Application of Riblets on Turbine Blade Endwall Secondary Flow Control

Within the past ten years, significant improvements have been achieved in the laser manufacturing process. It is feasible now to obtain various small-scale surface features (such as dimples, riblets, grooves, etc.) with the current manufacturing readiness level of laser surface texturing techniques. In this paper, the aerodynamic impact of the employment of riblets on turbine endwall has been investigated through combined CFD and experimental studies in a low speed linear cascade environment. Detailed comparisons of the flow structures have been made for cases with and without riblets on the endwall. The results show that endwall riblets can effectively reduce the strength of the pressure side leg of the horseshoe vortex, lower the cross passage pressure gradient, and alleviate the lift up of the passage vortex. A test section with seven passages and eight blades was used to validate the CFD observations. Both numerical and experimental results indicate that, the addition of riblets can be an effective approach to reduce the endwall secondary flow, and there is a large space for further optimization.Copyright © 2014 by ASME