Deposition Near Film Cooling Holes on a High Pressure Turbine Vane

Deposition on film-cooled turbine components was studied in an accelerated test facility. The accelerated deposition facility seeds a natural-gas burning combustor with finely-ground coal ash particulate at 1180°C and 180 m/s (M = 0.25). Both cylindrical and shaped holes, with and without TBC coating, were studied over a range of blowing ratios from 0.5 to 4.0. Coolant density ratios were maintained at values from 2.1 to 2.4. Deposition patterns generated with the cylindrical film cooling holes indicated regions of low deposition in the path of the coolant, with heightened deposition between film holes. This distinctive pattern was more accentuated at higher blowing ratios. Optical temperature measurements of the turbine component surface during deposition showed elevated temperatures between coolant paths. This temperature non-uniformity became more accentuated as deposition increased, highlighting a mechanism for deposition growth that has been documented on in-service turbines as well. The shaped-hole components exhibited little or no deposition in the region just downstream of the holes, due to the distributed coolant film. Close cylindrical hole spacing of 2.25d displayed similar behavior to the shaped hole configuration.