PARAMETRIC CYCLE STUDIES OF THE WATER-ENHANCED TURBOFAN CONCEPT

The Water-Enhanced Turbofan is a promising revolutionary concept which addresses the most climate-relevant emissions of aviation: carbon dioxide, nitrogen oxides as well as water vapor and particulate matter which form contrail cirrus. The concept combines the traditional Joule/Brayton cycle with a Clausius-Rankine steam cycle to a dual-fluid cycle also known as the Cheng cycle. While previous publications cover the basic thermodynamics of the concept and give an overview of the potential climate impact reduction, this paper aims to give an overview of important design parameters and their impact on the cycle. In addition, the fuel burn on aircraft system level is assessed with exchange factors for thrust specific fuel consumption and propulsion system weight. A cooling air model for conceptual design which covers the main effects of steam injection on the required cooling air mass flow is employed. For the heat exchangers a substitute model is used. The substitute model is based on a one-dimensional, discretized tool, using a predefined sizing rule and a linearization for changing inlet condition. After the main design parameters are identified, parameter studies are performed using a multi-design-point approach. It is shown, that the vaporization process is a major design driver. Furthermore, the water injection mass flow rate is an important parameter both for design and for the operation of the engine as an additional degree of freedom.