Research On Heat Dissipation Of Traveling-wave Ultrasonic Motor Driven Pulsatile Blood Pump

The pulsatile blood pumps(BPs)work like the native heart,generate normal pulsatile hemodynamics,and thus provide excellent unloading for the ventricle.Currentlly,using the circulation assist by pulsatile BP as a therapeutic treatment for myocardial recovery has become a research hotspot in the field of cardiovascular medicine.However,the pulsatile BPs utilize the electromagnetic motors as the actuators,and have large pump sizes,which seriously restricts them in the clinical applications.This is because too large pump size will influence patient's quality of life and postoperative recovery,and especially used in implantation treatment,becomes a contraindication for patients with a small body surface.Over tranditional electromagnetic motors,traveling-wave ultrasonic motors(TUSMs)have advantages of high output power density,approaching-heart-beat rotation speed,and fast response,which present a good promise as the actuators of pulsatile BPs for reducing the pump size.However,the working temperature rise caused by heat generation in TUSMs has a significant influence on the motor characteristics,and results in substantial degradation of output performance and operational reliability,which is the major technical challenge preventing TUSMs from practical application.Therefore,how to maintain the output characteristics of TUSM in the long-time work mode becomes the primary issue for developing the TUSM driven pulsatile BP(TUSM BP).To yield continuous high-performance motor output of TUSM,this paper proposes to address the issue of motion stability of TUSM by cooling method.Then,two cooling solutions are designed for in vitro and in vivo circulation assistant modes,respectively,aiming to achieve a pulsatile BP with smaller pump size and sufficient pump output for circulation assist.This paper deals with the research on heat dissipation of TUSM BP,including main contents as follows:1.The heat generation mechanisms of TUSM are analyzed,and a theoretical model of the motor temperature rise is developed.Through finite element simulation and performance test of TUSM,how the working temperature rise influencing the motor output is analyzed and verified.Then,the cooling method is proposed to overcome with the problem of motor temperature rise,and the design scheme of water cooling is determined.Feasibility and effectiveness of water cooling are verified through theoretical analysis and experimental test of the prototype motor,respectively.2.The dynamic model of TUSM BP is built.Using finite element method,the temperature field of TUSM BP is analyzed to quantify the effect of motor temperature rise on the pump output.The design scheme of water cooling is utilized to enhance the pump output by suppressing the motor temperature rise.The prototype TUSM BP with water cooling is fabricated and its hydraulic performance is tested by connecting to a mock circulation loop,which preliminarily shows TUSM BP meets the requirements for systemic circulation assist.3.TUSM BP cooled by the circulation blood is proposed to deal with the heat dissipation when TUSM BP is used for implantation treatment.The cooling structure of TUSM BP is designed based on heat transfer of heat pipe,and the temperature field analysis demonstrates that the design of heat pipe for TUSM BP would satisfy the requirement of motor temperature rise for the pump output.The prototype TUSM BP with heat pipes is fabricated,and the feasibility of heat-pipe TUSM BP is preliminarily verified by experiments.