Hydrodynamic coupling is a type of fluid machinery that uses fluid kinetic energy to transmit power. In this paper, Meridional profile optimization of Fully-filled fluid coupling was performed to improve transmitted torque. The response surface method, a global optimization method, combined with CFD was introduced to find optimum Meridional profile of blades. The torque coefficient was applied as an objective function. The response surface method was adopted with three design variables: hydraulic diameter ratio of blades, central core position, and meridional profile of the hub. Results showed that the best diameter ratio occurred at d/D = 0.67. To specify an optimal position for the central core, a dimensionless parameter (b/d) was introduced. With regression analysis, it was found that the optimal point occurs at about b/d = 0.37. It was confirmed with the results of contour and vector plots. Three types of curves (circular, elliptical, and cubic Bezier curve) were employed to optimize the meridional shape of blades. The circular curve was applied in the design of the hub in the reference geometry. Relative to the circular curve hub, the use of elliptic curve had no significant effect on the objective function. Two dimensionless parameters, l1/d and l2/d were defined to investigate the effect of Bezier curves on the performance of hydrodynamic coupling. The optimum values for design variables of l1/d and l2/d were obtained 0.80 and 0.88, respectively.
