Distributed propulsion

For distributed propulsion on rail see: Multiple unit

Distributed propulsion (DP) is a type of powered flight propulsion system for fixed wing aircraft in which airflows and forces are distributed about a vessel. Its goal is to increase performance in fuel efficiency, emissions, noise, field length, and handling performance as compared to the use of a single large engine, jet, or propeller. DP is typically accomplished by spanwise distribution of partially or fully embedded multiple small engines or fans across the width of wing. It may instead employ ducting of exhaust gases along the entire trailing edge of a wing.

Types

Any fixed wing aircraft with more than one propulsor can be considered a distributed propulsion aircraft. However, in common modern usage DP describes a propulsion system scheme with distributed exhaust, a large number of distributed engines (typically fully or partially embedded within the wing), or a large number of distributed fans with a common core^[1]. These implementations are often proposed in conjunction with blended wing body (BWB) or hybrid wing body (HWB) aircraft.

Implementation approaches include jet flaps, transverse or cross-flow fans (CFF), multiple small engines (typically gas turbines), or multiple fans driven by a smaller number of engine cores. In the last case, the power transmission between the fans and engines may be linked by ducting hot gas^[2], mechanical gears^[3], or electric power lines^[4].

While some of these concepts were tested on full scale aircraft in the 1960 - 1970's, such as the Hunting H.126, they were not fielded in production aircraft. More recently, several full-size and smaller unmanned aerial vehicle (UAV) projects have proposed DP approaches to meet noise abatement^[5], fuel efficiency, and field length goals. Advancements in materials engineering, cryogenic cooling systems, novel fuels^[6], and high fidelity computational fluid dynamics (CFD) modeling and analysis^[7] have been credited for the renewed interest in DP approaches.

Benefits

Recent analytic and experimental distributed propulsion studies suggest several improvements in aircraft performance^[8]. They include fuel consumption efficiency, noise abatement, steep climbing for short take off and landing (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.^[9]

References

1. ^ Gohardani et al. 'Challenges of Future Aircraft Propulsion: A Review of Distributed Propulsion Technology And Its Potential Application for the All Electric Commercial Aircraft', Progress in Aerospace Sciences, Volume 47, Issue 5, July 2011, Pages 369-391.
2. ^ Winborn, B. 'The ADAM III V/STOL concept', American Institute of Aeronautics and Astronautics 69-201 (1969).
3. ^ Silent Aircraft Initiative
4. ^ Kim, Brown, and Felder. Distributed Turboelectric Propulsion for Hybrid Wing Body Aircraft. 2008 International Powered Lift Conference, Royal Aeronautical Society.
5. ^ Silent Aircraft Initiative
6. ^ Sehra and Whitlow. 'Propulsion and power for 21st century aviation'. Progress in Aerospace Sciences Volume 40, Issues 4-5, May-July 2004, Pages 199-235
7. ^ Dang and Bushnell. 'Aerodynamics of cross-flow flans and their application to aircraft propulsion and flow control', in Progress in Aerospace Sciences, Volume 45 Issues 1-3, pp 1-29. 2009
8. ^ Epstein, A. 'Distributed Propulsion: New Opportunities For An Old Concept'. Report (2007)
9. ^ Kim, Hyun Dae, ‘Distributed Propulsion Vehicles’, in 27th International Congress of the Aeronautical Sciences, 2011, pp. 1–11.

External links

• Gas Turbine Laboratory, Massachusetts Institute of Technology
• Metis Design Corporation, Distributed Propulsion using small, low thrust engines: Micro-Turbofan™ and the Compact Liftfan