Study On The Chemical Reaction Kinetics Mechanism Of HAN-based Propellant And The Working Process Of Thruster

High performance and non-toxicity will be the main research direction of liquid monopropellant in the future.Green and non-toxic hydroxylamine nitrate（HAN）-based liquid propellant has become one of the next-generation monopropellants to replace hydrazine propellant due to its excellent performance.However,due to the complex reaction process of HAN-based propellants,there are few researches on the chemical reaction kinetics mechanism at the microscopic level and the working process of HAN-based thrusters.Therefore,it is of great significance to study the chemical reaction mechanism of HAN-based propellant and the working process of HAN-based thruster.In this paper,based on the research background of HAN-based propellant,the quantum chemistry method was used to perfect the thermodynamic file of HAN/methanol and construct the reaction mechanism of HAN/methanol propellant.Then,the thermodynamic file and reaction mechanism model were applied to the numerical simulation of catalytic decomposition and combustion process of HAN-based thruster,and the influence of HAN and methanol ratio changes on its working process was discussed.HAN and NH₂OH molecules with different structures were constructed by Gaussian software,and the most stable structures were obtained by analysis.On this basis,the bond length,bond angle,dihedral angle,infrared spectra and Raman spectra of HAN and NH₂OH stable structures were calculated.The thermodynamic parameters of HAN and NH₂OH at different temperatures were obtained by Kisthelp software,and the coefficients of the temperature function required in the thermodynamic file were obtained by fitting.The detailed chemical reaction kinetic mechanism of HAN/methanol was constructed,and its accuracy was verified according to the existing experimental data.Then,the detailed chemical reaction kinetic mechanism of HAN/methanol was further simplified,and the simplified chemical reaction mechanism of HAN/methanol was obtained and compared with the detailed mechanism to ensure its accuracy.By analyzing the sensitivity of temperature and important species of HAN/methanol simplified chemical reaction mechanism model,the reactions that have a great influence on it were identified.The transition states,intrinsic reaction coordinate（IRC）and reaction barriers of important reactions HAN+H₂O→NH₂OH+HNO₃+H₂O,NH₂OH+HNO₃→HONO+HNO+H₂O,NH₂OH+HONO→N₂O+2H₂O,NH₂OH+HNO→N₂+2H₂O and CH₃OH+O=CH₂OH+OH were studied by quantum chemistry method.And the chemical reaction rate constants were calculated at different temperatures by the transition state theory.On this basis,the kinetic parameters of the chemical reactions were obtained according to Arrhenius equation.Based on the HAN/methanol thermodynamics file and chemical reaction mechanism file calculated in this paper,the distribution characteristics of temperature,pressure,Mach number,reactants,intermediates and products in HAN-based thruster were studied by numerical simulation under stable working condition.In addition,the effects of the ratio of HAN and methanol on the temperature,pressure and important species in the process of HAN-based thruster decomposition and combustion were investigated,which also has reference significance for studying the mass fraction ratio of hydroxylamine nitrate and methanol in HAN-based propellant.