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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Distributed propulsion</span></span>

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</style><div role="note" class="hatnote navigation-not-searchable">For distributed propulsion on railway trains, see <a href="Multiple_unit" title="Multiple unit">Multiple unit</a>.</div>

<p>In aeronautics, <b>Distributed propulsion</b> is an arrangement in which the propulsive and related air flows are distributed over the aerodynamic surfaces of an aircraft. The purpose is to improve the craft's aerodynamic, propulsive and/or structural efficiency over an equivalent conventional design.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p><p>Anticipated benefits include improved <a href="Fuel_efficiency" title="Fuel efficiency">fuel efficiency</a>, emissions, noise, landing field length and handling.

</p><p>Distributed propulsion may be accomplished by spanwise distribution of partially or fully embedded multiple small engines or fans along the wing. Alternatively, it may involve ducting exhaust gases along the wing's entire trailing edge.

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<div class="mw-heading mw-heading2"><h2 id="Design_principles">Design principles</h2></div>

<div class="mw-heading mw-heading3"><h3 id="Definition">Definition</h3></div>

<p>Distributed propulsion on an aircraft is typically characterised not only by the distributed nature of the propulsive thrust but also by utilisation of the effect this has on the aircraft aerodynamics.<sup id="cite_ref-epstein_2-0" class="reference"><a href="#cite_note-epstein-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The propulsive air flows are distributed over the aerodynamic surfaces of the craft, typically spanwise over a fixed wing. These flows may interact with other air flowing over the wing and substantially affect the <a href="Aerodynamics" title="Aerodynamics">aerodynamics</a>. However there is no accepted formal definition.<sup id="cite_ref-kim2010_3-0" class="reference"><a href="#cite_note-kim2010-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-burston_4-0" class="reference"><a href="#cite_note-burston-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p><p>Three broad classes of distributed propulsion system have been identified:<sup id="cite_ref-burston_4-1" class="reference"><a href="#cite_note-burston-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

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<ul><li>Distributed exhaust, such as jet flaps.</li>

<li>Multiple discrete propulsors (fans, propellers or jets), which may be powered individually or by remote drive from fewer engines.</li>

<li><a href="Cross-flow_fan" class="mw-redirect" title="Cross-flow fan">Cross-flow fans</a>, which are a type of <a href="Rotor_wing" title="Rotor wing">horizontal-axis rotor</a>.</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Aerodynamic_functions">Aerodynamic functions</h3></div>

<p>In addition to providing propulsion, distributed propulsion arrangements have been studied with a view to providing various aerodynamic functions. These include:<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>

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<ul><li>Direct reenergizing of the boundary layer</li>

<li>Flow separation control</li>

<li>Powered lift/circulation control</li>

<li>Viscous drag reduction</li>

<li>Vortex/vorticity control</li>

<li>Vehicle control/vectored thrust</li></ul>

<div class="mw-heading mw-heading3"><h3 id="Potential_benefits">Potential benefits</h3></div>

<p>Several areas have been identified in which distributed propulsion may offer benefits over conventional designs.<sup id="cite_ref-epstein_2-1" class="reference"><a href="#cite_note-epstein-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> These include fuel efficiency, noise abatement, steep climbing for <a href="STOL" title="STOL">short take off and landing</a> (STOL), novel control approaches (in particular eliminating control surfaces for roll, pitch and yaw moments), and high bypass ratios. It has also been suggested that smaller propulsors will be cheaper to manufacture and easier to handle during assembly and maintenance.<sup id="cite_ref-kim2010_3-1" class="reference"><a href="#cite_note-kim2010-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Distributed_propulsors">Distributed propulsors</h2></div>

<p>The multiple propulsion unit strategy involves three or more propulsion units. These units are arranged in Leader or Follower configurations. They are classified into five intensity classes (A–E) and three thrust-to-weight ratio categories (I-III). They can be arranged within/above/around or across the wing(s)/fuselage(s) or airframe.

</p><p>Leader arrangements employ propulsion units to directly generate thrust, i.e., distributed engines. The Follower arrangement uses secondary propulsion unit(s), such as multiple fans that are powered by a single engine. In the last case, the power transmission between the fans and engines may be linked by ducting hot gas, mechanical gears, or electric power lines.

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<div class="mw-heading mw-heading3"><h3 id="Distributed_electric_propulsion">Distributed electric propulsion</h3></div>

<p>Distributed electric propulsion (DEP) comprises multiple small fans or propellers driven by electric motors. Typically, each individual thruster is direct driven by its own relatively small and lightweight electric motor. The electrical power may be provided by any suitable source.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>

</p><p>The advantages of distributed propulsion for lightweight, high <a href="Aspect_ratio" title="Aspect ratio">aspect ratio</a> solar-powered aeroplanes are exemplified in the AeroVironment <a href="NASA_Pathfinder" title="NASA Pathfinder">HALSOL/Pathfinder</a>/<a href="AeroVironment_Helios_Prototype" title="AeroVironment Helios Prototype">Helios</a> projects, begun in 1983, and the University of Michigan X-HALE, flown from around 2012.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Distributing the electric motors along the span was able to control how the airframe flexed in flight, allowing the structure to be much lighter than the conventional rigid equivalent.<sup id="cite_ref-burston_4-2" class="reference"><a href="#cite_note-burston-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading3"><h3 id="Aeroelasticity">Aeroelasticity</h3></div>

<p>When heavy propulsion units are distributed along a wing, this allows the wing structure to be made lighter. However their weight and thrust can interact with the natural tendency of the wing to flex under varying loads (<a href="Aeroelasticity" title="Aeroelasticity">aeroelasticity</a>). This can cause problems, for example it was a major cause of a crash involving the <a href="NASA_Helios" class="mw-redirect" title="NASA Helios">NASA Helios</a> research aircraft. One solution investigated is the use of active aeroelastic controls to correct or even make use of wing flexing during flight.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="History">History</h2></div>

<p>Multi-engine installations have been a feature of aeroplanes since the introduction of the <a href="Sikorsky_Ilya_Muromets" title="Sikorsky Ilya Muromets">Sikorsky Ilya Muromets</a> shortly before World War One. However most do not significantly modify the airflow over the wings and are not always treated as distributed propulsion.

</p><p>In 1963 the <a href="Hunting_H.126" title="Hunting H.126">Hunting H.126</a> research aircraft was built to investigate the direct use of a jet flap for propulsion, while the <a href="ShinMaywa_US-2" title="ShinMaywa US-2">ShinMaywa US-2</a> flying boat of 2003 used blown flaps to improve short takeoff and landing (STOL) performance and subsequently entered production.<sup id="cite_ref-burston_4-3" class="reference"><a href="#cite_note-burston-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p><p><a href="FanWing" title="FanWing">FanWing</a> began development of the crossflow fan as a combined lift and propulsion system in 1997 and over the next few years flew several models and research drones. Subsequent research in the US focused on the use of a crossflow fan inset into the wing upper trailing edge, as the primary driver for boundary layer control and jet flap propulsion.<sup id="cite_ref-kim2010_3-2" class="reference"><a href="#cite_note-kim2010-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>

</p><p>More recently, several <a href="Unmanned_aerial_vehicle" title="Unmanned aerial vehicle">unmanned aerial vehicle</a> (UAV) projects have explored the potential of distributed propulsion to offer noise abatement, fuel efficiency and short-field performance. As of 2022 a manned <a href="List_of_X-planes" title="List of X-planes">X-plane</a>, the <a href="NASA_X-57_Maxwell" title="NASA X-57 Maxwell">X-57 Maxwell</a> is under development at NASA and several prototypes of a light aircraft, the <a href="Lilium_Jet" title="Lilium Jet">Lilium Jet</a>, have flown in Germany.

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<div class="mw-heading mw-heading3"><h3 id="List_of_aircraft_with_distributed_propulsion">List of aircraft with distributed propulsion</h3></div>

<ul><li><a href="Aurora_XV-24_LightningStrike" title="Aurora XV-24 LightningStrike">Aurora XV-24 LightningStrike</a>: Distributed electric fans. Research UAV. Flew in 2016.</li>

<li><a href="Ball-Bartoe_Jetwing" title="Ball-Bartoe Jetwing">Ball-Bartoe Jetwing</a>: Jet-flap. Manned research aircraft. Flew from 1977.</li>

<li><a href="English_Electric_P.10" class="mw-redirect" title="English Electric P.10">English Electric P.10</a>: Turbojets installed in wings with distributed ramjets. 1950s concept.</li>

<li><a href="FanWing" title="FanWing">FanWing</a>: Cross-flow fan. Series of research UAVs.</li>

<li><a href="Hunting_H.126" title="Hunting H.126">Hunting H.126</a>: Jet-flap. Manned research aircraft. Flew from 1963.</li>

<li><a href="Lilium_Jet" title="Lilium Jet">Lilium Jet</a>: Distributed electric fans. Series of unmanned prototypes.</li>

<li><a href="NASA_X-57_Maxwell" title="NASA X-57 Maxwell">NASA X-57 Maxwell</a> (Sceptor): Distributed electric fans. Manned research aircraft. Development halted.</li>

<li><a href="Electra_EL-2_Goldfinch" title="Electra EL-2 Goldfinch">Electra EL-2 Goldfinch</a>: Distributed electric fans. Manned demonstrator. Under development.</li></ul>

<ul><li><a href="Index_of_aviation_articles" title="Index of aviation articles">Index of aviation articles</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://aerospace.illinois.edu/news/test-flight-successful-propulsion-controlled-aircraftphase-ii-funded">"Test flight successful on propulsion-controlled aircraft—phase II funded"</a>.</cite></span>

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<li id="cite_note-epstein-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-epstein_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-epstein_2-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Epstein, A. H. (2007) <a rel="nofollow" class="external text" href="https://apps.dtic.mil/sti/pdfs/ADA516809.pdf">"Distributed Propulsion: New Opportunities For An Old Concept"</a>. MIT. (retrieved 16 June 2022).</span>

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<li id="cite_note-kim2010-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-kim2010_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-kim2010_3-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-kim2010_3-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text">Kim, Hyun Dae. (2010) <a rel="nofollow" class="external text" href="http://www.icas.org/ICAS_ARCHIVE/ICAS2010/PAPERS/225.PDF">"Distributed Propulsion Vehicles"</a>, 27th International Congress of the Aeronautical Sciences, ICAS 2010, pp. 1–11. (retrieved 16 June 2022)</span>

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<li id="cite_note-burston-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-burston_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-burston_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-burston_4-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-burston_4-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text">Burston et al. <a rel="nofollow" class="external text" href="https://www.sciencedirect.com/science/article/pii/S0360544221030371">"Design principles and digital control of advanced distributed propulsion systems"</a>. in: Karakoç et al (ed). <i>Energy</i> special issue on <i>Emerging Energy Technologies and Alternative Fuels for Aviation</i>, Volume 241, 15 February 2022.</span>

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<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"> Gohardani, A.S. (2013) "A synergistic glance at the prospects of distributed propulsion technology and the electric aircraft concept for future unmanned air vehicles and commercial/military aviation." <i>Progress in Aerospace Sciences</i>, Volume 57. February 2013. Pages 25-70. (<a rel="nofollow" class="external text" href="http://www.sciencedirect.com/science/article/pii/S0376042112000735">Link</a>: paywalled)</span>

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<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite id="CITEREFKim,_Hyun_D2020" class="citation report cs1">Kim, Hyun D (2020-06-22). <a rel="nofollow" class="external text" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180004729.pdf">A Review of Distributed Electric Propulsion Concepts for Air Vehicle Technology</a> <span class="cs1-format">(PDF)</span> (Report). NASA.</cite></span>

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<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text">Jones, Jessica <a rel="nofollow" class="external text" href="https://a2srl.engin.umich.edu/research/flexible/xhale/"><i>X-HALE: Flight Testing A Very Flexible UAV for Nonlinear Aeroelastic Tests</i></a>, University of Michigan. (retrieved 17 June 2022)</span>

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<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">Nhan T. Nguyen, Nhan T. et. al. (2018) <a rel="nofollow" class="external text" href="https://ntrs.nasa.gov/api/citations/20180001283/downloads/20180001283.pdf">"Distributed Propulsion Aircraft with Aeroelastic Wing Shaping Control for Improved Aerodynamic Efficiency"</a>, NASA. (retrieved 26 June 2022)</span>

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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

This article is issued from <a class="external text" title="Last edited on 2024-11-16" href="https://en.wikipedia.org/wiki/?title=Distributed_propulsion&oldid=1257849531">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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