Méthodologie de design de turbomachines de petite taille appliquée au développement d'une pompe d'assistance cardiaque

Abstract

This thesis presents a new design methodology for small size turbomachinery, applied to the development of a ventricular assist blood pump (VAD).

A review of mechanical circulatory support systems allows to identify the suitable one for our application, which is a rotary pump with continuous flow. The choice of a mixed topology for the latter is given with the assistance of the characteristic parameters of pumps, Ns and Ds, evaluated at the point of operation, that is 5 l/min against 100 mmHg.

The rotor produces the sought effect of pumping, it is thus significant and we make an exhaustive analysis of it in order to understand it better. With this intention, the geometrical parameters of the rotor are studied through variations, determined by a Design of Experiment.

The implementation of each experiment follows a well defined procedure of resolution.

Then we apply this methodology to the conception of the prototype V of Cardianove Inc. It is noted that this prototype presents a mixed topology. The rotor design depends on nondimensional geometrical parameters: D1/D2, L1/D2, h1/D2, i2/D2, α_inlet, α_outlet/α _inlet. The execution of the DOE through the use of Cordier algorithm, makes it possible to generate response surfaces for three response variables: the hydraulic efficiency η, the rotation speed N and the diameter D. One then seeks the optimum parameter configuration in order to obtain a pump maximizing simultaneously the efficiency and the diameter while minimizing the rotation speed. The responses are strongly influenced by the following factors: α _outlet/α_inlet, h1/D2, L1/D2 and α_inlet. One can thus conclude that the factors D1/D2 and i2/D2 have little influence on the process. The optimal geometry is validated using numerical simulations, then again subjected to the Cordier algorithm in order to have a pump operating with the best performance at the nominal point of operation. One thus obtains a pump of internal diameter of 8.06 mm having an efficiency of 37.5%, at a rotation speed of 1200 rad/s. We conclude with the methodology validation through experimental inquiries on the hydraulic and hemolysis performance of the prototype V. The hydraulic performance behaves as well as numerically, while the hemolysis index obtained suggests the need of design modifications in order to improve it. (Abstract shortened by UMI.)