## 3 Results
### Cooperation of the RL Agents and GA  
The GA process was integrated into the RL framework as one kind of MDP step. Case 1, as shown in Figure 12, obtained a significant efficiency improvement, but the pressure ratio was lower than that of the reference. The agent trained as described in Section 3.1 provided a way to directly improve the pressure ratio by directly modifying the design variables of the case 1 rotor.  
Figure 12: Operating characteristics of selected individuals. (**a**) Flow-pressure ratio. (**b**) Flow efficiency.  
Figure 13 showed the operation characteristics of the modified rotors, in which the pressure ratio increased incrementally, and the efficiency declined slightly. After 12 steps, the rotor gained a pressure ratio equal to the reference for almost all mass flows, and a higher efficiency was also maintained. The chock mass flow rate of the GA case 1 rotor was less than the reference, and the agent also improved the chock mass flow rate of the modified agents.  
The variations in the near-peak efficiency performance metrics \(\pi_{W}\) and \(\eta_{W}\) were plotted in Figure 14. The performance of different rotors at the same mass flow rate \(\dot{m}_{W,0}\) was also considered, where \(\dot{m}_{W,0}\) was the peak efficiency mass flow rate of the reference rotor. The parameters \(\pi_{W,0}\) and \(\eta_{W,0}\) denoted the pressure ratio and efficiency of the reference rotor at \(\dot{m}_{W,0}\), respectively. The pressure ratio at \(\dot{m}_{W,0}\) raised by approximately 0.52% from the GA case 1 result. The efficiency at \(\dot{m}_{W,0}\) became higher than \(\pi_{W,0}\) after modification by the agent, and the \(\pi\) at near-peak efficiency also improved. The pressure ratio was found to be further increased when agent modification was conducted over additional steps.  
The variations in the geometric parameters \(m,\theta,\chi_{in},\chi_{out}\), and \(\beta_{y}\) through the spanwise direction were shown in Figure 15. A combined sweep feature was introduced in GA case 1,  
Figure 14: Performance variation during modification.  
Figure 13: Operation characteristics of the modified rotors. (**a**) Flow-pressure ratio. (**b**) Flow efficiency.  
and the rotor swept forward over most of the span and swept back at the tip region. The agent reduced the amplitude of the sweep feature in both forward and backward directions. Case 1 also acquired a blade lean feature with negative \(d\theta\), and the agent diminished this feature. The agent also changed \(\chi_{in}\) and \(\chi_{out}\), so the airfoil segment angle \(\Delta\beta\) rose at the tip and decreased at the hub relative to the GA case. The parameter \(\beta_{y}\) improved at all spans in case 1 and was diminished by the agent, especially at the tip and hub. Rotors were also plotted in \(Z-R\) and \(Z-\theta r\) surfaces as shown in Figure 16, where the parameter variations showed its effect on the rotor geometries.  
Figure 16: Rotors in \(Z-R\) and \(Z-\theta r\) surface.  
Figure 15: Geometry variation distribution of the span after cooperation: (**a**) meridional coordinate, (**b**) tangential direction, (**c**) inlet camber angle, (**d**) outlet camber angle, and (**e**) incidence angle.