Computational modelling of the preflow phase during start-up of an upper-stage rocket engine

A computational analysis of the oxidiser preflow during start-up of a storable propellant upper-stage rocket engine is presented. To account for flash-evaporation of the superheated liquid oxidiser new physical models and numerical solution techniques are developed and implemented into the framework of an iterative Euler-Lagrange method. The computed three-dimensional two-phase flow field and spray deposit distribution in combustion chamber and nozzle extension is analysed. The influence of liquid injection temperature, initial droplet sizes and wall temperature on the preflow is assessed by detailed parametric studies. Validated by experimental data, the results are used to derive transfer functions describing the preflow dynamics on a system level.