The effects of simulated particle deposition on film cooling

Diminishing natural gas resources has increased incentive to develop cleaner, more efficient combined cycle power plants capable of burning alternative fuels such as coal-derived synthesis gas (syngas). Although syngas is typically filtered, particulate matter still exists in the hot gas path that has proven to be detrimental to the life of turbine components. Solid and molten particles deposit on film cooled surfaces that can alter cooling dynamics and block cooling holes. To gain an understanding of the effects that particle deposits have on film cooling, a methodology was developed to simulate deposition in a low speed wind tunnel using a low melt wax, which can simulate solid and molten phases. A facility was constructed to simulate particle deposition on a flat plate with a row of film cooling holes. Infrared thermography was used to measure wall temperatures for quantifying spatially resolved adiabatic effectiveness values in the vicinity of the film cooling holes as deposition occurred. Results showed that deposition reduced cooling effectiveness by approximately 20% at momentum flux ratios of 0.23 and 0.5 and only 6% at a momentum flux ratio of 0.95.