Research On Emissivity In-situ Measurement System And Calibration Method

Emissivity is a parameter that characterizes the ability of an object to radiate outward energy approximates a black body.The accurate measurement of this parameter is of great value for non-contact temperature measurement,aerospace,aircraft stealth,and the nuclear industry.There are many methods for measuring the emissivity of materials,but laboratory precision measurement is the mainstay.Most existing emissivity measurement systems for laboratories are bulky and equipped with precision optical systems,which have poor environmental adaptability.This thesis studies the in-situ measurement system that can quickly and accurately measure emissivity,and effectively respond to the emissivity of complex environments on industrial sites.The research work of this thesis is mainly divided into two parts.The first part is to study the specific design and implementation of the emissivity measurement system.Based on the basic theory of radiative heat transfer,and considering the influence of air transmission and external background radiation,according to the emissivity measurement principle of the energy method,this thesis derives the emissivity calculation model and designs and implements the emissivity measurement system.According to the background radiation and strong vibration environment of the system,a strong cold air refrigeration detector is designed and the design of the collimator tube is optimized.The test results show that the radiation measurement method based on the field angle constraint and atmospheric compensation can effectively suppress the background radiation.On the other hand,the use of Fourier infrared spectrometer to study the calibration method of the measurement system.Because the emissivity is related to the temperature,roughness,and measurement band of the material,calibrating the accuracy of the measurement system is a major technical problem.In this thesis,the Fourier infrared spectrometer is calibrated based on the dual temperature method,and the RBF neural network is used as a prediction model to predict the spectral emissivity in the range of 2 ? 3.5 ?m band to solve the problem that the measurement band of the Fourier spectrometer does not match the measurement band of the detector.Using the band emissivity formula to calculate the predicted complete spectral emissivity data to obtain the band emissivity of 2 ? 16?m,and finally completed the calibration work.At the end of this thesis,through a large number of sample tests,it was verified that the error of the emissivity measurement result of the measurement system relative to the emissivity measurement result of the Fourier spectrometer does not exceed 0.07,and the emissivity measurement result of the system is consistent with the objective law of material emissivity change,the test results show that the measurement system has good application prospects.