Study On The Design Of High Temperature Spectral Emissivity Measurement Device Of Thermal Insulation Materials

Spectral emissivity is the most basic radiation physical parameter of materials,and plays an important role in various engineering technologies and scientific research fields.The transmission conversion hypersonic vehicle has become a research hotspot.Some materials with high refractive index and low resonance coefficient are more and more existing.The research of emissivity measurement generally adopts reverse heating combined with thermocouple temperature measurement.For conventional high resonance coefficient In terms of materials,this method can meet the requirements of heating and temperature measurement,but the thermal insulation material will produce a great temperature gradient along the thickness direction of the sample at high temperature,resulti ng in inaccurate temperature measurement and unsatisfactory heating effect of replacing the sample.Therefore,to solve the problem of temperature measurement in high-temperature emissivity measurement,it is necessary to design a more reasonable sample high-temperature heating device.This research focuses on the problems of inaccurate temperature measurement and unsatisfactory heating effect in the measurement of high-temperature spectral emissivity of thermal insulation materials with low thermal conduct ivity.The main research contents are carried out from the aspects of emissivity measurement principle,heating device design,and heating device working condition simulation.Including the following aspects.A method that can simultaneously measure the sample temperature and spectral emissivity is proposed.Using reasonable assumptions,the dynamic spectral radiation information of the sample within a small temperature difference is used to construct an overdetermined set of equations each containing the s pectral emissivity and the sample temperature as unknowns.In order to conduct simulation experiments,it is assumed that there are three different types of spectral emissivity models,and a genetic algorithm with large mutations is used to transform the overdetermined equations including temperature and emissivity.The results show that the principle of spectral emissivity measurement has the accuracy and reliability of a certain resolution.It is a bold attempt to overcome the difficulty of measuring emissivity at high temperature.Subsequently,the sample heating device for emissivity measurement was designed.Through investigation and repeated comparison,the final sample heating scheme was mainly determined by adding light heating on the front side and radiant heating from the high temperature cavity on the back side.And the overall design of the sample heating device,according to the constraints in the measurement process,using nonlinear programming to determine the key dimensions of the overall structure parameters.Finally,the designed sample heating device is modeled,unstructured grid is divided and the calculation model is determined,and specific simulation analysis is carried out on different heating conditions and when heating samples of diff erent properties.It is determined that for low thermal conductivity samples,the frontal laser heating scheme is first considered and the required laser power is determined according to the target high temperature,then the influence of the specimem thickness and thermal conductivity on the heating effect is analy sed,and the specific heating schemes for different samples are determined.Through research,a method for obtaining the sample temperature and the spectral radiance at the same time is proposed.The overall design of the heating device for the measurement of the high-temperature emissivity of the insulating material is completed,which provides a reliable reference.