SU1415170A2 - Device for determining concentration of free gas in liquid - Google Patents

Abstract

This invention relates to a measurement technique. The aim of the invention is to increase the reliability and expansion of functional capabilities by also determining the size of gas bubbles in a liquid. A low-frequency radio pulse and two high-frequency radio pulses are emitted into the test medium at the beginning of the transition process and in the established low-frequency mode. The hydrophone 2 receives acoustic signals and selects them in frequency by amplifiers 11 and 12. Two high-frequency radio pulses arrive at counter 15, the second of which travels to the meter 14 timeslots. The first pulse passes to the meter 13 time intervals. According to the indications of the meter 13 time intervals judge the concentration of gas in the liquid. According to the indications of the meter 14 time intervals judge the size of gas bubbles in the liquid. The ratio of the readings of these meters take the conclusion of the change in frequency of the emitted ultrasonic vibrations. 3 il. (L

Description

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The invention relates to devices for determining the concentration of free gas in liquids by an acoustic method and is an improvement of the device according to the authors. St. No. 896544.

The aim of the invention is to increase the reliability and expansion of functionality by measuring also the size of gas bubbles in a liquid.

FIG. 1 is a block diagram of the device; in fig. 2 - voltage waveforms; in fig. 3 shows dependencies explaining the essence of the invention from a physical point of view.

The device consists of hydrophones 2 immersed in liquid 1, two emitters 3 and 4, and an additional hydrophone 5. Emitter 3 is connected to the generator 6 of high-frequency oscillations, and the radiator 4 is connected to the generator 7 of low-frequency oscillations. An additional hydrophone 5 is connected via a shaper of 8 rectangular pulses, a counter 9, an OR 10 circuit is connected to a generator 6 of high-frequency oscillations. The hydrophone 2 is connected to the selective amplifiers And and 12. The first inputs of the meter 13 time intervals through the counter 15 are connected to the output of the selective amplifier 11. The second inputs of the meters 13 and 14 time intervals through the counter 16 are connected to the output of the selective amplifier 12. The generator 17 sync pulses connected to generator 7 low-frequency oscillations, meters 13 and 14 time intervals, counters 9, 15 and 16 and is designed to synchronize their work in time.

The device works in the following way.

The clock generator 17 generates a sequence of video pulses, the frequency of which is determined by the required sampling rate (Fig. 2a). Under the influence of these pulses, the counters 9, 15 and 16 and the time meters 13 and 14 are reset, and the low-frequency oscillator 7 generates a radio pulse (Fig. 26) supplied to the radiator 4. The emitted acoustic oscillations are received by the hydrophone 2 and additional hydrophone 5, having direct acoustic contact with the emitter 4. An additional hydrophone simulates the operation of the main hydrophone 2, providing the phase shifts Df with it when the temperature of the medium changes (Fig. 2c). To eliminate the measurement error due to these shifts, the high-frequency oscillator in the device is triggered by electrical oscillations from the additional hydrophone 5. The low-frequency oscillations from the hydrophone 5 are converted into rectangular pulses 8 into rectangular pulses (Fig. 2, plot 4). counter 9, which

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counts the number of periods of low-frequency oscillations and performs the role of a delay in the generation of high-frequency radio pulses (Fig. 2g) relative to the onset of low-frequency oscillations (Fig. 2c). The counter 9 in this device is connected by two of its conclusions through the scheme OR 10 to the generator 6 high-frequency oscillations and starts the last pulses (Fig. 2e, e). If the pulse e, as in the known device, corresponds to the highest period of oscillation g, then the pulse g is formed by the counter 9 at the beginning of the oscillation in (in this case it corresponds to the second oscillation period). Thus, two high-frequency pulses are emitted within one low-frequency oscillation, one of which is synchronized with the low-frequency radio pulse at the very beginning and the second in the stationary part (about 5-10 periods from the beginning of the low-frequency pulse). This is done in order to measure the difference between the travel times d t and the low-frequency and high-frequency ultrasonic signals for different degrees of excitation of gas bubbles in the test liquid under the action of the low-frequency ultrasonic field. The transient process of establishing forced oscillations of bubbles of resonant and near-resonant sizes lasts a considerable time and takes 5-10 periods of a low-frequency signal (this depends on the quality of the bubbles). Within the limits of the transient process of establishing oscillations of a bubble, the phase relations of its oscillations and the ultrasonic wave undergo significant changes, which causes a variable (increasing) effect of the bubbles on the speed of propagation of the low-frequency signal. Bubbles, weakly disturbed by the ultrasonic wave (at the beginning of the transition process), provide a small value of the difference L ti, bubbles that oscillate in the steady state (at least strongly disturbed by the ultrasonic wave), provide large values of the difference .i (Fig. 2, p) .

As for nonresonant bubbles, their transient process lasts a little, they are almost immediately disturbed by the ultrasonic wave to their established amplitude and phase values. This determines that the indications of time intervals are the same, both at the beginning of the ultrasonic low-frequency pulse and in its stationary part (D t., Mg).

The dependences of DS (), b.c () of the propagation velocity of a periodic ultrasonic perturbation with frequency f for the first period of this perturbation, as well as for the stationary mode in a liquid with bubbles of radius r are shown in fig. 3. The figures shaded parts of the curves for near-resonant frequencies of the signal. It can be seen that in these areas the deviations l C, and d Cr (differ greatly from each other on different curves (for example, at point 2). On not-shaded areas far from the resonant frequency fo of bubbles (for example, at point 1) D Q and L GI., The signal propagation rates are the same for both the first signal period and the steady state.

By comparing the readings D t or 1 of two meters 13 and 14 time intervals, it is possible to judge whether the frequency of the low-frequency signal satisfies the condition of its correct choice (in this case, the values of d are the same) or the bubbles have grown so much that the selection condition is violated (D t ., "Ata). In the latter case, you should either decide to lower the frequency of the measuring signal to make accurate measurements, or state the facts of reaching bubbles of a certain size during their growth and consider further measurements of the concentration to be inaccurate.

Subsequently, the operation of the device is dried in the following ways. Selective amplifiers 11 and 12 provide the necessary amplification, selection and formation of received low-frequency (Fig. 2h) and high-frequency oscillations (Fig. 2i). A square wave is formed from the low-frequency oscillations (Fig. 2o), and pulses from the high-frequency oscillations (Fig. 2k). The latter arrive at the first input of the meter 13 time intervals and the input of the counter 15. The first of the pulses

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(Fig. 2k) starts the meter 13, after which the input of the latter is blocked. The second of the pulses (Fig. 2k) provides the triggering of the counter 15 (Fig. 2n), as a result of which a trigger on the first input of the time meter 14 is provided. The counting of the meters 13 and 14 is stopped by the second inputs using pulses (Fig. 2p, p) produced by the counter 16. The function of the latter is to extract from the square wave (Fig. 2o) those periods that were used to start the high-frequency generator.

Claims (1)

Invention Formula A device for determining the concentration of free gas in a liquid by ed. St. No. 896544, characterized in that, in order to increase reliability and enhancement 0 functionality by measuring the size of gas bubbles in a liquid as well, it is equipped with an OR circuit, two inputs of which are connected to the outputs of different bits of the first counter, and the output to the input of the high-frequency oscillator, and connected in series by the third counter and the second time meter intervals, the second input of which is connected to the second output of the second counter, the output of the high-frequency amplifier The 0 signal is connected to the input of the third counter, and the output of the sync pulse generator is connected to the reset inputs of the second time interval meter and the third counter. five S WV JOJO-q rLTLnrb Au (tjl 1st, period of periodical cescosis f Statsaotrnogo mode periodic ultrasubboobooy dozpush, ene ag 3