2.2.1 No.1 Main Bearing
As shown in Figure 5 (a), journal in No. 1 bearing moves widely along the lower part of the bearing between starboard and port side. Journal center locus of aft side in the bearing moves towards bottom as compared with locus of fore side. Consequently, the journal of aft side in the bearing is tilting towards bottom, and the journal of fore side is tilting towards top.
Eccentricity of aft side in vertical direction towards the bottom is the largest at 0 deg of crank angle in one cycle of crank rotation. It shows that gas pressure force by combustion of No. 1 cylinder is greater than centrifugal force of No.1 crank throw.
2.2.2 No.2 Main Bearing
As shown in figure 5 (b), journal center locus in No.2 bearing is smaller than the locus in No. 1 bearing. The journal moves near the bottom of the bearing. Eccentricity of fore side of journal in vertical direction towards bottom is the largest at 0 deg of crank angle. The locus of aft side is the largest at 103 deg. It shows that the gas pressure forces by combustion both of No. 1 and of No.2 cylinder influence on minimum oil film thickness.
2.2.3 No.4 Main Bearing
As shown in figure 5 (c), journal in No.4 bearing moves widely along the lower part of the bearing between starboard and port side. Journal center loci at both ends are similar to each other, expect at 206 deg and 257 deg of crank angle, where those angles are the combustion of No.4 and No.3 cylinder, respectively.
Eccentricity at 309 deg to at 154 deg is distant locus from the center of bearing in one cycle. Because of sequential firing, centrifugal force of crank throw is the sum of No.3 and No.4 crank throw, so the force has greater influence on the bearing than others. It shows that the centrifugal force of crank throw influences on minimum oil film thickness.
2.2.4 No.8 Main Bearing
As shown in figure 5 (d), journal in No.8 bearing moves circular along the bearing clearance. Only at 51 deg of crank angle, combustion of No.7 cylinder influences on the locus.
While the journal moves along the lower part of bearing, journal center locus of fore side moves towards bottom of the bearing clearance as compared with the locus of aft side. It shows that centrifugal force of No.7 crank throw and tension of chain in aft side of No.8 bearing influence on minimum film thickness.
These results are utilized to evaluate the validity of theoretical calculation as follow section.
3. THEORETICAL CALCULATION
3.1 Theoretical Calculation Model
In order to simulate journal movement behavior, theoretical calculation model has been developed. Figure 6 shows the schematic model of theoretical calculation. Strong point of this model is that journal movement behavior in each bearing under initial uneven alignment condition can be calculated simultaneously in very short calculating time.
Fig. 5 Journal center loci by measurement
