For our analysis of the
Eaton Roots-type supercharger, we limited ourselves to a thermal
analysis of the housing. The M90 was determined to have certain
errors that, while they did not show as free surfaces, did kill
any attempt to analyze effectively as a free surface. The M62 did
not have this problem, so we analyzed it, and based on that analysis
have made some recommendations to improve the design.
We determined that our
model was too detailed for the analysis that we wanted to do when
we received errors trying to mesh the volume. We simplified the
model to a featureless, semi-cylindrical box, with a trapezoidal
box attached. The semi-cylinder had two overlapping circular holes
for the rotors, while the trapezoid had a circular opening in the
endplate that tapered to a cylinder where it met the rotor holes.
The base plate was modified only in that the bolt holes were plugged,
as would be done in an actual mounting. The simplified model is
The bottom surface was
constrained to 120° Celsius (250° Fahrenheit), the intake
(the hole in the trapezoid) to 36° C/ 97° F, and the other
surfaces exposed directly to the engine bay were set at 76°
C/169° F. Surfaces exposed to the engine bay that shared an
edge with the bottom mounting plate were left unconstrained.
The model was meshed
with a four-node tetragonal mesh, with nodes set at 10 mm apart.
We thought that would provide a good balance between a finer, more
accurate mesh versus leaving enough memory to compute the necessary
matrix. If anything, we erred on the side of caution, having run
out of memory several dozen times during this project, once nearly
fatally for the model.
The maximum temperature
experienced by the model was 120° C, and the minimum was 38°
C. These happened in the expected places-the bottom of the housing
and the inner wall of the intake respectively. The most severe gradient
was where the intake had its nearest approach to the base of the
housing, and that too is to be expected. The separation is small,
and the temperature goes from its highest value to its lowest in
the space of a handful of centimeters. Alleviating this temperature
gradient was the basis of our recommendations.
We suggest that in order
to boost the performance of the Eaton M62 Roots blower, that an
independent water jacket be added to the system, to be mounted between
the housing and the engine block. This would not only cool the housing,
but could also serve as an intercooler for the air fed to the engine
from the supercharger. Failing that, a spacer could be used to reduce
the heat flux from the engine and hence lower the temperature of
the lower surface of the supercharger housing, thus limiting the
temperature gradient experienced near the intake.
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