Aircraft propelled by a turbojet engine with contrarotating fans

Abstract

An aircraft propelled by a turbojet having contrarotating fans, the turbojet being incorporated at the rear of a fuselage of the aircraft and in line therewith and including two gas generators that feed a working turbine having two contrarotating turbine rotors for driving two fans arranged downstream from the gas generators, and distinct air intakes for feeding each gas generator, the air intakes being connected to the fuselage of the aircraft so as to take in at least a portion of the boundary layer formed around the fuselage of the aircraft.

Claims

1. An aircraft propelled by a turbojet having two contrarotating fans, the turbojet being incorporated at the rear of a fuselage of the aircraft and in line with the fuselage and comprising two gas generators that feed a single working turbine having two contrarotating turbine rotors for driving the two contrarotating fans, the two contrarotating fans being arranged downstream from the two gas generators, and distinct air intakes for feeding each gas generator, said air intakes being connected to the fuselage of the aircraft, wherein the turbojet further comprises a mixer disposed in a zone of convergence of two primary flow passages, said mixer being disposed upstream from the two contrarotating fans and along an axis of the single working turbine and being configured and arranged to mix gas streams from an output end of the two primary flow passages and coming from the two gas generators, to create a single uniform gas stream to feed the single working turbine, the two gas generators further being disposed in the two primary flow passages and forming a V-shape between them wherein each of the two primary flow passages and each of the corresponding gas generator lies at an angle in the range 80 to 120 relative to a longitudinal axis of the fuselage of the aircraft and wherein the two contrarotating fans are ducted by a nacelle fastened to a vertical empennage of the aircraft and wherein the nacelle comprises a secondary flow passage disposed radially outward of the zone of convergence of the primary flow passages and rearward of the air intakes and configured and arranged to feed air from a portion of the boundary layer not taken into the two gas generators to the two contrarotating fans in a region radially outward of the single working turbine.

2. An aircraft according to claim 1, wherein the two contrarotating fans present an outside diameter that is substantially identical to the maximum diameter of the fuselage of the aircraft.

3. An aircraft according to claim 1, wherein the working turbine and the two contrarotating fans are centered on the longitudinal axis of the fuselage of the aircraft.

4. An aircraft according to claim 1, wherein all of the output of the two gas generators is directed to the mixer.

5. An aircraft according to claim 1, wherein the angle is selected to, in the event of a failure of a disk of one of the two gas generators, avoid debris impacting against the other of the two gas generators or against one of the two contrarotating fans.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other characteristics and advantages of the invention appear from the following description made with reference to the accompanying drawings which show an embodiment having no limiting character. In the figures:

(2) FIG. 1 is a diagrammatic view in perspective of a civil aircraft in accordance with the invention; and

(3) FIG. 2 shows the turbojet of the FIG. 1 aircraft in longitudinal section on II-II.

DETAILED DESCRIPTION OF THE INVENTION

(4) The invention relates to any aircraft, whether civil or military, e.g. to drones and to civil airplanes of the kind shown in FIG. 1.

(5) FIG. 1 thus shows a civil airplane 1 in accordance with the invention. The airplane has a turbojet 10 incorporated at the rear of the fuselage 2 of the airplane, in line therewith.

(6) As shown more clearly in FIG. 2, the turbojet 10 is centered on a longitudinal axis X-X of the fuselage 2 of the airplane. The turbojet comprises in particular, from upstream to downstream in the gas flow direction, two distinct gas generators 12a and 12b that are arranged in parallel and that feed a single working turbine 14.

(7) In known manner, each gas generator 12a, 12b comprises a low pressure compressor, a high pressure compressor, a combustion chamber, a low pressure turbine, and a high pressure turbine (not shown in the figures).

(8) Furthermore, each gas generator 12a, 12b is housed in a respective primary flow passage 16a, 16b. Between them, these two primary flow passages preferably form a V-shape that is open in the upstream direction and that converges on the longitudinal axis X-X.

(9) Also preferably, each of the primary flow passages 16a and 16b housing a gas generator lies at an angle in the range 80 to 120 relative to a longitudinal axis of the fuselage of the airplane.

(10) A mixer (not shown in the figures) is positioned in the zone of convergence of the two primary flow passages 16a and 16b. The function of this mixer is to mix the gas streams coming from the two gas generators so as to create a single uniform gas stream that is to feed the working turbine 14.

(11) Distinct air intakes 18a and 18b for feeding each of the gas generators are also provided. These air intakes are connected to the fuselage 2 of the airplane so as to take in at least a portion of the boundary layer formed around the fuselage of the airplane. More precisely, their inside walls are directly incorporated in the fuselage of the airplane.

(12) The working turbine 14 that is fed by the two gas generators has two contrarotating turbine rotors 14a and 14b for driving contrarotating rotation of two fans 20a and 20b that are located behind the turbojet and that are arranged in series in a secondary flow passage 22. These turbine rotors are coaxial and centered on the longitudinal axis X-X. The working turbine 14 is housed inside a structure (not shown in the figures) that is situated inside the fuselage, the fuselage also supporting an annular central body 24 centered on the longitudinal axis X-X.

(13) The two fans 20a and 20b are ducted by a nacelle 26 that is fastened directly to the vertical empennage 4 of the airplane. These fans present an outside diameter D that corresponds substantially to the maximum diameter E of the fuselage 2 of the airplane.

(14) The rear position of the fans and their large outside diameter thus enables them to be fed with air by the portion of the boundary layer that has not been taken into the gas generators.

(15) As a result, since the flow speed of the boundary layer is relatively low, the speed of rotation of the fans also remains relatively low, thereby making it possible to increase the propulsion efficiency of the turbojet and to reduce its sound emissions.

(16) Furthermore, since the boundary layer is sucked in (by the gas generators and by the fans of the turbojet), and since the front sectional area of the airplane is small (the turbojet is hidden behind the fuselage of the airplane), the aerodynamic drag of the airplane is limited.

(17) It should be observed that the equipment associated with the turbojet (not shown in the figures) may be arranged around the gas generators where there is available space.

(18) It should also be observed that the main problems of turbojet failure can be avoided. In particular, in the event of one gas generator failing, the other gas generator can continue to feed the working turbine in order to produce the necessary thrust. Likewise, in the event of a disk of a gas generator bursting, the V-shaped arrangement of the gas generators makes it possible to avoid debris impacting against the other gas generator or against one of the fans.