RU2047097C1 - Method and device for measuring flow rate of liquid or gas - Google Patents

Abstract

FIELD: measurement of flow rates of liquids and gases. SUBSTANCE: method consists in shaping the signals of ultrasonic frequency by and counter flow at different aliquant frequencies, modulating the signals thus shaped by frequency in proportion with time of their propagation, measuring the difference of time of propagation by separating the modulated components, mixing them and separating the difference signal of beating and determining the flow rate. Device for realization of this method has two self-excited oscillators 1 and 2, two amplifiers 3 and 4, two acoustic radiators U₁ and U₂, two acoustic receivers F₁ and F₂, axle of pipe 5, two preamplifiers 6 and 7, two synchronizing detectors 8 and 9, two modulators 10 and 11, mixer 12, two amplifiers 13 and 15, detector 14 and recording unit 16. EFFECT: enhanced efficiency. 3 cl, 2 dwg

Description

 The invention relates to measuring technique and can be used to measure the flow of liquid or gas in pipelines.

 Known methods and devices for measuring mass or volume flow using the dependence of the propagation time of ultrasound in a liquid or gas medium on the flow velocity [1] containing electronic keys for generating short ultrasonic signals, require broadband transmission and reception of these signals, which in combination with a significant attenuation of the signal between the emitter and the receiver (-80 EB or more) significantly complicates the device, in particular because of measures taken to protect against interference broadband th and highly sensitive channel for receiving and converting signals.

 The closest in technical essence to the proposed method for measuring the flow of liquid or gas and a device for its implementation is a pulse-frequency method [2] used in an ultrasonic flow meter for measuring the transit time of ultrasonic discrete signals in the form of trains in a liquid or gas stream in which the repetition rate The trains are proportional to the flow rate.

 The formation of ultrasonic trains in this ultrasonic flow meter is also carried out by electronic keys, and discrete-pulse signal generation occurs with unaccounted for time delays, comparable with the repetition period and duration of the trains, which reduces the accuracy of the measurements.

 The technical result, the solution of which the invention is directed, consists in increasing the accuracy of the ultrasonic method for measuring the flow of liquid or gas and simplifying the device that implements the method.

 To do this, in the method of measuring the flow rate of a liquid or gas, which consists in generating ultrasonic frequency signals along the flow and against it and determining the flow rate by measuring the difference in the propagation times of the signals along the flow and against it, the signals are generated at various non-multiple frequencies, the generated signals are modulated in frequency proportional to the time of their propagation, and the measurement of the difference of the propagation times of the signals is carried out by isolating the modulation components, mixing them and highlighting the difference signal of the beats.

 Into a device for implementing this method, comprising a measuring section of a pipeline with a calibrated cross-section and two paired acoustic pairs of emitters and receivers fixed on it, included in the corresponding sync rings, consisting of a self-oscillator and a sync ring amplifier connected to the emitter in series, as well as a recording unit, introduced a series-connected mixer, a first amplifier, a detector, and a second amplifier connected by an output to the input of the registration unit, and in each a sync ring the paired acoustic pairs of the emitter and receiver are made with a fundamental resonance frequency equal to the frequency of the oscillator of the corresponding sync ring, and a preamplifier connected to the input to the output of the receiver, a sync ring detector and a modulator connected to the second input of the sync ring amplifier are also introduced in series, the outputs synchro ring detectors are connected to the corresponding inputs of the mixer.

 Figure 1 is a block diagram of a specific example of a device that implements a method for measuring the flow of liquid or gas; figure 2 shows an electronic circuit of a specific example of one of the synchro rings of a device that implements a method of measuring the flow of liquid or gas.

 The invention is illustrated by the following examples.

Each of the synchro rings of a device that implements a method of measuring liquid or gas flow rate consists of an ultrasonic oscillation oscillator on a transistor T ₁ (Fig. 1) of an inductive three-point, a sync ring amplifier on transistors T ₂ and T ₃ , where the transistor T ₃ also acts as a modulator and with an acoustic emitter of the first or second synchro ring U ₁ and U _2, respectively, of an acoustic receiver P ₁ and P ₂ , respectively, located at a distance l ₁ and l ₂ from the acoustic emitter U ₁ and U _2, respectively, with each pairing This acoustic pair of emitter and receiver is made with a fundamental resonance frequency equal to the frequency of the oscillator of the corresponding sync ring, and their active surfaces are in contact with the liquid or gaseous medium of the line, a pre-amplifier on transistors T ₄ and T ₅ with an input connected to the output of the acoustic signal receiver P ₁ and R _2, respectively, of the positive feedback regulator on the potentiometer R ₁ , the sync ring detector on the diode D ₁ with a filter of high harmonics of modulation R * C *, a modulation transformer T _p , the bias circuit of the operating point of the transistor T ₃ , consisting of a potentiometer R ₂ , the secondary winding of the modulation transformer T _p and the resistor R ₃ .

Elements of the synchro rings in the block diagram (Fig. 2) are self-oscillators 1 and 2, amplifiers 3 and 4 of the synchro-rings connected to acoustic emitters U ₁ and U ₂ , paired with each of them acoustic receivers P ₁ and P _2, respectively, and acoustic emitters U ₁ and U ₂ and the receivers P ₁ and P _{2 are} fixed on the pipe segment 5 so that the projection of the direction of the beam A from the emitter U ₁ to the receiver P ₁ on the axis of the pipe 5 is opposite in the direction of the projection of the beam B from the emitter U ₂ to the receiver P ₂ on this axis.

Acoustic receivers P ₁ and P _{2 are} connected respectively to a serial circuit from a preamplifier 6, 7, a sync ring detector 8, 9, a modulator 10, 11. occupying a sync ring on a sync ring amplifier 3, 4.

 The outputs of the detectors 8 and 9 of the synchro ring are connected respectively to the inputs of the mixer 12, the output of which is connected to a serial circuit consisting of a first amplifier 13, a detector 14, a second amplifier 15 and a recording unit 16, for example, a frequency counter or pulse counter with a digitized scale or board.

 The work of each sync ring is as follows.

The voltage from the oscillator of the carrier of the ultrasonic frequency is supplied to the gate of the transistor T ₂ (Fig. 1) and after preliminary amplification is supplied to the gate of the transistor T ₃ , the operating point of which is offset to the beginning of the current-voltage characteristic by a negative voltage, which is set by the potentiometer R ₂ . After amplification of the sync ring amplifier on the transistor T ₃ , the carrier frequency voltage is supplied to the acoustic emitter U ₁ , U ₂ , the main resonance frequency of which coincides with the carrier frequency of the corresponding oscillator, the frequencies of which are multiple. The emitter U ₁ or U ₂ emits a signal of ultrasonic frequency, the intensity of which is maximum due to the fact that the carrier frequency is equal to the fundamental resonance frequency of the acoustic emitter U ₁ or U ₂ . Since the carrier frequencies of the synchro-rings also coincide with the main resonance frequency of the receivers P ₁ or P _2, respectively, the attenuation of the acoustic signal in a liquid or gaseous medium due to scattering is substantially compensated. In addition, as a result of selective resonant reception of an acoustic signal in a narrow frequency band, intermodulation interference between the synchro rings is significantly suppressed due to the multiple carrier frequencies between them.

The received acoustic signal from the receiver P ₁ or P _{2 is} fed to the gate of the transistor T ₄ and after preliminary amplification and repetition on the transistor T _{5 is} detected by a sync ring diode D ₁ .

· n (1) где С скорость ультразвука, несущей частоты в жидкой или газовой среде; λ_м длина волны модуляционной огибающей; l расстояние от излучателя до приемника; n номер гармоники.Positive feedback of self-excitation at a low modulation frequency occurs when the signal level in the modulator circuit of the transistor T _{3 is} sufficient, when the phase of the carrier frequency modulation coincides with the low-frequency phase on the output winding of the modulation transformer T _p , which is achieved when the modulation phase on the acoustic emitter U ₁ , U ₂ and receiver P ₁ , P ₂ coincide (Fig. 1a) or opposite (Fig. 1b) depending on the inclusion of the ends of the output winding of the modulation transformer T _p , i.e. separately for a number of even harmonics (n 2,4,6.) and a number of odd harmonics (n 1,2,3.), which corresponds to the modulation frequency
f _m =

· N (1) where C is the speed of ultrasound, the carrier frequency in a liquid or gas medium; λ _m wavelength of the modulation envelope; l distance from the emitter to the receiver; n harmonic number.

Filtering the higher harmonics of each frequency series f _{m is} carried out by selecting the capacitor C * and the resistance R * at a certain threshold value of the modulation depth, which is adjusted by the potentiometer R ₁ .

As a result of suppressing the higher harmonics of the modulation and adjusting the excitation threshold of the potentiometers R ₁ , the modulation is excited only at the lowest modulation frequency, which is inversely proportional to the delay time of the signal along the path between the acoustic emitter and the associated receiver and, therefore, a directly proportional to the ultrasound propagation velocity, t. e.

· m (2) где m принимает два взаимоисключающих значения 1 или 2 в зависимости от включения концов выходной обмотки модуляционного трансформатора.f _m =

· M (2) where m takes two mutually exclusive values 1 or 2 depending on the inclusion of the ends of the output winding of the modulation transformer.

The speed of ultrasound between the emitter and the receiver and the receiver in the direction of flow With ₁ is
С ₁ С _о + v˙cos α ₁ , (3) a against the flow of С ₂ is
С ₂ С _о v˙cos α ₂ , (4) where С _{о is the} speed of ultrasound in a stationary medium; v flow rate; α ₁ and α ₂ are the projection angles of the flow velocity on the direction of ultrasound propagation from the acoustic emitter to the receiver (Fig. 2), respectively, of direction A and direction B.

f_м1-f

+

cos α₁+

cos

(5)
Настройкой расстояний l₁ и l₂ в статическом состоянии жидкости или газа (v 0) добиваются нулевых биений Δ f 0, что соответствует равенству l₁ l₂ l, в результате чего частота биений оказывается прямопропорциональной скорости потока v с точностью до аддитивной величины нулевых биений и не зависит от скорости распространения ультразвука в среде, т.е.After applying the filtered modulation signal from the detectors 8 and 9 of the synchro ring to the mixer 12, beats with a difference frequency Δ f as a function of the flow rate occur at the output of the latter
Δf

f _m1 -f

+

cos α ₁ +

cos

(5)
By setting the distances l ₁ and l ₂ in the static state of a liquid or gas (v 0), zero beats Δ f 0 are achieved, which corresponds to the equality l ₁ l ₂ l, as a result of which the beat frequency is directly proportional to the flow velocity v accurate to the additive value of zero beats and does not depend on the propagation velocity of ultrasound in the medium, i.e.

(cos α₁+cos α₂)·v
(6)
После усиления на первом усилителе 13, выделения частоты биений на детекторе 14 и усиления на втором усилителе 15 сигнал с частотой биений Δ f поступает на блок 16 регистрации.Δf

(cos α ₁ + cos α ₂ ) v
(6)
After amplification on the first amplifier 13, isolation of the beat frequency at the detector 14 and amplification on the second amplifier 15, the signal with the beat frequency Δ f is supplied to the recording unit 16.

 If, for example, a frequency meter is used as a recording unit, then its readings will be proportional to the second flow rate. If a pulse counter with a continuous count is used, then its readings will be proportional to the flow rate during the count.

Claims (2)

 1. The method of measuring the flow rate of a liquid or gas, which consists in generating ultrasonic frequency signals along the flow and against it, measuring the difference in the propagation times of the signal along the flow and against it and determining the flow rate, characterized in that the signal generation is carried out at various non-multiple frequencies, modulate the generated signals in a frequency proportional to the time of their propagation, and the measurement of the difference in the propagation times of the signals is carried out by isolating the mating components their knowledge and highlight the difference signal of the beats.  2. A device for measuring the flow rate of a liquid or gas, comprising a measuring section of a pipeline with a calibrated cross-section and two acoustic pairs of emitters and receivers fixed to it, included in the corresponding synchro rings, consisting of a servo generator and a synchro ring amplifier connected to the emitter in series, as well as a unit registration, characterized in that a series-connected mixer, a first amplifier, a detector and a second amplifier, a connected output are introduced into it m to the input of the registration unit, and in each sync ring the paired acoustic pairs of the emitter and receiver are made with a fundamental frequency equal to the frequency of the oscillator of the corresponding sync ring, and a series pre-amplifier connected to the receiver output by an input, a sync ring detector and a modulator connected to the second the input of the sync ring amplifier, while the outputs of the sync ring detectors are connected to the corresponding inputs of the mixer.

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