• 대한전기학회논문지:시스템및제어부문D
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• 제51권10호
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• pp.477-482
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• 2002

One of the key technologic requirements for rotary blood pumps is the sealing of the motor shaft. A mechanical seal, a journal bearing, magnetic coupling, and magnetic suspension have been developed, but they have drawbacks such as wear, thrombus formation, and power consumption. A magnetic fluid seal is durable, simple, and non power consumptive. Long-term experiments confirmed these advantages. The seal body was composed of a Nd-Fe-B magnet and two pole pieces; the seal was formed by injecting magnetic fluid into the gap (50${\mu}m$) between the pole pieces and the motor shaft. To contain the ferro-fluid in the seal and to minimize the possibility of magnetic fluid making contact with blood, a shield with a small cavity was attached to the pole piece. While submerged in blood, the sealing pressure of the seal was measured and found to be 31kPa with magnetic fluid LS-40 (saturated magnetization, 24.3 KA/m) at a motor speed of 10,000 rpm and 53kPa under static conditions(0mmHg). The specially designed magnetic fluid seal for keeping liquids out is useful for axial flow blood pumps. The magnetic fluid seal was incorporated into an intra-cardiac axial flow blood pump.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권9호
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• pp.431-437
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• 2002

Low hemolysis is one of the key factors in the production of successful rotary blood pumps. It is, however, difficult to identify the areas where hemolysis occurs. Computational fluid dynamics(CFD) analysis enables the engineer to predict hemolysis on a computer Fluid dynamics in five different axial flow pumps was analyzed 3-dimensionally using CFD software. The impeller was rotated at a speed which supplied a flow of 5L/min at a pressure difference of 100mmHg. Changes in the turbulent kinetic energy along streamlines through the pumps were computed. Reynolds' shear stress( (equation omitted) ) was calculated using the turbulent kinetic energy. Hemolysis was evaluated based on Reynolds'shear stress and its exposure time(t) : dHb/Hb=3.62$\times$10$^{-5}$ $t^{0.785}$$\tau$$^{2.416}$ . Hemolysis of the pumps was measured in vitro using fresh bovine blood to which citrate phosphate dextrose was added to prevent clotting. A pump flow of 5L/min was maintained at a pressure difference of 100mmHg for 3h. The normalized index of hemolysis(NIH) as measured. Reynolds' shear stress was high behind the impellers. The measured NIH and the calculated hemolysis(dHb/Hb) shoed a good correlation; NIH=0.0003(dHb/Hb) (r=0.90, n=6) in the range of NIH between 0.003 and 1.1. CFD analysis can predict the in vitro results of hemolysis as well as the areas where hemolysis occurs.ysis occurs.

• 대한의용생체공학회:의공학회지
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• 제21권4호
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• pp.353-362
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• 2000

축류형 혈액펌프에서 발생하는 용혈이 이 펌프의 성공여부를 결정짓는 주요한 요인의 하나이다. 지금까지는 용혈을 알아내기 위해서는 in-vitro 적인 실험에 의하여 용혈량을 추정하였으나, 수치유체해석에 의한 용혈량의 추정이 가능하다고 생각된다. 따라서, 본 연구에서는 다양한 형태의 임펠러에 대하여, 난류모델은 k-$\varepsilon$모델을 사용하여 3차원 수치유체역학 해석을 시도하였다. 수치유체해석에 있어서는 펌프 유입측에 입자를 흘려 넣어 이 입자가 매일 10ms마다 받는 난류에너지를 구하여 전단응력으로 환산하였다. 해석결과 전단응력은 주로 임펠러의 후방에서 나타나는 것을 알 수 있었다. 수치유체해석결과의 신뢰성을 확인하기 위하여 임펠러의 in-vitro 실험에 의한 용혈시험 결과를 비교하였으나, 양자 사이에 상관도는 높은 것을 알 수 있었다. 상기한바와 같이 유체 해석에 의한 용혈 예측은 물론 용혈이 발생하는 주요 부위의 예측이 가능함을 시사하고 있어, 축류형 혈액펌프 개발시 용혈 특성 개선을 위한 설계도구로써의 유용함을 확인하였다.