Ph.D. Proposal Presentation by Peter J. Christiansen
Tuesday, December 3, 2002

(Dr. Samuel Shelton, advisor)

"Aircraft Conceptual Design Utilizing Second Law Energy System Analysis"


Second law analysis (SLA) techniques have been used to analyze and optimize the design of numerous energy systems; e.g. power plants and refrigeration. The application of SLA to aircraft and aircraft systems design is in the early stages of development. The ability of traditional thermodynamic SLA techniques to properly evaluate and ultimately optimize the aircraft as an energy system has been questioned.

The goal of this study is to use a very general SLA technique based on first principles, the direct entropy method, to develop an analysis and optimization methodology that is useful during an aircraft’s conceptual design phase. This approach will allow for trading off design parameters. During this early stage of development when detailed designs are not available, the costs associated with making changes are minimal, but the impact on the final design is large.

An aircraft is generally designed to meet a given set of performance requirements, or constraints. These include speed, payload, range, noise, and runway length requirements. While meeting these constraints, an aircraft designer must consider several figures-of-merit, including manufacturing costs and fuel requirements. In most designs, the most dominant figure-of-merit is the fuel requirement, since increasing fuel load creates compounding penalties in all sub-systems. The SLA methods address this fuel requirement in a direct and fundamental way. Using fundamental first and second law principles, it is the goal of this research to develop closed form equations, which express the fuel requirement as a function of targetable aircraft system design parameters.

The entropy method will be individually applied to each process required for flight. The individual systems that will be analyzed are: airframe with aerodynamic effects, propeller, reciprocating engine, turboprop engine, turbojet engine, and a turbofan engine. These subsystem models will then be integrated into a comprehensive aircraft system model. This will allow for the determination of the effects of changing components or design parameters on fuel requirements, and identify sub-systems, processes, and technologies with the most improvement impact.