Numerical simulation of cryogenic flows under high-pressure conditions

Abstract

The accurate numerical modeling of fluids under high-pressure conditions, e.g. in rocket combustion chambers, poses many difficult challenges. First of all, the thermodynamic state of the fluid under consideration must be modeled ranging from low cryogenic temperatures at injection to high temperatures in the flame zone. Depending on the external pressure, the fluid will undergo a transition from super- to subcritical when heated up, or in case of subcritical injection, jet break-up and evaporation will occur. All these phenomena need to be accounted for by a suitable thermodynamic model. In addition to the thermodynamic modeling, the strong non-linearity in the equation of state causes spurious pressure oscillations in combination with conservative numerical schemes commonly used in compressible solvers. This work presents recent advances in the development of Reynolds-Averaged Navier-Stokes simulations (RANS) and Detached-Eddy simulation models (DES) for rocket combustion applications. Even though RANS simulations can't resolve small scale unsteady flow features, there is a need for fast and reliable complementary tools that can provide design variables like wall heat fluxes and chamber pressure at a much lower cost than scale-resolving simulations. In order to better understand which main physical processes need to be modeled in RANS approaches, we present results from scale-resolving Detached-Eddy simulations of the numerical test case by Ruiz et al. All results are obtained with a real-gas extension of the DLR TAU code. The framework is then applied to a lab-scale combustion chamber experiment from DLR Lampoldshausen for which results are presented and discussed.