Experimental investigations on flow characteristics of impingement/swirl cooling structures inside a blade leading edge

Experimental investigations were conducted to study the flow characteristics of impingement/swirl cooling structures inside a turbine-blade leading edge (LE) using particle image velocimetry. The Reynolds number (Re) was maintained at either 10 000 or 20 000. The effects of Re and the ratio of the impingement-cooling (IC) hole offset distance to the IC hole diameter (e/d) on the flow phenomena and the characteristics of the impingement/swirl cooling structures inside the blade LE were analyzed. The effects of the coolant-outflow mode were also taken into consideration. The results show that when e/d = 0, the diffusion flow of the impingement jet moves more to the side of the LE with a larger rounded corner, and this phenomenon is particularly obvious at Re = 20 000. Regardless of the e/d value, both the impingement-jet velocity and vorticity increase significantly at a higher Re value. The velocity of the impingement jet reaching the internal impingement target surface of the LE decreases significantly as e/d is changed from 1.5 to −1.5 with Re = 20 000. Generally speaking, regardless of the e/d value, the impingement jet can form a swirling vortex on the side with the larger rounded corner. Under the conditions of Re = 20 000 and e/d = 1.5, regardless of the coolant-outflow mode, the flow velocity of the impingement jet decreases monotonically along the flow direction, and this is more obvious inside the LE model without film-cooling holes.