Combined Steam Power Cycle and Turbofan Engine for Improvement in Aviation Climate Impacts

Abstract

Despite significant innovations in aviation technology over the last 70 years resulting in enormous efficiency improvement, the rising demand for air travel means that aviation carbon emissions continue to increase each year. The rate of improvement to aircraft propulsion engines is diminishing and additional improvements often add significant engine cost or weight. With the goal of reducing aviation’s contribution to global climate change, future aircraft engine designers must consider concepts that stray from the traditional turbofan engine. In this thesis, I develop an engine cycle model combining the turbofan engine with a steam power cycle and use the model to explore the benefits of applying this concept to aircraft engines. In order to study the impact to engine performance and emissions from adding a steam cycle, the engine model needs to be capable of representing the water phase changes and the heat exchangers required to drive those phase changes. My contribution is the development of such a model – with special attention to the modeling of water properties and phase change of water – which ties heat exchanger models into an engine thermodynamic model. The engine cycle as well as heat exchanger parameters including water-to-air ratio, combustor exit temperature, overall pressure ratio, and water pressure are varied to explore the impact to overall engine performance, including the impact of the added heat exchanger weight. This thesis covers the development and initial testing of this model, which enables future studies in engines with phase changing heat exchangers or water injection with the goal of assisting the search for the future engine technologies that will reduce harmful impacts of aviation while continuing to allow air travel.