Wu Peng, Zhang Ke-Jia, Xiang Wen-Jing, Du Guan-Ting
Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, China.
Artificial Organ Technology Laboratory, School of Mechanical and Electrical Engineering, Soochow University, Suzhou, China.
Biomech Model Mechanobiol. 2024 Oct;23(5):1571-1589. doi: 10.1007/s10237-024-01855-1. Epub 2024 May 31.
Secondary flow path is one of the crucial aspects during the design of centrifugal blood pumps. Small clearance size increases stress level and blood damage, while large clearance size can improve blood washout and reduce stress level. Nonetheless, large clearance also leads to strong secondary flows, causing further blood damage. Maglev blood pumps rely on magnetic force to achieve rotor suspension and allow more design freedom of clearance size. This study aims to characterize turbulent flow field and secondary flow as well as its effects on the primary flow and pump performance, in two representative commercial maglev blood pumps of CH-VAD and HeartMate III, which feature distinct designs of secondary flow path. The narrow and long secondary flow path of CH-VAD resulted in low secondary flow rates and low disturbance to the primary flow. The flow loss and blood damage potential of the CH-VAD mainly occurred at the secondary flow path, as well as the blade clearances. By contrast, the wide clearances in HeartMate III induced significant disturbance to the primary flow, resulting in large incidence angle, strong secondary flows and high flow loss. At higher flow rates, the incidence angle was even larger, causing larger separation, leading to a significant decrease of efficiency and steeper performance curve compared with CH-VAD. This study shows that maglev bearings do not guarantee good blood compatibility, and more attention should be paid to the influence of secondary flows on pump performance when designing centrifugal blood pumps.
二次流道是离心式血泵设计中的关键因素之一。较小的间隙尺寸会增加应力水平和血液损伤，而较大的间隙尺寸可以改善血液冲洗并降低应力水平。尽管如此，较大的间隙也会导致强烈的二次流，进而造成进一步的血液损伤。磁悬浮血泵依靠磁力实现转子悬浮，从而在间隙尺寸的设计上有更大的自由度。本研究旨在对CH-VAD和HeartMate III这两款具有代表性的商用磁悬浮血泵中的湍流场和二次流及其对主流和泵性能的影响进行表征，这两款血泵具有不同的二次流道设计。CH-VAD狭窄且长的二次流道导致二次流率较低，对主流的扰动也较小。CH-VAD的流动损失和血液损伤可能性主要发生在二次流道以及叶片间隙处。相比之下，HeartMate III中的宽间隙对主流产生了显著扰动，导致入射角较大、二次流较强且流动损失较高。在较高流量下，入射角甚至更大，导致更大的分离，与CH-VAD相比，效率显著降低且性能曲线更陡峭。本研究表明，磁悬浮轴承并不能保证良好的血液相容性，在设计离心式血泵时，应更多地关注二次流对泵性能的影响。
