Analytical Characterization and Multi-Objective Optimization of Scramjet Intake Performance

Scramjet engines are a promising airbreathing propulsion technology for high-speed transportation as well as accessto-space. The air intake plays a major role in determining the overall performance of scramjets. Designing high-performance intakes by taking both aerodynamic and thermodynamic characteristics into account represents a significant task. This paper presents new knowledge on scramjet intake performance along with underlying physical ground that has been obtained by comprehensive analytical formulations of global intake characteristics derived on a theoretical basis. Heat transfer across the intake surface has been found to be responsible for the trade-off between compression efficiency and drag under assumptions of a fixed contraction ratio or mean exit temperature, while the mean exit temperature and the contraction ratio are the decisive factors for the compression ratio and efficiency. Multi-objective design optimization has then been performed to verify these trade-offs and examine their influence on intake design. The resultant optimal solutions have been found to underpin the design strategy based on these relations. The new insights gained from this study conduce to rapid and reliable design of high-performance intakes.