Gas turbine endwall film cooling and heat transfer characteristics with a multi-cavity slashface gap design

Abstract

A novel multi-cavity slashface gap with different cavity obstruction modes, compared with a typical single-cavity slashface, is designed to arrange coolant flow on a gas turbine endwall. Solving the steady Reynolds averaged Navier–Stokes equations, the interaction condition between the coolant jet and cascade secondary vortices is studied. The corresponding film cooling and aero-thermal performances of the endwall are evaluated. The obtained results indicate that the dual-cavity slashface urges the coolant from the fore cavity to stagnate on the obstruction and to be redirected toward the spanwise direction. Consequently, the coolant downstream migration tendency near the obstruction is restricted, and the cooling effectiveness downstream of the obstruction increases. When the blowing ratio (M) is 0.5, the cavity obstruction is most effective when placed at 30%Ls and 50%Ls in redirecting the coolant to eject out more quickly. The endwall cooling effectiveness in the vicinity is increased from 0.2 to 0.4. The influence of the obstruction is the most moderate when M=1.0. The cooling effectiveness upstream of the obstruction is only increased by 0.06 in the DC-10% case. Another mainstream ingestion region appears downstream of the obstruction, and the lack of coolant decreases the average endwall cooling effectiveness by 0.04. At a high blowing ratio (M=1.5), the ingestion and ejection velocities at the slashface are the highest, and the obstruction can only influence the region of z/Cax < 0.4. After penetrating directly into the mainstream of the coolant, an uncovered region is formed on the endwall, and its average cooling effectiveness is increased by up to 0.08 with an increasing net heat flux reduction of 0.2 in the DC-30% case. This paper provides insights into elaborate purge flow control for turbine cooling designers.