Research On Inversion Gorithms Of Thermophysical Properties

Inverse Heat Conduction Problem(IHCP) has a wide range of applications in the aviation industry. In order to estimate the thermal parameters of the target object, this paper has studied the IHCP. Based on the influencing factors of thermal inversion, this paper has explored the methods to improve the accuracy of the algorithms and has made valuable data.The study discussed the inversion algorithm based on Differential Equations first. The direct problem was dealt with Crank-Nicolson implicit difference method. In time of solving IHCP, we used the iterative conjugate gradient method(CGM). Through a computer-generated noise, we tested the sensitivity of algorithm to measurement noise. After that, we tried planar heat source method of inversion algorithm. In this time, we converted it into one-dimensional inverse problem of optimization with the Newton method. Finally, we discussed the influence of several parameters on the inversion results. In addition, we designed the structure of the measurement device. The design included the structure of the heating device and the electronic control part, which was based on the thermal conductivity of stable-state.Simulation results showed that, in the absence of temperature noise, both of the inversion algorithms reached the accuracy of 3%. Added 2% of temperature noise, the accuracy of the former fell to about 20%, the latter to 5%. Besides, the latter’s calculation-time was short than 1% of the former.The study suggests that, the algorithm based on Differential Equations is more sensitive to temperature noise than the planar heat source method, on the one hand. On the other hand, the former can be used on the IHCP with multiple unknown parameters, while the other only for single parameter.