Numerical Simulation of Ignition Process for the Monomethyl Hydrazine–Nitrogen Tetroxide Thrusters

Abstract

The numerical simulation of the ignition process of the monomethyl hydrazine–nitrogen tetroxide attitude-control thrusters is difficult because of the complex hypergolic gas–liquid chemical reaction between the propellants. To calculate the thruster ignition delay accurately, a 36-step gas-phase chemical kinetics model and a one-step finite-rate liquid-phase hypergolic reaction are proposed. These chemical mechanisms are integrated into the Euler–Lagrange-based transient spray combustion simulation platform. The calculated ignition pressure curve of a 2 kN thruster coincides well with that from the experiment. The numerical and experimental ignition delays are 2.4 and 3.1 ms, respectively. A parameter study shows that the liquid-phase reaction at the propellant impingement points consumes 22–44% propellant and provides energy to heat the gas mixtures, which is essential for a successful gas-phase ignition. The lower limit of ignition delay was estimated as 1.5 ms under design restrictions for most thrusters.