# Structural Design and Optimization of Herringbone Grooved Journal Bearings Considering Turbulent
## 3 Results
### Performance Comparison of Bearings with Different Structures  
We kept other parameters unchanged, changed the eccentricity from 0.1 to 0.8, and analyzed the changes in the static and dynamic performance of the convergent HGJBs and constant-width HGJBs, as shown in Figure 14.  
Figure 14: _Cont._  
Figure 13: Comparison of two bearing oil film thickness and pressure: (**a,b,e,f**) are the calculation results of the constant—width HGJBs; (**c,d,g,h**) are the calculation results of the convergent HGJBs.  
Figure 14 shows that the bearing load capacity increases with the increase of eccentricity. Increasing the eccentricity makes the minimum oil film thickness of the bearing smaller, and the wedge effect is more significant, so the bearing load capacity increases. Under large eccentricity, the oil film thickness is of smaller order of magnitude. As the eccentricity increases, a smaller thickness change will have a greater impact on the oil film pressure. When the eccentricity changes from 0.6 to 0.8, the bearing load capacity of the convergent HGJBs increases by 86.25%. Since the groove of the convergent HGJBs also changes in the width direction, the lubricating oil flows from the wide port to the narrow port, resulting in a greater wedge effect. Under small eccentricity, the bearing load capacity difference between convergent HGJBs and constant-width HGJBs is small, and under large eccentricity, the performance difference between the two is larger. When the eccentricity is 0.8, the bearing load capacity of the convergent HGJBs is 87.76% larger than that of the constant-width HGJBs.  
With the increase of eccentricity, the minimum oil film thickness decreases, and the pressure gradient increases, which leads to an increase in bearing side leakage. The friction power increases with the increase of eccentricity, so that the average temperature rise of the bearing also increases. Compared with the constant-width HGJBs, the groove shape of the convergent HGJBs is in a convergent state, resulting in a smaller herringbone groove area and a smaller overall oil film thickness. Therefore, its lubricating oil reserve is less, resulting in convergent HGJBs having smaller side leakage and greater friction power resistance. When the eccentricity is 0.5, the side leakage is 4.83% smaller than that of the constant-width HGJBs, which causes the average temperature rise to increase. But it can be seen from the Figure 11 that there is not much difference between the side leakage and the average temperature rise between the both.  
Figure 14: Comparison of two bearing static performance and dynamic performance: (**a**) Dimensionless load capacity (**b**) Side leakage (**c**) Dimensionless friction power (**d**) Average temperature rise (**e**) Dimensionless principal stiffness (**f**) Dimensionless principal damping.  
Stiffness and damping coefficients are important indicators to measure the stability of the bearing. With the increase of eccentricity, the stiffness and damping coefficients of the bearing basically keep increasing. When the eccentricity is small, the increase is slower, and when the eccentricity is large, the increase in the stiffness and damping coefficients is larger in both. Compared with the constant-width HGJBs, the convergent HGJBs has larger stiffness and damping coefficients. When the eccentricity is 0.8, the stiffness of the convergent HGJBs is about four times that of the constant-width HGJBs. Therefore, the optimized convergent HGJBs has larger load capacity and dynamic performance. Although the temperature rise has increased, the amplitude is not large and belongs to the controllable range.