REDUCED-ORDER MODELING OF EXTREME SPEED TURBOCHARGERS

In order to improve their efficiency and performance, aircraft intermittent combustion engines often incorporate turbochargers that are adapted from ground-based applications. These turbochargers experience conditions outside of their design operating envelope and are found to experience high-cycle fatigue brought on by aerodynamically-induced blade resonances. The onset of fluid-structural interactions, such as flutter and forced response, in turbochargers at these conditions has not been extensively studied. A reduced-order model of the aeroelastic response of the turbine is developed using the Euler-Lagrange equation informed by numerical data from uncoupled computational fluid dynamic (CFD) and computational structural dynamic (CSD) calculations. The structural response of the reduced-order model is derived from a method of assumed modes approach. The unsteady fluid response is described by a modified version of piston theory as a first step towards including inhomogeneous aerodynamic forcing. Details of the reduced order model are given. The capability of the reduced-order model to predict the presence of flutter from a subset of the uncoupled numerical simulation data is discussed.