Numerical Investigation on Flow and Cooling Characteristics of a Micro-Ribbed Vane Endwall

The secondary flow originated from the inherent pressure gradient inside the vane cascade has a strong impact on the endwall cooling performance as the crossflow sweeps the upstream coolant jet towards the suction side, resulting in intensifying thermal load near the pressure side endwall. Hence a novel ribbed-endwall is introduced to suppress passage crossflow. The effects of the mass flow ratio and the rib layout were examined using numerical simulations by solving the three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations with the shear stress transport (SST) k-ω turbulence model. The results indicate that the ribs effectively prevent the coolant migrating from the pressure side to the suction side, helping the coolant jet to spread along the lateral orientation. Therefore, the endwall adiabatic film cooling effectiveness is substantially improved. The maximum cooling effectiveness is achieved for the case with three-ribs when the height of the rib equals one hole diameter among all cases. The area-averaged adiabatic cooling effectiveness is enhanced by 31.6% relative to the flat endwall when the mass flow ratio of coolant to mainstream equals to 0.52%. More importantly, the ribbed-endwall obtains a relatively lower level of aerodynamic loss owing to the reduced lateral migration inside the vane cascade.