3.1.1 Simplification of Engine Element for modeling
The following items are deliberated and examined for developing the model.
a. Crankshaft
Figure 7 shows the schematic model of crankshaft. To simplify the calculation, crankshaft is assumed as a straight series of connected beam. Stiffness of crankshaft has been approximately formulated, so the stiffness can be calculated with only main dimension of crankshaft.
Deformation of crankshaft due to torsional moment is considered in this model. The relation between deformation and torsional moment is also approximately formulated. The deformation is added at the middle of the shaft between two adjacent bearings with perpendicular direction to crank throw.
b. Bearing support
Stiffness of engine is determined by finite element analysis result in this study.
c. Lubrication of bearing
Figure 8 shows the schematic model of main bearing and bearing supports. In order to calculate journal center locus in bearing, mobility method (See by Booker [1]) is used for approximate solution of the Reynolds equation.
d. External Force on Crankshaft
As shown in figure 7, the forces acting on the crankshaft are as follows:
Centrifugal force of crank throw
Inertia force of reciprocating mass
Centrifugal force of rotating mass
Gas pressure force
Weight of shaft
3.1.2 Method for Numerical Calculation
a. Transfer Matrix Method
In order to calculate journal tilting angle and bearing load, the series of connected beam model is solved by the use of transfer matrix method.
Fig. 6 Schematic model of theoretical calculation
Fig. 7 Schematic model of crankshaft
Fig. 8 Schematic model of bearing and support
