Flash-evaporation of oxidizer spray during start-up of an upper-stage rocket engine

Abstract

The low-pressure oxidizer preflow during start-up of an upper-stage rocket engine is analyzed computationally. An iterative Euler-Lagrange approach is used to describe the three-dimensional two-phase flow of oxidizer vapour and spray which is characterized by intense phase transfer. Multipoint injection and flash-atomization of liquid oxidizer is modelled by stochastic droplet injection according to injector locations and spray characteristics. Based on the framework of classical D²-theory, a flash-evaporation model is developed to describe heat and mass transfer between superheated liquid droplets and vapour flow. The computed transsonic flow field agrees well with experimental characteristics such as pressure level and temperature decrease and further provides detailed local information on vapour flow homogeneity and liquid wall deposit.