Annu Int Conf IEEE Eng Med Biol Soc. 2021 Nov;2021:5419-5424. doi: 10.1109/EMBC46164.2021.9630426.
High and low shear regions in rotary blood pumps require sufficient washout flow to minimize blood residence time, thereby preventing hemolysis or regions of stasis that can lead to pump thrombosis. Spiral groove bearings (SGBs) both enhance pump washout and reduce erythrocyte exposure to high shear. Narrow groove theory (NGT) has been used as an analytical tool to estimate the flow performance of a flat SGB during the design stage. However, NGT cannot accurately predict the performance of a conical SGB. In this study, we formulated an analytical model from the established NGT by adding an inertia correction term to incorporate variations in centrifugal force, which improved washout prediction in a conical SGB. The modified NGT model was then validated by comparison with experimental results. The results show that the modified NFT analytical model can reasonably predict washout rate when the spiral groove geometry favors creep flow conditions. The conical half angle of the SGB had the most significant impact on washout, with a decrease in half angle leading to large increases in wash-out flow. Small half angles also maintained viscous pumping at larger Reynolds numbers. In summary, the modified NGT can be a useful tool for designing conical SGBs for rotary blood pump washout within the creep flow regime.
在旋转血泵中，高剪切和低剪切区域需要足够的冲洗流量以最小化血液停留时间，从而防止溶血或停滞区域导致泵血栓形成。螺旋槽轴承（SGB）既能增强泵的冲洗效果，又能减少红细胞暴露于高剪切力下。窄槽理论（NGT）已被用作分析工具，以在设计阶段估计扁平 SGB 的流动性能。然而，NGT 不能准确预测锥形 SGB 的性能。在这项研究中，我们通过添加惯性修正项来从已建立的 NGT 中推导出分析模型，以纳入离心力的变化，从而改善了锥形 SGB 的冲洗预测。然后，通过与实验结果进行比较来验证修正后的 NGT 模型。结果表明，当螺旋槽几何形状有利于蠕动流条件时，修正后的 NFT 分析模型可以合理地预测冲洗率。SGB 的锥形半角对冲洗效果的影响最大，半角减小会导致冲洗流量大幅增加。小的半角也能在较大的雷诺数下保持粘性泵送。总之，修正后的 NGT 可以成为设计蠕动流旋转血泵锥形 SGB 的有用工具。
