# Design Approach and Mechanism Analysis for Cavitation-Tolerant Torque Converter Blades
## 5 Conclusions  
Transient simulation and hydrodynamic performance prediction of the three-dimensional cavitation flow field of an HTC are conducted and verified through experiments. To suppress the stator cavitation, we propose the use of two types of cavitation suppression slots (Plan 1 and Plans 2-4) in the blade profile design of the stator cascade. The suppression effects of slot width and slot position on the stator cavitation are investigated and compared. The following conclusions are drawn:  
1. Simulation of the HTC cavitation flow field shows that cavitation mainly occurs in the leading edge of the suction side of the turbine and the stator, and the stator cavitation is severe. The mass flow rate of the torque converter at low \(SR\)s is very large. Hence, the suction side of the blade has a very low local pressure, which is the main reason that the cavitation of the torque converter mainly occurs at \(SR\) = 0, 0.1, 0.2, and 0.3. The stator cavitation is classified as unstable shedding cavitation, and there are periodic processes of cavitation inception, development, shedding, and collapse. The turbine cavitation is a stably attached cavitation. 2. According to the calculation and comparison of the cavitation flow field of the slotted stator, the method of slotting both the pressure and suction sides (Plan 1) is not as effective as the method of slotting the suction side (Plans 2-4) in suppressing the stator cavitation. The slot width and slot position play an essential role in the suppression of the stator cavitation. First, the most effective slot position lies between S0.15 and S0.6 on the stator blade suction side, and the stator cavitation can be suppressed completely. Second, when the slot width reaches 2 mm, the stator cavitation can be fully suppressed. However, the suppression effect of the slot width on the stator cavitation is not as good as the suppression effect of the slot position. 3. As for the method of slotting both the pressure and suction sides, when the position of the slot entrance (blade pressure side) is fixed, the closer the slot exit (blade suction  
Figure 15: Effect of slot position on \(T_{\text{bg0}}\) and stator vapor volume (slot width = 2 mm). side) to the leading edge of the blade suction side, the better the cavitation suppression effect of the stator. For the method of slotting one side of the suction side, when the position of the slot exit (blade suction side) is fixed (S0.15), the position of the slot entrance (blade suction side) has the same effect on the cavitation suppression of the stator, which can almost completely suppress the stator cavitation. The larger the slot width, the better the cavitation suppression effect of the stator, but it will severely compromise the hydrodynamic performance of the torque converter. Ideally, the slot width should not exceed 2 mm. The slotted stator blades will seriously affect the hydrodynamic performance of a torque converter. [PERSON] and [PERSON] proposed that the parametric design and sensitivity analysis of a geometric contour curve with a B-spline can effectively improve the smoothness and design efficiency of the curve [29]. [PERSON] et al. verified the influence of the initial population sampling on the convergence of advanced optimization algorithms such as MOGA-II and NSGA-II and concluded that a reasonable distribution of the initial population sampling can speed up the convergence of the optimization algorithm [30]. In addition, the Kriging model has prominent advantages in constructing the surrogate model with multiple independent variables and objective functions. [PERSON] et al. optimized the diffuser's contoured cavities using Bezier curves to maximize pressure recovery and minimize flow separation, thereby achieving key hydrodynamic performance indicators such as improving diffuser efficiency [31; 32].