Study On Velocity Measurement For Small-diameter Pipeline Fluid Based On The Bidirectional Acoustic Resonance Principle

Pipeline flow measurement is widely used in all walks of life,ultrasonic flowmeter is a new principle flowmeter which has a better development.Nowadays,the large-diameter pipeline flow measurement of the acoustic flowmeter has made great progress.However,in the small-diameter pipeline,the traditional acoustic flowmeter can't effectively increase the propagation distance of the ultrasonic wave.In the low-flow system,the time shift caused by flow rate is very small,so accurate measurrement of the time difference is very difficult.In view of these problems,this paper discusses the phase change of acoustic wave in the pipeline with laminar flow background,and proposes a new method of measuring the velocity of pipeline fluid based on the principle of acoustic resonance,which provides a kind of flow measurement for small diameter and low velocity piping system.In this paper,the bidirectional high-order acoustic resonance velocity measurement system was studied as follows:1)The overall scheme is proposed.The principle of bidirectional high-order acoustic resonance velocity measurement is proposed.In this paper,based on the influence of the velocity distribution on the acoustic phase,the principle of acoustic resonance velocity measurement is introduced in detail.At the same time,the difference between the method and the traditional frequency difference method is analyzed.2)Acoustic design and realization of bidirectional resonance velocity measurement System.Aiming at the problem that the bidirectional measurement of the traditional ultrasornic flowmeter is not synchronized,a method of realizing the bidirectional synchronous velocity measurement by using the acoustic characteristics of the standing wave tube and the through-hole silencer is proposed.On the basis of discussing the acoustic characteristics of the standing wave tube,the method of separating the different frequency sonic wave through the node and the antinode position is put forward.The acoustic design process of the position of the node and the antinode of the standing wave tube is described in detail,and the effectiveness of the standing wave tube in separating the acoustic wave is verified by modeling and simulation.At the same time,the specific structure of the through-hole silencer is determined by calculation and simulation.3)Principle and realization of electro-acoustic hybrid resonance circuit.The electro-acoustic hybrid resonant circuit mainly includes two parts:electro-acoustic conversion module and acoustic-electro conversion module.The principle and realization of two modules are discussed in detail.The pre-amplifier circuit,filter circuit,automatic gain control circuit and transducer drive circuit are made a detailed description.By analyzing the tuning principle of the transducer,the driving transformer is designed and the electromagnetic simulation of the driving transformer is carried out.Finally,a gas experiment platform is established to verify the principle of bidirectional high-order acoustic resonance velocity measurement.By analyzing the influence of temperature on the resonant frequency,the validity of the effect of bidirectional difference frequency on elimination temperature is verified.