Europe's environmental engine targets for 2020 can be met using engines with a bypass ratio of 14, according to an analysis tool developed for the European Union's Environmentally Friendly Aero-engine (Vital) project.
Europe's targets, set by the Advisory Council for Aeronautical Research in Europe (ACARE), are reductions of 50% in perceived noise, 80% in nitrogen oxides output and 50% in carbon dioxide emissions. The ratio is the difference between the fan drawn air going into and around the engine core. Today's engines' bypass ratios are less than 10.
The bypass ratio of 14 was calculated by the Techno-economic Environmental Risk Assessment (TERA) 2020 tool. This uses a variety of data including plant costs to determine the optimal engine type. For Vital it will help the project determine which of the three engine architectures under study can achieve the ACARE targets. Snecma's contra-rotating concept, Rolls-Royce's direct drive design and MTU Aero Engines' geared system were the three turbofan architectures studied, although MTU does not intend to develop such an engine.
Cranfield University TERA 2020 researcher Stephen Ogaji says that TERA shows a bypass ratio of 14 across the three architectures under study tended to give the results sought by ACARE.
R-R and Snecma emphasise that TERA's results to date have been based on existing public domain data and not confidential commercial engine and airline operation data. The TERA 2020 tool also showed that a bypass ratio of 12 was optimal for fuel burn, not 14, which only improved noise. Beyond a ratio of 12, drag and wing integration issues were found to reduce specific fuel consumption.
TERA 2020 will be used by Vital's participants and is being deployed for the EU validation of radical engine architecture systems, or Dream project, and the ongoing sixth framework New Aero Engine Core Concepts study.