Hufgard Fabian, Duernhofer Christian, Fasoulas Stefanos, Loehle Stefan
High Enthalpy Flow Diagnostics Group (HEFDiG), Institute of Space Systems, University of Stuttgart, Pfaffenwaldring 29, 70569, Stuttgart, Germany.
Sci Rep. 2023 Aug 11;13(1):13109. doi: 10.1038/s41598-023-40281-8.
This paper presents a new method in theory and experiment to adjust the transpiration cooling based on the actual measured heat flux. This is particularly useful in extreme heating environments, e.g. atmospheric entry flight or combustion chamber applications. In such environments, usually cooling is set constant based on the vehicle design, yet a mass efficient and performant cooling is sought after. We present a method with real-time surface heat flux determination of the transpiration cooled wall and an automatic adjustment of the cooling. The heat flux is determined based on a system identification process. The heat flux measurement itself is derived non-intrusively from the measurement of pressure inside the plenum, i.e. the region between mass flow controller and porous wall. The particular advantage of this system is that the heat shield material is not weakened by any sensor system and its performance is optimized with respect to cooling needed at a certain heating level. Another new feature of the pressure heat flux transformation is the attenuation of a destabilizing positive feedback loop, where the transpiration cooling controller's 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. The controlled cooling was demonstrated in a hot air plasma flow with a reference heat flux of up to 1.4 MW/m[Formula: see text]. The results show the performance and verify the applicability in a real flight environment.
本文在理论和实验方面提出了一种基于实际测量热流来调节发汗冷却的新方法。这在极端加热环境中特别有用，例如大气再入飞行或燃烧室应用。在这种环境中，通常根据飞行器设计将冷却设置为恒定值，但人们追求的是高效且高性能的冷却。我们提出了一种对发汗冷却壁进行实时表面热流测定并自动调节冷却的方法。热流是基于系统辨识过程确定的。热流测量本身是通过对气室（即质量流量控制器和多孔壁之间的区域）内压力的测量以非侵入方式得出的。该系统的特别优势在于隔热罩材料不会因任何传感器系统而性能削弱，并且其性能针对特定加热水平所需的冷却进行了优化。压力 - 热流转换的另一个新特点是减弱了一个不稳定的正反馈回路，在该回路中，发汗冷却控制器的输出（即质量流量）强烈影响其输入（即气室压力）。我们描述了用于热流测定的模型参数的辨识过程，这些参数是通过校准方法找到并验证的。在参考热流高达1.4 MW/m² 的热空气等离子体流中展示了受控冷却。结果显示了其性能，并验证了在实际飞行环境中的适用性。
