CFD-Based Design Optimization of the Outlet Stator of a Rotodynamic Cardiac Assist Device

Two designs of an outlet stator for an axial flow left ventricular assist device are analyzed at nominal operating conditions. The original stator assembly (design 1) has significant flow separation and reversal. A second stator assembly (design 2) replaces part of the original tubular outer housing with a converging-diverging throat section with the intention of locally improving the fluid dynamics. Both stator designs are analyzed using computational fluid dynamics (CFD) analysis and experimental flow visualization. The computational and experimental methods indicate persistent regions of flow separation in design 1 and increased surface washing in design 2. However, the improved fluid dynamics of design 2 is accompanied by a significant decrease in pressure recovery as compared to design 1. To resolve these apparently conflicting end point behaviors, CFD-based design optimization is used to evolve the outer housing shape of a third stator assembly to simultaneously reduce flow stasis and maintain a high level of pressure recovery. During the optimization process, several insightful guidelines for designing efficient outlet stators of axial flow turbomachines become evident.