Propulsion system for aircraft, in particular lightweight aircraft

Abstract

A propulsion system for aircraft, in particular lightweight aircraft, provides a low-noise and low-cost aircraft. The propulsion system includes at least two ducted propellers (3, 3). The ducts of are provided laterally on the fuselage (4) of the aircraft in such a way that the common net thrust of the ducted propellers is substantially collinear to the net drag.

Claims

1. An aircraft comprising a propulsion system, the propulsion system comprising: at least two propellers comprising rotor blades; at least two ducts cooperating with the at least two propellers to form at least two ducted propellers, the at least two ducts being disposed laterally on a fuselage of an aircraft so that a common resultant thrust force {right arrow over (F)}.sub.S of the ducted propellers is essentially collinear with a resultant drag force {right arrow over (F)}.sub.W; wings of the aircraft protruding from an outside surface of the two ducts in a spanwise direction; a continuous joint between an outer duct surface and the fuselage and/or a wing assembly of the aircraft; wherein the aircraft is in the form of a low-wing aircraft with a wing/fuselage transition with a contour in which the ducts are integrated to some extent, whereby wings and/or the fuselage are at least partly in a duct form.

2. The propulsion system as claimed in claim 1, wherein the ducts of the ducted propellers are at least partly integrated within the structure of the aircraft, in a region of the fuselage and/or in a region of a wing assembly.

3. The propulsion system as claimed in claim 1, wherein the disposition of the ducted propellers provides an undisturbed air flow to the ducted propellers, so that the propeller blades, while circulating, do not experience any changes in cyclical pressure, speed or angle of attack.

4. The propulsion system as claimed in claim 1, wherein a propeller slipstream is essentially parallel to a wing slipstream in cruising flight.

5. The propulsion system as claimed in claim 1, wherein looking in the direction of flight, the leading duct edge is essentially disposed at a height of a trailing edge of wings.

6. The propulsion system as claimed in claim 1, wherein a leading duct edge and/or a trailing duct edge are designed such that none of the edges span a planar surface, wherein the leading duct edge and/or the trailing duct edge are of a spiral form.

7. The propulsion system as claimed in claim 1, further comprising a boom supporting each duct, wherein the boom protrudes outwards to an extent that the respective duct does not intersect or contact a fuselage surface and/or a wing surface, a spacing is provided that prevents an inflow of a boundary layer from surfaces before plane of the respective ducted propeller and a flow channel between the fuselage surface and/or the wing surface and the duct has essentially constant cross sections in a flow direction.

8. The propulsion system as claimed in claim 1, wherein far the rotor blades include blade tips which contact the duct, at least one of the blade tips and the duct being made of a material that is eroded without damage and/or that is elastic yielding.

9. The propulsion system as claimed in claim 1, wherein the rotor blades comprise variable profile lengths that are not outwardly tapered.

10. The propulsion system as claimed in claim 1, wherein angles of attack of the rotor blades increase towards an outside of the rotor blades.

11. The propulsion system as claimed in claim 1, wherein the blades do not extend directly radially and are inclined and/or curved.

12. The propulsion system as claimed in claim 1, further comprising a controllable canard wing, by means of which displacement of the center of gravity as a result of different loading is compensated.

13. A propulsion system for an aircraft with a fuselage and wings, the propulsion system comprising: at least two propellers comprising rotor blades; at least two ducts cooperating with the at least two propellers to form at least two ducted propellers, the at least two ducts being disposed laterally on the fuselage of the aircraft so that a common resultant thrust force {right arrow over (F)}.sub.S of the ducted propellers is essentially collinear with a resultant drag force {right arrow over (F)}.sub.W, the two ducts having a leading duct edge and a trailing duct edge, in a direction of flight of the aircraft, the leading duct edge is disposed at a position of a trailing edge of the wings, the leading duct edge and the trailing duct edge being designed such that none of the edges span a planar surface, wherein the leading duct edge and the trailing duct edge are of a spiral form.

14. An aircraft system comprising: a fuselage; two ducts mounted on said fuselage, one said duct being mounted on one lateral side of said fuselage, an other said duct being mounted on an opposite lateral side of said fuselage, each of said ducts having an outer surface; two wings extending radially outward from said fuselage, at least a portion of each of said two wings being separate from said two ducts, a separate one of said wings being mounted on each of said sides of said fuselage, each of said wings extending laterally outward from said fuselage further than an entirety of said outer surface of an adjacent said duct extends laterally outward from said fuselage; two propellers comprising rotor blades, said two propellers cooperating with said two ducts to form two ducted propellers, said two ducted propellers being disposed laterally on said fuselage to form a common resultant thrust force {right arrow over (F)}.sub.S with a direction that is substantially collinear with a direction of a resultant drag force ?{square root over (F)}.sub.W of the aircraft.

15. A system in accordance with claim 14, wherein: said wings are directly connected to said fuselage.

16. A system in accordance with claim 14, wherein: an entry plane of each of said two ducts is arranged closer to a trailing edge of an adjacent said wing than to a leading edge of said adjacent wing with respect to a direction of flight of the aircraft.

17. A system in accordance with claim 14, wherein: said two ducts have a leading duct edge and a trailing duct edge in a direction of flight of the aircraft, said leading duct edge and said trailing duct edge being designed such that none of said edges span a planar surface, wherein said leading duct edge and said trailing duct edge are of a spiral form.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a side view of an aircraft;

(3) FIG. 2 is a front view of an aircraft;

(4) FIG. 3 is a top perspective view of an aircraft;

(5) FIG. 4 is a top view of an aircraft;

(6) FIG. 5 is a top perspective view of an aircraft;

(7) FIG. 6 is a front view of an aircraft; and

(8) FIG. 7 is front view of a ducted propeller with differently designed rotor blades.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) A specific example of the invention is explained below using FIGS. 1 to 7, wherein FIGS. 1 to 6 show different perspectives of an aircraft. The aircraft 1 illustrated in the figures comprises two wings 2, 2 and is in the form of a low-wing aircraft with a low-lying landing gear 10. As its propulsion system the aircraft 1 comprises two ducted propellers 3, 3 that are disposed laterally on the fuselage of the aircraft 4 and on the trailing edge of the wings 2, 2.

(10) The ducted propellers 3, 3 each comprise a duct 5, 5 with a leading edge 6 and a trailing edge 7 as well as a hub 8, 8. As can be clearly seen in FIG. 1, the leading and trailing edges 6, 7 are of a spiral form and do not lie in a plane. In the case of the illustrated embodiment, the ducted propellers 3, 3 are integrated within the structure of the aircraft 1. Specifically, the ducts 5, 5 are joined to the respective wings 2, 2 on the one hand and on the other hand to the fuselage 4 of the aircraft 1, so that both the wings 2, 2 and also the fuselage of the aircraft 4 form parts of the duct 5, 5. It can further be seen in FIG. 1 that the resultant thrust force F.sub.S is disposed essentially collinear with the resultant d F.sub.W, whereby pitching moments are prevented in the event of changes in thrust.

(11) In the case of the embodiment illustrated in FIG. 6, the fans (ducted propellers 3, 3) are mounted on booms 10, 10 such that the ducted propellers 3, 3 are at a distance from the fuselage 4 of the aircraft 1. In this case the magnitude of the distance is selected such that there is no diffusor between the fuselage and the duct. In this case the partial integration of the duct 5, 5 within the fuselage 4 is omitted.

(12) Finally, FIG. 7 shows the frontal view of a ducted propeller 3 with three examples of differently designed rotor blades 11, 12, 13. While the rotor blade 13 protrudes approximately radially, the rotor blade 12 is precisely oriented at an angle to the radial line R and rotor blade 11 follows a curve.

(13) The aircraft 1 according to FIG. 5 shows an embodiment with canard wings 9, 9 by way of example.

(14) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.