JP3627729B2 - Flow measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate measuring device that measures the flow rate and flow rate of gas and liquid.
[0002]
[Prior art]
Conventionally, as this type of flow rate measuring device, there is a membrane gas meter provided with a metering membrane as disclosed in JP-A-8-210893.
[0003]
As shown in FIG. 11, this type of membrane gas meter has a pair of measuring chambers (not shown) including an inlet 1 through which a gas to be measured flows in, an outlet 2 through which gas flows out, and a measuring membrane (not shown). And a display unit 4 for displaying the amount of gas that has passed through the metering unit 3.
[0004]
In such a configuration, the metering operation of the membrane gas meter, as is known in the art, is to reciprocate the metering membrane with a gas pressure in a pair of metering chambers having a constant volume, and measure the flow rate by the number of operations. is there.
[0005]
[Problems to be solved by the invention]
However, in the conventional example, in contrast to a security function for detecting and notifying gas leakage from a gas pipe or gas appliance downstream from the gas meter, the amount of gas approximately equal to the volume of the measuring chamber provided in the gas meter is used for detection of leakage. There is a problem that it is necessary to pass through, and that a minute leak (for example, a flow rate of about 3 liters per hour) requires a long time until the leak is detected (for example, 1 hour when the volume of the measuring chamber is 3 liters). In addition, when the fluid passing through the gas meter is accompanied by flow velocity pulsation due to pressure pulsation or the like, it is difficult to measure the instantaneous value of the flow rate.
[0006]
An object of the present invention is to solve the above-described problems, and it is an object of the present invention to realize instantaneous flow rate measurement and improve measurement accuracy even when a fluid flowing through a measurement flow path causes flow velocity pulsation due to pressure pulsation or the like.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a measurement channel through which a fluid to be measured flows, a flow rate detection unit that detects a flow rate in the measurement channel, and a measurement control that causes the flow rate detection unit to perform measurement operations at predetermined time intervals. Based on the signals from the control unit and the measurement control unit For pulsating flow, set the measurement interval equal to or less than that for steady flow. A flow rate calculation unit that calculates a flow rate or a flow rate, and a measurement control unit that includes a flow rate correction unit that calculates a flow rate by adding a flow rate correction coefficient to the flow rate or the flow rate. The flow rate is calculated by using the same flow rate correction coefficient at any time, obtaining the average value of the flow velocity or flow rate at the time of pulsation to the average value, and adding the flow rate correction coefficient to the average value. This is a flow rate measuring device.
[0008]
According to the above invention, the correction error is reduced at the time of pulsating flow to the same correction coefficient as that at the steady flow without pulsation, the instantaneous flow rate can be measured with high accuracy even during the pulsating flow, and the inspection man-hours can be reduced. Productivity can be improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention, a measurement channel through which a fluid to be measured flows, a flow rate detection unit that detects a flow rate in the measurement channel at predetermined time intervals, and the flow rate detection unit are measured at predetermined time intervals. Based on the measurement control unit to be operated and the signal from the measurement control unit For pulsating flow, set the measurement interval equal to or less than that for steady flow. A flow rate calculation unit that calculates a flow rate or a flow rate, and a measurement control unit that includes a flow rate correction unit that calculates a flow rate by adding a flow rate correction coefficient to the flow rate or the flow rate. Use the same flow correction factor when there is no flow The flow rate measuring apparatus is characterized in that an average value of the flow velocity or flow rate is obtained at the time, and the flow rate is calculated in consideration of the flow rate correction coefficient. As a result, the instantaneous flow rate can be measured with high accuracy in the pulsating flow as in the steady flow, and the productivity can be improved by reducing the number of inspection steps.
[0010]
According to a second aspect of the present invention, the measurement control unit includes a measurement time setting unit that obtains a pulsation cycle, sets a measurement time that is an integral multiple of the pulsation cycle, and operates the flow velocity detection unit with the measurement time. The flow rate measuring device. Accordingly, the flow rate measurement with higher accuracy and higher reliability can be performed by measuring the average flow velocity in one cycle or several cycles of the pulsation in consideration of the pulsation cycle of the flow.
[0011]
According to a third aspect of the present invention, the measurement flow path has a substantially rectangular cross section, the measurement flow path has a substantially rectangular cross section, and the flow velocity detection means is constant from the wall surface in the height direction on the short side of the substantially rectangular cross section. This is a flow rate measuring device installed at a distance of. This makes it easy to detect changes in the flow velocity and improves measurement accuracy, and regulates the distance from the wall surface in the height direction regardless of the aspect ratio of the rectangular cross section. The road can be easily configured, and productivity and cost reduction can be improved by sharing parts.
[0012]
According to a fourth aspect of the present invention, the fixed distance is a height of a measurement flow path indicating a flow velocity average value of an instantaneous flow velocity distribution. Thereby, the measurement accuracy at the time of the pulsating flow can be improved by measuring the average flow velocity value in the measurement flow path at the instantaneous moment of the pulsating flow.
[0013]
The invention according to claim 5 is the flow rate measuring device in which the flow velocity detecting means is arranged at the center in the flow direction of the measurement channel. As a result, in the pulsating flow in which the flow is reversed between the forward direction and the reverse direction of the measurement flow path, the symmetry of the forward flow and the reverse flow can be improved to improve the measurement accuracy during the pulsating flow.
[0014]
A sixth aspect of the present invention is a flow rate measuring device in which flow stabilizing means are provided at equidistant positions on the upstream side and the downstream side of the flow velocity detecting means. As a result, the flow flowing into the measurement flow path can be further stabilized with respect to the flow in either the forward or reverse direction, and the measurement accuracy can be further improved.
[0015]
The invention according to claim 7 is a flow rate measuring device in which an introduction portion that is an inlet of a measurement flow path and a lead-out portion that is an outlet are provided at equidistant positions on the upstream side and the downstream side of the flow velocity detection means. This equalizes the upstream and downstream flow conditions that flow into or out of the measurement flow path for both forward and reverse flow directions, thereby improving the symmetry between the forward flow and the reverse flow. Measurement accuracy can be improved.
[0016]
According to an eighth aspect of the present invention, the introduction part and the lead-out part have the same cross section, and an inflow part having a bent part is connected to the introduction part so as to intersect the measurement channel, and an outflow having a bent part. It is a flow rate measuring apparatus which connected the part to the derivation part so that a part may intersect the measurement channel. As a result, it is possible to achieve further downsizing of the device by arranging the bent portion, and by making the shape of the inlet side or the outlet side substantially the same, the flow in the forward and reverse directions can be reduced. Measurement accuracy can be improved by increasing flow symmetry.
[0017]
According to a ninth aspect of the present invention, the flow velocity detecting means is provided with ultrasonic transmitters / receivers on the upstream side and the downstream side of the measurement channel, and transmits / receives ultrasonic waves between the ultrasonic transmitter / receivers, based on the transmission / reception signals. It is an ultrasonic flow rate measuring device that detects the flow velocity. This improves the accuracy of measurement accuracy because it measures the average flow velocity of the measurement channel in a wide area where the ultrasonic wave propagates, and further flows to measure a region with a width in the height direction of the measurement channel. Even if there is a variation, the instantaneous average flow velocity during pulsation can be measured and the measurement accuracy can be improved.
[0018]
The invention according to claim 10 is the flow rate measuring device in which the height of the cross section of the measurement channel is larger than the dimension of the transmission / reception surface of the ultrasonic transceiver. As a result, the transmitted ultrasonic waves can be effectively sent into the measurement flow path, and the drive input to the ultrasonic transmitter / receiver can be reduced to reduce the consumption consumption. In addition, the device can be miniaturized as a compact ultrasonic transceiver.
[0019]
The invention according to claim 11 is a flow rate measuring device in which the ultrasonic transmitter / receiver has an ultrasonic wavelength, a transmission surface dimension, and an inter-installation distance that are transmitted through an ultrasonic wave propagation path while the transmitted ultrasonic wave is a plane wave. . As a result, the transmitted ultrasonic wave propagates as a plane wave without spreading in the ultrasonic wave propagation path, reducing the influence of the reflected wave from the inner wall surface of the measurement flow path, and improving the waveform detection accuracy of the ultrasonic wave propagation measurement using the direct wave. The measurement accuracy can be improved by increasing the frequency, and the ultrasonic wave is propagated by plane waves to promote local measurement in the height direction of the measurement flow path, and the measurement accuracy of the instantaneous average flow velocity at the time of pulsation is enhanced to improve the pulsation flow. The flow measurement accuracy can be further improved.
[0020]
The invention according to claim 12 At predetermined time intervals Based on the step of detecting the flow of the measurement channel and the detected flow For pulsating flow, set the measurement interval equal to or less than that for steady flow. Uses the same flow rate correction coefficient both in the process of calculating the flow rate or flow velocity and when there is no pulsation and when there is no pulsation. flow A flow rate measurement method including a step of sometimes obtaining an average value of the flow rate or flow velocity and obtaining a flow rate by adding the flow rate correction coefficient to the average value.
[0021]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0022]
(Example 1)
FIG. 1 is a cross-sectional view of a flow rate measuring apparatus showing Embodiment 1 of the present invention. In the figure, 5 is a measurement flow path surrounded by the flow path wall 6, and 7 is a flow velocity detection means provided in the measurement flow path 5. The flow velocity detection means 7 detects a flow velocity at a specific location in the measurement flow path 5, and a small detection unit such as a thermal flow sensor is projected into the measurement flow path 5.
[0023]
Reference numeral 8 denotes a flow stabilizing means provided on the upstream side of the flow velocity detecting means 7, and includes a lattice-shaped direction regulating portion 8a for adjusting the flow direction and a fluctuation suppressing portion 8b formed of a mesh body such as a mesh for reducing flow velocity fluctuations. Yes. Reference numeral 9 is an introduction part provided on the upstream side of the measurement flow path 5 and serves as an inlet to the measurement flow path 5 of the fluid to be measured. Reference numeral 10 is provided on the downstream side of the measurement flow path 5 from the measurement flow path 5 of the measurement fluid. It is the derivation part used as an exit. Here, the cross section orthogonal to the flow (indicated by an arrow in the figure) of the measurement channel 5 is a rectangle or a substantially rectangle, the longitudinal direction of the rectangular cross section is the width W, and the short direction is the height H (not shown). ).
[0024]
Reference numeral 11 denotes a measurement control unit, which is connected to the flow rate detection unit 7 and causes the flow rate detection unit 7 to perform a measurement operation at a predetermined time interval. The flow rate is calculated based on a signal from the measurement control unit 12 and the flow rate is calculated. And a flow rate correction unit 14 that calculates an actual flow rate in the measurement flow path 5 by adding a correction coefficient based on the measured flow rate value. Reference numeral 15 denotes a pulsation determination unit that determines whether or not there is a pulsation of the fluid flowing through the measurement flow path 5 based on a flow velocity signal from the measurement control unit 12 entering the flow rate calculation unit 13, and the pulsation determination unit 15 has a pulsation. Is determined, the signal is sent to the measurement control unit 12 so that the measurement interval by the flow velocity detecting means 7 is equal to or less than that in the steady flow without pulsation. Reference numeral 16 denotes a measurement time setting unit. When the pulsation determination unit 15 determines that there is pulsation, the pulsation cycle is obtained, and a measurement time that is an integer multiple or almost an integral multiple of the pulsation cycle is set. Thus, the flow rate detecting means 7 is not only operated at a predetermined time interval, but also sends a signal so as to perform the measurement operation over a measurement time corresponding to the pulsation cycle.
[0025]
2 and 3 show experimental results obtained by measuring the flow velocity distribution of the pulsating flow in the channel having a rectangular cross section. FIG. 2 shows the case where the flow path height H = 17 mm (width W = 17 mm), the pulsation frequency 10 Hz, the flow rate 25 L / h, and the pressure fluctuation width ± 180 Pa. The flow velocity distribution shape is 1 cycle (100 ms). It turns out that it changes sequentially with the passage of time. Further, the flow velocity distribution indicated by “average pulsation” in the figure is an average of one cycle of the pulsating flow, and the flow velocity distribution indicated by “steady flow 25 L / h” is the flow velocity distribution at the steady flow 25 L / h without pulsation. It can be seen that the flow velocity distribution of the “pulsation average” and the flow velocity distribution of the “steady flow 25 L / h” are in good agreement. FIG. 3 shows the case where the flow path height H = 10 mm (width W = 30 mm), the pulsation frequency 10 Hz, the flow rate 25 L / h, and the pressure fluctuation width ± 180 Pa in the same manner as in FIG. It can be seen that the flow rate distribution of “pulsation average” and the flow rate distribution of “steady flow 25 L / h” are in good agreement. This result could be confirmed in any case where the flow rate was increased to 40, 100 L / h, the pulsation frequency was changed, or the pressure fluctuation range was changed. Accordingly, it was found that when the flow rate flowing through the measurement flow path 5 is obtained, the same flow rate correction coefficient can be used in the case of the pulsating flow as in the steady flow.
[0026]
Next, the operation of the flow rate measuring device based on the experimental results shown in FIGS. 2 and 3 will be described. The flow rate detecting means 7 is operated to measure the flow of the measurement channel 5 at a predetermined time interval by the measurement control unit 12, and the flow rate (or flow rate) is calculated by the flow rate calculation unit 13 based on the signal from the measurement control unit 12. If the pulsation determining unit 15 determines that there is pulsation at this time, a signal is sent to the measurement control unit 12 to shorten the measurement interval by the flow velocity detection means 7 to the same or less than that in the steady flow without pulsation. By continuing the measurement at a measurement interval shortened to the same or less, it is possible to measure the flow velocity (or flow rate) with high accuracy even for the pulsating flow. Further, an average flow velocity (or flow rate) is obtained with respect to the changing flow velocity (or flow rate) obtained in this manner, and the flow rate correction unit 14 adds a correction coefficient corresponding to the cross-sectional shape or measurement location to measure the flow rate. Calculate the flow rate of the road. However, since the same flow rate correction coefficient can be used for both the pulsating flow and the steady flow, there is no error due to the difference in the correction value, the measurement accuracy is improved, and the productivity can be improved by reducing the inspection man-hours. Needless to say, when the measurement interval by the flow velocity detection means 7 is increased in order to reduce power consumption during steady flow, the measurement interval by the flow velocity detection means 7 is obviously shortened during pulsation.
[0027]
Further, when the pulsating flow is detected in the measurement control means 11, a measurement time setting unit 16 for setting a measurement time that is an integral multiple or almost an integral multiple of the pulsation cycle is added, so that the flow velocity detection means 7 performs a measurement operation at a predetermined time interval. In addition, the measurement operation is performed over a measurement time that is an integral multiple of the pulsation period. This makes it possible to clearly define the time-series flow velocity data used as the basis for calculating the average flow rate, and further improve the measurement accuracy of the average flow velocity during pulsation.
[0028]
Thus, based on the output of the flow velocity detecting means 7, the flow rate calculation unit 13 for calculating the flow rate with a measurement interval equal to or less than that during steady flow and the flow rate correction coefficient during pulsation are the same as during steady flow. By providing the measurement control means 11 having the flow rate correction unit 14 for reducing the measurement error, the measurement time interval is shortened during pulsating flow, the correction error is reduced by setting the flow rate correction coefficient to be the same as during steady flow without pulsation, As with steady flow, the instantaneous flow rate can be measured with high accuracy and productivity can be improved by reducing the number of inspection steps.
[0029]
In addition, the measurement control means 11 includes a measurement time setting unit 16 that sets a measurement time that is substantially an integral multiple of the pulsation cycle at the time of the pulsation flow. The flow rate can be measured with higher accuracy and reliability by measuring the average flow velocity.
[0030]
(Example 2)
FIG. 4 is a longitudinal sectional view of a flow rate measuring apparatus showing Embodiment 2 of the present invention. 4, the same members and functions as those in the embodiment of FIG. 1 are denoted by the same reference numerals, detailed description thereof is omitted, and different points will be mainly described.
[0031]
In FIG. 4, the flow velocity detection means 7 is installed at a certain distance Lh from one wall surface in the height H direction of the measurement channel 5 having a rectangular cross section. Accordingly, the flow velocity detection means 7 detects the flow velocity in a region away from the wall surface in the height H direction of the measurement channel 5 by a certain distance, and measures the flow rate.
[0032]
5 and 6 show the measurement results of the flow velocity distribution of the pulsating flow in the rectangular cross-section flow path. The instantaneous flow velocity distribution (shown as “instantaneous flow velocity distribution” in the figure) and the average flow velocity in this flow velocity distribution (“ It is shown as time passes). FIG. 5 shows the case where the flow path height is H = 17 mm (width W = 17 mm), the pulsation frequency is 10 Hz, the flow rate is 25 L / h, and the pressure fluctuation range is ± 50 Pa. The flow rate increases from the minimum state to the maximum state. Indicates the time (measured from 0 ms to 52 ms). As shown in FIG. 5, it can be seen that there is a large change in flow velocity in the immediate vicinity of the wall surface, and further, the flow velocity distribution shape changes gradually with time from the minimum state to the maximum state, but the average velocity value of the instantaneous flow velocity distribution is high. It can be seen that there is a substantially constant distance from the wall in direction H. Now, looking at the position from the wall surface on the H = 0 mm side (left side in the figure), the intersection of the “instantaneous flow velocity distribution” and the “instantaneous average flow velocity” at the same measurement time exists at H = 3 to 4 mm. That is, by arranging the flow velocity detection means 7 at a position 3 to 4 mm from the wall surface in the height H direction of the measurement flow path 5, the instantaneous average flow velocity of the cross section is correctly obtained with respect to the flow velocity distribution that changes instantaneously in the pulsating flow. Therefore, the average flow velocity over the pulsation cycle can be measured more accurately, and the measurement accuracy can be improved. Even when the flow velocity is reduced (not shown) when the flow velocity changes from the maximum state to the minimum state, the position where the instantaneous cross-sectional average flow velocity is almost the same is 3 to 4 mm from the wall surface in the height H direction of the measurement channel 5. It is in. In addition, a measurement error due to variation in the measurement position becomes very close to the wall surface. Therefore, by installing the flow velocity detection means at a certain distance from the wall surface, the change in the flow velocity can be easily detected and the measurement accuracy can be improved.
[0033]
FIG. 6 shows a case where the flow path height H is 10 mm (width W = 30 mm), the pulsation frequency is 10 Hz, the flow rate is 25 L / h, and the pressure fluctuation range is ± 180 Pa. The flow rate decreases from the maximum state to the minimum state. Indicates time (measured from 50 ms to 0 ms). As in FIG. 5, the instantaneous flow velocity distribution in FIG. 6 changes sequentially, but the average velocity value of the instantaneous flow velocity distribution is approximately 1 to 3 mm from the wall in the height direction H. I understand. Even when the flow velocity is increased (not shown) when the flow velocity changes from the minimum state to the maximum state, the position at which the average flow velocity of the instantaneous cross section becomes approximately 1 to 3 mm from the wall surface in the height H direction of the measurement channel 5. It is in.
[0034]
Furthermore, when the flow rate during pulsation is increased to 40, 100 L / h, or when the pulsation frequency is changed, the average velocity value of the instantaneous flow velocity distribution is obtained when the height of the measurement channel 5 is 10 mm or more. 1 to 5 mm from the wall surface in the height direction H. The same can be expected even when the height of the measurement channel 5 is about 8 mm.
[0035]
Thus, by installing the flow velocity detection means 7 at a certain distance from the wall surface in the height direction, which is the short side of the substantially rectangular cross section, it is easy to detect changes in the flow velocity, and the measurement accuracy can be improved. Regardless of the aspect ratio, the distance from the wall surface in the height direction is specified, so the flow path with different measurement ranges can be easily configured by changing the width dimension of the rectangular cross section, and productivity and cost reduction are achieved by sharing parts. It can be improved.
[0036]
In addition, the installation distance from the wall in the height direction of the flow velocity detection means is set to the height region of the measurement flow path indicating the average value in the instantaneous flow velocity distribution at the time of pulsation of the fluid to be measured, so that the instantaneous pulsating flow By measuring the average flow velocity value in the measurement flow channel at the moment, the measurement accuracy during pulsating flow can be improved.
[0037]
In addition, the flow velocity detecting means is arranged at a position where the height of the measurement channel is 10 mm or more and the installation distance from the wall defining the height of the measurement channel is 1 to 5 mm, regardless of the aspect ratio of the rectangular cross section. The measurement accuracy at the time of pulsating flow can be improved by measuring the average flow velocity value in the measurement channel at the momentary moment of pulsating flow.
[0038]
Note that the flow rate detection means can improve the measurement accuracy of the pulsating flow by measuring with a width of about several millimeters in the height H direction instead of the pinpoint.
[0039]
(Example 3)
A third embodiment of the present invention is shown in FIGS. FIG. 7 is a transverse sectional view of the flow rate measuring device, FIG. 8 is a longitudinal sectional view of the flow rate measuring device, and FIG. 9 is a local longitudinal sectional view of the flow rate measuring device. 7 to 9, the same members and functions as those in the embodiment of FIG. 1 are denoted by the same reference numerals, detailed description thereof is omitted, and different points will be mainly described.
[0040]
In the figure, as the flow velocity detection means 7, upstream and downstream ultrasonic transceivers 7a and 7b attached to the flow path wall 6 are provided so as to face each other. The upstream ultrasonic transmitter / receiver 7 a and the downstream ultrasonic transmitter / receiver 7 b are separated from each other by a distance L so as to cross the width W direction of the measurement flow path 5 and are inclined by an angle θ with respect to the fluid flow direction of the measurement flow path 5. Installed. Further, the central axes of the ultrasonic transmitters / receivers 7 a and 7 b are set apart from the wall surface in the height H direction of the measurement channel 5 by a certain distance Lh. The central axes of the ultrasonic transmitters / receivers 7a and 7b are the centers of ultrasonic transmission / reception characteristics, and may or may not coincide with the center on the outer shape.
[0041]
Reference numerals 17 and 18 denote upstream and downstream opening holes that allow the ultrasonic transmitters / receivers 7a and 7b to face the measurement channel 5. Reference numeral 19 denotes an ultrasonic wave propagation path (a region indicated by a two-dot chain line) in which an ultrasonic wave transmitted between the opposing ultrasonic transceivers 7a and 7b directly propagates to the other side. The flow stabilizing means 8 is provided on the upstream side and the downstream side of the ultrasonic wave propagation path 19. Reference numeral 20 denotes an inflow suppressing body that reduces the flow of fluid into the opening holes 17 and 18. Since this inflow suppressing body 20 is provided flush with the flow path wall 6 and has fine holes through which ultrasonic waves can pass, the length Ld of the ultrasonic wave propagation path 19 in the measurement flow path 5 is the upstream side and The dimensions are clearly defined by being separated by the inflow suppression body 20 on the downstream side. 21 is an inflow path connected to the introduction part 9 of the measurement flow path 5, and 22 is an outflow path connected to the lead-out part 10 of the measurement flow path 5. The inflow path 21 and the outflow path 22 intersect the measurement flow path 5 to form upstream and downstream bent portions 23. Although the inflow path 21 and the outflow path 22 are bent at right angles to the height H direction of the measurement flow path 5, it is needless to say that the bending direction can be any direction, and the bending angle can be arbitrarily set. And can be miniaturized.
[0042]
The ultrasonic transmitters / receivers 7 a and 7 b as the flow velocity detecting means 7 are arranged so that the central position P of the ultrasonic propagation path 19 is the center of the length M in the flow direction of the measurement flow path 5. For this reason, in the pulsating flow in which the flow is reversed with respect to the forward direction and the reverse direction of the measurement flow path 5, the symmetry of the forward flow and the reverse flow can be enhanced to improve the measurement accuracy during the pulsating flow.
[0043]
Further, the upstream and downstream flow stabilizing means 8 are arranged at substantially equal distances on the upstream and downstream sides with respect to the central position P of the ultrasonic transmitters / receivers 7 a and 7 b as the flow velocity detecting means 7. For this reason, the flow which flows into the measurement flow path 5 can be further stabilized with respect to the flow in any of the forward and reverse directions, and the measurement accuracy can be further improved.
[0044]
Further, an introduction part 9 that is an inlet of the measurement flow path 5 and a lead-out part 10 that is an outlet are provided at substantially equidistant positions on the upstream and downstream sides of the ultrasonic transmitters and receivers 7a and 7b as the flow velocity detecting means 7. . For this reason, the flow conditions on the upstream side and the downstream side flowing into or out of the measurement flow path 5 are equalized with respect to the flow in either the forward or reverse direction, thereby improving the symmetry between the forward flow and the reverse flow. The measurement accuracy can be improved.
[0045]
Further, the introduction part 9 and the lead-out part 10 have substantially the same cross section, and a bent part 23 is formed in the introduction part 9 and the lead-out part 10 by the inflow path 21 and the outflow path 22 intersecting the measurement flow path 5. Yes. For this reason, further miniaturization of the apparatus can be realized by arranging the bent portion 23, and the measurement flow path can be applied to the flow in either the forward or reverse direction by making the shape of the inlet side or the outlet side substantially the same. The measurement accuracy can be improved by increasing the symmetry of the flow at 5.
[0046]
In addition, as shown in FIG. 9, the cross-sectional height H of the measurement channel 5 is larger than the outer dimension D of the transmission / reception surface 24 of the ultrasonic transmitters / receivers 7a, 7b. Therefore, the transmitted ultrasonic waves can be effectively sent into the measurement flow path, and the drive input to the ultrasonic transmitter / receiver can be reduced to reduce the consumption consumption. Further, even if it is inserted into the opening holes 17 and 18 provided in the flow path wall 6 forming the measurement flow path 5 and attached via a support member 25 having a vibration-proofing and hermetic sealing action, a compact configuration can be realized. The device can be miniaturized as a sound wave transmitter / receiver.
[0047]
Next, the operation of this ultrasonic flow measuring device will be described. The flow that has entered the measurement channel 5 from the introduction unit 9 is a fluctuation control unit that is formed of a grid-like direction regulating unit 8a that adjusts the flow direction in the upstream flow stabilizing means 8 and a mesh body such as a mesh that reduces flow rate fluctuations. A flow velocity distribution in which the flow is stabilized by 8 b is formed in the ultrasonic wave propagation path 19. When pulsation occurs in the flow due to pressure pulsation, and the pulsation level increases and the flow direction is reversed, the flow entering the measurement channel 5 from the derivation unit 10 is downstream even in reverse flow. A flow velocity distribution stabilized by the action of the flow stabilizing means 8 on the side is formed in the ultrasonic wave propagation path 19. The flow velocity is measured by transmitting and receiving ultrasonic waves with respect to the stabilized flow formed in the ultrasonic wave propagation path 19 in this way.
[0048]
Next, the flow measurement operation using ultrasonic waves will be described. In the measurement flow path 5, the ultrasonic wave is transmitted and received between the ultrasonic transmitters / receivers 7 a and 7 b across the width W of the cross section of the measurement flow path 5 by the action of the measurement control unit 12. That is, the propagation time T1 until the ultrasonic wave emitted from the upstream ultrasonic transmitter / receiver 7a is received by the downstream ultrasonic transmitter / receiver 7b is measured. On the other hand, the propagation time T2 until the ultrasonic wave emitted from the ultrasonic transmitter / receiver 7b on the downstream side is received by the ultrasonic transmitter / receiver 7a on the upstream side is measured. Based on the propagation times T1 and T2 thus measured, the flow rate is calculated by the calculation unit 13 by the following calculation formula.
[0049]
Now, the angle between the flow velocity V of the fluid to be measured in the flow direction of the measurement flow path 5 and the ultrasonic propagation path 19 is θ, the distance between the ultrasonic transceivers 7a and 7b is L, and the sound velocity of the fluid to be measured is C. Then, the flow velocity V is calculated by the following equation.
[0050]
T1 = L / (C + V cos θ)
T2 = L / (C−Vcos θ)
The speed of sound C is eliminated from the equation that subtracts the reciprocal of T2 from the reciprocal of T1.
V = (L / 2 cos θ) ((1 / T1) − (1 / T2))
Since θ and L are known, the flow velocity V can be calculated from the values of T1 and T2.
[0051]
From the flow velocity V and the cross-sectional area S orthogonal to the flow direction of the measurement channel 5, the flow rate Q is
Q = KVS
Here, K is a correction coefficient in consideration of the flow velocity distribution in the cross-sectional area S, and the true cross-sectional average flow rate can be obtained with a value suitable for the flow path shape in the flow rate correction unit 14.
[0052]
When the flow velocity is measured by this ultrasonic method, the ultrasonic wave transmitted from the transmission / reception surface 24 having the outer dimension D propagates with a width in the height direction, and the measurement channel section in a wide area where the ultrasonic wave propagates. The measurement accuracy can be improved by measuring the average flow velocity, and the instantaneous average flow velocity at the time of pulsation can be obtained even if the flow varies due to the measurement of the width of the measurement flow path. Measurement can be performed and measurement accuracy can be improved.
[0053]
As described above, the flow velocity detection means is arranged at the center of the flow direction of the measurement flow path, and in the pulsating flow in which the flow is reversed between the forward direction and the reverse direction of the measurement flow path, the forward flow and the reverse flow are symmetrical. To improve the measurement accuracy during pulsating flow.
[0054]
In addition, flow stabilization means are provided at approximately equal distances on the upstream and downstream sides of the flow velocity detection means, and the flow flowing into the measurement flow path is further stabilized against flow in either forward or reverse direction. Measurement accuracy can be further improved.
[0055]
In addition, an introduction part that is the inlet of the measurement flow path and a lead-out part that is the outlet of the measurement flow path are provided at approximately equidistant positions on the upstream side and downstream side of the flow velocity detection means. The flow conditions on the upstream side and the downstream side that flow into or out of the measurement flow path are equalized to increase the symmetry between the forward flow and the reverse flow, and the measurement accuracy during pulsating flow can be improved.
[0056]
The introduction part and the lead-out part have substantially the same cross section and are provided with a bent part intersecting with the measurement flow path. Further, by arranging the bent portion, the apparatus can be further miniaturized, and the flow in the measurement flow path can be performed in both forward and reverse directions by making the shape of the inlet side or the outlet side substantially the same. The measurement accuracy can be improved by increasing the symmetry.
[0057]
Further, the flow velocity detecting means is provided with ultrasonic transmitters / receivers on the upstream side and the downstream side of the measurement channel, and transmits / receives ultrasonic waves between the ultrasonic transmitter / receivers, and detects the flow rate based on the transmitted / received signals. It is a thing. And it can improve the reliability of measurement accuracy because it measures the average flow velocity of the measurement channel in a wide area where ultrasonic waves propagate, and it can be used to measure the area with a width in the height direction of the measurement channel. Even if variations occur, the instantaneous average flow velocity during pulsation can be measured and measurement accuracy can be improved.
[0058]
Moreover, the cross-sectional height of the measurement channel is larger than the transmission / reception surface of the ultrasonic transceiver. And the transmitted ultrasonic wave can be effectively sent into the measurement flow path, and the drive input to the ultrasonic transmitter / receiver can be reduced to reduce the consumption consumption. In addition, the device can be miniaturized as a compact ultrasonic transceiver.
[0059]
(Example 4)
FIG. 10 is an ultrasonic wave propagation state diagram of an ultrasonic wave transmitter / receiver showing Embodiment 4 of the present invention.
[0060]
In the figure, a general propagation state of ultrasonic waves from the ultrasonic transceiver 7a or 7b is shown. The ultrasonic wave transmitted from the transmission surface 26 of the ultrasonic transmitter / receiver 7a travels straight by a plane wave in the near field up to the last max 27 (indicated by an arrow in the figure), and a spherical wave in the far field of the last max 27 or higher. It spreads at a certain angle and proceeds. The distance X to the last max 27 is expressed by the following equation.
[0061]
X = D2 / 4λ
Here, D is the diameter of the transmission surface of the ultrasonic transceiver, and λ is the wavelength of the ultrasonic wave.
[0062]
In the embodiment shown in FIG. 7, by setting the ultrasonic propagation path length Ld in the measurement flow path 5 to be equal to or less than the distance X to the last max (Ld ≦ X), the ultrasonic wave does not spread and travels by a plane wave. Utilizing the near-field region for propagation time measurement, reducing the generation of ultrasonic reflected waves from the inner wall surface of the measurement channel 5 and increasing the detection accuracy of the ultrasonic propagation waveform during direct wave propagation time measurement The measurement accuracy of flow velocity can be improved.
[0063]
Further, by propagating with a plane wave, local measurement in the height direction of the measurement flow path 5 is promoted, and the measurement accuracy of the instantaneous instantaneous average flow velocity at the time of pulsation can be improved to further improve the flow measurement accuracy of the pulsating flow. .
[0064]
In addition, in order to reduce the measurement area in the height direction and increase the local measurement accuracy, it is necessary to reduce the diameter D of the transmission surface, and the outer dimension D of the transmission surface is reduced to ensure the distance X to the last max. It can be seen that it is effective to further shorten the wavelength of the ultrasonic wave.
[0065]
In this way, the ultrasonic transmitter / receiver uses the ultrasonic wavelength, transmission surface dimensions, and distance between installations as the transmitted ultrasonic wave remains a plane wave and propagates through the ultrasonic propagation path. Propagation with plane waves without spreading in the road reduces the influence of reflected waves from the inner wall surface of the measurement flow path, improves the accuracy of waveform detection for ultrasonic wave propagation measurement by direct waves, and improves the measurement accuracy. By propagating the sound wave, local measurement in the height direction of the measurement flow path is promoted, and the measurement accuracy of the instantaneous average flow velocity at the time of pulsation can be increased to further improve the flow rate measurement accuracy of the pulsating flow.
[0066]
【The invention's effect】
As is clear from the above description, according to the flow rate measuring device of the present invention, even when the fluid flowing through the measurement flow channel is pulsating due to pressure pulsation or the like, instantaneous flow rate measurement can be performed and measurement accuracy can be improved. .
[Brief description of the drawings]
FIG. 1 is a structural explanatory diagram of a flow rate measuring apparatus according to a first embodiment of the present invention.
FIG. 2 is a flow velocity distribution characteristic diagram of a pulsating flow that is the basis of Embodiment 1 of the present invention.
FIG. 3 is another flow velocity distribution characteristic diagram of the pulsating flow that is the basis of the first embodiment of the present invention.
FIG. 4 is an explanatory diagram of a flow rate measuring apparatus according to a second embodiment of the present invention.
FIG. 5 is a flow velocity distribution characteristic diagram of a pulsating flow that is the basis of Example 2 of the present invention.
FIG. 6 is another flow velocity distribution characteristic diagram of the pulsating flow that is the basis of Embodiment 2 of the present invention.
FIG. 7 is an explanatory diagram of a flow rate measuring device according to a third embodiment of the present invention.
FIG. 8 is a longitudinal sectional view of a flow rate measuring device according to Embodiment 3 of the present invention.
FIG. 9 is a partial cross-sectional view of a flow rate measuring device according to Embodiment 3 of the present invention.
FIG. 10 is an ultrasonic propagation state diagram of the ultrasonic transceiver according to the fourth embodiment of the present invention.
FIG. 11 is a configuration diagram of a conventional flow rate measuring device.
[Explanation of symbols]
5 Measurement channel
7 Flow rate detection means
7a, 7b Ultrasonic transceiver
8 Flow stabilization means
9 Introduction
10 Deriving part
11 Measurement control means
13 Flow rate calculator
14 Flow rate correction unit
16 Measurement time setting section
23 Bending part
24 Transmission and reception surface
26 Transmission surface
27 Last Max

Claims (12)

A measurement flow path through which the fluid to be measured flows, a flow velocity detection means for detecting a flow velocity in the measurement flow path, a measurement control section for measuring the flow velocity detection means at predetermined time intervals, and signals from the measurement control section Measurement control having a flow rate calculation unit for calculating a flow rate or a flow rate with a measurement interval equal to or less than that for a steady flow during a pulsating flow and a flow rate correction unit for calculating a flow rate by adding a flow rate correction coefficient to the flow rate or flow rate The flow rate correction unit uses the same flow rate correction coefficient when there is pulsation and when there is no pulsation, obtains an average value of the flow velocity or flow rate during pulsation flow , and adds the flow rate to the average value. A flow rate measuring apparatus characterized by calculating a flow rate in consideration of a correction coefficient. 2. The flow measurement according to claim 1, further comprising: a measurement time setting unit that obtains a pulsation period, sets a measurement time that is an integral multiple of the pulsation period, and operates the flow velocity detection unit with the measurement time. apparatus. 3. The flow rate measuring device according to claim 1, wherein the measurement flow path has a substantially rectangular cross section, and the flow velocity detection unit is installed at a certain distance from a wall surface in a height direction on the short side of the substantially rectangular cross section. The flow rate measuring apparatus according to claim 3, wherein the certain distance is a height of a measurement flow path indicating a flow velocity average value of an instantaneous flow velocity distribution. The flow rate measuring device according to claim 1, wherein the flow velocity detecting means is arranged at the center in the flow direction of the measurement channel. The flow rate measuring device according to any one of claims 1 to 5, wherein flow stabilizing means are provided at equidistant positions on the upstream side and the downstream side of the flow velocity detecting means. The flow rate measurement according to any one of claims 1 to 6, wherein an introduction portion that is an inlet of a measurement channel and a lead-out portion that is an outlet are provided at equidistant positions on the upstream side and the downstream side of the flow velocity detection means. apparatus. The introduction part and the lead-out part have the same cross section, and an inflow part having a bent part is connected to the introduction part so as to intersect the measurement channel, and an outflow part having a bent part intersects the measurement channel. The flow rate measuring device according to claim 7, connected to the derivation unit. The flow velocity detecting means is provided with ultrasonic transmitters / receivers on the upstream side and downstream side of the measurement flow path, and transmits and receives ultrasonic waves between the ultrasonic transmitters / receivers and detects the flow rate based on the transmission / reception signals. The flow measuring device according to any one of claims 1 to 8. The flow rate measurement device according to claim 9, wherein the height of the cross section of the measurement channel is larger than the dimension of the transmission / reception surface of the ultrasonic transceiver. The flow rate measuring device according to claim 9 or 10, wherein the ultrasonic transmitter / receiver has an ultrasonic wavelength, a transmission surface dimension, and an installation distance that are transmitted through an ultrasonic wave propagation path while the transmitted ultrasonic wave is a plane wave. There is a step of detecting the flow of the measurement channel at a predetermined time interval, a step of calculating the flow rate or the flow velocity by setting the measurement interval to be equal to or less than that of the steady flow based on the detected flow, and a pulsation The flow rate includes the step of using the same flow rate correction coefficient in both time and no pulsation, obtaining an average value of the flow rate or flow velocity at the time of pulsating flow , and obtaining the flow rate by adding the flow rate correction coefficient to the average value Measurement method.

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