Transpiration cooling with phase change is a novel active thermal protection method with higher cooling efficiency. The modified two-phase mixture model and the multi-domain coupling computation are adopted to study its transient response. Different fluctuation periods of coolant mass flux and different thermal conductivities of the porous matrix are discussed, respectively. The simulation results show that there are clear delay and accumulation effect in the transient response, and the coolant injection pressure is much more sensitive than the temperature to the coolant mass flux. Moreover, both temperature and injection pressure have their own extreme values during transient response. Then, the instability on the porous matrix surface is closely related to the location of the coolant phase transition. Using the porous matrix with greater thermal conductivity can not only help to reduce the surface temperature of the structure under steady condition, but also has stronger stability under transient condition. The research of this work is of great guidance and practical importance for the extension of the application of transpiration cooling with phase change in the real environment.

View full abstract

In aero engines, rotating labyrinth seals are widely used to suppress the flow leakage between static and rotating components. These seals are usually designed with light weight to further enhance the engine performance. Hence, they are susceptible to flutter vibration due to their low stiffness. In this study, the ways to optimize both seal leakage performance and flutter margin are investigated using fluid-structure interaction (FSI) simulation and machine learning. Through this study, it is found that by optimizing sub cavity geometries between seal fins, both the leakage performance and flutter margin can be effectively improved.

View full abstract