Analysis and Evaluation of Innovative Aero Engine Core Concepts

Doctoral thesis, 2011

Turbofan engines, which power the majority of the modern aircraft today, have achieved such a high maturity that small improvements of the engine performance requires a large investment. More innovative technologies, including those related to the engine cores, become increasingly attractive due to the high fuel price in recent years as well as the strict regulations on emissions. In this thesis three different innovative core concepts based on alternative cycles are analysed. The first requires introducing an intercooler into a high bypass ratio engine. Intercooling can reduce the high pressure compressor exit temperature and enables a very high overall pressure ratio and thus also high thermal efficiency. The second innovative concept is the intercooled recuperated core. Recuperation can recover energy from the exhausts and improve the engine thermal efficiency. The third innovative concept makes use of a variable core cycle. By adopting a variable core cycle, one can keep the thermal efficiency at a relatively high level during cruise conditions. To analyse and evaluate these concepts, the performance, dimensions and weight of the relevant components have been modelled with empirical correlations, industrial input and with CAD/CFD tools. These component models were integrated into system simulation tools and multidisciplinary optimisation studies were carried out to explore the design space. The potential of the innovative core concepts are evaluated and they demonstrate fuel reduction potential to a varying degree. The complicated interrelationship between the design parameters of these engines has also been analysed. Furthermore, it was found that modification of the engine gas path is necessary due to the influence from the new components. The knowledge accumulated in this thesis helps the engine designers enhance the understanding of these new concepts and select a better approach for future air transport.