Conceptual Study of Counter-Rotating Turbofan Engines

Abstract

The dramatic growth that air traffic has experienced in the last years is not likely to slow down in the future. The situation for the airlines has however been critical due to the large share of the operating costs corresponding to fuel. On the other hand, the society demands quieter aircraft which is then translated into stricter regulations. The Advisory Council for Aeronautics Research in Europe (ACARE) has set an ambitious array of objectives to be accomplished by 2020. It is often claimed that complying with those targets will not require evolution but, rather, revolution. One of the potential future engine configurations being considered is the counter-rotating turbofan (CRTF) concept. This paper addresses the possibilities of improvement that the CRTF can offer with respect to the specific fuel consumption, emissions and noise as compared to the baseline engine, the GE90. Semi-empirical correlations and methodologies have been used for the study. First a Blade Element Method (BEM) is developed to estimate the performance of the fan and to build confidence upon the applied loss and deviation angle models. Next, the design methodology is applied to three cases: a single-stage fan featuring the reference properties of the GE90 engine; a counter-rotating fan (CRF) fan with similar properties as a GE90 fan, but with a lower rotational speed; and a CRF with higher fan pressure ratio (FPR) for lower specific fuel consumption. Finally, noise emission by all the three configurations are estimated by noise models available in the literature. Reductions of equivalent perceived noise level (EPNL) were found to be possible if a CRF is used instead of the baseline single-stage arrangement. Other noise descriptors are also reduced by a similar amount. Approximately equal noise levels are expected if the CRF is of higher pressure than the baseline.

System Architecture Optimization: An Open Source Multidisciplinary Aircraft Jet Engine Architecting Problem

“…dual cycle) [18]? Is a Counter-Rotating Fan (CRTF) included [19]? Can the fan nozzle be variable [20]?…”