# Cost-Effective Design Modification of a Sleeve Bearing with Large Bearing Clearance
## 5 Conclusions  
The design modification employed on the LGB of the hydropower machine improved the dynamics of the system. Both experimental and simulation results showed that the redesigned LGB, i.e., the four-lobe bearing with lower bearing clearance, provided a stability advantage and reduced the overall vibration amplitudes. * The large bearing clearance of the original LGB allowed for greater shaft movement, resulted in the system's elevated overall vibration amplitudes, and subjected the UGB and TB to carrying relatively larger loads. * The design modification increased the second and third modes of the system above the 1X-synchronous line within the speed range, up to the runaway speed, and all the critical speeds were effectively eliminated. * For operation at the nominal speed with UMP, the design modification significantly increased the second and third modes by 73% and 423%, respectively. Similarly, the damping ratios of the first seven modes increased, except for the third mode, which decreased by 40%. However, the damped natural frequency of the third mode increased from 1.6 \(\times\)\(\Omega_{0}\) to 8.38 \(\times\)\(\Omega_{0}\) (i.e., 423% increment), and the vibration amplitudes at this frequency were much smaller and were insignificant to producing mechanical failure. * Furthermore, the simulated unbalance responses were reduced by 29%, 66%, and 7% at the UGB and LGB locations, respectively. In the field measurement, the peak-to-peak amplitudes at the three bearing locations were reduced by 35%, 67%, and 47%, respectively. \begin{table}
\begin{tabular}{l c c c c c c} \hline \multirow{2}{*}{**Cases**} & \multicolumn{2}{c}{**UGB**} & \multicolumn{2}{c}{**LGB**} & \multicolumn{2}{c}{**TB**} \\ \cline{2-7}  & **X (mm)** & **Y (mm)** & **X (mm)** & **Y (mm)** & **X (mm)** & **Y (mm)** \\ \hline \multirow{2}{*}{0 MW 0 kV} & 0.02 & 0.02 & \(<\)0.01 & \(<\)0.01 & \(<\)0.01 & \(<\)0.01 \\  & (0.01) & (0.01) & (0.01) & (0.01) & (0.01) & (0.01) \\ \hline \multirow{2}{*}{0 MW 12.4 kV} & 0.025 & 0.02 & 0.03 & 0.03 & \(<\)0.01 & \(<\)0.01 \\  & (0.075) & (0.07) & (0.01) & (0.01) & (0.01) & (0.01) \\ \hline \multirow{2}{*}{13 MW} & 0.03 & 0.025 & 0.03 & 0.03 & \(<\)0.01 & \(<\)0.01 \\  & (0.07) & (0.07) & (0.02) & (0.02) & (0.02) & (0.02) \\ \hline \multirow{2}{*}{26 MW} & 0.025 & 0.02 & 0.03 & 0.03 & \(<\)0.01 & \(<\)0.01 \\  & (0.065) & (0.06) & (0.015) & (0.015) & (0.015) & (0.015) \\ \hline \multirow{2}{*}{38 MW} & 0.03 & 0.02 & 0.025 & 0.025 & \(<\)0.01 & \(<\)0.01 \\  & (0.06) & (0.055) & (0.015) & (0.015) & (0.01) & (0.01) \\ \hline \multirow{2}{*}{52 MW} & 0.02 & 0.02 & 0.025 & 0.025 & \(<\)0.01 & \(<\)0.01 \\  & (0.06) & (0.06) & (0.01) & (0.01) & (0.01) & (0.01) \\ \hline \end{tabular}
\end{table} 
Table 6: Summary of peak-to-peak amplitudes of MMB (\(C_{b}\) = 0.45 mm) at the three bearing housing locations. Values in parentheses show results from the MMO (\(C_{b}\) = 1.6 mm). \begin{table}
\begin{tabular}{l|c c c c c c} \hline \multirow{2}{*}{**Cases**} & \multicolumn{2}{c}{**UGB**} & \multicolumn{2}{c}{**LGB**} & \multicolumn{2}{c}{**TB**} \\ \cline{2-7}  & **X (mm)** & **Y (mm)** & **X (mm)** & **Y (mm)** & **X (mm)** & **Y (mm)** \\ \hline
0 MW 0 kV & 0.11 (0.13) & 0.12 (0.12) & 0.1 (0.2) & 0.1 (0.2) & 0.04 (0.11) & 0.04 (0.11) \\ \hline
0 MW 12.4 kV & 0.23 (0.36) & 0.23 (0.35) & 0.3 (0.92) & 0.3 (0.92) & 0.15 (0.29) & 0.15 (0.28) \\ \hline
13 MW & 0.23 (0.36) & 0.22 (0.36) & 0.31 (0.91) & 0.3 (0.91) & 0.1 (0.29) & 0.1 (0.29) \\ \hline
26 MW & 0.21 (0.33) & 0.21 (0.33) & 0.3 (0.82) & 0.29 (0.82) & 0.04 (0.25) & 0.04 (0.24) \\ \hline
38 MW & 0.2 (0.32) & 0.2 (0.31) & 0.29 (0.82) & 0.29 (0.81) & 0.04 (0.19) & 0.04 (0.18) \\ \hline
52 MW & 0.19 (0.33) & 0.19 (0.32) & 0.28 (0.83) & 0.26 (0.82) & 0.04 (0.15) & 0.04 (0.14) \\ \hline \end{tabular}
\end{table} 
Table 5: Summary of peak-to-peak amplitudes of MMB (\(C_{b}\) = 0.45 mm) at the three bearing locations. Values in parentheses show results from the MMO (\(C_{b}\) = 1.6 mm). **Author Contributions:** Conceptualization, G.B.B., J.-O.A. and R.G.