Parametric design method for a hydrodynamic torque converter and its hydrodynamic-cavitation characteristics analysis

Abstract

As a fluid transmission device, the hydrodynamic torque converter (HTC) achieves flexible transmission through energy conversion between impeller cascades and fluid. High-speed, high-power operating conditions and highly twisted cascade systems lead to highly developed three-dimensional (3D) turbulence and intense cavitating phase-change flow inside the HTC. Thus, improving hydrodynamic performance and suppressing cavitation have become key aspects of high-performance HTC design. The turbine blade, the most twisted one in the cascade system, largely determines the fluid flow direction in the HTC. Based on this, this paper investigates the effects and control mechanisms of key turbine blade parameters on HTC cavitation and hydrodynamic performance. First, it proposes to adopt catenary and cycloid curves for turbine blade parametric design, deriving the relationship between blade control parameters (leading/trailing edge angles, peak position and height of the camber line, peak position and height of blade thickness) and the two curves. Then, it analyzes the impacts of turbine camber line parameters (deflection angle, peak position and height of turbine camber line) on HTC hydrodynamic and cavitation performance. Finally, it clarifies the regulatory mechanisms of these key parameters from the perspective of the internal flow field. Results show that increasing the camber line peak position and height reduces the stall torque ratio ( TR 0 ), pump torque coefficient ( λ B0 ) and cavitation volume of the HTC. This is because the change induces significant flow separation at the turbine leading edge and stator suction side, elevates local static pressure, reduces meridional velocity and pump inlet-outlet dynamic pressure increment, and finally decreases TR 0 and λ B0 while effectively suppressing HTC cavitation. In addition, the increase of the deflection angle of the camber line will lead to the suppression of cavitation. The proposed turbine blade parametric design and cavitation suppression method provide a reference for high-performance turbomachinery design.