## 4 Discussion and Analysis
### Performances of Friction Pairs with Single Texture Patterns  
#### 4.2.1 Friction Coefficient  
Figure 6 shows the tests of the three different single textures with triangular, elliptical, and conventional spiral grooves under 250 rpm. The friction coefficient range and average friction coefficient are listed in Table 6 for 2-B1, 2-B2, and 2-B3 groups under 200 rpm and 200 N. According to Figure 6 and Table 6, the average friction coefficient of the 2-B1 group (triangles) was only 0.060, which was much smaller than the friction coefficient (0.071) of the 1-A1 group at a rotational speed of 250 rpm shown in Figure 4. A more complicated change was presented by the friction coefficient of the 2-B2 group (ellipses), and the amplitude of the 2-B2 group was smaller than that of the 2-B1 group. This was because the edges of the ellipses were smoother than the edges of the triangles. However, the average friction coefficient of the 2-B2 group was 0.129, which was 82.46% higher than the friction coefficient of the 1-A1 group at the rotational speed of 250 rpm shown in Figure 4. A steady and the lowest variation amplitude was presented by the friction coefficient of the 2-B3 group (conventional spiral grooves) and the average friction coefficient of the 2-B3 group was 0.081. The differences in the friction coefficient due to the different textures could be attributed to the following three reasons: (1) Since the boundaries of the elliptical micro-dimples were smoother, as fluid entered the elliptical micro-dimples, the micro-dimples were filled with more fluid, so adding the film thickness. Meanwhile, negative pressure formed readily during the operating process, resulting in an insufficient hydrodynamic pressure effect of the elliptical texture and an inability to improve the operating state of the friction pairs; (2) A strong 'convergent wedge effect' was produced by the sharp regions of the triangular micro-dimples. In addition, the lubrication of the micro-gap fluid was improved because of obvious directionality of the triangles; (3) The conventional spiral groove texture was a micro-groove with a large area and a small density, which was the complete opposite of the characteristics of the triangular and elliptical micro-dimples, which had small areas and large densities. An evident Rayleigh step was formed by the  
Figure 5: Surface temperature of friction pairs with different materials under 100–300 rpm.  
conventional spiral grooves that offset part of the vortex the was formed by fluid backflow because of the longer fluid domain wall, thus a vibration suppression effect was created.  
From the above testing results, the following results can be concluded: (1) The average friction coefficient of the 2-B1 group (0.060) is smaller than that of the 1-A1 group (0.071), and the average friction coefficient of the 2-B2 group (0.129) is larger than that of the 1-A1 group; (2) For micro-dimple textures (triangular and elliptical), the shape is a key factor for affecting the tribological performance of a mechanical seal; (3) The effect of the micro-groove texture (conventional spiral grooves) is mainly reflected in the hydrodynamics, which can improve the stability of a mechanical seal.