Adjusting Transpiration Cooling to Real Time Surface Heat Flux Estimation

Abstract

We present a new approach in theory and experiment to automatically adjust the transpiration cooling to the actual thermal load, i.e. the Cooling Adjustment for Transpiration Systems (CATS). This approach bases on the real-time determination of surface heat flux at the transpiration cooled wall. The heat flux is essentially calculated from a non-intrusive measurement of pressure in the plenum, i.e. the region between mass flow controller and porous wall. This pressure heat flux transformation additionally attenuates a destabilizing positive feedback loop, where the transpiration cooling controllers output (i.e. mass flow rate) strongly influences its input (i.e. plenum pressure). We describe the identification of the model parameters for the heat flux determination, which are found and verified by a calibration approach. CATS was demonstrated in the plasma wind tunnel PWK4 at the Institute of Space Systems, Stuttgart. The results show the CATS performance, which proves the usefulness of the proposed approach to automatically adjust the transpiration cooling to the actual thermal load.