A detailed kinetic model for the pyrolysis and oxidation of monomethylhydrazine

Hydrazine-based fuels, especially monomethylhydrazine(MMH), are widely used as liquid rocket engine propellants for deep space exploration and attitude control because of their high-energy content, versatility, and reactivity. The combustion process of MMH strongly influences heat release and engine performance. An accurate and detailed kinetic model is of crucial importance to predict the pyrolysis and combustion behavior of MMH with oxidizers in liquid rocket engines. In this study, a new detailed MMH pyrolysis and oxidation kinetic model (including 106 species and 710 reactions) was developed by incorporating recent advances in ab initio calculations and experimental studies. The kinetic model was tested and validated against a comprehensive set of experimental data from MMH pyrolysis and oxidation over a wide range of operating conditions with the temperature range of 884–1418 K and the pressure from 0.32 to 5.2 atm. The proposed kinetic model displays good predictions of induction delay from pyrolysis conditions, ignition delay time from oxidation conditions, and speciation experimental profiles from both pyrolysis and oxidation. In particular, the prediction of the ignition delay time from 30 sets of MMH oxidation by O₂ experiments presents satisfactory agreement with the experimental measurements, with a maximum deviation below a factor of two. This is significantly improved compared to previous MMH models. According to the kinetic modeling, the NN fission and the H-abstraction of MMH by CH₃ were found to be the most sensitive reactions for the consumption of MMH in pyrolysis conditions. Nevertheless, the fission of the NN bonds in MMH and its radicals plays a significant role in MMH oxidation by O₂. Sensitivity analysis of the ignition delay time indicates that sequential H-abstraction reactions were crucial for the ignition of MMH with O₂.