Biomedical Engineering Reference
In-Depth Information
where P
max
= Maximum pressure exerted by air on the rotor, P
min
= Minimum
pressure exerted by air on the rotor, P
inlet
= Air pressure at the inlet. Maximum
pressure and minimum pressure exerted by air can be obtained by FLUENT.
Inlet pressure was used to non-dimensionalize the value of the pressure
coefficient.
3.
E
XPERIMENTAL
R
ESULTS AND
D
ISCUSSIONS
Flow topology and pressure variation of rotor geometries such as rotor
with 90-degree blade angle, rotor with inlets, inclined at 45 degree to the z-
axis of the rotor, and two-stage rotor are described and pressure coefficient
values for all geometries are calculated. The optimum design of the high-speed
spindle is identified based on the magnitude of the pressure coefficient.
3.1. Numerical Results
Numerical simulations of the spindle geometries were carried out using
FLUENT. Air was the ideal gas with an inlet pressure of 60 psi and an outlet
pressure of zero, and the rotor was considered to be at no-slip conditions at the
wall with specific rotational speeds such as half-million rpm, one million rpm,
etc. The total number of control volumes for the numerical grid was
approximately between 437,000 and 532,000 based on the geometry of the
rotor, and the number of iterations for numerical simulations was 200. The
maximum continuity loops are advantageous for achieving convergence
especially for high-speed flows and the value of maximum continuity loops
was specified as 2 for numerical simulations of all geometries under
consideration. The governing equations such as continuity equation,
momentum equation, energy equation, and equation of state were solved by
FLUENT to provide the pressure distribution on the rotor. The pressure values
were obtained using FLUENT and the pressure coefficient values were
calculated using Equation (9).
