A Revised Model of Ammonium Perchlorate Combustion with Detailed Kinetics
Creators: name:  P. BERNIGAUD 
name:   D. DAVIDENKO 
name:   L. CATOIRE 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS
SOLID ROCKET MOTOR

description: Ammonium perchlorate (AP) is a widely used ingredient for solid propellants with a polymeric binder such as hydroxyl-terminated polybutadiene (HTPB). This kind of solid composite propellant finds applications in civilian and military rocket systems. Whereas the binder provides combustible gases via its pyrolysis, AP acts as the oxidizer. The combustion process is controlled by the modal distribution of AP particles within the propellant. The composite propellant can hence be tailored to meet specific requirements using a suitable AP particles loading. In order to design a composite propellant, it is important to understand and model correctly the AP combustion process, including the condensed phase. Significant experimental work was conducted in the past in order to obtain data necessary to build and validate numerical models. Atwood et al. [1] measured the AP burning rate at various pressures. Ermolin et al. [2] provided measurements of reacting species profiles within the AP flame, and proposed a first detailed kinetic model. Efforts to develop more accurate detailed kinetics models for ammonium perchlorate combustion have been continued by researchers such as Gross [3] and Smyth [4]. Ammonium perchlorate (NH 3 HClO 4 ) decomposes in the solid phase via two main pathways: direct sublimation, forming NH 3 and HClO 4 , and decomposition producing some other gaseous species. The presence of NH 3 as a major decomposition product implies that correct prediction of the AP combustion can only be achieved using a suitable model of the chemistry involving NH 3 , its subsequent radicals, and NO x . In this study we propose a revised detailed kinetic model for AP combustion, leveraging recent advances in the modeling of ammonia chemistry. Shrestha et al. [5] recently proposed a detailed kinetic model for the oxidation of ammonia, which was validated against species sampling in jet-stirred reactors, measurements of laminar flame speed and ignition delay time. The use of experiments in jet-stirred reactors, involving simple chemical systems, allows for the validation of kinetic submechanisms within the model. These experiments were used as test cases for our kinetic model and results were compared against a reference mechanism for AP combustion from the literature [4]. We observed deficiencies in the reference mechanism, which is unable to predict correctly the kinetics of simple chemical systems such as the NO 2 to NO conversion at high temperature or the oxidation of H 2 , justifying the need for a revised mechanism for AP combustion. Our kinetic model provides good results for the jet-stirred reactor cases and also correctly predicts laminar flame speeds for NH 3 / air as well as ignition delays for NH 3 / O 2 systems. A new model of AP decomposition in the condensed phase is proposed to be used with the gas-phase mechanism. As a final validation stage for the AP combustion model, AP laminar flame was simulated in the 1D coupled approach by solving transport equations for the chemical species and energy in the gaseous phase together with the heat transfer in the condensed phase and suitable interface conditions. This allows for the calculation of the regression rate, surface temperature, temperature sensitivity and species profiles for prescribed initial temperature of AP and ambient pressure. Stability analysis of the coupled model is carried out employing the Zeldovich-Novozhilov method. The new AP combustion model produces results in good agreement with available experimental data over a wide range of pressure.