# Design Approach and Mechanism Analysis for Cavitation-Tolerant Torque Converter Blades
###### Abstract  
As the development of hydrodynamic torque converters (HTCs) points toward increasing the pump input power and pump rotation speed, the negative effects of cavitation are worsening. Most studies focus on suppressing fluid machinery cavitation to attenuate the negative effects of cavitation, such as noise, vibration, and blade damage. Therefore, we proposed two stator cavitation suppression slotting methods to suppress stator cavitation in HTCs: (1) slotting both sides of the pressure and suction sides and (2) slotting one side of the suction side. The key design parameters are analyzed, including the slot width and slot position of the stator blade. Findings show that a wider slot enlarges the mass flow rate ventilation through the slot, thus reducing the cavitation risk but decreasing the hydrodynamic performance. The most effective slot position for the second proposed method (slotting one side of the suction side) is between S0.15 (stator suction side dimensionless distance 0.15 location) and S0.6 (stator blade suction side); here, the stator cavitation can be suppressed completely. The capacity factor (\(T_{\text{bg}}\)) and torque ratio (\(K\)) are decreased by 6.81% and 3.23%, respectively, under the stalling speed ratio, whereas the stator cavitation almost completely disappears. Therefore, the new method of slotting one side of the stator suction side completely suppresses the stator cavitation and significantly shortens the cavitation duration. The new method of slotting one side of the blade suction side can serve as a reference for turbomachinery design. hydrodynamic torque converter; stator cavitation; suppression slot; hydrodynamic performance; cavitation duration +
Footnote †: journal: Applied sciences  
an equal-width straight slot, which allowed flow ventilation from the pressure side to the suction side of the blade [4; 5; 6]. They concluded that the slot width and slot slope greatly influenced the lift coefficient of the wind turbine blades. [PERSON] added segmented blades to an HTC turbine; the blades were inspired by the wing design and could effectively improve the stall capacity factor (\(T_{\text{bg0}}\)) and the stall torque ratio (\(K_{0}\)) [7]. Flow control technology has also been widely used to suppress cavitation in fluid machinery, as shown in Figure 1. Amromin processed local cavities on the leading edge of a hydrofoil suction side to regulate the pressure distribution therein and thus suppress cavitation [8]. [PERSON] investigated the mechanism of cloud cavitation and found that unstable shedding cavitation could be controlled effectively by continuous tangential liquid injection at different flow rates on the suction side of a hydrofoil [9]. [PERSON] and [PERSON] placed obstacles and an artificial cavitation bubble generator on the suction side of a hydrofoil to suppress the unstable cavitation caused by the re-entrant jet [10; 11]. [PERSON] examined the influence of the blade profile on the development of stator cavitation and proposed a blade profile design to reduce cavitation and improve hydrodynamic performance [12; 13]. According to [PERSON], a slot enabling flow ventilation from the nose to the suction side could alleviate the unstable cavitation behavior on the surface of a hydrofoil [14]. In the study of [PERSON], \"J grooves\" were added to the casing wall near the blade tip of an inducer; this design almost fully suppressed the cavitation surge under low flow rates [15]. [PERSON] proposed the placement of a flexible thread at the tip of a propeller, which could greatly suppress the generation of vortex cavitation at the propeller tip [16]. Slotted designs have a significant effect on suppressing fluid machinery cavitation. Therefore, the mechanism of fluid control technology in cavitation suppression should be understood, and effective fluid control technology solutions should be developed. Previous researchers mostly focused on the traditional slotting method, which allows fluid intake on the pressure side and fluid ejection on the suction side of the blade.