Endwall film cooling performance considering the effects of micro-riblets configurations and layouts

The wedge-shaped enriched coolant zone is always found in the turbine endwall cooling due to the influence of horse shoe vortex inside the passage. Which leads to the hot region along the pressure side, becoming one of the biggest challenges to turbine cooling design. In order to increase the cooling performance of the pressure side hot region, riblets are introduced to reorganize the cooling jet trace near endwall. The effects of the riblets layout, shape and length on the endwall cooling performance were investigated using verified simulation method. The results indicate that the riblets have significant influence on the endwall adiabatic effectiveness. Case D with four riblets arranged along pressure side and one riblet at the suction side leading edge obtains higher adiabatic effectiveness than other riblets layouts, especially at pressure side region. The area-averaged endwall adiabatic effectiveness for Case D is increased by 104.7% relative to the baseline. Moreover, the riblets shape has little effect on the endwall cooling performance. However, Case F with triangular riblets achieves the best cooling performance at pressure side endwall region by decreasing the recirculating vortex downstream of riblets. In addition, the length of riblets has significant effects on endwall cooling performance with small cooling jet MFR. Because the riblet will extend to enriched coolant zone and more cooling jet can be guided to move towards the pressure side as W is increased.