Numerical Analysis Of Heat Transfer Process Of Equipment With Internal Defects And Experimental Research

The majority of industrial equipment is widely used in daily production,and its working environment is complex,often under the condition of long-term alternating load,which causes the internal fatigue of the equipment to be easily damaged,and it is fatal to the use of the equipment.Fatigue damage exists inside the equipment,the surface is not obvious,it is difficult to find by the naked eye,which brings great difficulty to the equipment detection.This paper will use infrared non-destructive testing technology to detect the internal defects of the equipment,taking CNG composite gas cylinder as the research object.A large number of literatures indicate that the fatigue damage of composite gas cylinders is mostly located in the wound layer.Therefore,the internal defects of the wound layer are taken as the research object,and the infrared nondestructive testing of the composite gas cylinder is carried out by manually applying thermal excitation to the gas cylinder..The research work of this paper is mainly as follows.(1)Establish a mathematical model of the heat transfer process of a two-layer flat plate with internal defects.The finite element method is used to solve the differential equation of heat conduction discretely.The numerical simulation experiment is used to analyze the internal temperature of the defect(such as defect area,depth,etc.).The effect of the difference,and the law of its influence.(2)The heat transfer process model of the composite gas cylinder with internal defects was established.The internal temperature field of the composite gas cylinder was numerically simulated by finite element software.The position and size of the internal defects of the composite gas cylinder were analyzed for the detectability of the detection surface.The experiment provides theoretical guidance.(3)The experimental platform was set up,and the gas cylinder was thermally excited by hot steam,and the temperature information of the detection surface was collected by an infrared thermal imager.The steady-state detection and transient detection methods are adopted to detect the gas cylinder,and the temperature information of the gas cylinder detection surface is collected in real time,which is convenient for later analysis.(4)Based on the infrared detection experiment of composite gas cylinder,the internal boundary heat flow inversion model of composite gas cylinder was established based on conjugate gradient method.The numerical inversion experiment was carried out to prove the feasibility of the inversion algorithm for boundary heat flow identification.Taking the experimental information of the cylinder as the input information of the inversion model,the internal heat flow of the cylinder during the steady state detection and transient detection experiments is identified.