JPS63103918A - Flowmeter for open channel - Google Patents

Abstract

PURPOSE:To accurately measure the flow rate of an open channel by measuring a flow velocity and a water level at the same time by using an ultrasonic wave, and finding the sectional area of a flow from the value of the water level and integrating the flow velocity. CONSTITUTION:Two couples of ultrasonic oscillators 3 an 4 are installed on the open channel tube 1 and receivers 5 and 6 are provided. At this time, those combinations are set at a constant interval (l) so that ultrasonic waves are reflected by the surface of liquid 2 flowing in the open channel tube 1 and received by the receivers respectively. Then, signals from the receivers 5 and 6 are stored in memories 10 and 11 for a specific time and the pattern contents of the memory 10 are compared by a pattern matching comparator 18 with the contents of the memory 11 while made different in time, but by bit, an the result is outputted to a peak point detector 15. The detector 15 detects the peak point of the comparison result signal to obtain the flow velocity V from the time delay tau up to the peak point. The phase difference phi between the signal from the receiver 5 and the output of an oscillator 7, on the other hand, is detected 18 to obtain the sectional area A of the fluid. Further, the flow rate Q is found from a specific expression and displayed 20.

Description

[Detailed Description of the Invention] [Industrial Field of Application] [Prior Art] Conventionally, the flow rate measurement in an open channel involves measuring the water level using ultrasonic waves and calculating the flow rate by calculating the water level. Alternatively, the drilling mud flow meter Ul uses a paddle sensor of the type that measures the flow rate as a relative measurement by displaying the flow rate as a percentage by the inclination of a paddle provided in the flow path.

[Problems to be Solved by the Invention] As mentioned above, in the flow rate #f ApI of an open channel, an ultrasonic water level gauge 71p1 type flow meter or a paddle sensor (also in the paddle sensor, in principle, a mechanical water level gauge A111) is used. The relationship between water level and flow rate is significantly affected by changes in viscosity and density. For this reason, it has the drawback of significantly lower accuracy when measuring slurry or drilling mud whose viscosity and density vary. In addition, a Doppler set of flowmeters is used as a method for measuring the flow velocity in an open channel, but this Doppler set of flowmeters measures the velocity of solids in the water, so it is possible to measure the speed difference between the water and solids. Therefore, it has the disadvantage that the measured velocity is lower than the flow velocity of water.

SUMMARY OF THE INVENTION An object of the present invention is to provide an open channel flowmeter that can solve the above-mentioned conventional problems.

two pairs of ultrasonic oscillators that emit ultrasonic waves towards the water surface, two pairs of receivers that each receive the ultrasonic waves reflected from the water surface, and convert the signals output from each of these receivers into digital signals. an A/D converter that stores the digital signals outputted from each of these A/D converters for a predetermined period of time, and a memory that reads out the contents of each of the memories while shifting the time at a predetermined routine time. Calculating the flow velocity of the fluid flowing through the open channel, and calculating the water level height of the fluid based on the phase shift between the waveform of each of the ultrasonic oscillators and the waveform of each of the receivers, and calculating the cross-sectional area of the fluid. The present invention is characterized in that it includes an arithmetic device that calculates the flow rate of the fluid by integrating the flow velocity of the fluid and the cross-sectional area.

[Function] According to the present invention, in order to accurately measure the flow rate of an open channel, the flow velocity and water level are simultaneously measured using ultrasonic waves, the cross-sectional area of the flow is determined from the water level value, and the cross-sectional area is calculated and integrated with the flow velocity. Find the flow rate by In addition, in order to measure the flow velocity in an open channel where the water level fluctuates, two pairs of ultrasonic oscillators are arranged above the water surface along the flow direction, and the ultrasonic emission signal emitted towards the water surface is detected by the turbulence on the water surface. A signal modulated by the shape of is detected, the modulated signals from the two pairs of receivers are time-shifted, then pattern matched, and the speed is calculated as the reciprocal of the shift time of the best matching.

[Embodiment] FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, in which two pairs of ultrasonic oscillators 3.4 are installed in an open channel pipe 1, and a receiver 5.
．． 6 will be provided. The respective oscillator-receiver combinations are spaced apart by a fixed distance l and arranged so that the ultrasound waves are reflected at the surface of the fluid 2 flowing through the open channel pipe 1 and captured by the respective receivers. In this case, the reflected wave is attenuated relative to the incident wave by scattering due to the unevenness of the flowing water surface, and the output waveform from the receiver 5.6 is modulated by the pattern of the unevenness on the surface of the fluid 2. The pattern on the surface of the fluid 2 is not steady but random, but if the distance between the receivers 5.6 is not too large,
It is considered that the uneven pattern on the surface is maintained while the fluid 2 flows from the receiver 5 to the receiver 6. In the present invention, the velocity of the fluid 2 is obtained by detecting the temporal shift in the uneven patterns on the surface detected by the receivers 5 and 6 using signal processing technology.

The operation of the embodiment of the present invention described above will be explained below. The signals from the receivers 5.6 are passed through an amplifier and a high speed A/
The signal passes through the D converters 8 and 9 and is stored in the memory 10.degree. 11 for a predetermined period of time. The pattern signals stored in the memories 10 and 11 are matched by comparing the contents of the memory 0 for the signal from the upstream receiver 5 with the contents of the memory 1 by a pattern matching comparator 13 after shifting the time. The result of the degree is output to the peak point detector 15. Next, the peak point detector 15 detects the peak point of the comparison result signal, and there is a delay until the peak point (that is, the receiver 5 and the receiver 6
Obtain τ (deviation time of the pattern detected in ).

v - (i: distance between receivers 5 and 6 °) τ The flow velocity can be obtained from Equation 16 above.

- the signal from the force receiver 5 is used to determine the phase difference with the oscillator 7 in a phase difference detector 18;

It is converted to the water level height H using Equation 19.

In the case of a circular pipe, the water level height H is converted to the cross-sectional area A of the fluid using the following equation 19'.

Next, the flow rate is determined by Q=VXAXα using equation 17. This a is a coefficient for making the surface velocity of the fluid 2 the overall average velocity. The flow rate thus obtained from equation 17 is displayed on the display 20. .

FIG. 2 shows the principle of determining the delay time τ by comparing patterns.

[Effect of the invention] According to the present invention, the following excellent effects can be achieved.

(1) By measuring fluid velocity and fluid cross-sectional area, it is possible to accurately measure the flow rate in an open channel even if the viscosity and density change.

(2) Since the flow velocity is detected by measuring the pattern on the fluid surface, the velocity of the fluid can be measured without any discrepancy between the velocity of granular solids and water, unlike the Doppler flow meter.

(3) With conventional electromagnetic flowmeters, it was impossible to measure the tM and tM of oil or muddy water, but according to the present invention, these measurements are possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the principle for determining the delay time τ from the reflection pattern from the fluid surface in the present invention. 1... Open channel pipe, 2... Fluid, 3, 4... Ultrasonic oscillator, 5, 6... Receiver, 8, 9... Amplifier and high speed A/Di converter, 10. 11...Memory, 12.
...Memory delay shift, 13...Pattern matching comparator, 15...Peak point detector, 18.
...Phase difference detector.

Claims (1)

[Claims] Two pairs of ultrasonic oscillators that are arranged in parallel above an open channel at a certain distance from each other, each of which emits ultrasonic waves toward the water surface, and two pairs of receivers that each receive ultrasonic waves reflected from the water surface. and an A/D converter that converts the signals output from each of these receivers into digital signals, respectively.
A memory that stores each digital signal output from each of these A/D converters for a predetermined time, and reads out the contents of each memory while shifting time at a predetermined routine time to determine the flow rate of the fluid flowing through the open channel. , calculate the water level height of the fluid from the phase shift between the waveform of each ultrasonic oscillator and the waveform of each receiver, calculate the cross-sectional area of the fluid, and calculate the flow velocity of the fluid and the cross-sectional area of the fluid. 1. A flowmeter for an open channel, comprising: a calculation device that calculates the flow rate of the fluid by integrating the cross-sectional area.