Mitch Wolff (Advisor), Christopher R. Marks (Committee Member), Rolf Sondergaard (Committee Member)
Master of Science in Mechanical Engineering (MSME)
The low-pressure turbine is an important component of a gas turbine engine, powering the low-pressure spool which provides the bulk of the thrust in medium- and high-bypass engines. It is also a significant fraction of the engine weight and complexity as it can comprise up to a third of the total engine weight. One way to drastically reduce the weight of the low-pressure turbine is to utilize high lift blades. To advance high-lift technology, the Air Force Research Laboratory (AFRL) designed the L2F blade profile, which was implemented in the linear cascade at AFRL/RQT’s low speed wind tunnel facility. The L2F blade has very high lift and an excellent midspan performance, however, it was previously demonstrated to generate significant losses in the endwall region. These losses are primarily driven by the complex time-dependent three-dimensional vortical structures present in the region of the junction of the blade and the endwall, dominated by the Passage Vortex (PV). Aerodynamic flow control is one way to mitigate these losses. Previously, a pulsed endwall blowing system was implemented in the endwall region of the L2F blade which produced a loss reduction. This loss reduction was dependent on the pulsing frequency. In this research, the vortical structures for the baseline flow were characterized with respect to time. The time dependent behavior of the passage vortex motion, location, and strength were found for each pulsing frequency to determine a relationship with total pressure loss reduction. The flow through the passage of the tunnel was characterized with respect to time using high-speed stereoscopic particle image velocimetry. The flow for each test condition was characterized using Q-criterion to determine the strength of the passage vortex and its time dependent behavior. It was found that the passage vortex loses and gains strength in an unsteady manner at time scales between 1.9 < ΔT+ < 6.7. The largest total pressure loss reduction was found to correspond to the pulsing frequency at which the passage vortex was the weakest and moved the closest to the suction surface of the passage
Department or Program
Department of Mechanical and Materials Engineering
Year Degree Awarded
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