NUMERICAL AND EXPERIMENTAL ANALYSIS OF AN AXIAL FLOW VAD

Purpose: The streamlined and unobstructed flow path of our hydraulically efficient axial flow LVAD is the key factor that facilitates continuous washing of all surfaces contacting blood. One fluid region in particular, the diffuser, is challenging to manufacture due to the complexity of the twisted helical blades combined with a cross-sectional reduction along the length of the blades. This study quantifies and compares the influence of the diffuser geometry on the overall VAD performance. Methods: A combination of theoretical analysis, numerical simulations and experimental data is used for this study. The flow path design was optimized using extensive computational fluid dynamics analysis to achieve the desired operating performance combined with an exceptional flow path. Three computational models of the axial pump were investigated, and a comparison between computational predictions and experimental performance results are presented. Results: The models simulated flow rates of 2 to 12 liters per minute for 5, 000 to 8, 000 revolutions per minute over physiologic pressures with efficiencies of 26% to 32%. The CFD numerical estimations generally agree within 10% of the experimental measurements over the entire range of rotational speeds tested. Conclusions: No measurable difference was seen in the performance of the 3 and 6 bladed diffuser. The 3 bladed diffuser configuration is preferable due to its manufacturing advantages.