Inverse Method for Turbomachine Blades Using Existing Time-Marching Techniques

Abstract

A newly-developed inverse method for the design of turbomachine blades using existing time-marching techniques for the numerical solutions of the unsteady Euler equations is proposed. In this inverse method, the pitch-averaged tangential velocity (or the blade loading) is the specified quantity, and the corresponding blade geometry is Iteratively sought after. The presence of the blades are represented by a periodic array of discrete body forces which are included in the equations of motion. A four-stage Runge-Kutta time-stepping scheme is used to march a finite-volume formulation, of the unsteady Euler equations to a steady-state solution. Modification of the blade geometry during this time marching process is achieved using the slip boundary conditions on the blade surfaces. This method is demonstrated for the design of infinitely-thin cascaded blades in the subsonic, transonic, and supersonic flow regimes. Results are validated using an Euler analysis method and are compared against those obtained using a similar inverse method. Excellent agreement in the results are obtained between these different approaches.