A Method for Propulsion Technology Evaluation Via Thermodynamic Work Potential

Presented at the 8th AIAA/USAF/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, Long Beach, CA, September 6-8, 2000.The task of propulsion technology concept selection and integration is one of the most challenging problems in aerospace systems design. This is because of the tightly-coupled and inherently multidisciplinary nature of the problem, as well as the multitude of performance constraints and requirements placed on modern propulsion systems. In addition, as the cost of developing new and improved propulsion systems continues to rise, the attendant risk to the developer increases also. This leads to an aversion to risk that stifles innovation, particularly when it involves the introduction of new and untried technology concepts. Therefore, there is a need for analytical methods to quantify the impact of new technology in a comprehensive and consistent manner. Fortunately, recent developments in thermodynamic work potential (exergy) methods based on the second law of thermodynamics are enabling new and innovative approaches to systems design that have not been possible in the past. These methods allow the creation of a truly unified picture of aerothermodynamic and weight benefits associated with a given technology, and further allow the explicit calculation each individual contributing factor constituting that impact. This paper will describe the basic theory for technology evaluation via work potential, show how it can be directly related to vehicle mass properties (weight), and demonstrate its application on a classic propulsion technology selection problem applied to the Northrop F-5E aircraft