Internal Thermal Excitation Fuzzy Inversion And Temperature Field Reconstruction Of Composite Overwrapped Pressure Vessel

Composite overwrapped pressure vessel(COPV)has many advantages such as light weight,high strength and good fatigue resistance,and long service life.So it’s widely used in aerospace,automotive,medical,energy storage and transportation fields.In the process of COPV manufacturing and processing,non-destructive testing and gas filling,internal heat excitation generally exists.Accurately obtaining the internal thermal excitation information of COPV and reconstructing the temperature field of COPV on the basis of thermal excitation is a basic work in the related technical field.In this paper,the CNG gas cylinders of composite materials are used as the specific objects.The decentralized fuzzy inference(DFI)and double decentralized fuzzy inference(DDFI)methods based on fuzzy inference theory are used to study the internal thermal excitation inversion problem of COPV and the temperature field reconstruction of COPV.The main research work of the paper includes:(1)Combined with the steam flushing process inside the CNG cylinder during the inspection of the composite material CNG cylinder,the steam heating experiments inside the CNG cylinder experiment were carried out.The steady-state infrared thermal image and transient state of the outer surface of the CNG cylinder under different steam heating conditions were obtained.Through the comparative analysis of infrared thermal images,the influence of the internal thermal excitation intensity on the surface temperature of the gas cylinder and the distribution law of the internal thermal excitation during the steam flushing process of CNG gas cylinder were discussed.(2)A three-dimensional steady-state and unsteady heat transfer model of CNG composite cylinder was established,and the heat transfer process of the cylinder under different internal thermal excitation conditions was numerically simulated.The three-dimensional temperature field of CNG composite cylinder under different internal thermal excitation conditions was obtained.(3)A method was established to invert the internal thermal excitation distribution of COPV steady-state,which is Based on the thought of distributed fuzzy inference(DFI).With finite temperature measurement information on the surface of COPV,distributed fuzzy inference was conducted to obtain the inversion results of COPV steady-state internal thermal excitation distribution.With composite CNG cylinder as the object,simulation experiments are carried out to discussed the influence of initial guess value,the number of measuring point and surface temperature inversion result of the temperature measurement error,etc on the result of internal thermal excitation inversion.By using the part surface temperature of CNG gas cylinders in the steady state thermal excitation experiment,the internal thermal excitation distribution of CNG cylinder in steady-state was inverted.(4)On the basis of the aforementioned steady-state thermally excited distribution fuzzy inversion method,a time-space decoupling double decentralized fuzzy inference(DDFI)inversion scheme was established for the inverse problem of internal transient thermal excitation distribution of COPV.The method can use time sequence error vector of corresponding space for decentralized inference to invert the transient distribution of thermal excitation inside COPV.Furthermore,by using part of the surface temperature information obtained from the unsteady thermal excitation experiment of CNG cylinders,the inversion results of the transient distribution of thermal excitation inside CNG cylinders are obtained.(5)The temperature field of the CNG gas cylinder is reconstructed according to the inversion results of the internal thermal excitation of the CNG gas cylinder and the heat transfer model of the CNG gas cylinder.The reliability of inversion results of thermal excitation and temperature field reconstruction in CNG cylinders were verified by the experimental results.