Study On High Temperature Continuous Spectral Emissivity Measurement Technology Of Thermal Insulation Materials

Spectral emissivity is an important radiation property parameter of solid materials,which has important application requirements in various engineering and scientific research.With the development of hypersonic vehicle and high temperature technology,some new lightweight thermal insulation materials with low thermal conductivity have emerged.The spectral emissivity data of these materials at high temperature are the basic parameters of thermal insulation structure design However,the traditional measurement technology of emissivity of solid materials usually adopts the back heating technology of sample,which produces a great temperature gradient for thermal insulation materials at high temperature,and requires high heat flux density and power,resulting in the difficulty of continuous spectral emissivity measurement of thermal insulation materials at high temperature and lack of data.Therefore,it is not only an urgent need in the relevant engineering fields,but also an important theoretical value to study the measurement method and equipment technology of high temperature continuous spectral emissivity of thermal insulation materials and obtain high temperature continuous spectral emissivity data of thermal insulation materials.In this paper,the measurement of high temperature continuous spectral emissivity of thermal insulation materials is studied from the aspects of measuring principle and method,experimental device technology and measurement data analysis.The main contents include the following aspects.A method for measuring the high temperature continuous spectral emissivity of insulating materials using FTIR spectrometer based on the sample heated by high temperature radiation chamber is proposed.The measuring principle and system calibration method are studied.The radiation signal of sample is separated from the radiation signal of heating environment,and the relationship between the output data of FTIR spectrometer and the continuous spectral emissivity is derived.According to the principle and technical requirement of high temperature continuous spectral emissivity measurement for thermal insulation materials,the infrared continuous spectral emissivity measurement system for thermal insulation materials under 1500 ~oC was constructed by using the existing solid material transmission spectrum measurement device in the laboratory,through the transformation of high temperature heating chamber and measuring optical path,and the measurement system was debugged.The relationship between incident spectral radiation and signal output of FTIR spectrometer is calibrated by two-temperature method and blackbody furnace.The response function and background function curves of FTIR spectrometer are obtained,and the stability of response function with temperature is analyzed.The non-linearity error of the measurement system is analyzed by measuring the blackbody radiation signal.The wall temperature of the high temperature radiation chamber of the experimental device is calibrated by using standard SiC sample and its spectral emissivity data,and the corresponding relationship between the sample temperature and the wall temperature is obtained.On this basis,the continuous spectral normal emissivity data of two kinds of insulating materials(maximum heat-resistant 1100~oC)at 700 ~oC~1100 ~oC temperature range and 1.7?m~5.7?m wavelength were obtained by using the experimental device.The uncertainty of the measurement results and the influencing factors were analyzed.Through the research,a set of measurement methods and experimental devices for measuring the high temperature continuous spectral emissivity of thermal insulation materials have been preliminarily established,and the high temperature infrared continuous spectral emissivity data of two materials have been obtained,which can provide reference for the evaluation of high temperature thermal insulation performance and engineering application of these two materials.