| The main objective of this dissertation research is the design and optimization of a magnetically levitated axial flow ventricular assist device (LEV-VAD2), as a viable alternative to heart transplantation for patients suffering from congestive heart failure. The LEV-VAD2 design consists of an inducer region with stationary blades to reduce the tangential flow components and thus flow pre-rotation into the pump; an impeller, magnetically suspended, to impart kinetic energy to the fluid; and a stationary diffuser section with blades specifically designed to convert the kinetic energy to pressure. It measures 115 mm in length by 35 mm in diameter. The streamlined and unobstructed flow path of the LEV-VAD2 is its unique characteristic and is the key factor that facilitates continuous washing of all surfaces in contact with blood. This configuration provides a single pass blood path, which generates a minimal amount of turbulence in the flow field, reducing the likelihood of thrombosis and eliminating retrograde flow.; Design criteria used in the LEV-VAD2 flow path design are: (1) to deliver physiological pressure and flow rates; and (2) to minimize the irregular flow patterns and flow stasis while maintaining an acceptable hydraulic performance. As a design tool, computational fluid dynamics (CFD) analysis facilitated a deeper understanding of blood flow patterns inside of the LEV-VAD2. By means of CFD, flow field parameters have been determined for a wide range of pump operating conditions. The CFD performance analysis included: pressure-flow curves, hydraulic efficiencies, scalar fluid stress levels, exposure time to such stress, fluid forces acting on the impeller, and blood damage numerical estimations. A thorough CFD analysis allowed for optimization of the blood flow path such that an optimal trade-off among the hydraulic performance, specific requirements of a blood pump, and manufacturing requirements have been ultimately achieved.; Because of this favorable performance, the current design configuration of LEV-VAD2 was selected as the suitable candidate for titanium prototype manufacturing and further experimental testing. Extensive mock loop and acute animal testing will be underway at the Utah Artificial Heart Institute in the fall of 2006. In vivo animal testing will be performed to demonstrate that the LEV-VAD2 is safe and effective for long-term implantation. (Abstract shortened by UMI.)... |
