Endwall film cooling holes design upstream of the leading edge of a turbine vane

Endwall film cooling upstream of the leading edge (LE) of a vane presents a relatively complex flow phenomenon due to the horseshoe vortices (HVs) generated at the LE region. Upstream of the LE region, the coolant flow has difficulties to eject out. This research work focuses on controlling the jet holes coolant coverage upstream of the LE region. Compound angle holes in staggered arrangement are introduced and applied in the LE region to increase the coolant coverage. Six different arrangements of cooling holes are designed, with variations from one row or two rows arrangements, parallel or staggered arrangements, normal cylindrical holes or compound angle holes. Besides cooling holes with different shapes and arrangements, effect of the blowing ratio (BR) and turbulence intensity (TI) are also considered. The BR ranges from 1 to 3 and TI ranges from 1.3% to 15%. The calculated results show that the film cooling holes upstream of the LE of a vane have significant cooling effects on both the vane surfaces and the endwall. At small BRs, the film cooling effectiveness (η) on the endwall is considerable. When the BR is increased, the η on the vane surfaces is increased more quickly and becomes dominant. The coolant coverage in the vane-endwall junction region are not affected by the mainstream turbulence intensity and almost keep the same with the varied turbulence intensities. A single row of cylindrical holes (Case 1) and two rows of compound angle holes with staggered arrangement (Case 5) have relatively high overall averaged cooling effectiveness compared with other cases at different BRs. In addition, the high averaged cooling effectiveness on the endwall and vane surfaces by Case 5 is not affected by a change of the BRs.