JP2013217780A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement flow channel capable of removing influence of ultrasonic wall surface reflection in an ultrasonic flowmeter and capable of achieving also large flow rate measurement with a measuring device for a small flow rate.SOLUTION: A first flow channel 3a on the inside of a partition member 2 and a second flow channel 3b on the outside of the partition member 2 are configured by the cylindrical partition member 2 packaged concentrically with a measuring flow channel 1 whose cross section is circular, a flow rate of the second flow channel 3b is measured by using a pair of ultrasonic sensors 5, 6 and forming an ultrasonic propagation path of a V-shaped pass using a plane part formed on the outline of the partition member 2 as a reflection surface, and a flow rate of the whole measuring flow channel 1 is determined.

Description

  The present invention relates to a flow rate measuring device that measures the flow rate of a fluid such as gas or water using ultrasonic waves, and particularly corresponds to measurement of a large flow rate.

  Conventionally, this type of ultrasonic flow measuring device has a configuration in which a measurement channel 102 for measuring a part of the fluid is installed in a main channel 101 through which the measurement fluid flows, as shown in FIG. It was.

  In this configuration, the flow rate divided into the measurement flow channel 102 is measured, and the flow rate flowing through the main flow channel is obtained by calculation based on the diversion ratio with the preset overall flow rate. The flow of the entire pipe can be measured with the measurement system that is the measurement range.

  FIG. 11 shows the configuration of the measurement flow path 102. As shown in the figure, the cross section of the measurement flow path 102 has a rectangular shape, and at least a pair of the flow paths 102 arranged to face each other. The ultrasonic sensors 103 and 104 transmit and receive, and the flow velocity is obtained by the difference between the time when transmitting from the upstream side and the propagation time of ultrasonic waves when transmitting from the downstream side (see, for example, Patent Document 1 and Patent Document 2). ).

JP 2004-251686 A JP 2005-140729 A

  However, in the conventional configuration, since there is an upper limit of the measurement speed of the measurement unit with ultrasonic waves, it is necessary to match the specification of the measurement unit in order to satisfy the specification of the maximum measurement flow rate. In the ultrasonic flowmeter, as shown in FIG. 11, the ultrasonic wave transmitted from the transmitting side is reflected by the direct wave A reaching the receiving side without being reflected by the wall surface parallel to the ultrasonic wave propagation direction and the above-described wall surface. However, there is a reflected wave B that reaches the reception side, and the direct wave A and the reflected wave B have different phases, and this composite wave becomes a reception wave and is received by the ultrasonic sensor on the reception side.

  Therefore, the measurement of the propagation time by ultrasonic waves is performed using the received wave, so that the shape of the received wave is deformed. In designing the propagation path of the ultrasonic wave, the influence of the reflected wave must be minimized. Is required.

  The measurement flow path is divided into a main pipe flow path 101 that flows a large flow rate and a measurement flow path 102 that performs measurement, and measurement of the measurement flow path 102 is measured with ultrasonic waves, and a shunt flow between the main flow path 101 and the measurement flow path 102 is performed. The total flow rate is obtained from the ratio, but it is difficult to make this diversion ratio constant according to the measured flow rate, and correction according to the flow rate is necessary, and the diversion ratio depends on the type and temperature of the fluid to be measured. Therefore, the correction system is not only complicated, but also restricts the fluid and environment that can be measured.

  The present invention eliminates the above-mentioned conventional problems, prevents the influence of wall reflection without being restricted by the frequency of the ultrasonic sensor and the distance between the wall surfaces, and diverts the main channel and the measurement channel for measurement. A measuring means for preventing the ratio from changing depending on conditions is provided.

  In order to solve the above-described conventional problems, an ultrasonic flowmeter of the present invention includes a substantially circular flow channel having a substantially circular cross section, and a substantially circular cylindrical shape disposed concentrically with the flow channel inside the flow channel. A flow rate measuring means for measuring a flow velocity in a flow path constituted by a partition member, an inner wall of the flow path and an outer wall of the flow path member by an ultrasonic propagation time, and a flow rate of the entire flow path from the flow velocity measured by the flow speed measurement means. A flow rate calculating means for calculating a flow rate, and an ultrasonic wave propagation path in the flow velocity measuring means is between the inner wall of the flow path and the outer wall of the partition member.

  In addition, since there is substantially no side wall surface in the ultrasonic wave propagation path, it is possible to transmit and receive only direct waves, and it is not affected by the interference of wall reflection as in the past, and the ultrasonic sensor drive frequency. The flow path can be formed without considering the above.

  Moreover, although it is a measurement flow path of the bypass structure which calculates | requires the whole flow volume which flows through a measurement flow path by measuring a part of flow path, since the shape is axisymmetric, two flow paths inside and outside of a partition member Since it is easy to set the diversion ratio, it is possible to easily calculate and obtain the total flow rate from the flow velocity measured by ultrasonic measurement, and it is possible to easily measure a large flow rate with an ultrasonic measurement device for small flow rate .

  According to the ultrasonic flowmeter of the present invention, it is not affected by interference of wall surface reflection, and a flow path can be formed without considering the driving frequency of the ultrasonic sensor.

Sectional drawing of the ultrasonic flowmeter in Embodiment 1 of this invention Side surface sectional drawing of the ultrasonic flowmeter in Embodiment 1 of this invention System configuration diagram according to Embodiment 1 of the present invention Operation explanatory diagram of ultrasonic flow measurement in Embodiment 1 of the present invention Side view of ultrasonic flowmeter in embodiment 1 of the present invention Sectional drawing of the ultrasonic flowmeter in Embodiment 2 of this invention Side surface sectional drawing of the ultrasonic flowmeter in Embodiment 2 of this invention Side surface sectional drawing of the ultrasonic flowmeter of the other form in Embodiment 2 of this invention Sectional drawing of the ultrasonic flowmeter in Embodiment 3 of this invention Configuration diagram of bypass flow meter using conventional ultrasonic flow meter Configuration diagram of conventional ultrasonic flowmeter

  A first aspect of the present invention is a flow path having a substantially circular cross section, a substantially circular cylindrical partition member disposed concentrically with the flow path inside the flow path, an inner wall of the flow path, and the partition A flow velocity measuring means for measuring the flow velocity in the flow path constituted by the outer wall of the member by the propagation time of the ultrasonic wave, and a flow rate calculating means for calculating the flow rate of the entire flow path from the flow velocity measured by the flow velocity measuring means, By setting the ultrasonic wave propagation path in the flow velocity measuring means between the inner wall of the flow path and the outer wall of the partition member, only the direct wave is transmitted / received because the wall surface in the ultrasonic wave propagation direction of the measuring unit is eliminated, and the reflected wave on the wall surface. The direct propagation wave does not interfere with the received waveform, and the flow path can be formed without considering the driving frequency of the sensor. Further, since the amount of fluid flowing through the cylindrical flow path can be measured by measuring a part of the flow path, a large flow rate can be measured with a small-sized ultrasonic device.

In particular, according to a second invention, in the first invention, a pair of ultrasonic sensors disposed on the upstream side and the downstream side of the flow path, a flat surface provided on the outer surface of the partition member, and the outer surface of the partition member The ultrasonic wave transmitted from one ultrasonic sensor is reflected on the plane and propagates to the other ultrasonic sensor, and the ultrasonic sensor is disposed on the outer wall of the flow path. Since there is no need to provide a measuring unit in the center as in the prior art, the apparatus can be simplified.

  According to a third aspect of the invention, in particular, in the second aspect of the invention, the sectional shape of the partition member is a cylindrical shape that forms a polygonal shape. It is possible to configure multiple propagation paths, and by combining ultrasonic sensors with different measurement ranges and measurement systems with different configurations such as changing the length of the propagation path, a wider range of measurements and improved accuracy Can be achieved.

  In particular, in the fourth invention, in any one of the first to third inventions, since the fluid flows uniformly in the measurement flow path by having the rectifying member in the fluid inflow portion of the flow path, Up to a large flow rate, the diversion ratio of the flow rates flowing in the first flow path and the second flow path is constant, and even if the environment such as the type of fluid and temperature changes, the diversion ratio is also constant. It is easy to correct and easily obtain stable measurement accuracy.

  In the fifth aspect of the invention, in particular, in the fourth aspect of the invention, the flow rate can be accurately measured even at the time of back flow by having the rectifying member on the outflow side of the measurement flow path.

  In the sixth aspect of the invention, the rectifying member of the fourth or fifth aspect of the invention is made of a porous material, so that a sufficient rectifying effect can be exhibited and stable measurement accuracy can be easily ensured. It becomes possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a sectional view of an ultrasonic flow meter showing Embodiment 1 of the present invention. 2 is a cross-sectional view taken along line AA ′ shown in FIG.

  In the measurement channel 1 through which the fluid to be measured flows, a circular cylindrical partition member 2 is provided on the same axis as the measurement channel 1 via a support member (not shown) inside the measurement channel. A first flow path 3 a is formed by the internal space of the partition member 2. A second flow path 3 b is configured by a space formed by the inner wall of the measurement flow path 1 and the outer wall of the partition member 2.

  That is, the measurement flow path 1 is configured to be partitioned into a first flow path 3 a and a second flow path 3 b by the partition member 2.

  Further, a flow regulating member 4 is provided on the inflow side of the fluid to be measured (indicated by a white arrow) in the measurement flow path 1, and the flow rate per area flows into the first flow path 3a and the second flow path 3b. Is configured to be constant.

  Further, a pair of ultrasonic sensors 5 and 6 are installed in the measurement flow path 1 so as to be reflected by the plane 2a of the first flow path to form a V-shaped propagation path, and the ultrasonic sensor 5 arranged on the upstream side. Ultrasonic waves are transmitted and received between the ultrasonic sensors 6 arranged on the downstream side.

  FIG. 3 shows a block diagram of the ultrasonic flowmeter of the present embodiment, and the ultrasonic propagation time is measured by the ultrasonic sensors 5 and 6 arranged in the measurement flow path 1 as shown in the figure. The calculation circuit 7 calculates the flow velocity of the second flow path 3b from the ultrasonic wave propagation time.

From this flow velocity, the flow rate of the fluid to be measured flowing through the measurement flow channel 1 is calculated from the cross-sectional areas of the first flow channel 3a and the second flow channel 3b, and the result is obtained via the control means 8 of the measurement device 10. Is displayed on the display unit 9.

  In the present embodiment, the result is displayed on the display unit 9, but the measurement result may be output as numerical data to a data logger or the like, or equipped with a wireless system or wired data transfer function. It is also possible to output at other places.

  Hereinafter, the operation of ultrasonic measurement will be described with reference to FIG.

  First, ultrasonic waves are alternately transmitted and received between the ultrasonic sensors 5 and 6, and the difference between the propagation times of the ultrasonic waves in the forward direction and the reverse direction with respect to the flow of the fluid is measured at regular intervals and output as a propagation time difference signal. To do. In response to this propagation time difference signal, the arithmetic circuit 7 calculates the flow velocity of the fluid to be measured and the flow rate of the measurement channel.

  The propagation time T1 until the ultrasonic wave emitted from the upstream ultrasonic sensor 5 is received by the downstream ultrasonic sensor 6 is measured. On the other hand, the propagation time T2 until the ultrasonic wave emitted from the downstream ultrasonic sensor 6 is received by the upstream ultrasonic sensor 5 is measured.

  Based on the propagation times T1 and T2 measured in this way, the flow rate is calculated by an arithmetic circuit using the following arithmetic expression.

  If the angle between the flow velocity V of the fluid to be measured in the flow direction of the measurement channel and the ultrasonic propagation path is θ, the distance between the ultrasonic sensors is 2 × L, and the sound velocity of the fluid to be measured is C, the flow velocity V is calculated by the following equation.

Formula (1) T1 = 2 × L / (C + V cos θ)
Formula (2) T2 = 2 × L / (C−V cos θ)
The speed of sound C is eliminated from the equation for subtracting the reciprocal of T2 from the reciprocal of T1. Equation (3) V = (2 × 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.

  The operation of the ultrasonic flowmeter configured as described above will be described below with reference to FIGS. 5 is a view taken in the direction of arrow B in FIG.

  As a feature of the ultrasonic measurement method, since pressure loss does not occur in the measurement unit, the fluid to be measured flowing into the measurement flow path 1 is divided by the rectifying member 4 as a constant flow rate per unit area, and the first flow path 3a, It flows into the two flow paths 3b.

  The rectifying member 4 shown here uses a porous body having a honeycomb structure, but other members may of course be used as long as they have a rectifying action.

  The flow rate of a part of the fluid to be measured that has flowed into the second flow path 3b is measured by the above-described ultrasonic measurement principle, and the flow rate of the measurement flow path 1 is obtained by multiplying the correction coefficient that is obtained in advance. Can do.

  In the ultrasonic wave propagation path formed by the second flow path 3b, since there is no wall surface parallel to the propagation path, only the direct wave passing through the V-shaped path is received. Since the received wave is disturbed due to the interference of waves and the propagation time of the ultrasonic wave cannot be measured accurately, it is possible to construct a measurement system that is not easily affected by the characteristics of the sensor.

(Embodiment 2)
The second embodiment will be described with reference to FIGS. 6 is a cross-sectional view of the measurement channel of the second embodiment, and FIG. 7 is a cross-sectional view taken along the line CC ′ of FIG. In addition, the thing of the same code | symbol as FIG. 1 has the same structure, and abbreviate | omits description.

  As shown in FIG. 7, the measurement channel 12 is divided into a first channel 14a and a second channel 14b by a partition member 13, and the partition member 13 has a dodecagonal outer shape. Each side can be used as a reflection surface of a V-shaped path for ultrasonic propagation. In addition, the inner wall of the measurement channel 12 has a similar dodecagon.

  Further, the ultrasonic sensor includes the ultrasonic sensors 5 and 6 in FIG. 1 and ultrasonic sensors 15 and 16 having characteristics different from those of the ultrasonic sensors 5 and 6, and the reflecting surfaces of the ultrasonic sensors 5 and 6 are flat surfaces 13 a and 13 b. Thus, two propagation paths are configured, and an optimum measurement result can be obtained by appropriately selecting according to the flow rate and the type of the non-measurement fluid.

  Further, as shown in FIG. 8, by configuring the distance C between the ultrasonic sensors 5 and 6 and the distance D between the ultrasonic sensors 17 and 18 to be different, the two propagation distances are appropriately set according to the measurement flow rate range. It is also possible to make it selectable. In this case, the characteristics of the ultrasonic sensors 17 and 18 may be the same as or different from those of the ultrasonic sensors 5 and 6 and can be appropriately selected according to the flow rate and the type of non-measurement fluid.

  The range of flow velocity that can be measured varies depending on the characteristics of the sensor (for example, the drive frequency of the sensor and the sensitivity of the sensor) for ultrasonic flow measurement. For example, when the flow velocity is small, a higher sensor drive frequency is advantageous because the resolution of measurement increases, but when the flow velocity is large, a lower frequency is more stable and can measure stably against flow disturbance. is there.

  In the example shown in FIG. 7, the frequency characteristics of the two sets of ultrasonic sensors are set differently.

  On the other hand, as shown in FIG. 8, the longer propagation path allows stable measurement even at a low flow rate, but the attenuation of ultrasonic waves between the sensors increases, so the measurement tends to become unstable when the flow rate increases. .

  Therefore, the range of the flow velocity that can be stably measured is determined by the combination of the sensor characteristics and the ultrasonic propagation path. In the present embodiment, a plurality of different measurement units are formed with one measurement channel, and the measurement range can be expanded without changing the configuration of the measurement channel and the measurement accuracy can be changed by using according to the flow rate. It is possible to increase the range of application as a measuring device.

  In the present embodiment, the outer shape of the partition member 13 is a dodecagon, but the number of corners of the shape is not limited within a range where the reflection of ultrasonic waves can be used.

(Embodiment 3)
FIG. 9 shows a cross section of the measurement channel of the third embodiment, and the same reference numerals as those in FIG.

  As shown in FIG. 9, by providing a rectifying member 19 on the outflow side of the measurement channel 1, it is possible to measure a reverse flow in the ultrasonic measurement method, and therefore it is possible to accurately measure both forward and reverse flows. It becomes possible.

As described above, the ultrasonic flowmeter of the present invention has the effect of wall reflection by forming a V-shaped path using the outer wall of the first channel in the second channel provided in the measurement channel. In addition, the received waveform is stable and can be measured with high accuracy, and the second flow path of the measurement section and the main flow path of the main flow path are measured with a bypass-type measurement configuration in which a part of the measurement flow path is measured to obtain the total flow rate. Control of the diversion ratio of one flow path is easy, and application development to a large flowmeter can be easily achieved with a simple configuration with a small flow rate measuring device.

1, 12 Measurement channel (channel)
2, 13 Partition member 2a, 13a, 13b Plane 3a, 14a First flow path 3b, 14b Second flow path 4, 19 Rectification member 5, 6, 15, 16, 17, 18 Ultrasonic sensor (flow velocity measuring means)
7 Calculation circuit (flow rate calculation means)

Claims (6)

A flow path having a substantially circular cross section,
A substantially circular cylindrical partition member disposed concentrically with the flow path inside the flow path;
A flow velocity measuring means for measuring a flow velocity in a flow channel constituted by an inner wall of the flow channel and an outer wall of the partition member by an ultrasonic propagation time;
A flow rate calculating means for calculating the flow rate of the entire flow path from the flow rate measured by the flow rate measuring means,
The ultrasonic flowmeter which made the propagation path of the ultrasonic wave in the said flow velocity measurement means between the inner wall of the said flow path, and the outer wall of the said division member. A pair of ultrasonic sensors disposed on the upstream side and the downstream side of the flow path, and a plane provided on the outer surface of the partition member,
The ultrasonic flowmeter according to claim 1, wherein ultrasonic waves transmitted from one of the ultrasonic sensors are reflected on the plane and propagated to the other ultrasonic sensor. The ultrasonic flowmeter according to claim 2, wherein an outer cross-sectional shape of the partition member is a cylindrical shape having a polygonal shape. The ultrasonic flowmeter according to any one of claims 1 to 3, further comprising a rectifying member on a fluid inflow side of the flow path. The ultrasonic flowmeter according to claim 4, further comprising a rectifying member on the outflow side of the flow path. The ultrasonic flowmeter according to claim 4 or 5, wherein the rectifying member is made of a porous body.

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