Technological impacts
Successful development of an active flow control system which has proven to stand a high level of temperature and vibration typical of the ones that can be encountered in an aeronautical engine. The prototype developed is able to deliver a mass flow of 30g/s and to reach velocities up to 240 m/s in ambient conditions (wheras the fluid actuators existing in litterature were blowing 2g/s maximum)
Successful implementation of this system fed by engine bleed air (to be compared with usual research development using external devices). A TRL 4 can be considered as achieved, even if, of course, many improvements can still be made (compactness for example and flow rate reached). In terms of performance, on a single stage low speed compressor test bench, a very high SMI up to 140 % with a very high amplitude blowing and a moderate SMI (40 to 70%) with a positive energy balance. On the complete engine test bench, the AFC allows to reached SMI of the order of 50% at 54 of the engine full speed
Valuable knowledges and expertise were developed, in particular concerning design and integration of active flow control devices in a real engine, but also in the conduct of the test campaign itself. As initially planned, a strong emphasis was made on CFD, whose contribution was significant in the design process, leading to some precious guidelines for designing the actuators (in particular the injector) for future research in this area, saving valuable time
Scientific impacts
The experiments and the numerical simulation conducted on the single stage configuration have led to a better understanding of the physical mechanisms by which the jet interacts with the flow at the blade tip
Concerning the numerical strategy necessary to predict correctly the stall of an axial compressor with active flow control: several turbulence models and numerical methods have been tested and evaluated. Two different meshing strategies (Hybrid meshes and Chimera Techniques) have been investigated in order to take into account the actuators in a computational domain. They have been successfully applied and on the basis of the results obtained, some CFD guidelines have been proposed to efficiently simulate these kinds of phenomena. In particular, the Hybrid grid approach offers an efficient way to simulate turbomachinery flows with flow control; indeed, it combines the advantage of keeping structured grids for the blades (well adapted for blade flow simulation), and non-structured grids for the actuators (which are generally complex to mesh).
