Study On On-line Monitoring Method Of Fluid Velocity Based On Audible Sound Theory

In power plant boilers,real-time detection of state parameters is of great significance to the economy,stability and safety of operation.Real-time monitoring of primary air,secondary air and flue gas velocity in power plant boilers is very important for mastering furnace operation,optimizing combustion and controlling pollutant emissions.However,due to the large diameter and large flow rate of the pipeline conveying gas in the power station,some gas is high temperature and dusty and accompanied by corrosive gas.The traditional flow measurement method cannot be universally used in the flow measurement of the pipeline in the power station boiler.Therefore,a flow measurement method suitable for various pipelines is needed,which can accurately measure any gas flow rate in real time,so that the operation of power station boilers is more safe and reliable.Aiming at this problem,this paper proposes an online real-time detection system of gas velocity based on audible sound from the theory of acoustic wave,and demonstrates the feasibility of this method under different working conditions through a series of simulation and experimental work.At the same time,an optimization method is proposed for the existing problems of acoustic velocity measurement,which solves the problem of poor accuracy of acoustic velocity measurement in large-scale pipelines.Firstly,this paper summarizes and analyzes the commonly used gas flow rate methods,proposes an online real-time gas detection technology based on audible sound,analyzes its advantages and technical problems to be solved,and determines the research content and direction.The mechanism of acoustic velocity measurement by time difference method,the acoustic propagation characteristics of different pipelines and the mechanism of cross-correlation algorithm to calculate the acoustic propagation time are introduced systematically.Through simulation,the selection of sound source signals is further guided under the condition of complex background noise and improving the accuracy of crosscorrelation function.Secondly,in order to better understand the advantages and disadvantages and applicable conditions of acoustic velocity measurement,this paper classifies the application scenarios of acoustic velocity measurement,and discusses the velocity measurement of circular pipeline based on primary air pipeline and square pipeline based on secondary air pipeline and flue gas pipeline.Thirdly,the application of acoustic velocity measurement in gas velocity measurement in circular pipeline is studied by simulation and experiment,and the acoustic velocity measurement under cold condition and variable working condition is studied.The results show that the acoustic velocity measurement method based on audible sound has high accuracy and stability for circular pipelines,and the response speed is faster under variable working conditions,but the effect of acoustic velocity measurement is relatively reduced under low temperature and low speed conditions.These results show that acoustic velocity measurement is highly feasible in circular pipes.Finally,the applicability of acoustic velocity measurement in square pipes is experimentally verified.The results show that the acoustic velocity measurement has good accuracy and stability in the square pipe,but the measurement accuracy is low.Aiming at this problem,an optimization method of acoustic velocity measurement system is proposed,and the optimal scheme is obtained by comparing simulation with experiment.Through the velocity measurement experiment,the optimization method greatly improves the accuracy of acoustic velocity measurement,and has high accuracy and stability.It can better solve the technical problem of real-time online detection of pipeline flow rate in power plant boilers.