RU2313068C2 - Mode of measuring gas consumption in main pipelines and an arrangement for its execution - Google Patents

Abstract

FIELD: the invention is designed for measuring gas consumption in main pipelines.

SUBSTANCE: longitudinal ultrasound waves are excited along and against the gas flow due to excitation in the wall of a tube of Lamb's waves. Non-stationary component of the useful signal passed through the gas is selected by way of compensation of stationary signals propagating along the tube's wall. The operation of selecting the non-stationary part of the useful signal is repeated several times, the selection results are squared and summed up for receiving a functional being the square of derivative in the time of the useful signal. The arrangement for realization of the mode has two transmitting-receiving sections each of which includes an ultrasound converter mounted on the tube wall, transmitting and receiving blocks, a signal-interference compensation block, a storage block. A control block switched to a speed computing and gas consumption block is connected with each transmitting-receiving sections.

EFFECT: provides increase in accuracy of measuring in conditions of high stationary interferences.

3 cl, 3 dwg

Description

The invention relates to measuring equipment and can be used in devices for measuring the flow of liquid or gas in pipelines.

To measure gas flow in pipelines, ultrasonic flow meters are currently widely used, the operation of which is based on measuring the propagation time of ultrasound in the direction and against the flow of gas or liquid. Such flowmeters include, for example, an ultrasonic flow meter (RF patent No. 2106603, G01F 1/66, publ. 03/10/1998), as well as a device for measuring the flow of liquid or gas and a method for measuring it (RF patent No. 2047097, G01F 1 / 66, published on 10.27.95). Instruments of this type use ultrasonic transducers (USP) built into the pipe wall.

Another type of flowmeter uses an overhead SPD. This option of devices makes it easy to mount an ultrasonic protection device on pipelines without violating the integrity of the pipe and stopping the operation of the pipeline and therefore is the most promising. However, the use of overhead ultrasonic testing is hampered by the large difference in acoustic impedances of the pipe material and gas (five orders of magnitude). As a result, only a negligible part of the energy is emitted into the gas and then taken. At the same time, the acoustic vibrations arising in the pipe wall are many times higher than the acoustic vibrations in the gas, and therefore there is a need for a separation in time of the moments of arrival of these signals in the receiving ultrasonic transformer. Reflections of ultrasonic vibrations from inhomogeneities of the pipe wall (seams, flanges, bends, etc.), as well as the passage of waves along spiral paths along the pipe wall, can lead to stationary interference in the time interval of the appearance of a useful signal in the receiving ultrasonic protection device, which disrupts normal operation instrument.

A known method of measuring gas flow and an ultrasonic gas flow meter (US patent No. 6626049, priority from 03/31/2000, G01F 1/66), selected as a prototype, which uses overhead ultrasonic testing, exciting the Lamb wave in the pipe wall, which then excites in the gas longitudinal ultrasonic wave. This wave travels through the stream and excites in the opposite wall the Lamb wave, which is received by the second USP. Further, as in conventional flow meters, information is used on the propagation time of the signal upstream and downstream. To reduce the signals propagating along the pipe wall, a damping coating is used, which is placed on the pipe surface under ultrasonic transducers.

The disadvantages of this method and device are described above.

The objective of the invention is to overcome the difficulties of measurement in cases where the level and temporal location of stationary interference interferes with the measurement.

According to the invention, in a method for measuring gas flow in pipelines, which involves excitation of longitudinal ultrasonic waves in a gas upstream and against it by excitation of Lamb waves in the pipe wall, extracting a useful signal transmitted through the gas stream, measuring the difference in signal propagation times in the direction of flow and against it, calculating the flow rate and determining the gas flow rate, to isolate the useful signal that has passed through the gas flow, stationary signals are compensated, propagating moving along the pipe wall, for which the entire high-frequency ultrasonic pulse received as a result of sounding is remembered and then subtracted from the next received high-frequency ultrasonic pulse, which eliminates the stationary component masking the useful signal transmitted through the gas and the non-stationary component of the useful signal due to time fluctuations the delays and amplitudes associated with the turbulence of the gas flow is allocated, the operation of extracting the non-stationary part of the useful signal n repeats several times of selection are squared and summed, the resulting functional derivative of the square is at the time of the useful signal, which contains all the necessary time information of reception signal point, whereby it becomes possible to measure the gas flow rate in a large stationary noise.

A device for measuring gas flow in pipelines, including a control unit, two transceiver paths, each of which includes an ultrasonic transducer mounted on the pipe wall, connected to the output of the transmitting and input of the receiving units, the output of the receiving unit is connected to the input of the storage unit, the output of which is the output of the path connected to one of the inputs of the gas velocity and flow rate calculation unit, a signal-interference compensation unit is introduced into each path of the device, the input of which is connected to the output of iemnogo unit, and an output - to the input of the storage unit, wherein the control unit is connected to each transceiver unit of transmission paths, with a storage unit and the calculation speed and gas flow rate.

The compensation unit is a switch having two signal outputs, each of which is connected to its own memory unit, the outputs of which are connected to a subtracting device, the output of which is connected to an arithmetic device that calculates the square of the value received from the subtracting device, and the output of the arithmetic device is connected to the input accumulation block.

The invention meets the criterion of "novelty," and from the prior art, the claimed features have not been identified that distinguish the invention from the prototype. Therefore, the invention meets the criterion of "inventive step".

Figure 1 presents a block diagram of an ultrasonic flow meter that implements the inventive method of measurement, figure 2 is a diagram of a compensation unit, figure 3 is a detailed block diagram of a device - an example implementation, where:

1 - control unit

2 - ultrasonic transducer

3 - transmitting unit

4 - receiving unit

5 - compensation unit

6 - storage unit

7 - unit for calculating the speed and gas flow

8 - switch

9 - memory block

10 - subtracting block

11 - block squaring

12 - clock generator

13 - shaper control signals

14 - modulator

15 - programmable amplifier

16 - ADC.

A device for measuring gas flow in pipelines includes a control unit 1, two transceiver paths, each of which includes an ultrasonic transducer 2 mounted on the pipe wall, which is connected to the output of the transmitting 3 and the input of the receiving unit 4. The output of the receiving unit 4 is connected to the input of the compensation unit 5, the output of which, in turn, is connected to the input of the storage unit 6, the output of which is the output of the path and connected to one of the inputs of the unit for calculating the speed and flow rate of gas 7.

Each of the compensation units 5 can be a switch 8, the outputs of which are connected to the inputs of two memory units 9, the outputs of which are connected to the input of the subtracting unit 10, the output of which is connected to the input of the squaring block 11.

Each receiving unit 4 may be a programmable amplifier 15, the output of which is connected to the input of the ADC 16.

The control unit 1 may be a clock generator 12, the output of which is connected to the input of the modulator 14, the outputs of which are connected to the transmitting units 3, the outputs of which are connected to the ultrasonic transducers 2 and to the inputs of the programmable amplifiers 15. The output of the clock generator 12 is also connected to the input of the control driver signals 13, and its outputs are connected to blocks 15, 16, 8, 9, 10, 11, 6, 7.

The proposed method and device for extracting a useful signal that has passed through a gas stream uses the physical difference in the nature of this signal and a stationary interference signal, which is a complex sum of multiple reflections of the acoustic signal from inhomogeneities of the pipe walls. In contrast to the interference signal, the signal passing through the gas always has some phase and amplitude fluctuations even at the lowest Reynolds numbers, since even in purely laminar flows there is always a pulsating component (from different sources from 6 to 17%), whose velocity is some limits is a random function of time.

Measurement of the transit time of the ultrasonic packet in the direction of the flow and against it and, accordingly, the sending of the probe pulse can be carried out simultaneously or in turn by both ultrasonic protection devices. If the alternate sensing mode is selected, then first one SPD becomes the transmitting one, and the second one the receiving one, and then they change roles. In the case of simultaneous sounding, both SPDs emit a packet at the same time, and then switch to the reception mode. Since in both cases the functioning in both directions of sounding is symmetrical, then in the text work in only one direction is considered.

The device operates as follows.

The high-frequency oscillation packet generated in the modulator 14 enters through the transmitting unit 3 to the transmitting USP 2, which excites a Lamb wave in a resonant manner, which, moving along the generatrix of the pipe, in turn excites a longitudinal ultrasonic wave in the gas. Having reached the opposite wall of the pipe, it excites in it a similar Lamb wave, which along the pipe wall reaches the receiving USP 2.

From the receiving SPD 2, the received signal is fed to the input amplifier 15 with a programmable gain. From the output of the programmable amplifier 15, the signal is fed to the input of the ADC 16. The gain of the amplifier 15 is set so as to maintain the signal level at the input of the ADC 16 so that it corresponds to approximately 2/3 of the dynamic range of the ADC.

Further, from the output of the ADC 16, the received, amplified and converted signal in the form of a sequence of numbers is fed to the switch 8 of the compensation unit 5, which forwards this sequence in turn to one of the memory blocks 9. Moreover, one sequence corresponding to one received packet is stored in one block memory, and the next in another.

Next, from the output of the memory blocks 9, the sequences of numbers corresponding to the received packets are sent to the subtraction block 10, where the numbers with the same numbers are sequentially subtracted from the two input sequences. As a result of subtraction, the difference between stationary noises, the position of which relative to the probe pulse does not change during repeated soundings, turns out to be zero. Signals passing through a gas stream at different repetition periods of probing pulses will have different phases and amplitudes. Therefore, when subtracting, they will not be compensated.

The sequence of numbers from the output of the subtraction block 10 enters the squaring block 11, where each difference in the sequence is squared. Squaring is performed to bring all the numbers of difference sequences to the same sign, and to exclude their full or partial compensation during subsequent summation.

Next, the sequence of squares is fed into the storage unit 6, where a sequence of sums of squares is accumulated. The latter is a numerical representation of the square of the derivative of the received signal, multiplied by some constant coefficient, the value of which depends on the turbulence of the gas flow and the number of accumulated cycles. This sequence of numbers contains all the necessary information to determine the moment of arrival of the signal in the receiving SPD 2.

From the output of the storage unit 6, the sequence of accumulated sums of squares is transmitted to the gas velocity and flow rate calculation unit 7, in which all conventional calculations are performed, as a result of which the gas flow rate and its volumetric flow rate are calculated.

The control unit 1 contains a clock generator 12, a modulator 14 and a driver of control signals that determine the behavior of all blocks of the device. A key requirement for a clock is high phase stability, since the latter directly determines the temporal identity of successive emitted and received waveform packets and the exact linking of the numbers of sequences representing the packet after analog-to-digital conversion to a common timeline.

Claims (3)

1. The method of measuring gas flow in pipelines, which consists in the excitation of longitudinal ultrasonic waves in the gas upstream and against it by excitation in the wall of the pipe Lamb waves, the selection of the useful signal that has passed through the gas stream, measuring the difference in the propagation time of the signal in the direction of flow and against him, calculating the flow rate and determining the gas flow rate, characterized in that to isolate the useful signal that has passed through the gas stream, stationary signals are compensated by spreading moving along the pipe wall, for which the entire high-frequency ultrasonic pulse received as a result of sounding is memorized and then subtracted from the next received high-frequency ultrasonic pulse, which eliminates the stationary component masking the useful signal transmitted through the gas and the non-stationary component of the useful signal due to time fluctuations the delays and amplitudes associated with the turbulence of the gas flow is allocated, the operation of extracting the non-stationary part of the useful signal by toryayut several times of selection are squared and summed, the resulting functional derivative of the square is at the time of the useful signal, which contains all the necessary time information of reception signal point, whereby it becomes possible to measure the gas flow rate in a large stationary noise. 2. A device for measuring gas flow in pipelines, including a control unit, two transceiver paths, each of which includes an ultrasonic transducer mounted on the pipe wall, connected to the output of the transmitting and input of the receiving units, the output of the receiving unit is connected to the input of the storage unit, the output of which is the output of the path connected to one of the inputs of the gas velocity and gas flow rate calculating unit, characterized in that a signal-interference compensation unit is introduced into each path of the device, the input of which connected to the output of the receiving unit, and the output to the input of the storage unit, while the control unit is connected to each block of the transceiver paths, with the storage unit and the unit for calculating the gas velocity and flow rate. 3. The device according to claim 2, characterized in that the compensation unit is a switch having two signal outputs, each of which is connected to its own memory unit, the outputs of which are connected to a subtracting device, the output of which is connected to an arithmetic device that calculates the square of the value, received from the subtracting device, and the output of the arithmetic device is connected to the input of the storage unit.

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