Synfuel from gasification of coal, biomass, and/or petroleum coke is an alternative to natural gas in land-based industrial gas turbines. However, carryover fine particulate in the syngas may lead to a considerable amount of deposition on turbine blades, which reduces component life and system performance. Deposition experiments on film-cooled turbine components were performed in an accelerated test facility to examine the nature of flyash deposits near film cooling holes. Experimental results indicate that deposition capture efficiency decreased with increased blowing ratio. Shaped holes exhibited more span-wise coverage than cylindrical holes and effectively reduced deposition. The TBC layer increased surface temperature, resulting in increased deposition. Coupons with close hole spacing exhibited a more uniform low temperature region downstream and less deposition. Capture efficiencies for small particles were lower than for large particles, especially at low blowing ratios. The trench increased cooling effectiveness downstream, but did not reduce overall collection efficiency of particulates because the trench also acted as a particulate collector. In the numerical computations using a CFD code (FLUENT), the standard k-ω turbulence model and RANS were employed to compute flow field and heat transfer. A Lagrangian particle method was utilized to predict the ash particulate transport. User-defined subroutines were developed to describe and predict particle deposition rates on the turbine blade surface. Small particles had a greater tendency to stick to the surface. As the surface temperature rose above the transition temperature, large particles dominated the excessive deposition due to the high delivery rate. Backside impingement of coolant improved the overall cooling effectiveness. Experiments and CFD modeling results suggest that clean coolant dominated the initial deposition process by blowing off the particles and preventing particles from impacting on the surface. Initial deposits formed between coolant channels. Subsequent deposition occurred on top of initial deposits, due to increasing deposit surface temperature, which led to the formation of distinct ridges between coolant paths.
College and Department
Ira A. Fulton College of Engineering and Technology; Chemical Engineering
BYU ScholarsArchive Citation
Ai, Weiguo, "Deposition of Particulate from Coal-Derived Syngas on Gas Turbine Blades Near Film Cooling Holes" (2009). All Theses and Dissertations. 1916.
synfuel, ash deposition, film cooling, CFD modeling, gas turbine