Improvement Of Anti-interference Ability Of Acoustic CT Temperature Field Reconstruction System

Acoustic CT temperature field reconstruction technology is a new non-contact temperature field measurement technology,which has the advantages of non-interference with the measured temperature field and strong environmental adaptability.It has wide application prospects in the fields of industrial boiler temperature field monitoring,deep-sea hydrothermal outlet temperature distribution monitoring,storage grain temperature distribution monitoring and so on.The measurement accuracy of acoustic flight time is a key to the accuracy of temperature field reconstruction.There are all kinds of environmental noise in the actual measurement environment,such as the high decibel operating noise of nearby equipment.The observation noise caused by the same noise source in each receiver is related to each other.The commonly used cross-correlation time delay estimation method has good suppression effect on uncorrelated noise interference,but its suppression ability on correlated noise interference is very weak.When the ambient noise is large,the performance of cross-correlation time delay estimation method decreases sharply or even fails.In order to make the acoustic CT temperature field reconstruction system more resistant to noise interference,a sound wave time of flight measurement method based on Variational Mode Decomposition(VMD)and Cross-Correlation,VMD-CC method,is proposed in this paper.Firstly,the VMD parameters are adjusted adaptively by using the remote signal,that is,the number of decomposition layers is determined based on the residual,and the penalty factor is optimized by particle swarm optimization with the goal of minimizing the correlation coefficient between the residual and the original signal;Then VMD noise reduction is performed on the received signals at the near end and the far end respectively;Finally,the relative delay of near end and far end noise reduction signals is calculated by Cross-Correlation method.The measurement results of acoustic time of flight show that Cross-Correlation method,Cross-Correlation method with wavelet noise suppression and VMD-CC method have good resistance to uncorrelated Gaussian white noise;However,for environmental noise,that is,correlation noise,the anti-interference ability of VMD-CC method is significantly better than other methods.This paper also proposes a position optimization method for symmetrically arranged acoustic transceivers.Taking the maximum number of grids through which the sound line passes and the minimum reconstruction error of uniform temperature field as the objective function,the longicorn whisker algorithm is used for optimization.This method is used to optimize the positions of 8 transceivers in the measured area of the square.The simulation reconstruction results of common temperature field models show that the layout in this paper has a good effect on the reconstruction of various temperature field models,has universality,and the reconstruction error is smaller than the traditional uniform layout.