An experimental study on turbine vane Leading-Edge film cooling with deposition

Deposition of particles ingested into the hot turbine component of an aircraft engine could lead to degradation of turbine cooling performance and thus reduces service lifetime. It is thereby critical to gain basic knowledge of the deposition effects on the turbine cooling, of which cooling for the vane leading edge, where hot gas stagnates, is intricate. In this work, liquid wax is air-atomized into micro droplets to simulate a particle-laden flow condition where a vane leading-edge model cooled by five rows of staggered holes is immersed. To take circumferential pressure gradient at the leading edge of a real turbine vane into consideration, a rectangular obstacle is designed ahead of the test model and is shifted towards one side to form pressure and suction sides around the leading edge. Particularly, cooling effectiveness is measured by using an infrared thermography (IR) technique at an early-stage deposition for blowing ratios of 0.5-1.6. Additionally, an array of real-time IR images of surface temperatures is gathered to document the dynamic changings of film cooling with the accumulation of deposits on the leading edge for a longer exposure. Comparisons between the deposition and non-deposition cases reveal that for the incipient deposition, the deposits are helpful to improve cooling effectiveness except for the optimum blowing ratio of 0.8 at which film cooling on the non-deposition model has the best performance. Because of the high-pressure surroundings, the hole rows on the pressure side are more sensitive to deposition, where increases of 0.05-0.15 in cooling effectiveness are found due to deposition. Moreover, dynamic deposition shows that the heavy deposits and heating effects of the warm particles could generate a reduction of cooling effectiveness up to 76% for a longer exposure. The added value of this study lies in providing a better understanding of the deposition effects on film cooling at the turbine vane leading edge, which is helpful to design a robust cooling scheme for this region to withstand the deposits.