JPH0643908B2 - Flow velocity / flow rate measuring device and fluid carrying pipe equipped with the device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a flow velocity / flow rate measuring device for measuring the flow velocity or flow rate of a fluid by using, for example, ultrasonic waves, and a fluid transfer pipe equipped with the device.

<Background of the Invention> Conventionally, two types of apparatuses, which use ultrasonic waves, have been put into practical use: a transfer time difference method and a Doppler method. The former method is a method of obtaining a flow velocity and a flow rate by utilizing a difference in propagation time of ultrasonic waves when ultrasonic waves are emitted in a direction along a flow of a fluid and a direction opposite to the flow, The latter method is a method for obtaining the flow velocity and the flow rate by utilizing the fact that the Doppler effect is generated between the ultrasonic wave and the reflected wave when ultrasonic waves are emitted to the contaminants such as dust and bubbles in the fluid. However, in the former transmission time difference method, if contaminants such as dust are present in the fluid, the path of the ultrasonic waves will be obstructed, making it difficult to measure the flow velocity and flow rate, while in the latter case of the Doppler method, in the fluid. If no contaminants are mixed in, the reflected wave cannot be obtained, and similarly, it becomes difficult to measure the flow velocity and flow rate. Therefore, in each of these methods, whether or not the flow velocity and flow rate can be measured and their accuracy depend on the presence or absence of contaminants in the fluid. Therefore, in recent years, a correlation type flow velocity / flow rate measuring device capable of measuring the flow velocity / flow rate regardless of the presence or absence of a contaminant has been proposed. This correlation type device focuses on the fact that the ultrasonic waves propagating in the fluid to be measured are modulated by the presence of fine particles in the fluid, the vortex of the fluid, and the vibration. Then, the state of the fluid is extracted as a kind of noisy signal.

The conventional correlation type flow velocity / flow rate measuring device shown in FIG. 2 has a transmitter 1A that emits an ultrasonic wave and a receiver 2A that receives the ultrasonic wave in a direction orthogonal to a fluid flow (indicated by an arrow in the figure). Are arranged opposite to each other, and a similar transmitter 1 is provided at a position downstream of a fixed distance L.
B and the receiver 2B are provided, and the noise signals are extracted at these two points, and the flow velocity and flow rate of the fluid are measured from the correlation between the two signals. That is, in FIG. 2, assuming that the flow velocity of the fluid is V, the distance between the two sets of transmitters and receivers is L, and the time when the correlation is maximum is τ, the flow velocity V can be obtained by the following equation.

V = L / τ However, in the above-mentioned correlation type device, there is a problem that the storage property of the noise signal is poor and the fluid state collapses while the fluid moves the distance L, and the signal pattern changes. . As a result, the signals that do not match are correlated with each other, and in order to obtain sufficient measurement accuracy, it is necessary to set a long measurement time and average the data.

<Purpose of the Invention> The present invention is capable of measuring the flow velocity and flow rate regardless of the presence or absence of contaminants in the liquid, such as the transfer time difference method and the Doppler method, and improves the drawbacks of the conventional correlation type. An object of the present invention is to provide a flow velocity / flow rate measuring device and a fluid carrying pipe equipped with the device.

<Structure and Effect of the Invention> A first invention is a flow velocity / flow rate measuring device for measuring a flow velocity / flow rate of a fluid, which projects a detection wave such as an ultrasonic wave into the fluid in a direction orthogonal to the flow of the fluid. It is provided with a transmitting means and a receiving means which is arranged opposite to the transmitting means and receives a detection wave which propagates while being modulated in a fluid. At least one of the transmitting means and the receiving means is configured by arranging a plurality of transmitters or receivers in an array, and the transmitters or receivers are arranged in a group of the transmitters or receivers at a speed higher than the fluid flow velocity. A switching circuit is connected which sequentially switches to transmit and receive a detection wave. Further, the receiving means extracts a noisy signal obtained by demodulating a modulation component from the received signal at each switching cycle by the switching circuit, and the flow velocity / flow rate of the fluid based on the correlation between the signals before and after the extraction. An arithmetic processing circuit for calculating is connected. A second aspect of the present invention is a fluid carrying pipe including the flow velocity / flow rate measuring device having the above-mentioned configuration, wherein the flow velocity / flow rate of the fluid in the pipe is measured by the flow velocity / flow rate measuring device.

According to the present invention, since the correlation is obtained with a noisy signal by high-speed switching, the signal to be correlated is highly conserved, and the flow velocity and the flow rate can be measured in a short time and with high accuracy.
In addition, in the case of the method of the present invention, the possibility of measurement and its accuracy are not affected by the presence or absence of contaminants in the fluid as in the conventional transfer time difference method or Doppler method, and the invention object is achieved. Has a remarkable effect.

<Description of Embodiments> FIG. 1 shows a flow velocity / flow rate measuring device according to the present invention and a fluid carrying pipe provided with the device. The flow velocity / flow rate measuring device in the illustrated example measures the flow velocity and flow rate of a fluid flowing in the pipe 9 by using ultrasonic waves, and a pair of ultrasonic waves are provided on the outer surface of the pipe 9 in a direction orthogonal to the flow. The transmitter 1 and the receiver 2 are arranged opposite to each other. The transmitter 1 converts the high frequency signal output from the ultrasonic oscillator 3 into ultrasonic waves and projects the ultrasonic waves into the fluid in the tube 9. This ultrasonic wave is propagated while undergoing amplitude modulation or phase modulation due to the presence of fine particles in the fluid, the vortex of the fluid, vibration, etc., and reaches the receiving body 2 to be received. The receiver 2 is constructed by arranging a plurality of receivers 20 and 20 in line along the flow direction, and each receiver 20 is sequentially switched in the flow direction using a switching circuit 4 to receive modulation. To receive ultrasonic waves. This switching operation is called skinning, and the switching speed is set to a value sufficiently higher than the flow velocity. Here, the length of the receiver 2 is L,
When the number of receivers 20 forming the receiver 2 is N and the frequency of the switching signal of the switching circuit 4 output from the oscillator 40 is ₁ , the switching speed V _s is given by the following equation.

The switching circuit 4 outputs the ultrasonic signal received from the receiver 2 to the demodulation circuit 5 via the amplification circuit 41 in the arithmetic processing circuit 10. The demodulation circuit 5 demodulates the modulated component and detects it as a noisy signal I in the fluid. The noisy signal I is sent to the waveform discriminating circuit 6 and the variable delay circuit 7, respectively, and the waveform discriminating circuit 6 checks the phases of the noisy signal I and the delayed output signal J.

The variable delay circuit 7 is, for example, a BBD (Bucket Brigade).
Device), CCD (Charge Coupled Device), etc., and the number of stages is N, which is the same as the number of receivers, and the clock frequency for delay amount control is ₂ , the delay amount τ is expressed by the following equation. It

The waveform discrimination circuit 6 observes the noisy signal I at each scanning cycle, and the noisy signal applied to the previous scan (corresponding to the output of the variable delay circuit 7) and the noisy signal applied to this scan (the demodulation circuit 5). (Corresponding to the output of the above) and it is determined whether or not the two waveforms match. The defying period refers to the time required to switch all the receivers 20.

Assuming that the waveform of the noisy signal I output from the demodulation circuit 5 is S (t), the following equation holds between the signal waveforms to be collated when the waveform discrimination circuit 6 finds that the waveforms match.

From the above equation and equation, the flow velocity V is given by the following equation. However Δf = ₂ - _1.

Thus, when there is a phase difference between the two signal input waveforms, the waveform discriminating circuit 6 changes the clock frequency ₂ for controlling the delay amount of the variable delay circuit 7 to match the two waveforms. In this case, even if the switching frequency ₁ is changed, the waveforms can be matched. When the waveform discriminating circuit 6 discriminates the coincidence, the arithmetic circuit 8 inputs the switching frequency ₁ and the clock frequency ₂ of the switching circuit 4 to obtain the flow velocity V by the above equation, and further the flow velocity V
Calculate the flow rate by multiplying by the cross-sectional area of the fluid.

Although the above embodiment is a flow velocity / flow rate measuring device using ultrasonic waves, the present invention is not limited to ultrasonic waves and can be applied to devices using electromagnetic waves.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle and circuit configuration of a flow velocity / flow rate measuring device according to the present invention, and FIG. 2 is an explanatory diagram showing the configuration of a conventional example. 1 ... Sender, 2 ... Receiver 20 ... Receiver, 4 ... Switching circuit

Claims (2)

[Claims] 1. A flow velocity / flow rate measuring device for measuring a flow velocity / flow rate of a fluid, the transmitting means projecting a detection wave such as an ultrasonic wave into the fluid in a direction orthogonal to the flow of the fluid, and the transmitting means. A receiving means arranged to face each other and receiving a detection wave propagating while being modulated in a fluid, wherein at least one of the transmitting means and the receiving means is configured by arranging a plurality of transmitting or receiving elements in alignment. Along with
A switching circuit for transmitting and receiving a detection wave by sequentially switching each transmission or reception element at a speed higher than the flow velocity of the fluid is connected to the aggregate of transmission or reception elements, and the reception means modulates from the reception signal. A noisy signal obtained by demodulating the components is extracted for each switching cycle by the switching circuit, and an arithmetic processing circuit is connected to calculate the flow velocity / flow rate of the fluid from the correlation between the signals before and after the extraction. Flow velocity / flow rate measuring device. 2. A fluid carrying pipe provided with a flow velocity / flow rate measuring device for measuring a flow velocity / flow rate of a fluid, wherein the flow velocity / flow rate measuring device is an ultrasonic wave or the like in a direction orthogonal to the flow of the fluid into the pipe. Of the detection means, and a receiving means that is provided facing the transmission means and receives the detection wave that propagates while being modulated in the fluid, and at least one of the transmission means and the reception means , With multiple transmitters or receivers aligned and configured,
A switching circuit for transmitting and receiving a detection wave by sequentially switching each transmission or reception element at a speed higher than the flow velocity of the fluid is connected to the aggregate of transmission or reception elements, and the reception means modulates from the reception signal. A noisy signal obtained by demodulating the components is extracted for each switching cycle by the switching circuit, and an arithmetic processing circuit is connected to calculate the flow velocity / flow rate of the fluid from the correlation between the signals before and after the extraction. Fluid transfer pipe equipped with flow velocity / flow rate measuring device.