RU99118673A - ULTRASONIC METHOD FOR MEASURING FLOW SPEED - Google Patents

Claims (4)

1. A method of measuring the flow velocity based on the time difference, comprising measuring the propagation time of the ultrasonic wave in directions that are the same as the flow velocity and opposite to it, and calculating the flow velocity, comprising the steps of amplitude modulating the ultrasonic carrier with a frequency f _c to a frequency f modulation amplitude _m which is less than the frequency f _c the carrier, for a period τ (= 5 / f _m) whenever the time measurement of ultrasonic propagation, carry propagation Vp -modulirovannogo signal in directions that coincide with the flow rate and opposite to it, demodulates the received amplitude-modulated signals after propagation in directions coinciding with the flow rate and opposite to it, for detecting a signal f _m amplitude modulation measured time between the ultrasonic carrier amplitude modulation f _c f _m a frequency modulation and amplitude detection signal f _m amplitude modulation from the received signal, and the measurement of different con five times in the expression for the flow velocity measurement based on the time difference and the calculated flow rate signal with frequency f _m of the amplitude modulation determined by the following expression
f _p ≪ 10 [(C _max + V _max cosα) / L] ≅0.05f _c ,
where f _p is the maximum frequency at which the attenuation coefficient pulsates at the time of propagation of the ultrasonic wave in the fluid, C _max is the maximum speed of sound in the fluid, L is the ultrasound propagation distance, V _max is the maximum flow velocity expected in the interval L, and α is the angle that the propagation distance L and the direction of the flow velocity form. 2. The ultrasonic method for measuring the flow velocity according to claim 1, characterized in that the method for measuring the propagation time of an ultrasonic wave includes the steps of introducing the amplitude modulation voltage f _m , increasing from the zero phase to the "+" phase, into the amplitude modulator, and then administered amplitude-modulated output voltage and simultaneously the ultrasonic transducer is introduced in the output voltage of the demodulator, in turn, for detecting a signal f _m amplitude modulation is determined as the time the sync When the first period or one and a half periods of the amplitude modulation signal passes through the potential of crossing the zero level, the signal is demodulated, the amplitude-modulated ultrasonic wave propagates to the distance L of the interval, and then it is received by another ultrasonic transducer using the specified demodulator, and the signal f _m amplitude modulation is detected, the time is determined as the timing of the end of measurement The moment when the first period or one and a half period of the amplitude modulation signal passes through the potential of crossing the zero level is measured, and the propagation times of ultrasound are measured using the timing of the start and end times of the propagation of ultrasound. 3. A method of measuring the flow velocity based on the phase difference, which provides for the propagation / reception of an ultrasonic wave at a constant angle α in directions coinciding with the flow velocity and opposite to it, and the use of the phase difference of the ultrasound, which varies proportionally to the flow velocity, including stages where the amplitude modulation frequency of the ultrasonic wave in the frequency f _c f _m of amplitude modulation that is less than the frequency f _c, with continuous wave propagates in directions, which coincide with swift Stu flow and opposite to it, demodulates the received ultrasonic signal after spreading to the interval L in directions coinciding with the flow rate and opposite to it, for detecting a signal frequency f _m of the amplitude modulation measured phase difference Δψ _m1 between signals f _m of amplitude modulation, the signal frequency f _m amplitude modulation is detected and emitted in the direction coinciding with the flow velocity, and the phase difference Δψ _m2 between the signals f _m amplitude modulation received and demo which are modulated after propagation in the direction opposite to the flow velocity, multiples of m ₁ and m ₂ are obtained, except for the phase difference components βπ and γπ measured by the phase discriminator from the phase differences Δψ _c1 and Δψ _c2 between the phase of the ultrasonic wave f _c during propagation and the phase the received signal f _c using the following expressions
Δψ _c1 / π = Δψ _m1 (f _c / πf _m ) = m ₁ + β,
Δψ _c2 / π = Δψ _m2 (f _c / πf _m ) = m ₂ + γ,
where β <1.0 and γ <1.0,
remember m ₁ and m ₂ , measure the components of the βπ and γπ phase differences, add m ₁ π and m ₂ π to the measurement results to calculate the phase differences Δψ _c1 and Δψ _c2 and calculate the flow rate based on the following expression
V = [πf _c L / cosα] [(1 / Δψ _c1 ) - (1 / Δψ _c2 )],
select the frequency f _m amplitude modulation as follows
f _m = [(n + a) / 2L] (C _min -v _max ),
n = [a (C _min -v _max ) -b (C _max + v _max )] / (C _max -C _min + 2v _max )
remember n, and
Δψ _m1 = nπ + aπ,
Δψ _m2 = nπ + aπ,
measure the phase differences aπ and bπ, which can be measured by the discriminator of the phase difference in the above expression, and add nπ to them to obtain the phase differences Δψ _m1 and Δψ _m2 ,
wherein a (<1,0) is the coefficient for choosing the maximum measuring range (aπ) _{max of the} discriminator of the phase difference, equal to 0.95, and b (<1,0) is the coefficient for choosing the maximum measuring range of (bπ) _{max of the} discriminator of difference phases close to 0.2, C _max and C _min - the maximum and minimum expected sound speeds, v _max (= v _max cosα) - the maximum range of measurement of the flow velocity. 4. A method for measuring the phase difference ΔΦ _c between signals corresponding to the propagation of an ultrasonic wave in directions coinciding with the current velocity and opposite to it, and the subsequent reception of this wave if the sound speed C is measured separately or continuously, and calculating the current velocity V using the following expression
V = (ΔΦ _c C ² ) / (4πfLcosα),
including the stages at which the amplitude modulation of the ultrasonic wave f _c to the frequency f _m amplitude modulation is carried out, the amplitude-modulated signal is propagated in directions coinciding with the flow velocity and opposite to it, the received signals are demodulated after propagation, the phase difference ΔΦ _{m is} measured (< π) between them and get a multiple of m that exceeds π, the phase difference ΔΦ _c , using the following expression
ΔΦ _m • (f _c / πf _m ) = m + a (a <1,0),
measure the phase difference aπ between the received ultrasonic signals f _c at the same moment using a phase discriminator to obtain aπ, add mπ to them to obtain ΔΦ _c and calculate the flow velocity in accordance with the specified expression, and the frequency f _{m of} amplitude modulation is chosen using the following expression
f _m ≅C $\genfrac{}{}{0ex}{}{\text{2}}{\text{min}}$ / (4LV _max cosα).