Optimization of Microturbine Aerodynamics Using CFD, Inverse Design and FEM Structural Analysis: 1st Report — Compressor Design

In this paper, a new aerodynamic design procedure is presented for a centrifugal compressor stage of a microturbine system. To optimize the three-dimensional (3-D) flows and the performance, an inverse design method, which numerically generates the 3-D blade geometry for specified blade loading distribution, has been applied together with the numerical validation using CFD (Computational Fluid Dynamics) and FEM (Finite Element Method). The blade profile along the shroud surface of the impeller was optimized based on the 3-D inverse design and CFD. However, the blade profile towards the hub surface was modified geometrically to achieve a nearly radial blade element especially at the inducer part of the impeller, in order to meet the required structural strength. The modified impeller successfully kept similar aerodynamic performance as that of a blade with a fully 3-D shape, whilst showing improved structural reliability. So, the proposed method to adopt the blade profile designed by the inverse method along the shroud, and to geometrically modify the blade profile towards the hub, was confirmed to be effective to design a high-speed compressor impeller. The vaned diffuser has also been re-designed using the inverse design method. The corner separation in the conventional wedge-type diffuser channel was suppressed in the new design. The stage performance improvements were confirmed by stage calculations using CFD.