Biomedical Engineering Reference
In-Depth Information
speeds of the rotor such as half-million rpm, one million rpm, two million rpm,
and five million rpm. The number of control volumes considered for the
numerical simulation of basic geometry of the rotor was 437,273; for the
numerical simulation of rotor with fillets it was 439,092; for the numerical
simulation of rotor with 70-degree blade angle it was 488,786 and for the
numerical simulation of rotor with 90-degree blade angle it was 520,324. The
residual target for the convergence criterion was specified as 1e-6 and the
maximum number of iterations considered for convergence control was 200
for the described geometries. The values of the non-dimensional pressure
coefficients obtained form the numerical simulations are shown in Table 1.
From Table 1 it is observed that for a particular geometry as the rotating
speed of the rotor increases, the pressure coefficient value increases because of
the variation of pressure values on the surface of the rotor. Figure 1 shows the
variation of pressure coefficient for the specified geometries with the
rotational speeds of the rotor. From Table 1 it can be said that the pressure
coefficient values of rotor with 90-degree blade angle are less than those of the
other geometries of the rotor for the rotational speeds of half-million, one-
million, and two-million rpm of the rotor which is in the typical range of
micromachining operations. For two million and five million rpm rotational
speed of rotor, the rotor with a 70-degree blade angle possessed pressure
coefficient values that were less when compared to other geometries of the
rotor. The geometry of the rotor with 90-degree blade angle was considered to
be the optimum design compared to other geometries of the rotor for the
rotational speeds that are in the typical range of micromachining conditions.
Modifications in the spindle geometry were conducted by changing the
number of blades of the rotor, changing the angle of the inlets, and by
changing the number of inlets and outlets for the fluid. Numerical simulations
of the rotor with twelve blades, rotor with three inlets inclined at an angle of
30 degrees, rotor with three inlets inclined at an angle of 45 degrees, and rotor
with three inlets and three outlets were carried out. The number of control
volumes associated with the numerical simulation of rotor with twelve blades
it was 467,311; with that of rotor with three inlets inclined at an angle of 30
degrees it was 513,116; with that of rotor with three inlets inclined at an angle
of 45 degrees it was 532,447 and with that of rotor with three inlets and three
outlets it was 509,288. The residual target for satisfying the convergence
criterion was specified as 1e-6 and the maximum number of iterations
specified for convergence control was 200. The pressure coefficient values
obtained for these geometries for different rotational speeds of the rotor are
shown in Table 2.
