Dependency of Surface Temperature on Coolant Mass Flow and Heat Flux in Rocket Combustion Chambers

This paper presents the simulation and experimental results of the dependency of the surface temperature of a heat transfer test (HTT) panel representing liquid rocket engine combustion chamber geometry on the coolant mass flow rate and heat flow rate. The HTT panel is made of a high-conductivity copper material. This material is appropriate for the inner liner of lowly loaded regeneratively cooled combustion chambers like upper stages. In the experimental setup the HTT panel uses only a small section of the actual combustion chamber geometry, typically five cooling channels. The panel is heated by a high power diode laser providing realistic amounts of heat flux. For safety and cost reasons supercritical nitrogen is used as coolant instead of hydrogen or methane. Within the experiment different combinations of surface temperature, heat flux and mass flow rate were examined, in total 24 different test conditions. Subsequently a coupled steady state thermal fluid-structure-interaction analysis was conducted in ANSYS and validated with the experimental data. ANSYS CFX was used to analyze the nitrogen coolant fluid flow with a Shear Stress Turbulence (SST) model. ANSYS Mechanical was used for the thermal finite element analysis. The relevant thermophysical parameters like heat conductivity, diffusivity and heat capacity were measured for temperatures above 273 K. For lower temperatures these parameters were determined theoretically. The results gained in this study will be used for the accurate modeling of the heat transfer in a thermomechanical fatigue life analysis by adding a dedicated structural Finite Element (FE) Analysis in ANSYS Mechanical. The accurate modeling of thermomechanical fatigue is particularly important for reusability of rocket engines. Furthermore the results of the validated numerical simulation are useful for the estimation of heat transfer in new developments of liquid rocket engines, particularly upper stages.