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Hybrid power fan drive – results of a conceptual study

The introduction of electrical power supply to an aircraft propulsion system offers a wide design space for system architectures. Within the EU FP7 project ENOVAL, Bauhaus Luftfahrt has completed the concept study of a mechanically integrated parallel hybrid electric (MIPH) turbofan. Through a methodical downselection procedure, a most promising power plant system architectural concept was identified and conceptually elaborated for a short-range aircraft application. Therefore, the basic power plant, the electric systems architectural layout, and major electrical components were defined and important airframe integration aspects were evaluated.

Taking into account power plant operational robustness in case of electric system failure, a design degree of power hybridisation of 10 % at flow path sizing conditions was found to be most suitable for an MIPH turbofan. The analysis clearly indicates the necessity of specialised turbo component aerodynamic design, in order to realise the full potential of efficiency gain and MIPH turbofan operational flexibility. The integrated system assessment at aircraft level was performed for various design range requirements. Based on an advanced mid- to long-term battery specific energy target of 1000 Wh kg-1, the design fuel benefit for the MIPH technology on a 500 NM design range yielded 3.5 %. The evaluation result shows that the efficiency benefit of electrical power systems alone will not be able to deliver the required improvements for MIPH systems at aircraft level. Key to achieving major improvements is a more synergistic systems design integration.

This project has received funding from the European Union’s 7th Framework Programme for research, technological development and demonstration under grant agreement No. 604999.

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