Three-Dimensional Thermal Analysis of the HIFiRE-5 Ceramic Fin

Abstract

The German Aerospace Center (DLR) has developed a ceramic fin experiment (FinEx) for the HIFiRE-5 flight in order to test the performance of new structures with sharp leading edges during flight. The analysis of the thermal performance of the fin has been foreseen to be conducted by in-depth mounted thermocouples protocolling temperatures during flight. In a cooperative attempt between DLR and the Institut für Raumfahrtsysteme (IRS) of the University of Stuttgart, the thermal behavior is studied. In this paper, an approach is presented to determine the heat flux distribution onto the surface of the three-dimensional geometry of the fin. Using the Non-Integer System Identification (NISI) method, heat flux onto different surface elements is derived from only three thermocouples mounted inside the fin. Moreover, to increase accuracy, an area-weighted inverse method is used. The principal proof of concept is given based on a finite element thermal analysis of a cube. Measurements with a backup fin are used to show the approach experimentally in a plasma wind tunnel. Finally, the in-flight data has been evaluated and heat flux onto the fins during flight is presented. It can be concluded that the method is strongly dependent on surface discretization. However, the qualitative distribution is accurately determined. This approach allows to improve heat flux measurements for sparsely equipped flight hardware.