Closed loop control of stall flutter of turbo machinery blades

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This project studies stall flutter suppression by means of plasma actuation. Blade flutter describes the unstable dynamic behavior of turbomachinery blades interacting with the surrounding airflow. This leads to fast growing oscillation amplitudes, which at the end results in the destruction of the blading. In the case of transonic stall flutter, flow separations occur as a consequence of post shock compressions. In this work a closed loop control for transonic stall flutter on an aero engine fan will be numerically built up.The aeroelastic behaviour of the fan will be assessed by unsteady 3D computational fluid dynamic (CFD) simulations. The computations will be carried out on the computer facility of the Chair of Aero Engines at the Technische Universität Berlin. First the most unstable operating point in the regime of transonic stall flutter and the most unstable oscillation mode will be determined. Then CFD computations of the fan equipped with plasma actuators modeled numerically will be performed. A parametric study will be carried out to derive the plasma actuator position with the highest influence on the fan aeroelastic stability. This latter will be quantified by means of the energy method. A nonlinear reduced order model (ROM) for the unsteady aerodynamic response of the system will be developed. It will be used to build up an analytical aeroservoleastic model of the fan. This low order model will be used for the development of the control architecture without the need of time consuming CFD simulations. The control law will be then implemented in the CFD solver to check its operation with high fidelity simulations. Namely, unsteady 3D simulations will be performed to assess ultimately the capabilities of the closed-loop plasma-based control in increasing the fan aeroelastic stability.