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Accession Number N20120012959
Title Comparison of Various Supersonic Turbine Tip Designs to Minimize Aerodynamic Loss and Tip Heating.
Publication Date Jul 2012
Media Count 14p
Personal Author A. Ameri V. Shyam
Abstract The rotor tips of axial turbines experience high heat flux and are the cause of aerodynamic losses due to tip clearance flows, and in the case of supersonic tips, shocks. As stage loadings increase, the flow in the tip gap approaches and exceeds sonic conditions. This introduces effects such as shock-boundary layer interactions and choked flow that are not observed for subsonic tip flows that have been studied extensively in literature. This work simulates the tip clearance flow for a flat tip, a diverging tip gap and several contoured tips to assess the possibility of minimizing tip heat flux while maintaining a constant massflow from the pressure side to the suction side of the rotor, through the tip clearance. The Computational Fluid Dynamics (CFD) code GlennHT was used for the simulations. Due to the strong favorable pressure gradients the simulations assumed laminar conditions in the tip gap. The nominal tip gap width to height ratio for this study is 6.0. The Reynolds number of the flow is 2.4 x 10(exp 5) based on nominal tip width and exit velocity. A wavy wall design was found to reduce heat flux by 5 percent but suffered from an additional 6 percent in aerodynamic loss coefficient. Conventional tip recesses are found to perform far worse than a flat tip due to severe shock heating. Overall, the baseline flat tip was the second best performer. A diverging converging tip gap with a hole was found to be the best choice. Average tip heat flux was reduced by 37 percent and aerodynamic losses were cut by over 6 percent.
Keywords Axial flow turbines
Blade tips
Computational fluid dynamics
Heat flux
Laminar flow
Mach number
Navier-stokes equation
Rotor aerodynamics
Supersonic flow
Supersonic heat transfer
Supersonic turbines

Source Agency National Aeronautics and Space Administration
NTIS Subject Category 51A - Aerodynamics
46B - Fluid Mechanics
Corporate Author National Aeronautics and Space Administration, Cleveland, OH. NASA John H. Glenn Research Center at Lewis Field.
Document Type Conference proceedings
Title Note N/A
NTIS Issue Number 1303
Contract Number N/A

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