PhDThe physiological and clinical considerations of centrifugal and axial pumps as ven-
tricular assist devices (VADs) demands limitations on the power, size and geometry
of the impellers. A typical pump design method is to rely on the characteristics
of previously designed pumps with known performance using empirical equations
and nondimensional parameters based on
uid dynamics similarity law. Such data
are widely available for industrial pumps operating in Reynolds number region of
108. VADs operate in Re<106 and therefore the similarity concept does not apply
between the industrial diagrams and the medical application of small pumps.
The present dissertation employs a parametric approached analytical model to in-
vestigate more than 150 axial and centrifugal pumps. The design parameters are
optimised using the response surface methodology. The effect of different design
parameters on the performance, force analysis and hemocompatibility of the pumps
is thoroughly investigated by modelling the haemolysis through a power-law equation. The results show an explicit and consistent relationship between the number of
blades, outlet width, outlet angle and the hemocompatibility of the device. Centrifu-
gal pumps showed signi cantly lower probability of blood complications compared
to axial pumps. The evaluation of the design characteristics helps pump designers
to select their parameters accordingly for a low probability of blood complications.
Furthermore, experimental techniques are employed to test more than 70 pumps in
different conditions of flow, pressure and rotational speed. The experimental results
validate the numerical simulations and create a database of empirical equations and
data points for small axial and centrifugal pumps. The specifi c speed and speci fic
diameters of the pumps are plotted on an ns − ds diagram to enable preliminary
design of small pumps for VADs suitable for different stages of congestive heart
failure (CHF)
