Seth A. Lawson

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.

Simulations of Multiphase Particle Deposition on Endwall Film-Cooling Holes in Transverse Trenches

Integrated gasification combined cycle (IGCC) power plants allow for increased efficiency and reduced emissions as compared to pulverized coal plants. A concern with IGCCs is that impurities in the fuel from the gasification of coal can deposit on turbine components reducing the performance of sophisticated film-cooling geometries. Studies have shown that recessing a row of film-cooling holes in a transverse trench can improve cooling performance; however, the question remains as to whether or not these improvements exist in severe environments such as when particle deposition occurs. Dynamic simulations of deposition were completed using wax injection in a large-scale vane cascade with endwall filmcooling. Endwall cooling effectiveness was quantified in two specific endwall locations using trenches with depths of 0.4D, 0.8D, and 1.2D, where D is the diameter of a film-cooling hole. The effects of trench depth, momentum flux ratio, and particle phase on adiabatic effectiveness were quantified using infrared thermography. Results showed that the 0.8D trench outperformed other geometries with and without deposition on the surface. Deposition of particles reduced the cooling effectiveness by as much as 15% at I = 0.23 with the trenched holes as compared to 30% for holes that were not placed in a transverse trench.

Simulations of Multiphase Particle Deposition on a Showerhead With Staggered Film-Cooling Holes

The demand for cleaner, more efficient energy has driven the motivation for improving the performance standards for gas turbines. Increasing the combustion temperature is one way to get the best possible performance from a gas turbine. One problem associated with increased combustion temperatures is that particles ingested in the fuel and air become more prone to deposition with an increase in turbine inlet temperature. Deposition on aero-engine turbine components caused by sand particle ingestion can impair turbine cooling methods and lead to reduced component life. It is necessary to understand the extent to which particle deposition affects turbine cooling in the leading edge region of the nozzle guide vane where intricate showerhead cooling geometries are utilized. For the current study, wax was used to dynamically simulate multiphase particle deposition on a large scale showerhead cooling geometry. The effects of deposition development, coolant blowing ratio, and particle temperature were tested. Infrared thermography was used to quantify the effects of deposition on cooling effectiveness. Although deposition decreased with an increase in coolant blowing ratio, results showed that reductions in cooling effectiveness caused by deposition increased with an increase in blowing ratio. Results also showed that effectiveness reduction increased with an increase in particle temperature. Reductions in cooling effectiveness reached as high as 36% at M ¼1.0. [DOI: 10.1115/1.4004757]

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.Copyright

Simulations of Multiphase Particle Deposition on a Nonaxisymmetric Contoured Endwall With Film-Cooling

Designing turbine components for maximum aerodynamic performance with adequate cooling is a critical challenge for gas turbine engineers, particularly at the endwall of a turbine, due to complex secondary flows. To complicate matters, impurities from the fuel and intake air can deposit on film-cooled components downstream of the combustor. Deposition-induced roughness can reduce cooling effectiveness and aerodynamic performance dramatically. One method commonly used for reducing the effects of secondary flows on aerodynamic performance is endwall contouring. The current study evaluates deposition effects on endwall contouring given the change to the secondary flow pattern. For the current study, deposition was dynamically simulated in a turbine cascade to determine its effects on film-cooling with and without endwall contouring. Computationally predicted impactions were in qualitative agreement with experimental deposition simulations, showing that contouring reduced deposition around strategically placed film-cooling holes. Deposition reduced cooling effectiveness by 50% on a flat endwall and 40% on an identically cooled contoured endwall. Although 40% is still a dramatic reduction in effectiveness, the method of using the endwall contouring to alter deposition effects shows promise.

Simulations of Multi-Phase Particle Deposition on a Non-Axisymmetric Contoured Endwall With Film-Cooling

Designing turbine components for maximum aerodynamic performance with adequate cooling is a critical challenge for gas turbine engineers, particularly at the endwall of a turbine due to complex secondary flows. To complicate matters, impurities from the fuel and intake air can deposit on film-cooled components downstream of the combustor. Deposition induced roughness can reduce cooling effectiveness and aerodynamic performance dramatically. One method commonly used for reducing the effects of secondary flows on aerodynamic performance is endwall contouring. The current study evaluates deposition effects on endwall contouring given the change to the secondary flow pattern.For the current study, deposition was dynamically simulated in a turbine cascade to determine its effects on film-cooling with and without endwall contouring. Computationally predicted impactions were in qualitative agreement with experimental deposition simulations showing that contouring reduced deposition around strategically placed film-cooling holes. Deposition reduced cooling effectiveness by 50% on a flat endwall and 40% on an identically cooled contoured endwall. Although 40% is still a dramatic reduction in effectiveness, the method of using the endwall contouring to alter deposition effects shows promise.Copyright

Simulations of Multi-Phase Particle Deposition on a Showerhead With Staggered Film-Cooling Holes

The demand for cleaner, more efficient energy has driven the motivation for improving the performance standards for gas turbines. Increasing the combustion temperature is one way to get the best possible performance from a gas turbine. One problem associated with increased combustion temperatures is that particles ingested in the fuel and air become more prone to deposition with an increase in turbine inlet temperature. Deposition on aero-engine turbine components caused by sand particle ingestion can impair turbine cooling methods and lead to reduced component life. It is necessary to understand the extent to which particle deposition affects turbine cooling in the leading edge region of the nozzle guide vane where intricate showerhead cooling geometries are utilized. For the current study, wax was used to dynamically simulate multi-phase particle deposition on a large scale showerhead cooling geometry. The effects of deposition development, coolant blowing ratio, and particle temperature were tested. Infrared thermography was used to quantify the effects of deposition on cooling effectiveness. Although deposition decreased with an increase in coolant blowing ratio, results showed that reductions in cooling effectiveness caused by deposition increased with an increase in blowing ratio. Results also showed that effectiveness reduction increased with an increase in particle temperature. Reductions in cooling effectiveness reached as high as 36% at M = 1.0.Copyright

Simulations of Multi-Phase Particle Deposition on Endwall Film-Cooling Holes in Transverse Trenches

Integrated gasification combined cycle (IGCC) power plants allow for increased efficiency and reduced emissions as compared to pulverized coal plants. A concern with IGCCs is that impurities in the fuel from the gasification of coal can deposit on turbine components reducing the performance of sophisticated film-cooling geometries. Studies have shown that recessing a row of film-cooling holes in a transverse trench can improve cooling performance; however, the question remains as to whether or not these improvements exist in severe environments such as when particle deposition occurs. Dynamic simulations of deposition were completed using wax injection in a large-scale vane cascade with endwall film-cooling. Endwall cooling effectiveness was quantified in two specific endwall locations using trenches with depths of 0.4D, 0.8D, and 1.2D, where D is the diameter of a film-cooling hole. The effects of trench depth, momentum flux ratio, and particle phase on adiabatic effectiveness were quantified using infrared thermography. Results showed that the 0.8D trench outperformed other geometries with and without deposition on the surface. Deposition of particles reduced the cooling effectiveness by as much as 15% at I = 0.23 with the trenched holes as compared to 30% for holes that were not placed in a transverse trench.Copyright

Simulations of Multi-Phase Particle Deposition on Endwall Film-Cooling

Demand for clean energy has increased motivation to d esign gas turbines capable of burning alternative fuels such as coal derived synthesis gas (syngas). One challenge associated with burning coal derived syngas is that trace amounts of particulate matter in the fuel and air can deposit on turbine hardware reducing the effectiveness of film cooling. For the current study, a method was developed to dynamically simulate multi-phase particle deposition through injection of a low melting temperature wax. The method was developed so the effects of deposition on endwall film cooling could be quantified using a large scale vane cascade in a low speed wind tunnel. A microcrystalline wax was injected into the mainstream flow using atomizing spray nozzles to simulate both solid and molten particulate matter in a turbine gas path. Infrared thermography was used to quantify cooling effectiveness with and without deposition at various locations on a film cooled endwall. Measured results indicated reductions in adiabatic effectiveness by as much as 30% whereby the reduction was highly dependent upon the location of the film-cooling holes relative to the vane. NOMENCLATURE a speed of sound A surface area C chord length Cp particle specific heat �hfus specific latent heat of fusion D film cooling hole diameter, D=0.46cm dp particle diameter h heat transfer coefficient