JP2009068894A - Ultrasonic flow meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flow meter whose measurement accuracy is less likely to deteriorate, having superior durability. <P>SOLUTION: This device for measuring fluid velocity has a pair of ultrasonic transmitting element A and receiving element B, installed opposite so that ultrasonic propagation path is orthogonal to the flow velocity direction; and an operation program for calculating V from measured T, based on the formula: V=ä(CT)<SP>2</SP>-D<SP>2</SP>}<SP>1/2</SP>/T, if the flow velocity is V, the sound velocity is C, an ultrasonic propagation time from the transmitting element A to the receiving element B is T, and the distance from the transmitting element A to the receiving element B is D. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic current meter.

An ultrasonic anemometer is widely used as an instrument for measuring a flow velocity such as a wind velocity in a tunnel and a gas flow velocity in a gas pipe. In the conventional ultrasonic velocimeter, as shown in FIG. 4, the ultrasonic elements a and b are arranged on the upstream side and the downstream side so that the ultrasonic propagation path is inclined with respect to the flow velocity direction, and ultrasonic waves are alternately generated. Are sent and received. Then, when the inclination angle of the propagation path with respect to the flow velocity is θ, the flow velocity V is obtained from the following equation based on the propagation time Tba in the direction opposite to the propagation time Tab from the element a to the element b (Non-patent Document 1). .
V = (L / 2 cos θ) (1 / Tab−1 / ba)
http://www.oval.co.jp/techinfo/ultrasonic/ultrasonic1.html

However, since the conventional ultrasonic anemometer needs to incline the propagation path with respect to the flow velocity, the transmitting surface, the receiving surface, and the tube inner surface cannot be made flush with each other as shown in FIG. For this reason, a step occurs between the transmitting surface and the receiving surface and the inner surface of the pipe, and in the case of the structure in which the transmitting surface and the receiving surface are recessed from the inner surface of the tube as shown in the figure, dust accumulates in the recess and the measurement accuracy decreases. On the contrary, when it protrudes, there is a problem that the element deteriorates due to wear.
Therefore, an object of the present invention is to propose an ultrasonic anemometer that is less likely to reduce measurement accuracy and has excellent durability.

In order to solve the problem, the ultrasonic anemometer of the present invention is
For measuring fluid velocity,
A pair of ultrasonic transmitting elements and receiving elements installed so that the ultrasonic propagation path is orthogonal to the flow velocity direction;
When the flow velocity is V, the sound velocity is C, the ultrasonic wave propagation time from the transmitting element to the receiving element is T, and the distance from the transmitting element to the receiving element is D,
V = {(CT) ² −D ² } ^1/2 / T
And an arithmetic program for calculating V from the measured T.

Ultrasound propagates in such a way that concentric ripples centering on the transmitting element spread, rather than in one direction. Therefore, as shown in FIG. 1, the ripple P emitted from the transmitting element A moves by the distance X in the direction of the flow velocity V before reaching the receiving element B.
Therefore, when the propagation distance is L, L = CT and X = VT are substituted into L ² = X ² + D ² , and V is obtained as described above. Therefore, the flow velocity V can be measured by measuring the propagation time T.
In addition, since the transmitting element and the receiving element are disposed so that the propagation path is orthogonal to the flow velocity direction, when the fluid flows in the pipe, the transmitting surface of the transmitting element and the receiving surface of the receiving element The transmitting element and the receiving element can be attached to the inner surface of the tube so that is flush with the inner surface of the tube. Therefore, no dust is collected and the element is not worn.

  Since dust does not accumulate, measurement accuracy is unlikely to deteriorate, and the element does not wear, resulting in excellent durability. Therefore, long-term measurement can be performed with a certain accuracy.

FIG. 2 is a block diagram of the ultrasonic current meter according to the embodiment of the present invention. As shown in FIG. 3, the anemometer 1 measures the flow velocity of the gas in the tube W and includes a transmitter 2, a receiver 3, and a microprocessor 4. An ultrasonic transmission element A and a reception element B are connected to connection terminals of the transmission unit 2 and the reception unit 3, respectively. A straight line connecting the transmitting element A and the receiving element B is orthogonal to the tube axis. The transmitting element A and the receiving element B are attached to the inner surface of the tube W so that the transmitting surface of the transmitting device A and the receiving surface of the receiving device B are flush with the inner surface of the tube W. The microprocessor 4 includes a calculation unit 41 and includes a calculation program for calculating V from the measured T based on the formula V = {(CT) ² −D ² } ^1/2 / T. .

  When measuring the flow velocity, the frequency of which is determined by the microprocessor 4 and the ultrasonic wave whose transmission wave number is determined is transmitted from the transmitting element A. At the same time, the transmission time is recorded in the microprocessor 4. The ultrasonic wave is received by the receiving element B, converted into an electric signal through a preamplifier, a band limiting filter, a variable gain amplifier, and a detector, and input to the microprocessor 4. The propagation time T is obtained from the difference between the transmission time and the input time, and the flow velocity V is calculated by the calculation unit 41.

According to this embodiment, since there is no step between the transmitting surface of the transmitting element A and the receiving surface of the receiving element B and the inner surface of the tube W, dust does not collect and the elements A and B do not wear. Therefore, long-term measurement can be performed with a certain accuracy.
In addition, although the problem of the present invention is solved by the above formula, if the speed of sound is included in the formula, the influence of the quality of the fluid greatly appears. The elements A and B are preferably arranged on the side.

It is a figure explaining the effect | action of invention. It is a block diagram of the ultrasonic current meter concerning an embodiment. It is sectional drawing which shows the attachment state of the ultrasonic velocity meter which concerns on embodiment. It is sectional drawing which shows the attachment state of the conventional ultrasonic velocity meter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic anemometer 2 Transmitter part 3 Receiver part 4 Microprocessor A Transmitter element B Receiver element W Tube

Claims (2)

For measuring fluid velocity,
A pair of ultrasonic transmitting elements and receiving elements installed so that the ultrasonic propagation path is orthogonal to the flow velocity direction;
When the flow velocity is V, the sound velocity is C, the ultrasonic wave propagation time from the transmitting element to the receiving element is T, and the distance from the transmitting element to the receiving element is D,
V = {(CT) ² −D ² } ^1/2 / T
And an arithmetic program for calculating V from the measured T based on the above.   The fluid flows in the pipe, and the transmitting element and the receiving element are attached to the inner surface of the pipe so that the transmitting surface of the transmitting element and the receiving surface of the receiving element are flush with the inner surface of the pipe. The described ultrasonic current meter.

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