Analysis

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.

1: Model

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 shown below.

2: Constraints

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.

3: Mesh

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.

4: Results

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.

5: 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.

(Click for a larger image)