A Study of Deposition on a Turbine Vane With a Thermal Barrier Coating and Various Film Cooling Geometries

Abstract

Recent interest has been shown in using synthetic gaseous (syngas) fuels to power gas turbine engines. An important issue concerning these fuels is the potential for increased contaminant deposition that can inhibit cooling designs and expedite the material degradation of vital turbine components. The purpose of this study was to provide a detailed understanding of how contaminants deposit on the surface of a turbine vane with a thermal barrier coating (TBC). The vane model used in this study was designed to match the thermal behavior of real engine components by properly scaling the convective heat transfer coefficients as well as the thermal conductivity of the vane wall. Four different film cooling configurations were studied: round holes, craters, a trench, and a modified trench. The contaminants used in this study were small particles of paraffin wax that were sprayed into the mainstream flow of the wind tunnel. The wax particles modeled both the molten nature of contaminants in an engine as well as the particle trajectory by properly matching the expected range of Stokes number. This study found that the presence of film cooling significantly increased the accumulation of deposits. It was also found that the deposition behavior was strongly affected by the film cooling configuration that was used on the pressure side of the vane. The craters and trench performed the best in mitigating the accumulation of deposits immediately downstream of the film cooling configuration. In general, the presence of deposits reduced the film cooling performance on the surface of the TBC. However, the additional thermal insulation provided by the deposits improved the cooling performance at the interface of the TBC and vane wall.

Experimental Study of Particle Deposition on Surface at Different Mainstream Velocity and Temperature

“…Temperature increases were found to decrease particle capture efficiency at inlet temperatures above the particle melting point. However, excessively high inlet temperatures may cause damage to the component surface [12,33]. Therefore, it is not reasonable to achieve low capture efficiency and normal engine performance only by increasing gas temperature.…”

A review of multiphase flow and deposition effects in film-cooled gas turbines

“…The vane was covered with TBC, and the TBC also provided a trench depth of above 1-D. Comparison of photographs before and after deposition was conducted in [50]. In addition, Kistenmacher et al [51] studied the effect of contaminant deposition on the realistic trench based on a similar experimental facility.…”

Numerical investigation on the improved three-hole cooling unit with the trench

“…Various novel shaped film-cooling holes have been proposed, and Bunker summed up the previous shaped cooling holes, including trenched holes, in detail in the literature (Bunker, 2005) in 2005. It was first demonstrated by Bunker (2002) that the transverse trench fed by discrete cooling holes, especially for shallow slots, was beneficial to film-cooling effectiveness in a large range of blowing ratios, and the trench designs could reduce deposition formation, compared with traditional round cooling holes (Kistenmacher et al, 2014;Davidson et al, 2014). In respect of machining feasibility, the holes embedded in the trench are realistic for components with the thermal barrier coating (TBC) (Bunker, 2002;Kistenmacher et al, 2014), and a typical manufacturing process of masking hole area was discussed briefly in the literature (Lu et al, 2009).…”