| This dissertation addresses in detail three main topics for advancing the state-of-the-art in hypersonic aerospace systems: (1) the development of a synergistic method based on entropy generation in order to analyze, evaluate, and optimize vehicle performance, (2) the development and analysis of innovative unconventional flow-control methods for increasing vehicle performance utilizing entropy generation as a fundamental descriptor and predictor of performance, and (3) an investigation of issues arising when evaluating (predicting) actual flight vehicle performance using ground test facilities.; Vehicle performance is analyzed beginning from fundamental considerations involving fluid and thermodynamic balance relationships. The results enable the use of entropy generation as the true "common currency" (single loss parameter) for systematic and consistent evaluation of performance losses across the vehicle as an integrated system. Innovative flow control methods are modeled using state of the art CFD codes in which the flow is energized in targeted local zones with emphasis on shock wave modification. Substantial drag reductions are observed such that drag can decrease to 25% of the baseline. Full vehicle studies are then conducted by comparing traditional and flow-controlled designs and very similar axial force is found with an accompanying increase in lift for the flow-control design to account for on-board energy-addition components. Finally, a full engine flowpath configuration is designed for computational studies of ground test performance versus actual flight performance with emphasis on understanding the effect of ground-based vitiate (test contaminant). It is observed that the presence of vitiate in the test medium can also have a significant first-order effect on ignition delay as well as the thermodynamic response to a given heat release in the fuel. |
