JP3583114B2 - Ultrasonic flow velocity measuring device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic flow velocity measuring device that measures the flow velocity of a gas or other fluid using ultrasonic waves.
[0002]
2. Description of the Related Art
2. Description of the Related Art Conventionally, when determining the flow rate of a gas or other fluid, the flow rate of the fluid is continuously or periodically measured, and the flow rate is calculated based on the measured flow rate. As one of such fluid flow velocity measuring methods, a method using ultrasonic waves is known.
[0003]
The principle of such an ultrasonic flow velocity measuring method will be described with reference to FIG. In FIG. 5, (1) is an ultrasonic flow velocity measuring tube through which a fluid such as gas flows. In the ultrasonic flow velocity measuring tube (1), cylindrical ultrasonic vibrators (2) and (3) are arranged on the upstream side and the downstream side in the flow direction so as to face each other with a predetermined distance therebetween. I have. The ultrasonic vibrators (2) and (3) are driven by a driving pulse from a driving pulse generating circuit (6), vibrate, generate and transmit ultrasonic waves, and receive transmitted ultrasonic waves. The reception wave when the ultrasonic transducers (3) and (2) vibrate is output from the reception amplification circuit (6).
[0004]
The propagation time until the ultrasonic wave transmitted from the upstream ultrasonic transducer (2) in the forward direction with respect to the flow is received by the downstream ultrasonic transducer (3) is determined. The difference from the propagation time until the ultrasonic wave transmitted from the ultrasonic transducer (3) in the opposite direction to the flow is received by the upstream ultrasonic transducer (2) is related to the flow velocity. The flow velocity of the fluid is measured by obtaining the difference between the propagation times of the ultrasonic waves by using a clock wave or the like.
[0005]
In FIG. 5, reference numeral (8) denotes a switching circuit for switching the connection between each of the ultrasonic transducers (2) and (3) and the drive pulse generation circuit (6) and the reception amplification circuit (7). (4) is connected to the ultrasonic transducer (2) on the upstream side, the ultrasonic transducer (3) on the downstream side and the receiving amplifier circuit (7), and the propagation time from the upstream side to the downstream side is measured. By the operation of the switching circuit (8), the drive pulse generating circuit (6) is connected to the downstream ultrasonic oscillator (3), and the upstream ultrasonic oscillator (2) is connected to the receiving amplifier circuit (7). And the propagation time from the downstream side to the upstream side is measured.
[0006]
However, when the ultrasonic vibrators (2) and (3) are arranged in an opposed manner as described above, only the straight ultrasonic waves transmitted vertically from the ultrasonic vibrators (2) and (3) are opposed. The ultrasonic transducers (3) and (2) are received in the same phase as they are, but most of the ultrasonic waves other than the straight ultrasonic waves are reflected at least once on the inner surface of the flow velocity measuring tube, and are then opposed to each other. (3) The signals are received in phases different from those in (2). Therefore, there is a problem that the amplitude of the received wave output from the reception amplifier circuit (7) is small as a whole, and the flow velocity of the fluid cannot be measured accurately.
[0007]
The present invention has been made in view of the above-described problems, and has as its object to provide an ultrasonic flow velocity measuring device that can increase the amplitude of a received wave and can accurately measure the flow velocity of a fluid. And
[0008]
[Means for Solving the Problems]
According to the present invention, in order to achieve the above object, ultrasonic vibrators (2) and (3) are arranged on an upstream side and a downstream side of a measurement fluid flowing through a flow velocity measuring pipe (1), respectively. (2) The ultrasonic wave generated and transmitted mutually from (3), the transmitted ultrasonic waves are mutually received, and the flow velocity is measured based on the difference between the propagation times of the ultrasonic waves. In the flow velocity measuring device,
Ultrasonic reflectors (4) and (5) are provided on the upstream and downstream sides of the flow velocity measuring tube (1), respectively, so as to correspond to the ultrasonic transducers (2) and (3),
The ultrasonic reflectors (4) and (5) are arranged such that the normal line a of an arbitrary point Q on the reflection surface corresponds to the point Q and corresponds to the point P and the point on the radiation surface of the ultrasonic transducer (2) (3). An angle formed between a line connecting the virtual radiation point R located behind P and the axis c of the flow velocity measuring tube (1) is bisected.
[0009]
According to this, most of the ultrasonic waves transmitted from the ultrasonic transducer on the transmitting side are reflected by the ultrasonic reflecting portion on the transmitting side so as to be parallel to the axial direction of the flow velocity measuring pipe, and pass through the flow measuring pipe. After passing in parallel to the axial direction, the light is reflected by the ultrasonic transducer on the reception side so as to be received by the ultrasonic transducer on the reception side.
[0010]
For this reason, most of the ultrasonic waves transmitted from the ultrasonic transducer on the transmitting side are received by the ultrasonic transducer on the receiving side in the same phase, so that the amplitude of the received wave can be increased, and the fluid The flow velocity can be measured with high accuracy. In addition, most of the ultrasonic waves transmitted from the ultrasonic transducer on the transmission side can pass through the flow velocity measurement tube in a cross section fully parallel to the axial direction. The flow velocity of the fluid can be measured with high accuracy even when the flow is unevenly distributed.
[0011]
Further, it is preferable that the ultrasonic reflecting portion is formed so as to satisfy a condition of the following expression [1] on at least a part of the reflecting surface.
[0012]
m = − ｛γx / (Gy) + √ [1+ (γx / (Gy)) ² ] (1)
O: Intersecting point (x, y) between axis d of ultrasonic transducers (2) and (3) and axis c of flow velocity measuring tube (1): Ultrasonic reflecting members (4) and (5) having intersection O as the origin Position m on the reflecting surface of the ultrasonic wave reflecting member (4) (5) Slope at position (x, y) on the reflecting surface r: Diameter b of the radiating surface of the ultrasonic transducers (2) and (3) b: Length y in the y direction of the flow velocity measuring tube (1): 1-r / b
G: Distance in the y direction from the origin O to the radiation surface of the ultrasonic transducers (2) and (3) According to this, the ultrasonic reflecting portion having the above-described effects can be formed simply and reliably. .
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 is a sectional view of an ultrasonic flow velocity measuring apparatus according to an embodiment of the present invention as viewed from above, and FIG. 2 is a view of the ultrasonic flow velocity measuring apparatus as viewed from the side (viewed along the line II in FIG. 1). FIG.
[0015]
1 and 2, (1) is a U-shaped flow rate measuring tube through which a fluid flows, (1a) is an accommodation portion provided at a bent portion of the flow rate measuring tube (1), and (1b) is a flow rate measuring tube ( 1) The flow velocity measuring unit provided in the lower horizontal part, (2) and (3) are the ultrasonic vibrators provided in the housing part (1a), and (4) and (5) are the same in the housing part (1a). Ultrasonic reflecting members made of metal or the like provided at positions corresponding to the ultrasonic transducers (2) and (3), respectively.
[0016]
Further, (6) is a drive pulse circuit for generating drive pulses applied to the ultrasonic transducers (2) and (3), and (7) is based on ultrasonic waves received by the ultrasonic transducers (2) and (3). (8) is a switching circuit for switching the connection between the ultrasonic transducers (2) and (3) and the drive pulse generating circuit (6) and the receiving amplifier circuit (7). Are the same as those shown in FIG. 5, and therefore the same reference numerals are given and the description thereof will be omitted.
[0017]
In this embodiment, as shown in FIG. 1, the axial direction of the flow velocity measuring portion (1b) of the flow velocity measuring tube (1) is in the x direction, and the axial directions of the ultrasonic vibrators (2) and (3) are in the y direction. And As shown in FIG. 2, a direction perpendicular to both the x direction and the y direction is defined as a z direction.
[0018]
The flow velocity measurement pipe (1) is formed in a rectangular cross section, and flows in from an upstream end (left end in FIG. 2) of the flow velocity measurement pipe (1) as shown in FIG. The fluid passes through the flow velocity measuring unit (1a) as it is, and after the flow velocity is measured during the passage, the fluid flows from the downstream end (the right end in FIG. 2) of the flow velocity measuring unit (1a). It is spilled.
[0019]
As shown in FIG. 1, the ultrasonic reflecting members (4) and (5) are curved in the xy directions so that their reflecting surfaces face each other. Specifically, as shown in FIG. 3, the ultrasonic reflecting members (4) and (5) have an ultrasonic transducer (where a normal a of an arbitrary point Q on the reflecting surface thereof corresponds to the point Q). 2) The angle (θ ₁ + θ ₂ ) formed by the line b connecting the point P on the radiation surface of (3) and the axis c of the flow velocity measuring tube (1) (or the parallel line c ′ of the axis c) is formed. It is formed so as to be equally divided.
[0020]
The ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) on the transmitting side are transmitted in the xy direction at the ultrasonic reflecting sections (4) and (5) on the transmitting side, and the axis of the flow velocity measuring tube (1) is changed. After being reflected so as to be parallel to the direction and passing through the inside of the flow velocity measuring section (1b) of the flow velocity measuring pipe (1) in parallel to the axial direction, the ultrasonic reflection sections (5) and (4) on the receiving side will be described later. The light is reflected so as to converge to the virtual radiation point R, and is received by the ultrasonic transducers (3) and (2) on the receiving side.
[0021]
In particular, in this embodiment, the ultrasonic reflecting members (4) and (5) are formed in such a shape that their reflecting surfaces satisfy the condition of the following expression [1].
[0022]
m = − ｛γx / (Gy) + √ [1+ (γx / (Gy)) ² ] (1)
O: Intersecting point (x, y) between axis d of ultrasonic transducers (2) and (3) and axis c of flow velocity measuring tube (1): Position (coordinate) on the reflecting surface with intersection O as the origin
m: inclination at the position (x, y) on the reflection surface r: diameter of the radiation surface of the ultrasonic transducers (2), (3) b: length of the flow velocity measuring tube (1) in the y direction γ: 1-r / B
G: Distance in the y-direction from the origin O to the radiation surfaces of the ultrasonic transducers (2) and (3) The ultrasonic reflecting members (4) and (5) are formed in such a shape for the following reason. Note that, for convenience of explanation, the ultrasonic reflecting member (4) will be described.
[0023]
First, in FIG.
P: Ultrasonic transmission point (reception point)
Q: reflection point R corresponding to transmission point P: virtual emission point O: intersection (x, y) of axis d of ultrasonic transducer (2) and axis c of flow velocity measuring tube (1): intersection O is the origin Position G on the reflecting surface to be defined G: Distance in the y direction from the origin O to the radiation surface of the ultrasonic transducer (2) r: Diameter b of the radiation surface of the ultrasonic transducer (2) b: Flow velocity measurement tube (1) Θ: the angle between the normal a of the Q point and the straight line b θ2: the angle x between the normal a of the Q point and the parallel axis c ′ of the flow velocity measuring tube (1) xp: ultrasonic vibration If the distance from the axis d of the child (2) to the transmission point P is:
For the line segment PQ (straight line b),
tan (θ ₁ + θ ₂ ) = (G−y) / (x−xp) [2]
It becomes.
Also, the condition of the normal line at point Q is
tan θ ₂ = dx / dy ... [3]
It becomes.
Also, if x and xp are considered to correspond proportionally,
x / b = xp / r ... [4]
And γ (gamma) = 1−r / b,
x-xp
= X-xr / b
= X (1-r / b)
= Xγ ... [5]
It becomes.
Here, if θ1 = θ2 = θ (∵reflection condition) and dx / dy = 1 / m, the left expression of the above expression [2] becomes:
tan (θ1 + θ2)
= Tan (2θ)
^{= 2tanθ / (1-tan 2} θ)
^{= 2m / (1-m 2} ) ... [6]
It becomes.
On the other hand, from the above equation [5], the right equation of the above equation [2] becomes:
(Gy) / (x-xp) = (Gy) / xγ ... [7]
It becomes.
Therefore, according to the above equations [6] and [7],
^{2m / (1-m 2)} = (G-y) / xγ
∴m ² + 2mxγ / (G−y) −1 = 0 ... [8]
Solving the above equation [8] for m gives
m = − ｛γx / (Gy) ± √ [1+ (γx / (Gy)) ² ] ... [9]
It becomes. Because m <0,
m = − ｛γx / (Gy) + √ [1+ (γx / (Gy)) ² ] ... [1]
And the above equation [1] is derived.
Then, according to the above equation [1], y = ∫mdx... [10]
As a result, the shape of the reflecting surface of the ultrasonic reflecting member (4) in the xy directions can be obtained.
[0024]
The shape of the other ultrasonic reflecting member (5) in the xy directions can be obtained in the same manner as described above.
[0025]
Further, as shown in FIG. 2, the ultrasonic reflecting members (4) and (5) have their reflecting surfaces formed in an arc shape in the xz direction. As shown in FIG. 4, this arc is an arc centered on a point R ′ which is twice as long as the virtual radiation point R from the reflection surfaces of the ultrasonic reflection members (4) and (5). The reason why the ultrasonic reflecting members (4) and (5) are formed in this way is that the ultrasonic waves emitted from the radiating point at a distance of 1/2 of the diameter of the arc are parallel to the axial direction c in the arc. The reason for this is to utilize the property that, while being reflected, the ultrasonic wave incident parallel to the axial direction c is reflected so as to converge to the virtual radiation point R in the arc.
[0026]
The ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) on the transmitting side are transmitted in the xz direction at the ultrasonic reflecting portions (4) and (5) on the transmitting side, and the axis of the flow velocity measuring tube (1) is changed. After being reflected parallel to the direction and passing through the flow velocity measuring section (1b) of the flow velocity measuring pipe (1) in parallel with the axial direction, virtual radiation occurs at the ultrasonic reflecting sections (5) and (4) on the receiving side. The light is reflected so as to converge to the point R, and is received by the ultrasonic transducer on the receiving side.
[0027]
Next, an ultrasonic flow velocity measuring method using the ultrasonic flow velocity measuring device shown in FIGS. 1 and 2 will be described.
[0028]
First, by the operation of the switching circuit (8), the drive pulse generation circuit (6) is connected to the upstream ultrasonic vibrator (2), and the downstream ultrasonic vibrator (3) is connected to the reception amplifier circuit (7). Then, when a drive pulse is generated by the drive pulse generation circuit (6) and applied to the ultrasonic vibrator (2), ultrasonic waves are transmitted radially from the ultrasonic vibrator (2).
[0029]
The ultrasonic waves transmitted from the upstream ultrasonic transducer (2) are parallel to each other in the axial direction of the flow velocity measuring tube (1) on the reflection surface of the ultrasonic reflection member (4) on the upstream side. The light is reflected and passes through the flow velocity measuring section (1b) of the flow velocity measuring pipe (1) in parallel with the axial direction. In this embodiment, since the reflecting surfaces of the ultrasonic reflecting members (4) and (5) are formed in the above-described curved or arcuate shape in the xy and xz directions, the ultrasonic reflecting members (4) and (5). The ultrasonic wave reflected by the can pass through the cross section of the flow velocity measuring part (1b) fully. The one-dot chain line in FIG. 2 indicates the actual reflection area (within the circle) on the reflection surface of the reflection members (4) and (5).
[0030]
Then, the ultrasonic waves that have passed through the flow velocity measuring section (1b) in parallel with the axial direction converge on the ultrasonic transducer (3) on the downstream side on the reflecting surface of the ultrasonic reflecting member (5) on the downstream side. And is received by the ultrasonic transducer (3) in the same phase as it is.
[0031]
In the reception amplifier circuit (7), a reception wave corresponding to the ultrasonic wave received by the ultrasonic transducer (3) on the downstream side is output. The received wave at this time has an increased amplitude because most of the ultrasonic waves are received in phase.
[0032]
Thereafter, based on the reception wave output from the reception amplification circuit (7), the ultrasonic wave is transmitted from the upstream ultrasonic vibrator (2) to the downstream ultrasonic vibrator (3). The forward propagation time until the ultrasonic wave is received is determined.
[0033]
Next, by the operation of the switching circuit (8), the drive pulse generation circuit (6) is connected to the downstream ultrasonic oscillator (3), and the upstream ultrasonic oscillator (2) is connected to the reception amplifier circuit (7). Then, when the drive pulse is generated by the drive pulse generation circuit (6) and applied to the ultrasonic vibrator (3), ultrasonic waves are transmitted radially from the ultrasonic vibrator (3). .
[0034]
Most of the ultrasonic waves transmitted from the ultrasonic transducer (3) follow the path opposite to the path of the ultrasonic wave transmitted from the ultrasonic transducer (2) described above, and are transmitted to the ultrasonic transducer (2). Received.
[0035]
Then, in the same manner as described above, based on the reception wave output from the reception amplification circuit (7), the ultrasonic vibration is transmitted from the downstream ultrasonic transducer (3) to the downstream ultrasonic vibration (3). The propagation time in the reverse direction until the child (2) receives the ultrasonic wave is obtained.
[0036]
Thus, the flow velocity of the fluid is obtained based on the difference between the propagation times of the ultrasonic waves in the forward and reverse directions, and the flow rate of the fluid is further obtained as necessary.
[0037]
As described above, most of the ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) on the transmitting side are received by the ultrasonic transducers (3) and (2) on the receiving side in the same phase. The amplitude of the wave can be increased, and the flow velocity of the fluid can be accurately measured.
[0038]
In addition, most of the ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) on the transmission side can pass through the flow velocity measuring tube (1) fully in cross section and parallel to the axial direction, so that the fluid is small. The flow velocity of the fluid can be measured with high accuracy even when the flow is unevenly distributed to any location in the flow velocity measurement pipe.
[0039]
In this embodiment, the ultrasonic reflecting portion is formed as an ultrasonic reflecting member (4) (5) separate from the flow velocity measuring tube (1), but is formed directly on the inner surface of the flow measuring tube (1). It may be.
[0040]
Also, the ultrasonic reflecting members (4) and (5) have the entire reflecting surface formed in the above-mentioned curved shape in the xy direction, but only a part of the reflecting surface is formed in the xy direction as described above. It may be formed into a curved shape.
[0041]
The ultrasonic reflecting members (4) and (5) have their reflecting surfaces formed in an arc shape in the xz direction, but only a part of the reflecting surface is formed in an arc shape in the xz direction. Alternatively, the entire reflecting surface may be formed in another shape other than a circular arc in the xz direction.
[0042]
Further, the arrangement of the ultrasonic transducers (2) and (3) and the ultrasonic reflection members (4) and (5) is not limited to the above-described one, and may be other arrangements. In short, after the ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) are reflected by one of the ultrasonic reflecting members (4) and (5), the other ultrasonic reflecting members (5) and (4) Any configuration may be used as long as it is reflected by the ultrasonic transducers (3) and (2) and received by the ultrasonic transducers (3) and (2).
[0043]
【The invention's effect】
According to the first aspect of the present invention, most of the ultrasonic waves transmitted from the transmitting and transmitting ultrasonic transducers are received in the same phase by the receiving ultrasonic transducers, thereby increasing the amplitude of the received wave. It is possible to accurately measure the flow velocity of the fluid. In addition, most of the ultrasonic waves transmitted from the ultrasonic transducer on the transmission side can pass through the flow velocity measurement tube in a cross section fully parallel to the axial direction. The flow velocity of the fluid can be measured with high accuracy even when the flow is unevenly distributed.
[0044]
According to the second aspect of the present invention, it is possible to easily and reliably form the ultrasonic reflecting portion having the above-described effects.
[Brief description of the drawings]
FIG. 1 is an upper sectional view of an ultrasonic flow velocity measuring device according to an embodiment of the present invention.
FIG. 2 is a sectional view of the ultrasonic flow velocity measuring device of FIG.
FIG. 3 is a diagram illustrating a state of reflection of an ultrasonic wave in an xy direction by an ultrasonic reflecting member.
FIG. 4 is a diagram showing a state of reflection of an ultrasonic wave in an xz direction by an ultrasonic reflecting member.
FIG. 5 is a schematic configuration diagram of a conventional ultrasonic flow velocity measuring device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Flow velocity measuring tube 2, 3 ... Ultrasonic oscillator 4, 5 ... Ultrasonic reflecting member 6 ... Drive pulse generation circuit 7 ... Reception amplification circuit 8 ... Switching circuit

Claims (2)

Ultrasonic vibrators (2) and (3) are arranged on the upstream and downstream sides of the measurement fluid flowing through the flow velocity measuring pipe (1), respectively, and ultrasonic waves are mutually transmitted from the ultrasonic vibrators (2) and (3). In an ultrasonic flow velocity measuring device that generates and transmits, mutually receives the transmitted ultrasonic waves, and measures the flow velocity based on the difference in the propagation time of the ultrasonic waves,
Ultrasonic reflectors (4) and (5) are provided on the upstream and downstream sides of the flow velocity measuring tube (1), respectively, so as to correspond to the ultrasonic transducers (2) and (3),
The ultrasonic reflectors (4) and (5) are arranged such that the normal line a of an arbitrary point Q on the reflection surface corresponds to the point Q and corresponds to the point P and the point on the radiation surface of the ultrasonic transducer (2) (3). Ultrasonic flow velocity measurement characterized in that an angle formed between a line connecting a virtual radiation point R located behind P and an axis c of the flow velocity measurement pipe (1) is bisected. apparatus. An ultrasonic flow velocity measuring device, wherein the ultrasonic reflecting section is formed so as to satisfy a condition of the following expression [1] on at least a part of its reflecting surface.
m =-｛γx / (Gy) + √ [1+ (γx / (Gy)) 2] (1)
O: Intersecting point (x, y) between axis d of ultrasonic transducers (2) and (3) and axis c of flow velocity measuring tube (1): Ultrasonic reflecting members (4) and (5) having intersection O as the origin Position m on the reflecting surface of the ultrasonic wave reflecting member (4) (5) Slope at position (x, y) on the reflecting surface r: Diameter b of the radiating surface of the ultrasonic transducers (2) and (3) b: Length y in the y direction of the flow velocity measuring tube (1): 1-r / b
G: Distance in the y direction from the origin O to the radiation surface of the ultrasonic transducers (2) and (3)

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