  PediaFlow is a miniature mixed-flow ventricular assist device for neonates
and toddlers. PediaFlow has a fully magnetically levitated rotor which improves
biocompatibility, but the increased length of the rotor creates a long annular
passage where fluid energy is lost. Therefore, a set of helical stator blades
was proposed immediately after the impeller stage to remove the swirling flow
and recover the dynamic head as static pressure. Automated computational fluid
dynamics (CFD) shape optimization of the stator blades was performed to
maximize pressure recovery at the operating point of 1.5 LPM and 16,000 RPM.
Additionally, the effect on hemolysis and thrombogenicity was assessed using
numerical modeling. The optimization algorithm favored fewer blades of greater
length over a larger number of short blades. The ratio of wrap angle to axial
length emerged as a key constraint to ensure the viability of a design. The
best design had 2 blades and generated 73 mmHg of pressure recovery in an
isolated stage. When re-introduced to the CFD simulation of the complete flow
path, the added stator stage increased the pump head by 46% and improved the
pump efficiency from 21.9% to 25.7% at the selected operating point. Automated
CFD shape optimization combined with in silico evaluation of hemocompatibility
can be an effective tool for exploring design choices and informing early
development process.
