A thesis is presented that investigates the effect of particle Stokes number and film cooling on the character of coal fly ash deposition on a turbine nozzle guide vane. The Turbine Reacting Flow Rig or TuRFR at The Ohio State University was used to produce coal fly ash deposits on real turbine hardware at operating conditions. CFM56-5B nozzle guide vane doublets were subjected to inlet temperatures of 1080 °C and a Mach number of 0.08 while seeding the flow with a sub-bituminous coal fly ash. The ash was processed to provide two different size distributions, that with a median Stokes number of 0.3 and Stokes number 4.0 and each ash was exposed to a vane set with and without film cooling. The transient character of deposit growth was investigated by a camera positioned to view the vanes during test time. Post-test measurements included using sophisticated metrology techniques to provide plots of deposit thickness and structure. The results were then compared to computation.
Deposits thickness was observed to be a large function of particle loading but in general small Stokes number ash deposits were observed to be half the thickness of the large Stokes number deposits for a given test condition. For those tests which involved film cooling, deposits only formed on the leading 50% of the vane pressure surface while those tests without film cooling had deposits on the entire pressure surface. Deposit location is thus observed to be a strong function of vane surface temperature. Values of average surface roughness and peak to peak roughness were calculated for all tests. Film
cooling was found to have a negligible effect on surface roughness while increased Stokes number was found to double the calculated roughness. The computational results were found to accurately depict initial deposit location, for both the un-cooled and cooled cases, but lacked the ability to accurately represent deposit evolution over time.