Cascade testing and flow analysis of three high-turning supercritical compressor blades were conducted. The blades were designed at an inlet Mach number (M1) of 0.87 and inlet flow angle of 48.4 deg, with high camber angles of about 55 deg. The baseline blade was a conventional Controlled Diffusion Airfoil (CDA) design and the other two were optimized blades. The blades were tested for an inlet Mach number range from 0.61 to 0.95 and an inlet flow angle range from 44.4 deg to 50.4 deg, at high Reynolds numbers (1.2-1.9x10^6 based on the blade chord). The test results have shown lower losses and better incidence robustness for the optimized blades at higher supercritical flow conditions (M1>0.83). At the design condition, 30% loss reduction was achieved. The blade-to-blade flow was computed by solving the two-dimensional steady Navier-Stokes equations. Experimental results, in conjunction with the CFD flowfield characterization, revealed the loss reduction mechanism: severe boundary layer separation occurred on the suction surface of the baseline blade while no separation occurred for the optimized blades. Furthermore, whether the boundary layer was separated or not was found due to different shock patterns, different shock-boundary layer interactions and different pressure distributions on the blades. For the baseline blade, the strong passage shock coincided with the adverse pressure gradient due to the high blade front camber at 20% chord, leading to the flow separation. For the optimized blades, the high blade camber shifted to more downstream (30-40% chord), resulting in stronger flow leading edge acceleration, less strength of the passage shock near the blade surface, favorable pressure gradient right after the passage shock, thus no flow separation occurred. The flow understanding obtained by the current research can be used to guide the design of high-turning compressor blades at higher supercritical flow conditions. / Ph. D.

The study of the flow of a fan blade was conducted to improve tonal fan noise reduction by optimizing an existing flow control configuration. The current configuration consisted of a trailing edge Slot with a flow control area of 0.045 in² per inch span with an exit angle of -3.3° with respect to the blade exit angle. Two other flow control configurations containing discrete jets were investigated. For the first configuration, the trailing edge jets (TEJ), the fan blade was modified with discrete jets spaced 0.3 inches apart with a flow control area of 0.01 in² per inch span positioned on the trailing edge aimed at -3.3° with respect to the blade exit angle. Similarly, discrete jets were also placed on the suction surface at 95.5% chord aimed at 15° with respect to the local blade surface. This configuration is referred to as the suction surface jet (SSJ). The discrete jets for both configurations were designed to be choked while injecting a mass flow rate of 1.00% of the fan through-flow. Computational Fluid Dynamics (CFD) was used to model new configurations and study subsequent changes in total pressure deficit using a blade design inlet Mach number of 0.73, Reynolds number based on chord length of 1.67 à 106, and design incidence angle of 0°. Experimental testing was later conducted in a 2D cascade tunnel. The TEJ and SSJ were tested at design blowing of 1.00% and at off-design conditions of 0.50%, 0.75%, and 1.25% fan through-flow. Results between the different flow control configurations were compared using a blowing coefficient. CFD showed the TEJ and SSJ offered aerodynamic improvement over the Slot configuration. Testing showed the SSJ outperformed the TEJ, as validated in CFD, producing wider and shallower wakes. SSJ area-averaged pressure losses were 25% less than TEJ at design. Noise predictions based on CFD findings showed that both TEJ and SSJ provided additional tonal sound power level attenuation over the Slot configuration at similar blowing coefficients, with the SSJ providing the most attenuation. Noise prediction based on experimental results concurred that the SSJ provided more total attenuation than the TEJ. Experimental results showed that the SSJ performed better aerodynamically and, based on analytical prediction, provided 2 dB more total attenuation than the TEJ. / Master of Science