Multidisciplinary Preliminary Design Study on the Evaporator in the Water-Enhanced Turbofan Concept

Kurzfassung

Many revolutionary aero engine cycles aim to increase the efficiency by recuperating heat from the exhaust gas. One such concept is the Water-Enhanced Turbofan (WET), which integrates a quasi-closed water loop incorporating an evaporator into the engine flow path. The potential in reduced climate impact is great from a thermodynamic perspective, but the integration of heat exchangers into aero engines is challenging due to mass and volume constraints. To address this, a multidisciplinary approach for the preliminary design of the evaporator of the WET concept is presented. Although the WET concept has been deprioritized by the industry, it is used as a demonstration case for the development of the methods. The presented workflow combines various preliminary design methods for aero engines with a dedicated heat exchanger sketching and rating approach, enabling the identification of suitable evaporator geometries that comply with engine integration constraints. Main geometric variations of the tube bundle evaporator in this paper consist of a variation in the tube length, the number of parallel tubes, the tube diameter and the spacing. Thereby, the conflicts regarding flow path design and integration are discussed. The results of this work show the strongly non-linear relationship between geometrical heat exchanger parameters and the engine efficiency. Furthermore, the influence of the evaporator design on engine design and the resulting penalties on aircraft level are addressed and considered while defining promising design parameter combinations.