Adjoint Method for Shape Optimization in Real Gas Flow Applications

Organic Rankine Cycles (ORC) are nowadays a well-established technology compared to steam Rankine Cycles for heat sources characterized by low to medium temperatures; typical applications of such systems range from geothermal to solar sources, as well as waste heat recovery. Despite their relatively simplicity and cost-eectiveness, ORC technology presents intrinsic diculties connected to the design of the turbine, due to complex gas-dynamic phenomena further complicated by strong real-gas eects typical of the expansion process in ORC turbines. Improvements in the uid-dynamic design of the turbo-expanders are therefore expected to considerably enhance the performance of the overall system. As a result the implementation of specic uid-dynamic design procedures, which generally imply the use of advanced optimization methods coupled with accurate ow solvers, is of paramount importance for the whole ORC technology. In this perspective this work focuses on the investigation of the potential of an adjoint-based method for shape optimization of turbomachinery blades in real gas ow applications. The abstract is organized as follows: in the rst Section a brief recall of the adjoint method is given, second Section details the optimization methodology, while in the nal Section the proposed design procedure is applied to the re-design of a supersonic cascade for ORC applications.