Mission-Integrated Exergy Analysis for Hypersonic Vehicles; Methodology and Application
Recently developed theoretical work in which energy (first law) and entropy (second law) considerations are consistently applied to aerospace vehicles is used in order to provide a detailed exergy (availability) and performance analysis for an air-breathing hypersonic vehicle. This vehicle performs an acceleration and climb mission in the atmosphere. Specifically, this paper first discusses the fundamental analytical relationship between entropy generation and conventional vehicle performance for both steady-state and mission-integrated applications; this relationship includes wake losses and their dominating impact on vehicle performance. A computational/analytical model of a generic hypersonic air-breathing vehicle (air-frame integrated, scramjet-powered X-43 like configuration) is then constructed using straight-forward and relatively common engineering techniques. This overall vehicle model produces both 1) the net forces experienced by the vehicle at arbitrary flight and operating conditions and 2) detailed and comprehensive entropy generation information associated with the vehicle and its wake. This vehicle model is coupled with the standard vehicle equations of motion in order to provide simplified flight trajectory (mission) analysis capability; vehicle and wing angles of attack, climb angle and fuel throttling can be controlled (varied) within the analysis of a defined mission. An acceleration and climb mission at constant free-stream dynamic pressure is performed; complete instantaneous and time-integrated audits of entropy generation in and over the vehicle and in the vehicle wake are produced for this mission. Entropy generation in the vehicle wake ranges from five to eight times the total entropy generation in and over the vehicle; the impact of irreversibility occurring in and over the vehicle itself on the total entropy generation in the wake is a small fraction of the overall wake losses. Fifteen percent of the overall energy input during the mission actually goes into productive acceleration and climb; the remainder goes into the generation of entropy due to irreversibility in and over the vehicle, and in the vehicle wake. The propulsion system is responsible for almost all entropy generation associated solely with the vehicle (excluding the overwhelmingly dominant contribution of the vehicle wake); entropy generation in the combustor alone represents 85% of the total propulsion system loss. The present work provides the basic methodology required for a complete and consistent 2nd law analysis of a high-speed vehicle mission, and also provides a quantitative demonstration of the methodology for a generic vehicle and mission
D. W. Riggins et al., "Mission-Integrated Exergy Analysis for Hypersonic Vehicles; Methodology and Application," Proceedings of the 50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition (2012, Nashville, TN), American Institute of Aeronautics and Astronautics (AIAA), Jan 2012.
The definitive version is available at https://doi.org/10.2514/6.2012-1121
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition (2012: Jan. 9-12, Nashville, TN)
Mechanical and Aerospace Engineering
Article - Conference proceedings
© 2012 American Institute of Aeronautics and Astronautics (AIAA), All rights reserved.
12 Jan 2012