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Particle Deposition Effects on Film Cooled Turbine Sections |
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Project Funded by: Department of Energy |
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Researcher: Seth Lawson |
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Figure 2. Turbine blade with particle deposition. |
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Another major objective of this project is to experiment with a contoured endwall. The goal is to determine a contoured endwall configuration that will reduce the aerodynamic losses resulting from secondary flow effects around the turbine airfoil. The current DOE project proposes the use of endwall contouring to improve the cooling benefits on the endwall and reduce the likelihood of particle deposition. |
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The DOE 2007-2010 project is a continuation of of earlier work performed within the PSU ExCCL lab. Much of this work focused on the effects of corrosion and deposition of exhaust gas particles on film cooling effectiveness. Specifically, the effect of near-hole deposition, the effect of partial film-cooling hole blockage, and the effect of spallation of a thermal barrier coating has been studied. The results showed that particle deposits located near the film cooling hole exits sometimes improved the film cooling effectiveness; however, studies also showed that partial hole blockage deteriorated film cooling effectiveness. For an endwall surface with spallation downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio. Figure 1 shows a photograph of a turbine vane with spallation and Figure 2 shows a photograph of a turbine blade with particle deposition. Figures 3 and 4 show the effect of deposition, spallation and hole blockage on surface temperatures represented in terms of adiabatic effectiveness levels. Figure 5 shows a summary of the results. |
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Figure 1. Turbine vane showing spallation. |
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Due to the continual depletion of natural gas resources, a new goal for the next generation of gas turbine power generation is to achieve greater efficiency by using new coal derived high hydrogen fuels. The problem with coal derived fuels is that the combustion products contain traces of ash and other contaminants that can deposit on turbine surfaces which can lead to the decrease in film cooling effectiveness in these regions. Adequate film cooling effectiveness is required to maintain surface temperatures that do not exceed the limits that the turbine components can withstand. Specifically, one of the most vulnerable sections of the turbine is the first vane row where the exhaust gas temperatures are hottest. It has been shown that deposited contaminants on endwall and airfoil surfaces can decrease film cooling effectiveness by 50%. The current DOE study proposes the development of techniques for simulating the active deposition of particles on turbine components. Using the simulation methodology, we can determine how contaminants are deposited around film cooling holes when they are placed in shallow trenches at various positions on the suction and pressure sides of the simulated vane. Once the particle deposition behavior is more fully understood, new trench configurations can be developed to maximize film cooling performance under contaminated conditions. |
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Figure 3. Adiabatic effectiveness contours comparing the effect of deposition and spallation at the leading edge. |
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Figure 4. Adiabatic effectiveness contours comparing the effect of single and multiple hole blockages at the leading edge. |
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Figure 5. Comparison of percent reduction on area-averaged adiabatic effectiveness due to surface distortions. |