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On the Performance of Variable-Geometry Ducted E-Fans
German Aerosp Ctr DLR, Inst Prop Technol, Dept Fan & Compressor, D-51147 Cologne, Germany..
German Aerosp Ctr DLR, Inst Prop Technol, Dept Fan & Compressor, D-51147 Cologne, Germany..
German Aerosp Ctr DLR, Inst Prop Technol, Dept Fan & Compressor, D-51147 Cologne, Germany..
German Aerosp Ctr DLR, Inst Prop Technol, Dept Fan & Compressor, D-51147 Cologne, Germany..
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2024 (English)In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 146, no 10, article id 101024Article in journal (Refereed) Published
Abstract [en]

Electrically driven ducted fans (e-fans), either underwing-mounted or located at the aft-fuselage, can potentially improve the system overall efficiency in hybrid-electric propulsion architectures by increasing their thrust share over the thrust generated by the main engines. However, the low design pressure ratio of such e-fans make them prone to operability issues at off-design conditions, i.e., takeoff, where nozzle pressure ratio is close or below the critical value. This paper investigates the operational limitations of such e-fans, proving the necessity of variable geometry. A component zooming approach is deployed by integrating a streamline curvature method within an aero-engine performance tool to investigate the e-fan installed performance and operability. The concepts of variable pitch fan (VPF) and variable area nozzle (VAN) are systematically explored to quantify any performance benefits, while the unavoidable added-weight challenges due to variable geometry are taken into account. Although e-fans with low design pressure ratio (PR) are more susceptible to operability issues compared to higher PR e-fans, the former show improved overall efficiency levels, mainly dominated by propulsive efficiency. It is found that variable geometry not only tackles operability but it can improve the off-design overall efficiency of e-fans even more. VPF mostly affects the component efficiency by reshaping the e-fan performance maps, while VAN has a greater impact on propulsive efficiency by moving the operating points.

Place, publisher, year, edition, pages
ASME , 2024. Vol. 146, no 10, article id 101024
Keywords [en]
e-fan, variable pitch fan, variable area nozzle, surge margin
National Category
Fluid Mechanics
Identifiers
URN: urn:nbn:se:mdh:diva-68563DOI: 10.1115/1.4066074ISI: 001312547200012Scopus ID: 2-s2.0-85214393249OAI: oai:DiVA.org:mdh-68563DiVA, id: diva2:1902779
Available from: 2024-10-02 Created: 2024-10-02 Last updated: 2025-11-24Bibliographically approved
In thesis
1. On the Design and Analysis of Electrified Aero-engine Families
Open this publication in new window or tab >>On the Design and Analysis of Electrified Aero-engine Families
2026 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rather than designing a new engine from scratch for every aircraft application, manufacturers often develop families of engines that share a common core; typically comprising the high-pressure compressor, combustor, and high-pressure turbine. This strategy reduces cost, shortens development time, and mitigates technical risk, making it an attractive option in today’s evolving aerospace landscape. Common-core variants are always associated with performance penalties compared to individually optimized clean-sheet engines because the initial core design is compromised to allow for adjustment of its component map entry points, but there is a high potential for better economics of the entire engine program.

To address these challenges, this thesis introduces a simulation methodology for assessing both conventional and electrified aero-engine architectures, including turbofans, turboprops, and distributed electric propulsion systems. Based on a multi-point synthesis approach, the framework supports performance evaluation across multiple fidelity levels: from 0D thermodynamic cycle modeling, to 1D mean-line design, and up to 2D throughflow component analysis.A particular focus is placed on electrically driven propulsors, evaluated both as standalone units and within turbo-electric configurations. These include variants featuring variable geometry, such as variable pitch fans and variable area nozzles, when necessary.

Building on the standalone engine modeling foundation, a novel methodology is introduced for simulating common-core engine variants within an aero-engine family. This extends the multi-point synthesis approach by treating the design point of each variant as an additional off-design condition of the baseline (first-to-enter-the-market) engine. To demonstrate its application, an electrified turboprop engine family is designed and analyzed across a range of power growth scenarios. Clean-sheet engine designs are developed in parallel to serve as benchmarks, enabling quantification of the performance penalties associated with enforcing commonality across various levels of power growth.

Place, publisher, year, edition, pages
Västerås: Mälardalens universitet, 2026
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 455
National Category
Environmental Engineering Vehicle and Aerospace Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-74488 (URN)978-91-7485-738-2 (ISBN)
Public defence
2026-01-23, Delta, Mälardalen University, Västerås, 09:00 (English)
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Supervisors
Available from: 2025-11-25 Created: 2025-11-24 Last updated: 2026-01-02Bibliographically approved

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Kavvalos, MavroudisKyprianidis, Konstantinos G.

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