| Pipeline system plays an important role in energy storage and transportation.The pipe network system can be seen everywhere in our daily production and life.The operation status of the pipe network is directly related to the vital interests of the general public.China’s pipeline network system is large in scale,and the failure rate of pipelines is high,among which blockage faults are common.In the early formation stage of the pipeline blockage fault,it shows different degrees of partial blockage.With the increase of the degree of blockage,the drainage capacity of the pipeline decreases,which will finally affect the normal operation of the pipeline,causing environmental pollution and waste of resources.Therefore,it is of great significance to study the detection and identification methods of pipeline blockage faults.The main research work of this paper is as follows:(1)Because of the complex pipeline structure and working conditions in the actual detection and analysis process,it is not easy to conduct direct experimental analysis.First of all,it is necessary to establish a mathematical model for the acoustic transmission track and solve the problem that the process is complex and difficult to obtain analytical solutions.In this paper,COMSOL simulation software is proposed to build a pipeline simulation model(time-frequency domain analysis model)based on the active acoustic detection method.Firstly,three physical fields of acoustic-solid interaction(frequency domain),boundary element mode,and acoustic-solid interaction(transient)are used to build a pipeline simulation model of acoustic active detection,analyze the propagation characteristics of acoustic waves under different pipeline working conditions,and then realize the simulation experiment of pipeline plugging detection under different working conditions.(2)Considering that the medium,length,and diameter in the pipeline have a great influence on the detection effect of fixed excitation frequency,the selection of excitation frequency in the current research is based on direct experience and lacks theoretical basis,resulting in a great difference in detection results and difficulty in accurately distinguishing different degrees of blockage in the pipeline.This paper presents an acoustic active detection method based on a fixed frequency.Firstly,the plane wave cutoff frequency of the known fluid medium in the pipe was studied theoretically,and the propagation characteristics of the sound wave in the axially symmetric pipe were analyzed by using the simulation model.The method of detection by the excited plane wave was proposed to realize the finite location of the blockage in the pipeline under a single working condition,and the linear regression prediction model was built to predict the degree of blockage.(3)When there is a change in the filling rate of the medium in the pipeline,the acoustic mode will change,so that the sensitive frequency of the blockage will change.It is necessary to select the excitation frequency through the filling rate to achieve effective detection.When the filling rate is unknown or changes with time,the medium in the pipe is unknown and not single,and the pipeline is asymmetric,the fixed frequency excitation cannot realize effective detection and other problems.This paper presents an acoustic active detection method based on frequency conversion excitation.Firstly,the simulation model is used to analyze the modal change and transmission loss of acoustic waves at different liquid levels.The change rule of the sensitive frequency band of blockages and pipe fittings under different liquid levels was obtained,and a frequency conversion excitation signal was designed to realize the effective positioning of plug and fittings under the environment of liquid level changes,and the correctness of the simulation results was verified by comparing with the experiment.Finally,GWOSVM was used to achieve classification and identification of pipeline status,and interactive verification with simulation and experiment was achieved,which proved the reliability of acquiring acoustic propagation characteristics through simulation analysis and the feasibility of low-frequency acoustic active detection method in industrial pipeline fault detection. |
