Inference of chemical kinetics and thermodynamic properties from constant-volume combustion of energetic materials

Abstract

Constant-volume combustion tests have been widely used to characterize the reactivity, the combustion efficiency, and the gas-generating performance of energetic materials. However, the currently used performance metrics (ignition delay time, pressurization rate, and maximum pressure) highly rely on the specific experimental condition, which leads to the challenge of fairly comparing the material performance tested in different conditions and laboratories. For this reason, there has been a need for a new metric independent of the experimental conditions, along with a novel analytical tool. In this work, we proposed a kinetic modeling framework to infer the chemical kinetics and thermodynamic properties from the pressure profiles in constant-volume combustion tests. In this framework, a physical model predicts the thermodynamic states of the system during the constant-volume combustion process, while an inverse model calibrates the model parameters to fit the model to the experimental observation via sensitivity analysis. We demonstrated the success of the framework in inferring the chemical kinetics and thermodynamic properties with both synthesized data and experimental measurements. Moreover, the physical model with the inferred properties enabled a comprehensive understanding of how gas release and temperature rise contribute to the pressure rise in the constant-volume reactor. Therefore, the classical constant-volume combustion experiments can be utilized to infer properties for the design of energetic materials with desired gas and heat generation profiles and for modeling the energetic behaviors in more complex systems.