Doctor of Philosophy, The Ohio State University, 2023, Aero/Astro Engineering

The feasibility of an active flow control enabled variable area turbine was explored. Pressurized air was ejected from the nozzle guide vanes to reduce the effective choke area, and mass flow rate through, the turbine inlet. A set of experimental and computational studies were conducted with varying actuator types and parameters to determine their effectiveness and develop models of the flow physics. Preliminary results from a simple quasi-1D converging-diverging nozzle, with an injection flow slot upstream of the throat, showed a 2.2:1 ratio between throttled mass flow rate and injected mass flow rate at a constant nozzle pressure ratio. The penetration of the injection flow and corresponding reduction in the primary flow streamtube were successfully visualized using a shadowgraph technique. Building on this success, a representative single passage nozzle guide vane transonic flowpath was constructed to demonstrate feasibility beyond the quasi-1D converging-diverging nozzle. Both secondary slot blowing from the vane pressure surface and vane suction surface just upstream of the passage throat again successfully reduced primary flow. In addition, fluidic vortex generators were used on the adjacent suction surface to reduce total pressure loss along the midspan and further throttle the primary flow. Computational fluid dynamics simulations were used to explore the effects of a variety of parameters on the flow blockage and actuator effectiveness. Simplified models were developed to describe the relationships of various factors impacting flow blockage, turning angle, and total pressure loss. Finally, the active flow control systems were simulated at engine relevant pressures and temperatures and found to have only a minimal drop in total pressure recovery and effectiveness, which could be predicted by the simplified blockage model.

Committee: Jeffrey Bons (Advisor); Datta Gaitonde (Committee Member); Randall Mathison (Committee Member) Subjects: Aerospace Engineering

Master of Science, The Ohio State University, 2020, Mechanical Engineering

The emissions resulting from fossil fuel consumption across various industries has lead to detrimental effects on the planet's ecosystems. The commercial aircraft industry is attempting to reduce their emissions with the use of more fuel efficient propulsive architectures. The electrification of propulsive systems are considered to be a promising advancement for future aircraft. The architecture under investigation in this study is a turboelectric distributed propulsion system for a regional aircraft that assumes weight, drag, and design improvements that as consistent with a system being deployed in 2035. This system has the ability for hybridization via an onboard energy storage system, comprising of a battery pack, to further reduce the fuel consumption of this advanced architecture. A quasi-static model was developed with the primary objective of predicting the performance of the propulsion system over the course of a mission. Empirical equations, performance maps, and experimental data was used to calibrate the subsystems of this model. In order to expand the fuel reduction potential of the turboshaft engines, a variable speed free power turbine and a variable area nozzle were added to the engines as additional controls to the engine's primary throttle. The optimal control strategy of the turbine's speed and nozzle throat area that minimized the mission fuel consumption was determined and the associated fuel savings have concluded. The results of this study were compared to the same system where the two parameters were held constant at their design values. This analysis was completed for the hybrid and non-hybrid system to determine the optimal control strategy of the engine with and without a secondary source of power and to determine the variation of the control if a secondary source is present. It was concluded that the optimal engine control strategy can obtain a maximum savings of 1.55% over the same system neglecting the two additiona (open full item for complete abstract)

Committee: Meyer Benzakein Prof (Advisor); Marcello Canova Prof (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering