Transfer Functions for the Inverse Design of Turbomachinery for Thermal Power Storage

This paper is part of a priority program developing inverse design methods for thermal power storage. Turbomachinery for use in thermal power storage face specific challenges. These lay in the unconventional working fluids employed and the operating conditions of the machines. This paper discusses the inverse design of turbomachines using an approach that combines optimized aerodynamic design with its feasibility in transfer functions. The transfer functions consider the aerodynamic design by means of the Cordier diagram. It provides correlations between several basic parameters necessary for the preliminary design and can thus be used as a basis for transfer functions. To ensure the feasibility of the design the mechanical stability of the rotor and the flow stability inside the flow path are implemented as limits on the design. A set of additional design constraints are included to simplify the design process in order to enable the automated method. A selection method is applied to select the most optimal machine applicable. This way a machine can be designed for any given problem without further assumptions or other input by the designer. The machines designed by this method are analyzed through variation of the input parameters. The most important parameter has been shown to be the specific work on the working fluid. The speed of sound of the fluid was shown to possess a limited impact on the design while the volume flow through the machine showed no impact.