SU1476311A1 - Ultrasonic flowmeter - Google Patents

Abstract

The invention relates to an ultrasonic flow measuring hydrodynamic technique and can be used to create instrumentation. The aim of the invention is to improve the accuracy of flow measurement. A waveguide piezoelectric transducer 7, a pulse generator 8, a switch 9, a time selector 10, a detector 11, an alternating voltage amplifier 12 and a controlled attenuator 5 are added to the flow measurement circuit, which allow the calculated flow rate to be corrected depending on whether the laminar or turbulent the flow passes through the pipeline. This is ensured by periodically probing the medium in the pipeline 3 with the help of a pulse generator 8, a switch 9 and a waveguide piezoelectric transducer 7. At the output of the detector 11 there is a constant voltage, if the flow is laminar, and the pulsating flow is at a turbulent flow. This voltage changes the transmission coefficient of the controlled attenuator 5, making the necessary correction to the flow rate. 1 il.

Description

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about with

The invention relates to an ultrasonic hydrodynamic technique and can be used to create instrumentation.

The purpose of the invention is to improve the accuracy of flow measurement.

The drawing shows a block diagram of an ultrasonic flow meter.

The circuit contains two piezoelectric transducers 1 and 2 installed on pipeline 3, measuring circuit 4, controlled attenuator 5, flow indicator b, waveguide piezoelectric transducer 7, generator 8, switch 9, time selector 10, detector 11, variable amplifier 12 tension

It is known that the hydrodynamic state of a fluid flow is characterized by a Reynolds number Re-Critical Reynolds number at which a laminar flow turns into a turbulent one is approximately equal to Re 2300. In a laminar mode of motion, the flow velocity in the pipeline changes according to the parabolic law. With the transition to the turbulent flow, the alignment of the velocity distribution plot over the flow cross section begins. Therefore, each turbulent flow can be represented as its own motion of turbulent formations that impose on averaged motion. In a turbulent flow, these formations either arise or disintegrate. The closer to the pipeline wall, the more uneven and larger the amplitude of the velocity pulsations. This affects the velocity distribution plot, and thus the choice of a mathematical algorithm for determining fluid flow through the pipeline.

The device works as follows.

On the conduit 3 with a diameter D, the installed piezo transducers 1 and 2 are alternately excited by the generator of electrical pulses of the measurement circuit 4. A piezoelectric transducer excited by an electrical signal emits an acoustic signal that passes a fluid in a pipeline and excites another piezoelectric transducer.

Measuring circuit 4 determines the flow rate using the formula

(-% Ј-),

where a is the angle between the ultrasound propagation vector and the flow velocity vector;

T |, T2 is the time of ultrasound propagation along T2 and against TI of the direction of fluid flow. An electrical signal proportional to the flow rate from measuring circuit 4 is fed to a controlled attenuator 5. Simultaneously with the measurement of the velocity

This flow is the measurement of turbulence in the pipeline. This happens as follows. Pulse generator

8, pulses are produced which are fed through a switch 9 to a waveguide piezoelectric transducer and excite it. Acoustic signals pass through the waveguide and are reflected from the boundary layer of the current. The reflected acoustic signals pass through the waveguide and excite the piezoelectric transducer. Electrical signals corresponding to the reflected through the switch

9 and the time selector 10 arrive at the detector 11. The time selector only transmits a pulse reflected from the boundary layer of the flow in the pipeline. The signal is detected by the detector 11, amplified by the variable voltage amplifier 12 and fed to a controlled attenuator 5. This electrical signal is proportional to the flow turbulence, and

0 controls an attenuator 6, the output of which is connected to an indicator graduated by units of flow. Depending on the mode of flow in the pipeline 3 at the outlet of the detector 11, there is a constant voltage at the laminar flow and a pulsating voltage at the turbulent flow. It is known that the flow rate during turbulent flow decreases as compared to laminar flow in proportion to the value of X-:

QSTD Vf / ha zH

Q

JTD2-V

,P

(1-1,5)

i with J c

where Q is the flow rate;

D is the diameter of the pipeline;

C is the flow rate;

9t dimensionless value, depending on flow turbulence.

Thus, correction for flow turbulence improves the accuracy of flow measurement in meters.

Claims (1)

Invention Formula An ultrasonic flow meter containing a pipe section with first and second piezoelectric transducers installed and a measuring circuit connected to them, a flow indicator, characterized in that, in order to improve the flow measurement accuracy in a wide range, a waveguide piezoelectric transducer, a pulse generator, a switch, a time selector, a detector, an AC voltage amplifier, and a controlled attenuator, the first output of the pulse generator through the switch connected to the waveguide Nomu transducer mounted on the pipeline wall, the switch output through the time selector, the detector and the AC voltage amplifier is connected to the control input of the controlled attenuator to the flow indicator; the second output of the ator connected by the signal input of the pulse generator is connected to the control to the output of the measuring circuit, and the output to the left input of the time selector.