## 5 Discussion
### Numerical Simulation Analysis of Single-Phase Flow Field in the Gearbox
#### 5.1.2 Analysis of Gas Field Pressure Under Different Gear Pitch Cone Angles and Speeds  
Figure 17 illustrates the pressure contour plots of the flow field at observation planes 1 and 2 under different gear pitch cone angles and rotational speeds. The analysis reveals that during the high-speed rotation of gears, the pressure in the engagement-in side area is significantly higher than that in the engagement-outside area, with the flow field pressure reaching its maximum near the engaged gear teeth. Notably, the rotation of the gears has relatively minor effects on the flow field pressure in areas far from the gear engagement zone. In longitudinal analysis, when the gear pitch cone angle remains constant, the internal air pressure of the gearbox gradually increases with the increase in gear speed, especially in the engagement-in side area. This is due to the increase in edge speed induced by higher gear speeds, leading to faster airflow velocity. The high-speed movement of gears results in a decrease in local static pressure and an increase in dynamic pressure, thereby raising the air pressure in this region. On the other hand, with a constant gear speed, the internal air pressure of the gearbox tends to decrease as the gear pitch cone angle increases, particularly in the engagement-in side area. This phenomenon can be attributed to smaller pitch cone angles allowing larger tooth-to-tooth gaps, thus promoting free airflow and reducing the obstruction and acceleration of airflow by the gears, and thereby leading to a decrease in dynamic pressure above the engagement-in side and ultimately causing a decline in overall air pressure.  
Figure 16: Cloud maps of gas field velocity at observation surface 1 and observation surface 2 under different gear pitch angles and rotational speeds.  
Figure 18 provides a detailed description of the pressure and velocity changes in the meshing area at different gear pitch angles as the gear speed varies. Specifically, the data in the figure come from the average pressure and velocity values measured at the three monitoring points in Figure 8. Analysis shows that as the gear speed gradually increases, the pressure on the meshing side of the gear significantly increases at various pitch angles. This phenomenon can be attributed to the higher contact frequency and more frequent impact caused by the increase in gear speed, resulting in higher pressure in the contact area.  
Figure 17: Gas field pressure cloud maps at observation surface 1 and observation surface 2 under different gear pitch cone angles and speed conditions.  
Figure 18: The law of the variation in meshing area pressure with gear speed under different gear pitch cone angle conditions.  
Interestingly, the pressure in the joint area is significantly lower at 4\({}^{\circ}\) and 2\({}^{\circ}\) pitch cone angles than at 0\({}^{\circ}\) pitch cone angles. This may be due to the smaller pitch cone angle causing changes in the gear contact line, thereby reducing stress concentration in the contact area. In addition, as the cone angle gradually increases, the pressure in the joint area shows a significant downward trend. This trend may be due to the increase in cone angle, which leads to a more uniform distribution of contact surfaces, thereby dispersing local pressure and reducing stress concentration in the contact area.