Experimental Investigation of Thermal Fluid-Structure Interaction in High-Enthalpy Flow

Kurzfassung

The thermo-mechanical behaviour of highly loaded components of space vehicles, as e.g. nosecaps and control surfaces, in a chemically reacting high-temperature flow fields can be predicted with larger restraints only. In combination with a lack of reliable flight data the use of common numerical or experimental design tools requires high safety margins, which increase the mass and subsequently also the costs of a space craft inappropriately. One of the most challenging tasks for a reliable design of hot structures is the coupling of flow solver codes with codes that provide the thermal and mechanical response of the structure. Today the codes are run independently in general with simplified boundary conditions, e.g. numerical flow simulations commonly assume a radiation-adiabatic wall temperature neglecting the amount of heat, that penetrates the structure or is conducted along the surface causing a reduction of heat load peaks. Furthermore, a feedback of correlated changes in the material parameters on the boundary layer flow is not considered. But before coupled simulations become common design tools, it is essential to validate their results by well-suited experiments in calibrated facilities using sophisitcated measurement techniques. Such experiments have to be performed in well calibrated long-duration high-enthalpy facilities. In the frame of the project IMENS (Integrated Multi-disciplinary dEsigN of hot Structures) an extensive test series was performed on a generic flap model. The tests were run in order to build up an experimental data base for the validation of 3D coupled numerical simulations. During the test campaign the model's angle of attack and the flap angles were varied. The generic flap model consists of a ramp and two flaps that can separately be inclined at two different angles. Below the flaps a cavity is formed representing the flap container. All parts are made of the thermal protection material C/C-SiC. When exposed to high enthalpy flow ramp and flaps are extremely heated. Therefore, the evolution of the surface temperature was recorded by two infrared cameras and 5 pyrometers during the tests. In addition, 19 thermocouples were installed to measure the temperature history inside the model. The tests showed that in all configurations due to material's thermal conductivity also the flaps' leeward side is heated within short time, giving rise to a significant radiation heating of the cavity, which at some locations by far exceeds the amount of convective heating.