# Structural Design and Optimization of Herringbone Grooved Journal Bearings Considering Turbulent
## 3 Results
### The Influence of the Number of Grooves on the Performance of HGJBs  
The number of grooves has a direct effect on the amount of lubricating oil storage, the number of pumping effects and step effects, and the stiffness of the bearings. We kept other parameters unchanged, took the number of grooves as 5, 8, 12, 15, 20, and 25; and analyzed the influence of the number of grooves on the performance of bearings with different structures as shown in Figure 15.  
Figure 15: _Cont._  
Figure 15 shows that when the number of grooves is small, as the number of grooves increases, the bearing load capacity of the oil film gradually increases. This is because when the number of grooves is small, the stepped dynamic pressure effect of the bearing is smaller, so the bearing load capacity is small; when the number of grooves gradually increases, the stepped dynamic pressure effect increases, so the bearing load capacity gradually increases. When the number of grooves is large, the pumping effect of the bearing reaches saturation, and the bearing load capacity remains basically unchanged at this time. When the number of grooves is 20, the bearing load capacity of the constant-width HGJBs reaches the maximum. Since the wedge effect is more pronounced in convergent HGJBs, the number of grooves corresponding to its maximum bearing load capacity is larger. The calculated number of grooves corresponding to the maximum bearing load capacity of the convergent HGJBs is 30. With the increase in the number of grooves, the bearing side leakage and friction power also show an increasing trend, and the average temperature rise of the bearing gradually decreases and tends to be flat. But the changes are not big. When the eccentricity is 0.5, the maximum friction power of the convergent HGJBs is 6.43% larger than the minimum friction power, and the maximum friction power of the constant-width HGJBs is 0.12% larger than the minimum friction power. In terms of friction, the number of grooves has a more significant influence on the convergent HGJBs.  
As the number of grooves increases, the stiffness and damping coefficients of the two bearings first increase and then gradually decrease. The larger the number of grooves, the faster the stiffness coefficient and damping coefficient decrease. This is because when the number of grooves is small, the pressure is relatively concentrated, and there is basically only one peak point. The pressure distribution before and after the peak point decreases sharply, and the stability is poor; when there are more grooves, the width of the ridge decreases, and the excessive shear stress of the local groove root causes the stiffness coefficient to decrease. At the same time, due to the pumping effect, the bearing pressure distribution is more concentrated, and the pressure distribution range is small, and the stability is worse. Compared with constant-width HGJBs, the stiffness and damping coefficients of convergent HGJBs are much larger. When the number of grooves is 20, the stiffness coefficient and damping coefficient of the convergent HGJBs are the largest. Because an increase in the number of grooves will increase the difficulty and cost of bearing processing, it is recommended that the number of convergent HGJBs be 15-20 and the number of constant-width HGJBs be 8-12 within the allowable range of processing.  
Figure 15: The influence of the number of grooves on the performance of HGJBs: (**a**) Dimensionless load capacity (**b**) Side leakage (**c**) Dimensionless friction power (**d**) Average temperature rise (**e**) Dimensionless principal stiffness (**f**) Dimensionless principal damping.