The influence of streamline bending inertia force on power loss is investigated.In order to analyze the combined effect of the inertia force and the path on the power loss,the accumulation effect expression of the inertia force on its path is derived.The calculation result shows that the accumulation effect of the unit inertia force on its path depends merely upon the velocity magnitude and the path scroll angle.As long as they are given,the accumulation effect is a constant and independent of the intermediate path.An important conclusion drawn is that the maximum inertia force rather than its accumulation effect plays a predominant role in the power loss.Thus,a new design method,minimum streamline curvature method,is proposed.Fluid particle movement inside a hydrodynamic torque converter can be regarded as curved movement on the circular surface and decomposed into a meridional component and a circumferential component.Each meridional streamline is designed to be close to a circular arc,while each torus streamline is constructed with a circular arc and a straight line segment.Based on the meridional streamline equation,the torus streamline equation and a streamlined thickness function,a blade surface equation of three-element centripetal-turbine hydrodynamic torque converter can be obtained. The influence of streamline bending inertia force on power loss is investigated. In order to analyze the combined effect of the inertia force and the path on the power loss, the accumulation effect expression of the inertia force on its path is derived. The calculation result shows that the accumulation effect of the unit inertia force on its path depends solely upon the velocity magnitude and the path scroll angle. As long as they are given, the accumulation effect is a constant and independent of the intermediate path. An important conclusion drawn is that the maximum inertia force than than its accumulation effect plays a predominant role in the power loss.Thus, a new design method, the minimum streamline curvature method, is proposed. Fluid particle movement inside a hydrodynamic torque converter can be regarded as curved movement on the circular surface and decomposed into a meridional component and a circumferential component. Each meridional streamline is designed to be close to a circular a rc, while while torus streamline is constructed with a circular arc and a straight line segment.Based on the meridional streamline equation, the torus streamline equation and a streamlined thickness function, a blade surface equation of three-element centripetal-turbine hydrodynamic torque converter can be obtained.