Objective Accurate temperature measurement under high temperature, high pressure, and high radiation conditions is always a difficult task. To address this challenge, we realize the non-contact temperature measurement of multi-component pyrotechnic composition deflagration process based on the radiation spectral temperature measurement technology, providing basic parameters for further defining the reaction steps and deflagration products of pyrotechnic compositions.

Methods By establishing the radiation spectral temperature retrieval model of multi-component pyrotechnic compositions and temperature indicating particles, a calculation method based on the emissivity of small condensed phase gray-body particles is given, and the radiation spectrum of the condensed phase particles is obtained by experiment to retrieve the temperature as indicated by the continuous thermal radiation spectrum. In order to improve the temperature retrieval accuracy, we propose an improved method to reduce the influence of ion peak broadening during the deflagration of multi-component pyrotechnic compositions by using the Wien transformation to analyze the spectral curve, we also use double square weighted fitting by combining the Bisquare algorithm and the least squares algorithm to remove the non-thermal radiation spectral lines to improve the accuracy of the retrieved temperature variation curve. This method provides a fast and anti-interference way for non-contact spectral temperature retrieval under specific conditions.

Results and Discussions The detonation of pyrotechnic agents mainly involves two exothermic processes. The first process is: under initial conditions, the oxidant and reducing agent undergo a violent reaction and generate a large amount of heat, and the pyrotechnic agent undergoes instantaneous detonation, with an instantaneous temperature rise to 2795 K; Afterwards, the temperature gradually decreased and a brief uniform distribution of temperature appeared around 25 ms, and before 100 ms, the temperature uniformly decreased to 1485 K. The second process followed by a second increase in temperature, which is analyzed to be due to the presence of cellulose, lignin, and unburned particulate dust in the charcoal that have not been thermally decomposed in the first stage. Under continuous heating conditions, surface carbonization cracks appear and cause combustion to release a large amount of heat. When the accumulated energy exceeds a certain critical value, intense combustion occurs, resulting in a second exothermic peak. After 150 ms, the secondary exothermic reaction had ended, and most of the carbon particles were consumed through secondary deflagration. The thermal radiation spectrum mainly came from alumina temperature indicating particles, and their good thermal conductivity led to a rapid decrease in system temperature, which was significantly faster than the first temperature decrease process.

Conclusions The entire temperature change process during the detonation of pyrotechnic agents exhibits a secondary exothermic phenomenon of a characteristic pattern of heating, cooling, reheating, and final cooling. This article determines whether there are non thermal radiation spectral lines based on the line shape and dispersion degree of the spectral lines, and adds weight coefficients of the Bisquare algorithm to improve the anti-interference ability of inversion to ion peaks and noise. It provides a new inversion idea and method for detecting temperature changes in the temperature field of pyrotechnic explosive detonation. This method can detect and analyze the secondary heating phenomenon in the detonation of pyrotechnic agents.