio order by the two types of ultrasonic beam patterns having different directivities in the flow path width direction, and an appropriate correction coefficient is assigned according to the flow velocity distribution pattern. By calculating the average flow velocity, the flow rate of the fluid to be measured can be calculated.

  As described above, the ultrasonic beam patterns having different directivities with at least two kinds of frequencies in the flow path width direction are transmitted and received, and the flow path width direction is divided into at least two different areas, thereby being different in the flow path width direction. Since the propagation time result corresponding to the flow velocity distribution is obtained, the value of the ratio of the propagation time by at least two kinds of ultrasonic beams is compared from the result of the propagation time, and based on the magnitude relationship, in the channel width direction By estimating the flow velocity distribution pattern and predicting an appropriate flow rate range, and assigning the optimum flow velocity distribution correction coefficient according to the ratio value, the average flow velocity across the channel cross section can be calculated and calculated. . For this reason, it is not affected by the flow velocity distribution in the width direction due to the flow rate region, and stable and highly accurate measurement can be realized over the entire flow rate region.

  In addition, from the flow velocity result calculated and calculated from the time measurement information, the flow velocity ratio value is compared, the flow velocity distribution pattern in the channel width direction is estimated based on the magnitude relationship, and a reasonable flow rate region is predicted. At the same time, by assigning an optimum flow velocity distribution correction coefficient according to the ratio value, it is possible to calculate and calculate the average flow velocity across the channel cross section. For this reason, it is not influenced by the flow velocity distribution in the width direction due to the flow rate range, and stable and highly accurate measurement can be realized over the entire flow rate range.

  As shown in FIGS. 6 and 8, the forward direct propagation time Tj1 and the backward direct propagation time Tg1 in the ultrasonic beam pattern 1 due to the high frequency, and the forward direct propagation in the ultrasonic beam pattern 2 due to the low frequency. When time Tj2 and reverse direct propagation time result: Tg2, the ratio is Tj1 / Tg1 = α, α is α3≈1, Tj2 / Tg2 = β, and β is β3≈1. In this case, the ratio of the propagation times by two different frequencies is almost equal to “1”, so that the flow velocity distribution pattern is estimated to be the turbulent flow region (3).

  Further, the value of the ratio between the flow velocity Vc calculated by the ultrasonic beam pattern 1 whose directivity is narrower than the flow path width and the flow velocity Vw calculated by the ultrasonic beam pattern 2 whose directivity is substantially equal to the flow path width is Vc. When it is estimated that the flow velocity distribution pattern of the turbulent flow region (3) is assumed as / Vw≈1, as shown in FIG. 2 (C), the ultrasonic beam with the center frequency within the frequency band of the ultrasonic transducer is used. The forward propagation time measurement and the backward propagation time measurement are performed with an ultrasonic beam that is the pattern 3 and has the maximum sound pressure in the center of the band.

That is, the forward direct propagation time Tj3 by direct propagation until the ultrasonic wave radiated from the ultrasonic transducer 10 is received by the downstream ultrasonic transducer 20 is set, and conversely, the downstream ultrasonic transducer is used. If the ultrasonic wave radiated from 20 is the direct propagation time Tg3 by the direct propagation until it is received by the ultrasonic transducer 10 on the upstream side,
V3 = {L / (2 · COSθ)} · (1 / Tj3-1 / Tg3) (12)
It is sufficient to calculate the average flow velocity directly and calculate the flow rate of the fluid to be measured.

  Further, as shown in FIGS. 8A and 8B, the average flow velocities V1 and V2 in the respective flow velocity patterns (ultrasonic beam patterns 1 and 2) are calculated based on the equations (8) to (11). be able to.

Similarly, in FIGS. 8A and 8B, when the gas type is city gas 13A, if the correction coefficients proportional to the magnitudes of ζ1 and ζ2 are φ5 and φ6, respectively, the average flow velocity V1 in each flow velocity pattern is shown. (Solid line) and V2 (dotted line) are
V1 = φ5 · (Vc + Vw) / 2 Formula (12)
V2 = φ6 · (Vc + Vw) / 2 Formula (13)
Can be calculated as

Or
V1 = φ5 ′ · Vc (14)
V2 = φ6 ′ · Vc (15)
It is also possible to calculate as However, φ5 ′ and φ6 ′ are other correction coefficients proportional to ζ1 and ζ2. Of course, the flow velocity may be calculated as a correction for Vw using another correction coefficient.
By changing the correction coefficient so as to be an appropriate correction coefficient according to the subtle difference in flow velocity distribution that varies depending on the type of gas, the average flow velocity can be calculated and the flow rate can be calculated regardless of the flow velocity distribution.

  Here, since the viscosity and density of the fluid differ depending on the type of fluid to be measured, the longitudinal wave velocity of the ultrasonic wave propagating through the gas type (medium) differs, and there is a difference in the directivity characteristics of the ultrasonic beam. appear. The correction coefficient value is slightly different depending on the flow path shape, dimensions, etc., depending on the area of the optimal ultrasonic beam, and the measurement with two types of ultrasonic beams with different directivity characteristics is the flow velocity distribution in the flow rate range. It may happen that a sufficient difference cannot be identified with respect to the difference in pattern.

FIG. 9 is a diagram for explaining the difference in flow velocity distribution of the ultrasonic beam pattern 1 depending on the type of fluid to be measured. FIG. 10 is a diagram for explaining the difference in flow velocity distribution of the ultrasonic beam pattern 2 depending on the type of fluid to be measured. It is a figure for doing.
FIG. 9A shows an example of the flow velocity distribution of the ultrasonic beam pattern 1 in the case of LPG, and the directivity of the ultrasonic beam pattern 1 by the high frequency at the upper limit of the band in the LPG is X (= θ ^1/2 ). To do. FIG. 9B shows an example of the flow velocity distribution of the ultrasonic beam pattern 1 in the case of city gas (13A), and the directivity characteristics due to direct propagation waves radiated from an ultrasonic transducer having the same piezoelectric element are expressed as X ′ ( = Θ ^1/2 ). Similarly, FIG. 10A shows an example of the flow velocity distribution of the ultrasonic beam pattern 2 in the case of LPG. The directivity of the ultrasonic beam pattern 2 at the low frequency at the lower limit of the band in the LPG is represented by Y (= θ ^{1 / 2} ). FIG. 10B shows an example of the flow velocity distribution of the ultrasonic beam pattern 1 in the case of city gas (13A), and the directivity characteristics due to the direct propagation wave radiated from the ultrasonic transducer having the same piezoelectric element are indicated by Y ′ ( = Θ ^1/2 ).

In the above, since the propagation speed of the longitudinal wave of LPG is slower than that of city gas (13A), the directivity X ′ (= θ ^1/2) by the direct propagation wave radiated from the ultrasonic transducer having the same piezoelectric element. ) And directivity Y ′ (= θ ^1/2 ) are both wider for city gas (13A). That is, the relationship is X ′> X, Y ′> Y. Therefore, in an ultrasonic transducer having the same piezoelectric element, when measuring a flow velocity distribution pattern due to a gas type (medium) having a large difference in velocity, an ultrasonic beam having a different spread depending on the gas type (medium) is classified. When crossing the flow velocity distribution pattern, due to the difference in the detection area depending on the beam area, a slight deviation occurs in the measured propagation time, and the correction coefficient is slightly different. Of course, subtle deviations will also occur in the flow velocity results calculated from the propagation time.

  Furthermore, when the channel dimensions are different, if the city gas (13A) is measured with two types of directional beams using the same ultrasonic transducer as in the LPG measurement, if the channel width is narrow, the directivity due to the medium is increased. Since the ultrasonic beam with the upper limit high frequency cannot be made narrower than the channel width, the directivity difference cannot be identified, making it difficult to estimate the flow velocity distribution pattern. On the other hand, if the expansion of the channel width is larger than the increase in directivity due to changes in the medium, the directivity due to the low frequency at the lower limit of the band can be expected to be equal to or greater than the channel width. In addition, the two types of directivity are concentrated in the central area of the flow velocity distribution, and the identification resolution of the flow velocity distribution may not be sufficiently obtained.

  Therefore, by adjusting and optimizing the dimensions of the piezoelectric elements that make up the ultrasonic transducer, the resonance frequency that varies depending on the dimensions, and the dimensions of the acoustic matching layer according to the gas type and the flow path dimensions, , Two different types of ultrasonic beam patterns are propagated to the area divided into two areas, the central area and the full width area, and the directional characteristics that are optimal for changes in gas types and channel dimensions Send and receive satisfactory ultrasonic beams. As a result, in each area divided in the width direction, a propagation time result by ultrasonic transmission / reception corresponding to a flow velocity distribution different in the flow path width direction is obtained, and the value of the propagation time ratio is calculated from the result of the propagation time. By comparing and estimating the appropriate flow rate range based on the magnitude relationship, the optimal flow rate distribution correction coefficient is allocated according to the ratio value, and the average flow rate can be calculated and calculated. Stable and highly accurate measurement can be realized without being affected by the flow velocity distribution in the width direction.

  Or, from the flow velocity result calculated and calculated from the time measurement result by ultrasonic transmission / reception, compare the flow velocity ratio value, predict the appropriate flow rate range based on the magnitude relationship, and at the same time optimize the ratio value A different flow velocity distribution correction coefficient may be assigned. In this case as well, the average flow velocity can be calculated and calculated, and stable and highly accurate measurement can be realized without being affected by the flow velocity distribution in the width direction depending on the flow rate region.

  An ultrasonic transducer is used to obtain two different types of ultrasonic beams necessary to determine the flow rate distribution pattern that changes with the flow path shape / dimension, measurement range, and measurement resolution, and the degree of flow velocity bias. The position of transmitting and receiving the ultrasonic beam radiated from and the number of beams may be changed to satisfy the optimum ultrasonic area.

FIG. 11 is a diagram for explaining the difference in the flow velocity distribution of the ultrasonic beam pattern 1 due to the expansion of the flow path width, and FIG. 12 illustrates the difference in the flow velocity distribution of the ultrasonic beam pattern 2 due to the expansion of the flow path width. It is a figure for doing.
11A shows an example of the flow velocity distribution of the ultrasonic beam pattern 1, FIG. 11B shows an example of the flow velocity distribution of the ultrasonic beam pattern 1 when the flow path width is enlarged, and FIG. ) Shows an example of the flow velocity distribution of the ultrasonic beam pattern 2, and FIG. 12B shows an example of the flow velocity distribution of the ultrasonic beam pattern 2 when the flow path width is enlarged.

  As described above, when the enlargement in the flow path width direction becomes conspicuous with the enlargement of the flow rate range (expansion of the flow measurement range), the flow velocity distribution is sufficiently estimated with the ultrasonic beam by the ultrasonic transducer having one piezoelectric element. It is not possible to secure an effective detection area necessary for this. This is because the directivity changes depending on the size of the piezoelectric element, the resonant frequency that changes with the size, and the size of the acoustic matching layer, and two types of ultrasonic beam patterns that sufficiently spread to the center of the channel width and the entire channel width. This is because it is difficult to optimize the frequency with one ultrasonic transducer.

  Although the optimum directivity can be ensured by lowering the resonance frequency of the piezoelectric element and widening the directivity, there is a limit to lowering the frequency in order to obtain measurement resolution. For this reason, it is almost impossible to satisfy the directivity necessary for identifying the flow velocity distribution while satisfying the measurement resolution with an ultrasonic transducer having one piezoelectric element. In particular, when the flow velocity distribution is not symmetrical at the center of the flow channel width and the flow channel width is wide, two different directivities sufficient to grasp the flow velocity distribution in the required detection area are provided. It becomes difficult to transmit and receive an ultrasonic beam.

  To solve such a problem, as shown in FIGS. 11B and 12B, for example, the piezoelectric element is divided into two, and an ultrasonic transducer 20 ′ having a configuration capable of independently operating is provided. It may be. The ultrasonic transducer 20 'includes an acoustic matching layer 21' and a piezoelectric element 22 'divided into two. The counterpart ultrasonic transducer paired with the ultrasonic transducer 20 'has the same configuration.

  In FIG. 11B, an ultrasonic beam area (1) in which a directly propagated wave propagates through the center of the center and the upper and lower boundaries with respect to the area of the center and the upper and lower boundaries with the center of the channel width as a boundary. , (2) is propagated. In FIG. 12B, the ultrasonic beam is an ultrasonic wave that satisfies the ultrasonic beam areas (3) and (4) that are the upper and lower boundaries of the center of the channel width and half the channel width. Propagate. Estimate the flow velocity distribution pattern in the channel width direction from the measurement results of the propagation time of two types of ultrasonic beams transmitted and received from the center of each piezoelectric element through the acoustic matching layer, and compare the ratio of propagation time ratios Then, based on the magnitude relationship, an appropriate flow rate range is estimated, and at the same time, an optimum flow velocity distribution correction coefficient is allocated according to the ratio value, thereby calculating and calculating the average flow velocity. Thereby, stable and highly accurate measurement can be realized without being affected by the flow velocity distribution in the width direction due to the flow rate region.

  In addition, from the flow velocity result calculated and calculated from the time measurement result by ultrasonic transmission / reception, the flow rate ratio value is compared, and based on the magnitude relationship, an appropriate flow rate range is predicted, and at the same time, the ratio value The average flow velocity may be calculated and calculated by assigning an optimal flow velocity distribution correction coefficient. Thereby, stable and highly accurate measurement can be realized without being affected by the flow velocity distribution in the width direction due to the flow rate region. Of course, when the measurement resolution is not so necessary, the ultrasonic beam may be optimized according to the frequency.

  As described above, the flow velocity distribution pattern can be estimated by a plurality of ultrasonic beams having different directivities, and as a result, the flow area can be predicted, and when the result is determined to be a turbulent flow area, the sound pressure of the ultrasonic wave is almost equal. By using an ultrasonic beam in the maximum center frequency band (± 50 kHz), even if the transmission / reception efficiency of the ultrasonic beam is reduced due to turbulence, the measurement is not affected by the measurement, and a stable flow velocity is calculated and measured. The flow rate of the fluid can be calculated.

  In addition, the appropriate value of the correction coefficient of the flow velocity distribution due to the flow rate in the same fluid varies slightly depending on the type of fluid and the flow path dimensions. Therefore, by applying another correction coefficient different from the flow velocity distribution correction coefficient based on at least one of the type of fluid, the flow path dimensions, and the flow rate range, the viscosity and density phases of the fluid in the flow path width direction. It is possible to assign an optimal correction factor that takes into account the effects of different and subtly changing flow velocity distributions.

Thus, the flow velocity distribution correction coefficient is based on at least one of the fluid type, the channel size, and the flow rate range so that the flow velocity distribution in the channel width direction is not affected by the fluid type and the channel size. By applying another correction coefficient different from, it is possible to optimize the correction coefficient, so that the influence of the flow velocity distribution in the width direction due to the flow area is not concerned, and stable and highly accurate over the entire flow area. Measurement can be realized.
That is, from the flow velocity result calculated and calculated from the time measurement information, the ratio value in each flow velocity value is compared, the flow velocity distribution pattern in the channel width direction is estimated based on the magnitude relationship, and an appropriate flow area is determined. At the same time as the prediction, the flow velocity distribution correction coefficient optimized according to the ratio value is changed, and further, based on at least one of the type of fluid, the channel size, and the flow range, what is the flow velocity distribution correction coefficient? By applying different correction coefficients, stable and highly accurate measurement can be realized over the entire flow rate range regardless of the type of fluid flow and the flow path dimensions.

  By changing the dimensions of the piezoelectric elements that make up the ultrasonic transducer, the resonance frequency associated therewith, and the dimensions of the acoustic matching layer according to the type of fluid that flows through the flow path and the shape and dimensions of the flow path, Even if there is a difference in the directivity of the ultrasonic wave propagating through the fluid due to the difference in the viscosity and density depending on the viscosity and density, The road width direction can be divided into at least two areas, and optimal ultrasonic beams can be transmitted and received.

  In each area divided in the width direction, it is possible to obtain the propagation time by ultrasonic transmission / reception according to the flow velocity distribution different in the channel width direction, and compare the propagation time ratio value from the propagation time result. Based on the magnitude relationship, the flow velocity distribution pattern in the flow channel width direction is estimated, and a reasonable flow rate region is predicted, and at the same time, the optimum flow velocity distribution correction coefficient is assigned according to the ratio value, The average flow velocity across the can be calculated and calculated. For this reason, it is not influenced by the flow velocity distribution in the width direction due to the flow rate region, and stable and highly accurate measurement can be realized over the entire flow rate region.

  Also, based on the flow velocity result calculated and calculated based on the time measurement result by ultrasonic transmission / reception, the flow rate ratio value is compared, and based on the magnitude relationship, the flow velocity distribution pattern in the channel width direction is estimated and validated. By predicting an appropriate flow rate region and assigning an optimum flow velocity distribution correction coefficient according to the ratio value, it is possible to calculate and calculate the average flow velocity across the cross section of the flow path. For this reason, it is not influenced by the flow velocity distribution in the width direction due to the flow rate region, and stable and highly accurate measurement can be realized over the entire flow rate region.

  By changing the number of ultrasonic beams emitted from the ultrasonic transducer according to the type of fluid flowing in the flow path and the difference in the measurement sound field associated with the flow range to be measured, the viscosity varies depending on the type of fluid, Even if there is a difference in flow velocity distribution depending on the density, and even if there is a difference in flow velocity distribution depending on the flow range to be measured, two types of ultrasonic beam patterns, that is, high-frequency ultrasonic waves that are narrower than the channel width A beam pattern and a low-frequency ultrasonic beam pattern substantially equal to the channel width can be transmitted and received.

  As a result, propagation time by ultrasonic transmission / reception corresponding to different flow velocity distributions in the channel width direction can be obtained in each area divided in the channel width direction. By comparing the values, estimating the flow velocity distribution pattern in the channel width direction based on the magnitude relationship, predicting an appropriate flow rate range, and assigning the optimum flow velocity distribution correction coefficient according to the ratio value The average flow velocity across the channel cross section can be calculated and calculated. As a result, stable and highly accurate measurement can be realized over the entire flow rate range without being affected by the flow velocity distribution in the width direction due to the flow rate range.

  Also, from the flow velocity result calculated and calculated from the time measurement result by ultrasonic transmission / reception, the ratio value of the flow velocity is compared and the flow velocity distribution pattern in the channel width direction is estimated based on the magnitude relationship, At the same time as predicting the flow rate region, by assigning an optimum flow velocity distribution correction coefficient according to the ratio value, the average flow velocity across the cross section of the flow path can be calculated and calculated. For this reason, it is not influenced by the flow velocity distribution in the width direction due to the flow rate region, and stable and highly accurate measurement can be realized over the entire flow rate region.

It is a figure which shows the example of arrangement | positioning of the ultrasonic element with which the ultrasonic flowmeter of this invention is provided. It is a figure which shows an example of the ultrasonic beam pattern from which a frequency band differs. It is a figure which shows the flow-velocity distribution state of the ultrasonic beam pattern of the upper limit frequency vicinity in the frequency band of an ultrasonic transducer. It is a figure which shows the flow rate distribution state of the ultrasonic beam pattern of the vicinity of the lower limit frequency within the frequency band of an ultrasonic transducer. It is a figure which shows the state of the detection area by the ultrasonic beam near the upper-lower limit frequency in the frequency band of an ultrasonic transducer, and the ultrasonic beam. It is a figure for demonstrating an example of the flow measurement method by the ultrasonic flowmeter of this invention. It is the figure which showed the relationship between the flow rate and ratio of flow velocity distribution when a medium is city gas (13A). It is a figure for demonstrating the mode of the flow-velocity distribution pattern (laminar flow area) in a flow path width direction. It is a figure for demonstrating the difference in the flow velocity distribution of the ultrasonic beam pattern by the kind of to-be-measured fluid. It is a figure for demonstrating the difference in the flow velocity distribution of the ultrasonic beam pattern by the kind of to-be-measured fluid. It is a figure for demonstrating the difference in the flow velocity distribution of an ultrasonic beam pattern by expansion of a flow path width. It is a figure for demonstrating the difference in the flow velocity distribution of an ultrasonic beam pattern by expansion of a flow path width.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 ... Ultrasonic element (ultrasonic transducer), 11, 21 ... Acoustic matching layer, 12, 22 ... Piezoelectric element, 13 ... Flow rate calculation part, 30 ... Flow path.

Claims (7)

Based on a flow path through which the fluid to be measured flows, a pair of ultrasonic elements arranged at positions facing each other across the flow path, and a propagation time of ultrasonic waves transmitted and received by the pair of ultrasonic elements An ultrasonic flowmeter comprising a flow rate calculation means for calculating a flow rate of fluid,
The pair of ultrasonic elements transmits and receives the two or more ultrasonic beam patterns having different directivities corresponding to two or more different frequencies included in the frequency band of the pair of ultrasonic elements, thereby transmitting the flow. Divide the width direction of the road into multiple detection areas,
The flow rate calculation unit estimates a flow velocity distribution of the fluid to be measured based on a propagation time of the two or more ultrasonic beam patterns transmitted and received between the pair of ultrasonic elements or a flow velocity calculated from the propagation time. And calculating the flow rate of the fluid under measurement from the estimated flow velocity distribution.   2. The ultrasonic flowmeter according to claim 1, wherein the two or more ultrasonic beam patterns have a beam width narrower than a width of the flow path corresponding to an upper limit frequency of the pair of ultrasonic elements. An ultrasonic flowmeter comprising: an ultrasonic beam pattern; and a second ultrasonic beam pattern having a beam width substantially equal to the width of the flow path corresponding to a lower limit frequency of the pair of ultrasonic elements. .   3. The ultrasonic flowmeter according to claim 1, wherein the flow rate calculation means is based on a value of a ratio of propagation times by the two or more ultrasonic beam patterns or a value of a ratio of flow rates calculated from the propagation times. An ultrasonic flowmeter characterized by estimating a flow velocity distribution in the width direction of the flow path and calculating a flow rate of the fluid to be measured from the estimated flow velocity distribution.   4. The ultrasonic flowmeter according to claim 3, wherein the flow rate calculation means calculates a flow velocity distribution in the width direction of the flow path based on a value of the propagation time ratio or a flow velocity ratio calculated from the propagation time. An ultrasonic flowmeter characterized by estimating and applying an optimum correction coefficient according to the estimated flow velocity distribution and calculating a flow rate of the fluid to be measured.   5. The ultrasonic flowmeter according to claim 4, wherein the flow rate calculation means gives another correction coefficient different from the correction coefficient based on at least one of a fluid type, a flow path dimension, and a flow rate range. Ultrasonic flow meter characterized by. 6. The ultrasonic flowmeter according to claim 2, wherein the pair of ultrasonic elements has a propagation time obtained from the two or more ultrasonic beam patterns or a flow velocity calculated from the propagation time. When the flow area of the fluid to be measured is determined to be a turbulent flow area, a center frequency band that is substantially in the middle of the upper and lower limit frequencies other than the first ultrasonic beam pattern and the second ultrasonic beam pattern. A third ultrasonic beam pattern corresponding to
The flow rate calculation means estimates a flow velocity distribution of the fluid to be measured based on a propagation time of the third ultrasonic beam pattern or a flow velocity calculated from the propagation time, and the measured flow rate from the estimated flow velocity distribution. An ultrasonic flowmeter for calculating a flow rate of a fluid. Based on a flow path through which the fluid to be measured flows, a pair of ultrasonic elements arranged at positions facing each other across the flow path, and a propagation time of ultrasonic waves transmitted and received by the pair of ultrasonic elements A flow rate measurement method using an ultrasonic flowmeter comprising a flow rate calculation means for calculating a flow rate of fluid,
A plurality of ultrasonic beam patterns having different directivities are transmitted / received corresponding to two or more different frequencies included in the frequency band of the pair of ultrasonic elements, thereby detecting a plurality of width directions of the flow path. Divided into areas,
Based on the propagation time of the two or more ultrasonic beam patterns transmitted and received between the pair of ultrasonic elements or the flow velocity calculated from the propagation time, the flow velocity distribution of the fluid to be measured is estimated, and the estimated flow velocity A flow rate measuring method, wherein the flow rate of the fluid to be measured is calculated from the distribution.

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