Internal Flow Field Analysis And Structure Optimization Of Membrane Oxygenator Based On Hemolysis Estimation

Extracorporeal membrane oxygenation（ECMO）is an advanced life support method mainly used to treat critically ill patients requiring temporary or long-term cardiopulmonary support.At the same time,ECMO is also the ultimate means of life support in ICU,the"last straw"for critically ill patients,and the"last line of defense"for COVID-19 prevention and control.Membrane oxygenator,as the core component of ECMO,is widely used in the adjuvant treatment of respiratory and circulatory diseases.Membrane oxygenators are prone to produce hemolysis and thrombosis in clinical application.The formation of hemolysis and thrombosis will not only hinder the normal operation of membrane oxygenator,shorten the service life of membrane oxygenator,but also bring certain sequelae to patients,and even endanger their lives in serious cases.It is of great significance to study and analyze the flow characteristics of the fluid in the internal flow field of the membrane oxygenator for solving the blood damage problem of the membrane oxygenator and promoting the development of the oxygenator industry.Based on the pressure drop experiment,this paper uses computational fluid dynamics to carry out numerical simulation and hemolysis estimation of the membrane oxygenator,and explore the influence of the flow characteristics of the fluid in the internal flow field of the membrane oxygenator on blood damage.The local structural parameters of the membrane oxygenator are optimized by orthogonal test.The specific work and main conclusions are as follows:1)Firstly,the structure and working principle of membrane oxygenator are analyzed,and the necessity of numerical simulation of membrane oxygenator is illustrated.The solid model of membrane oxygenator was established and calculated,and the distribution of velocity,pressure,turbulence intensity and wall shear stress in the flow field were obtained.Through the qualitative analysis of the quantitative indicators in the flow field,the high incidence area of blood injury was determined.Finally,the accuracy of the numerical simulation results is verified by the pressure drop experiment of the membrane oxygenator.2)In the inlet flow range of 2.0～6.0 L/min,the membrane oxygenator was evaluated for hemolysis and thrombus.The range of standard hemolysis parameters was 0.00285～0.0129 g/100L,and the degree of platelet activation was 3.99×10^-8～6.32×10^-8;The degree of platelet activation is far less than 1,indicating that the membrane oxygenator has strong antithrombotic ability.Therefore,when studying the problem of blood damage,hemolysis is mainly used.3)Aiming at the problem of large blood damage in membrane oxygenation,the structure of the high-incidence area of blood damage in the flow field was optimized.The results show that optimizing the structure of the high-incidence area of blood damage can effectively improve the distribution of pressure,velocity,turbulence intensity,and wall shear stress in the flow field.Compared with the original structure,the maximum standard hemolysis parameter value is reduced by 64.88%,and the hemolysis performance of membrane oxygenator is significantly improved.At this time,the standard hemolysis parameter value ranges from 0.0095 to 0.00453 g/100L.This study reduces the damage of blood cells and improves the hemolysis performance of membrane oxygenator,which provides theoretical guidance for the development of new membrane oxygenator and improvement of blood damage of membrane oxygenator.