A computational investigation into the combustion byproducts of a liquid monopropellant

A detailed chemical kinetic mechanism is developed for the gas-phase combustion of a liquid monopropellant, which is a blend of propylene-glycol-dinitrate, dibutyl-sebacate, and 2-nitro-diphenylamine (Otto Fuel II). The combustor is modeled as a steady-state burner-stabilized flame. The simulations reveal that not all of the dibutyl-sebacate is consumed in the flame, with approximately 5% persisting in the post-flame region. A large class of combustion byproducts are formed that have boiling points above the post-flame temperature and thus would be expected to condense out along the length of the combustor. This post-flame, two-phase behavior is hypothesized to be the cause of empirically observed oily build-up within the engine. This work represents a novel advancement in predictive modeling for propellant design, as it provides mechanistic insight into the possible origins of engine fouling. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.