Experimental Study of a Cascade of Low Pressure Turbine Blades with Upstream Periodic Stator Wakes
Master of Science in Mechanical Engineering (MSME)
The objective of this study is to experimentally study film cooling flows. A closed-loop wind tunnel with a four passage linear cascade of US Air Force Research Laboratory (AFRL) ultra-high-lift L1A low pressure turbine (LPT) blades and upstream wake generator is used in conjunction with Particle Image Velocimetry (PIV) flow visualization technique to study turbulent film cooling flows due to the interaction between vanes and blades. Further post-processing in the form of Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) modal analyses is performed to determine the relevant modes that characterize the coherent structures in the flow. An image patching algorithm is also implemented. The results obtained are used to characterize the periodic wake on the cascade flow. The periodic wake has been studied in detail near the leading edge of the suction side. The velocity data led to the mean velocity profile and maximum velocity deficit in the wake. The POD identified the most energetic modes representing the vortex shedding wavelength, and its harmonics, of the wake generator plates. The DMD confirmed the wake passage frequency. Implementation of the image patching algorithm with four domains was presented. The technique was successful in computing the average vector field. Further downstream of the leading edge, the POD modes are shown to become more chaotic and less energetic. The leading order mode pair loses close to half of their energy to lower order modes due to the cascading of turbulent kinetic energy to lower spatial scales and to viscous dissipation losses. When the wake is impinging on the leading edge, the boundary layer separates near the transition point. The boundary layer remains completely attached to the trailing edge when the wake is not impinging on the leading edge.
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Gonzalez Rodriguez, Carlos Rene, "Experimental Study of a Cascade of Low Pressure Turbine Blades with Upstream Periodic Stator Wakes" (2015). LSU Master's Theses. 1971.
Nikitopoulos, Dimitris E.