| Leakage of gas and liquid fuel or ignition of solid explosives may produce explosion transient flames whose temperature and thermal damage have always been important parameters for living and production safety and for research of warhead performance in military.When cooled mid-infrared thermal imager is used for testing the explosion transient flame temperature,the measurement accuracy of transient flame temperature of explosion will be affected by factors i.e.reference fixed value of flame emissivity,distance of test point,ambient temperature and humidity and temperature measurement range.At present,the temperature compensation of transient flame at home and abroad only focuses on the single range measurement and the radiation attenuation temperature compensation caused by atmospheric environment,and the radiation temperature attenuation caused by the dynamic emissivity of transient flame is not considered.To address foregoing problems,a temperature compensation model based on ranging,imaging aperture angle and field of view was established in this paper.The Schmidt method was applied to calculate the dynamic emissivity of the transient flame.Finally,the combined compensation model is constructed to realize the flame dynamic temperature combined compensation.The specific work is as follows:(1)Aiming at the radiation temperature attenuation caused by the measured target ranging,imaging aperture angle and field of view angle in the test,based on the infrared target radiation theory,geometric optics,infrared system photoelectric imaging principle,a temperature compensation method based on the system voltage error was proposed.The temperature stability,consistency and temperature response calibration of the infrared thermal imager were carried out by using standard black-body,and the temperature responsiveness of the infrared thermal imager in the compensation method was determined;The black-body was used to conduct the radiation temperature attenuation compensation simulation test caused by different ranging,and the calculated black-body temperature compensation results were closer to the preset black-body temperature value than before.The results initially verified the correctness of the mid-infrared ranging temperature compensation method based on system voltage error.(2)Based on Kirchhoff’s law and Stefan-Boltzmann’s law,using temperature radiation target as large area calibration source,a set of equations for the solution of dynamic flame emissivity is derived.The dynamic emissivity of pure butane flame was measured,and the emissivity of mid-infrared butane flame was 0.307±0.017 by using the method proposed in this paper.The results are in good agreement with those measured by Professor Zhou J.from Zhejiang University in the same infrared band,which preliminarily verifies the correctness of the method for calculating the flame dynamic emissivity.(3)In order to improve the compensation accuracy and avoid the limitation of single compensation,according to the composition of the effective radiation received by the thermal imager,the combined compensation model of the transient flame temperature of the explosion was constructed by combining the emissivity solution method and the temperature compensation method of the mid-infrared ranging.(4)The real explosion test was carried out.Firstly,based on the principle of colorimetric temperature measurement,the correction method of "temperature break point" of colorimetric thermometer is proposed to provide the temperature standard value for the transient flame temperature test of external explosion;Secondly,the radiance responsiveness and system bias of the colorimetric thermometer were obtained through the black-body calibration test;Finally,using the mid-infrared thermal imager,colorimetric thermometer and homemade radiation target for three times in the 1 kg-TNT explosion field test experiment,the temperature of the combined compensation method are used to get the calculated result compared with standard temperature,before the error compensation by 70.58%-93.51% down to 18.81%-48.51%,effectively improve the mid-infrared thermal imager in the measurement of TNT explosive transient flame temperature accuracy. |
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