阅读说明：本技术 飞行器推进机组及具有这种推进机组的飞行器后部 (Aircraft propulsion unit and rear part of an aircraft comprising such a propulsion unit ) 是由 C·尼格莱斯库 于 2019-06-28 设计创作，主要内容包括：飞行器推进机组及具有这种推进机组的飞行器后部。本发明涉及飞行器推进机组,包括：具有静止部分(2)和带动在动力装置(1)下游的风扇(4)旋转的旋转部分(3)的动力装置(1)、在风扇(4)下游的固定叶片组件(6)、内部容纳风扇(4)与固定叶片组件(6)的发动机舱(7)。推进机组还包括由至少两个同轴的轴组成的组件,风扇轴(10)将风扇(4)与旋转部分(3)相连,将固定叶片组件(6)与静止部分(2)相连的固定叶片轴(11)至少对于其部分长度在风扇轴(10)内同心延伸。刚性紧凑结构限制风扇叶片(5)端部与发动机舱(7)内部管道(8)内的风扇罩壳(9)间的间距变化。(Aircraft propulsion unit and aircraft rear section with such a propulsion unit. The invention relates to an aircraft propulsion unit comprising: the power plant (1) comprises a stationary part (2) and a rotating part (3) which drives a fan (4) downstream of the power plant (1) to rotate, a stationary blade assembly (6) downstream of the fan (4), and an engine compartment (7) which accommodates the fan (4) and the stationary blade assembly (6) therein. The propulsion unit further comprises an assembly of at least two coaxial shafts, a fan shaft (10) connecting the fan (4) to the rotating part (3), and a stationary blade shaft (11) connecting the stationary blade assembly (6) to the stationary part (2) extending concentrically within the fan shaft (10) at least for part of its length. The rigid compact structure limits the variation of the spacing between the ends of the fan blades (5) and the fan casing (9) inside the duct (8) inside the nacelle (7).)

1. An aircraft propulsion unit comprising:

-a power plant (1) having a stationary part (2) and a rotating part (3),

-a fan (4) having fan blades (5) which is rotated by the rotating part (3) downstream of the power plant (1),

-a fixed-blade assembly (6) located downstream of the fan (4), and

-a nacelle (7) having internally a fan casing (9) at the fan (4) and the fixed-blade assembly (6),

it is characterized in that the aircraft propulsion unit further comprises a shaft assembly consisting of at least two coaxial shafts, wherein:

-a fan shaft (10) connecting the fan (4) with the rotating part (3) of the power plant (1), and

-a fixed-blade shaft (11) connecting the fixed-blade assembly (6) with the stationary part (2) of the power plant (1), the fixed-blade shaft extending concentrically within the fan shaft (10) for at least a part of its length.

2. The aircraft propulsion unit according to claim 1, characterized in that the coaxial shaft assembly further comprises:

-a fan hub (12) connected to the stationary part (2) of the power plant (1), the fan hub extending concentrically around the fan shaft (10) over at least a part of the fan shaft length.

3. Aircraft propulsion unit according to claim 2, characterized in that it comprises at least:

-a first bearing module (13) mounted between the fixed blade shaft (11) and the fan shaft (10); and

-a second bearing module (14) mounted between the fan shaft (10) and the fan hub (12).

4. Aircraft propulsion unit according to any one of the preceding claims, characterised in that the power means comprise:

-an engine (17) with a rotor (18), and

-a planetary gear (19) connected to the rotor (18) of the engine (17) and carrying the fan (4) in rotation, said planetary gear (19) comprising:

-an input planetary gear (20) connected to the rotor (18) of the engine (17)

-an output planetary gear in the form of a crown (21) connected to the fan shaft (10); and

-a stationary planet carrier (22) connected to the stationary part (2) of the power plant (1) and to the stationary blade shaft (11).

5. Aircraft propulsion unit according to any of the preceding claims, characterized in that it further comprises:

-one or more stages of auxiliary fans (23) arranged between the fan (4) and the fixed-blade assembly (6), said auxiliary fans (23) being adapted to repressurize the propulsive air flow flowing at the footing of the fan blades (5) and at the footing of the fixed-blade assembly (6).

6. Aircraft propulsion unit according to claim 5, characterised in that the fan blades (5) are mounted by their footings on a fan disc (24) to form the fan (4);

the aircraft propulsion unit further comprises:

-a main axial extension (25) of a fan disc (24) extending downstream of said fan disc and carrying in rotation said auxiliary fan (23), and

-an auxiliary fan cowl (26) surrounding the auxiliary fan (23) and connected to the stationary blade assembly (6).

7. The aircraft propulsion unit according to any one of claims 1 to 6, characterised in that the fan casing (9) located inside the nacelle (7) is mechanically independent of the nacelle (7), being held by a fixed blade assembly (6) connected to the fan casing.

8. The aircraft propulsion unit according to any one of claims 1 to 6, characterised in that the fan casing (9) is mechanically connected to the nacelle (7), the fan casing being held by the fixed blade assembly (6) connected thereto; the nacelle (7) is thus connected to the stationary part (2) of the power plant (1) by means of a coaxial shaft assembly consisting of at least two coaxial shafts, a fixed blade assembly (6) and a fan casing (9).

9. An aircraft rear section comprising a rear fuselage section and at least one aircraft propulsion unit according to any one of claims 1 to 6, characterized in that:

-the stationary part (2) of the power unit (1) is mechanically connected to the rear fuselage part (27);

-a fan casing (9) located inside the nacelle (7) mechanically independent of the nacelle (7) and held by a fixed blade assembly (6) associated with the fan casing.

-the load (28) generated by the fan (4), the fan casing (9) and the fixed-blade assembly (6) is transmitted to the rear fuselage portion (27) through a coaxial shaft assembly consisting of at least two coaxial shafts; and

-a structural tension member (29) connecting the nacelle (7) with the rear fuselage portion (27), the structural tension member being dimensioned to transmit only the load of the nacelle to the rear fuselage portion (27).

10. An aircraft rear section comprising a rear fuselage section and at least one aircraft propulsion unit according to any one of claims 1 to 6, characterized in that:

-the stationary part (2) of the power plant (1) is mechanically connected to the rear fuselage part (27);

-said fan casing (9) is mechanically connected to the engine compartment (7), the fan casing being held by the fixed-blade assembly (6) connected thereto; the nacelle (7) is thus connected to the stationary part (2) of the power plant (1) by means of a coaxial shaft assembly consisting of at least two coaxial shafts, a fixed blade assembly (6) and a fan casing (9);

-the load (28) generated by the fan (4), nacelle (7), fan casing (9) and fixed blade assembly (6) is transmitted to the rear fuselage (27) through a coaxial shaft assembly consisting of at least two coaxial shafts.

Technical Field

The present invention relates to aircraft propulsion units, and in particular to their structure and their installation on aircraft.

Background

The general construction of a commercial aircraft most commonly has a fuselage, a wing comprising two wings, and a rear tail. Such aircraft also include one or more propulsion units, most commonly turbojet engines. The propulsion units may be mounted on the aircraft according to different configurations. The propulsion units are most often suspended below the wings by struts; but may also be fixed at the rear of the fuselage or at the tail by means of struts.

As the aircraft moves through the air, its exterior surfaces can affect the air flow. In particular, when the aerodynamic profile moves in the atmosphere, a boundary layer is generated at the surface of the aerodynamic profile. The boundary layer corresponds to a region where the air flow is slowed by the viscous contact of the air with the contoured surface.

Typically, the propulsion units are configured not to ingest boundary layers generated on the aerodynamic surfaces of the aircraft. For this reason, most often, the propulsion units are mounted so that their air intakes are located at a free air flow, i.e. an air flow which is little or not at all disturbed by the aircraft surface. This is the case, for example, when the thrust unit is suspended under the wing or at a distance from the fuselage behind the aircraft.

However, the propulsion unit has some advantages in swallowing the boundary layer: the propulsion efficiency of the aircraft can be improved and the specific consumption thereof, namely the consumption of hydrocarbon fuel relative to the mass of the aircraft, can be reduced. To take advantage of these advantages, the propulsion unit may thus also be configured to swallow the boundary layer. Such propulsion units are generally known by the acronym BLI ("Boundary layer induction"), i.e., "Boundary layer ingestion. One possible configuration of a BLI type propulsion unit on an aircraft is to mount it at the rear of the fuselage.

Patent application US-a1-2017/0081013 describes an example of a BLI propulsion unit mounted at the rear of the fuselage. The relative axial position of the propulsion unit components will then be indicated with respect to the direction of the propulsion air flow through the propulsion unit. An aircraft propulsion unit as described in said prior art document comprises a power plant having a stationary part and a rotating part, and a fan having fan blades and being rotated by the rotating part of the power plant. The fan is located downstream of the power plant. There is also a stationary blade assembly located downstream of the fan, and an engine nacelle having a fan shroud internally at the fan and stationary blade assembly.

In this configuration, the nacelle is mechanically connected to the aircraft fuselage by a structural tension member that is generally streamlined and located upstream of the fan. Loads from the engine compartment and the stationary blade assembly are transferred to the fuselage through structural tension members sized for this purpose. Thus, under the very large aerodynamic stresses acting on the nacelle and the fixed blade assembly, the nacelle and the fixed blade assembly move relative to the fuselage and the fan due to the deformation of the structural tensile member. Thus, the spacing between the fan blade tips and the fan shroud may vary widely along the fan perimeter depending on aircraft flight conditions and phases. The lack of rigidity in the components of the nacelle, the stationary blade assembly and the fan means that the clearance between the ends of the fan blades and the fan shroud must be large enough to accommodate the deformation and avoid a situation where the fan blades rub against the shroud. This large clearance has a severe negative impact on the performance and efficiency of the propulsion unit.

Disclosure of Invention

The present invention aims to solve this problem by providing an aircraft propulsion unit and an aircraft rear section comprising at least one propulsion unit.

The aircraft propulsion unit according to the invention is therefore characterized in that it comprises a coaxial shaft assembly consisting of at least two coaxial shafts, wherein the fan shaft connects the fan to the rotating part of the power plant, and the stationary blade shaft connects the stationary blade assembly to the stationary part of the power plant, the stationary blade shaft extending concentrically within the fan shaft for at least a part of its length.

This coaxial shaft assembly arrangement, consisting of coaxial shafts, may create a mechanical connection between the fan, the fixed blade assembly, and the fan casing. The fan-fixed blade-shroud assembly thus achieved is more compact and more rigid than prior art assemblies, limiting deformation without the need for reinforcing structural tension members connecting the nacelle to the rear of the fuselage.

In a particularly advantageous configuration of the aircraft propulsion unit, the coaxial shaft assembly further comprises a fan hub connected to the stationary part of the power plant, the fan hub extending concentrically around the fan shaft over at least a part of its length.

Preferably, the aircraft propulsion unit further comprises at least: the fan assembly includes a first bearing module mounted between the stationary blade shaft and the fan shaft, and a second bearing module mounted between the fan shaft and the fan hub.

More particularly, at least one of the first and second bearing modules includes at least a ball bearing and a roller bearing.

Advantageously, the power plant of the aircraft propulsion unit comprises an engine with a rotor, and a planetary gear train connected to the rotor of the engine and rotating a fan. The planetary gear train includes: the fan is driven by a power unit, and the power unit is driven by a fan shaft to rotate.

Additionally, the aircraft propulsion unit includes one or more stages of auxiliary fans of small radius, arranged between the fans and the fixed blade assembly. The auxiliary fan is adapted to repressurize the propulsive air stream flowing at the fan blade feet and the fixed blade assembly feet.

Preferably, in the aircraft propulsion unit, the fan blades are mounted on a fan disc by their feet to form said fan. The primary axial extension of the fan disc extends downstream of said fan disc and causes said auxiliary fan to rotate. An auxiliary fan fairing surrounds the auxiliary fan and is coupled to the fixed blade assembly.

Advantageously, in the aircraft propulsion unit, the fan casing located inside the nacelle is mechanically independent of the nacelle and is held by a fixed blade assembly associated with the fan casing.

Alternatively, in an aircraft propulsion unit, the fan casing is mechanically independent of the nacelle and is held by a fixed blade assembly associated with the fan casing; the nacelle is therefore connected to the stationary part of the power plant by means of a coaxial shaft assembly consisting of at least two coaxial shafts, a stationary blade assembly and a fan casing.

Advantageously, sliding means are added to the stationary blade shaft upstream of the first bearing module.

According to a second aspect of the invention, an aircraft rear section comprises an aft fuselage and at least one aircraft propulsion unit, wherein a stationary part of the power plant is mechanically connected to the aft fuselage. The fan casing, which is located inside the engine compartment, is mechanically independent of the engine compartment and is held by a fixed blade assembly connected to the fan casing. Thus, the load generated by the fan, the fan shroud, and the fixed blade assembly is transmitted to the rear of the body through a coaxial shaft assembly composed of at least two coaxial shafts. Furthermore, a structural tension member connects the nacelle to the rear of the fuselage, the structural tension member being dimensioned to transmit only the load of the nacelle to the rear of the fuselage.

Optionally, the fan casing is mechanically connected to the engine compartment, the fan casing being retained by a fixed blade assembly connected thereto. The nacelle is therefore connected to the stationary part of the power plant by means of a coaxial shaft assembly consisting of at least two coaxial shafts, a stationary blade assembly and a fan casing. Thus, the load generated by the fan, the engine compartment, the fan shroud and the fixed blade assembly is transmitted to the rear of the fuselage through a coaxial shaft assembly consisting of at least two coaxial shafts.

Drawings

Further characteristics and advantages of the invention will emerge from the following description of a non-limiting embodiment of the different aspects of the invention. The description is made with reference to the accompanying drawings, which are given as non-limiting examples of the invention:

figure 1a shows a half-sectional side view of a first embodiment of a propulsion unit according to the present invention;

figure 1b shows a half-sectional side view of another embodiment of the propulsion unit according to the present invention;

FIG. 2 shows a detailed view of the coaxial shaft assembly in the propulsion unit as shown in the semi-sectional side views of FIGS. 1a and 1 b;

FIG. 3 illustrates a side view, in half section, of a propulsion unit equipped with an auxiliary fan according to an embodiment of the present invention; and

figure 4 shows a half-sectional side view of a propulsion unit equipped with an auxiliary fan.

Detailed Description

Fig. 1a shows a boundary layer suction aircraft propulsion unit, also referred to as BLI propulsion unit. BLI is an acronym for Boundary Layer Ingestion. The relative axial position of the propulsion unit components will then be indicated relative to the direction of the propulsion air flow through the propulsion unit.

Typically, this type of propulsion unit comprises a power plant 1 with an engine 17 located at the rear part 27 of the fuselage. The engine has a rotor 18 normally engaged with the transmission. The transmission outlet is connected to a fan shaft 10 for driving the fan 4 in rotation. The transmission may be a planetary gear train 19, as shown in the figure, or any other transmission system that is capable of adjusting the rotational speed of the fan shaft 10 to match the rotational speed of the rotor 18. The engine 17 may be a turbine or a turbojet, as is most often the case, or may be any other type of engine, such as an electric motor. In a BLI type propulsion unit mounted at the rear of the fuselage 27, the engine is located at the rear of the fuselage. The fan 4 is located downstream of the engine 17 and is housed within an engine compartment 7 having an internal duct 8 in which the fan 4 sucks in air. A fan casing 9 facing the fan blades 5 is fitted in the inner duct 8 of the engine compartment 7. The fan casing 9 is fixed to the fixed blade assembly 6. Furthermore, the nacelle 7 is mechanically connected to the rear fuselage 27 of the aircraft by means of a structural tension member 29, generally streamlined and located upstream of the fan 4. The fixed blade assembly 6 is housed within a fan casing 9, fixed thereto downstream of the fan 4. The fixed blade assembly 6 is used to regulate the flow of propellant gas at the outlet of the fan 4 and to maintain the fan casing 9.

As shown in fig. 2, the fan shaft 10 connecting the fan 4 to the rotating part 3 of the power unit 1 for rotation of the fan is a shaft having an aperture in which the fixed blade shaft 11 engages over a major part of its length. The fixed-blade shaft is connected by one of its ends to the stationary part 2 of the power unit 1 and by the other end to the fixed-blade assembly to keep it stationary. The two shafts constituting the coaxial shaft assembly have a compact structure and are therefore less affected by deformation of these shafts. Furthermore, the special coaxial structure allows a mechanical connection between these two shafts, which results in a more rigid component, and therefore very little deformation of the fan housing 9, the fixed blade assembly 6 and the fan.

This coaxial arrangement of fan shaft 10 and stationary blade shaft 11 can extend to a fan hub 12 which is mechanically connected to the stationary part 2 of the power unit 1. In practice, the fan hub 12 is directly connected to the stationary part of the propulsion unit and surrounds the fan shaft 10 over part of its length. This particular arrangement, consisting of the fixed blade shaft 11 housed inside the fan shaft 10 itself housed in the fan hub 12, proves to be very compact and rigid. The shorter axis with fewer protrusions is less sensitive to deformation caused by radial loads generated by the fan 4 and the fixed blade assembly 6. This staggered shaft configuration also enables a rigid mechanical connection between the fixed blade assembly 6, the fan 4 and the stationary part 2 of the power plant 1 connected to the rear 27 of the aircraft fuselage. This example of the arrangement of the coaxial shaft assembly has the advantage of producing a particularly rigid and compact structure of fan 4/fixed blade assembly 6/fan casing 9, in which the torque around the axis of the coaxial shaft assembly, generated by the fixed blade assembly 6, fan 4, is transmitted to the planetary gear train via the fixed blade shaft 11 and the fan shaft 10, and all other loads caused by this structure are transmitted to the fan hub 12. The fan hub 12 is the outermost of the coaxially arranged shafts, and the diameter thereof is also the largest, thereby enhancing the embedding effect of the coaxial shaft assembly having reduced projections due to the compactness of assembly. This arrangement can significantly limit the possibility of deformation and therefore movement of this structure relative to the rear of the fuselage and between the fan 4, the fixed blade assembly 6 and the fan casing.

In a coaxial shaft assembly, a first bearing module 13 is mounted on the fixed blade shaft 11 and is located in a first bore formed in the fan shaft 10. The first bearing module 13 guides the fan shaft 10 to rotate around the fixed blade shaft 11. Due to the presence of fan hub 12, a second bearing module 14 is mounted in a second bore formed in fan hub 12 and mounted on fan shaft 10 to guide fan shaft 10 for rotation within fan hub 12. In this form, on the one hand, the coaxial shaft assembly makes it possible to obtain a particularly compact and rigid fan/fixed-blade assembly mechanically connected to the fuselage, so that the deformations between the fan 4, the fixed-blade assembly 6, the fan casing and the rear fuselage portion 27 are considerably reduced compared to the deformations of the assemblies known from the prior art. On the other hand, the coaxial shaft assembly thus completed is also particularly suitable for efficiently transferring to the rear of the fuselage the loads generated by the main fan and the fixed-blade assembly, taken up by the bearing module.

The first bearing module 13 and the second bearing module 14 may be formed of various bearings. According to a preferred embodiment of the invention, the first bearing module 13 and the second bearing module 14 are both formed by ball bearings 15 and roller bearings 16. Other variations are possible, such as using X-or O-mounted conical bearings, or even using a combination of ball stops and roller bearings. In the bearing arrangement of the described embodiment of the invention, the largest part of the axial load from the fan 4 is taken up by the ball bearing 15, which acts as an axial stop for the fan shaft; while the radial loads from the fan 4 and the fixed-blade assembly 6 are taken up by the roller bearings 16 and a smaller part by the ball bearings 15.

Additionally, the axial loads generated by the fixed-blade assembly 6 and the fixed-blade shaft 11 can be compensated for by axial movement of the fixed-blade shaft. This axial movement can be achieved by adding a sliding device 34 on the stationary blade shaft 11 upstream of the bearing, which makes it possible to avoid a hyperstatic mounting of the stationary blade shaft 11 and also to compensate for the longitudinal thermal expansion of the stationary blade shaft while preventing the rotation of the stationary blade assembly.

In the power plant of the propulsion unit, the transmission connected to the end of the rotor 18 of the engine 17 is advantageously constituted by a planetary gear set 19. The planetary gear 19 comprises firstly an input planetary gear 20 connected to the rotor 18 of the engine 17, secondly an output planetary gear formed by a crown 21 with internal toothing mechanically connected to the shaft of the fan 4 which rotates with it, and secondly a fixed planetary gear carrier 22 on which the planetary gears are mounted, transmitting the rotary motion of the input planetary gear 20 to the crown 21. On the one hand, the planet carrier 22 is connected to the stationary part 2 of the power unit 1 and therefore also to the fuselage, and on the other hand, the planet carrier is connected to the fixed blade shaft 11 by means of a sliding device 34 which allows axial sliding without allowing rotation between the planet carrier 22 and the fixed blade shaft 11. This particular arrangement of the planetary gear train at the engine outlet makes it possible to obtain a natural rigid and compact structure of the coaxial shaft assembly connected to the main components of the propulsion unit, while preventing the fixed blade assembly from rotating. Of course, other means of adjusting the speed of the fan shaft 10 to match the speed of the rotor 18 of the engine 17 may be used, as may other arrangements such as a planetary gear train having other fixed parts than the planet carrier.

Furthermore, in a propulsion assembly, when the engine is a turbine, in particular a turbojet, a distinction can be made between the two propulsion flows. As shown in fig. 3, a primary flow of propulsion gas 30 flows through the compressor and the turbojet combustion chamber, while a secondary flow of propulsion gas 31 flows through the fan 4 and the fixed blade assembly 6. Typically, a streamlined body of "fan/fixed blade" components is designed for a conventional propulsion unit. When they are transferred into BLI type structures, as is the case in the prior art documents cited above, some optimization problems arise. One of the problems relates to the disposal of the secondary flow portion flowing to the region at the base of the fan blades 5 and at the base of the fixed blade assembly 6. In fact, the secondary flow 31 of propellant gas is the boundary layer region where the flow rate of the propellant gas is relatively slow, which presents the fan with the difficulty of pressurising the propellant gas entering the secondary flow section to the same level as on the periphery of the fan blades 5. The lower supercharging Ratio of the Fan 4 at the foot of its blades 5, also known as the Fan Pressure Ratio or FPR ("Fan Pressure Ratio"), has a negative effect on the propulsion efficiency of the propulsion unit, in particular of the BLI type. It was also found that the aircraft frontal drag is not at an optimum, as evidenced by the excessive consumption of hydrocarbon fuel.

This problem can be solved by increasing the boost ratio in the blade foot region to obtain a higher FPR of the fan 4 at the foot at the end of the fan blade 5.

To this end, as shown in fig. 3, an auxiliary fan 23 is mounted between the fan 4 and the fixed-blade assembly 6 in a region located at the fan blades 5 and the footing of the fixed-blade assembly 6. The auxiliary fan has an outer diameter smaller than the outer diameter of the fan 4. The auxiliary fan may be a single stage compressor fan as shown in fig. 3, or may be a multi-stage compressor fan. An auxiliary fan cowl 26 in the form of a profiled structure surrounds the auxiliary fan 23. At the upstream end of the auxiliary fan cowl 26, a stationary gauge 35 is mounted upstream of the auxiliary fan 23. The auxiliary fan cowling 26 is stationary and mechanically connected to the fixed blade assembly 6. The auxiliary fan 23 is mechanically connected to the fan 4 so that the fan 4 can rotate the auxiliary fan 23. This mechanical connection can be achieved by means of an axial extension 25 of the fan disk 24, the fan blades 5 being fixed to the fan disk 24 by means of their feet or in any other way. The axial extension 25 extends downstream of the fan disk 24, and the base of the blades of the auxiliary fan 23 is fixed to the axial extension. Thus, the fan shaft 10 rotates the fan 4 via the fan disk 24, the fan shaft 10 is mechanically connected to the fan disk 24, the fan disk 24 rotates the auxiliary fan 23 via its axial extension 25, and the axial extension 25 is mechanically connected to the auxiliary fan.

In the absence of an auxiliary fan, the speed of the secondary flow 31 of propellant gas in the annular region of the jet plane 32 decreases as it approaches the inner radius of the inner duct 8, where the secondary flow 31 of propellant gas is subjected to the viscous effect of the boundary layer along the entire fuselage up to the rear end portion of the fuselage where the jet cone 33 is formed. By contrast, with the auxiliary fan 23, the speed of the secondary flow 31 of propulsion gas is made uniform over the entire annular area 32 at the outlet of the propulsion unit 32, thus increasing the propulsion efficiency of the latter.

As shown in fig. 3, the particular configuration of the auxiliary fan 23 as described above is advantageously combined with the coaxial shaft assembly described previously, contributing to its compactness and not compromising its rigidity. However, the auxiliary fan 23 structure as described above can be perfectly integrated into other types of aircraft propulsion units, whether they are BLI-type or conventional, depending from the wing or located aft of the fuselage. By way of example, fig. 4 shows the auxiliary fan 23 mounted on a propulsion unit similar to that mentioned in the above-mentioned prior art document.

The propulsion unit as described above can be mounted on the aircraft in different ways. In the following, the propulsion unit is described in an aircraft fuselage aft configuration. In this configuration, the engine 17 of the power unit 1 is mainly contained in the rear body 27. As indicated above, the engine 17 is a turbojet, the rear part of which, i.e. mainly the jet cone 33, may constitute the rear end of the aircraft fuselage. This is particularly true for propulsion units of the BLI type, and more particularly but not exclusively for rear propulsion units of aircraft known as BLI360 °. The rear fuselage of this type of aircraft may include one or more of the propulsion assemblies described above.

Next, a first embodiment variant of the invention will be described with the aid of fig. 1a, in which a propulsion unit of the BLI360 ° type is mounted in the rear fuselage 27 of an aircraft. In said first embodiment variant, the engine 17 of the propulsion unit is a turbojet. The stationary part 2 of the power unit 1 is mechanically connected to the rear fuselage part 27. The load 28 generated by the fan 4 and the fixed-blade assembly 6 is transmitted to the aircraft fuselage through the coaxial shaft assembly by the first bearing module 13 and the second bearing module 14 as described above. The loads here refer mainly to the radial loads generated by the fan 4 and the fixed-blade assembly 6 and the axial loads generated by the fan 4. The torque about the axis of rotation of the fan 4 and about the axis of rotation of the fixed-blade assembly 6 is transmitted through the fan shaft 10 and the fixed-blade shaft 11 to the crown 21 and the planet carrier 22 of the planetary gear train 19. The fan casing 9 is not mechanically connected to the engine compartment 7.

In this particular arrangement, the coaxial shaft assembly is connected to the fuselage and loads from the fan 4, the fixed blade assembly 6 and the fan casing 9 are transmitted to the rear portion 27 of the fuselage through this particularly rigid and compact arrangement. Thereby resulting in a substantial reduction in deformation of this part of the propulsion unit. This also reduces the clearance that needs to be provided between the ends of the fan blades 5 and the fan housing, and improves fan efficiency. This therefore also contributes directly to the optimization of the operation of the propulsion unit.

A structural tension member 29 mechanically connects the engine compartment 7 with the aft fuselage portion 27. The structural tension member 29 is streamlined in that the tension member is located at the entrance to the inner duct 8 and the fan 4 sucks in the secondary flow 31 of the incoming gas through the inner duct. The radial and axial loads generated by the fixed blade assembly 6 are transferred through the coaxial shaft assembly, through the first and second bearing modules 13, 14, and the structural tension member 29 should be sized to withstand only the aerodynamic stresses acting on the nacelle. Accordingly, the structural tension member may have a size smaller than that of the conventional structural tension member. The reduced size of the structural tensile member will therefore have a smaller effect on the secondary flow 31 flowing downstream of the fan 4, which also optimizes the propulsion efficiency of the thus designed propulsion unit.

A second embodiment variant of the invention, which is shown in fig. 1b, will be described next. This second embodiment variant of the invention differs from the first embodiment variant in that the nacelle 7 is mechanically connected to the fixed-blade assembly 6. In this arrangement, the fan casing 9 is an integral part of the engine compartment 7 or at least is mechanically connected thereto. Thus, the aerodynamic stresses experienced by the nacelle 7 are added to the load 28 generated by the fan 4 and the fixed blade assembly 6, transmitted by the coaxial shaft assembly from the first bearing module 13 and the second bearing module 14 to the aft fuselage portion 27. All the loads of the main components of the propulsion unit, i.e. the nacelle 7, the fan 4 and the fixed blade assembly 6, are transmitted to the rear fuselage portion 27 through the coaxial shaft assembly, the first bearing module 13 and the second bearing module 14, which is made possible by the enhanced rigidity and compactness obtained by this particular assembly according to the invention. The nacelle 7 is fixed directly on the fixed blade assembly 6, making the presence of structural tension members upstream of the fan superfluous. The influence of the structural tension member on the flow of the secondary flow 31 of propulsion gas upstream of the fan is thus eliminated, and the efficiency of the propulsion assembly is optimized.

In all variants of the invention, the combination of a coaxial shaft assembly comprising a fixed blade shaft and a fan shaft, and a mechanical connection between the shroud and the fixed blade assembly, allows the clearance between the fan blade ends and the shroud to be optimized by reducing the movement between the fan and the shroud. This result is obtained by reinforcing the fan/casing/fixed-blade component, which is obtained independently and complementarily by the coaxial shaft assembly on the one hand, and by the connection between the casing and the fixed-blade assembly on the other hand. The combination of these two effects makes it possible to obtain components that are particularly rigid and therefore less susceptible to deformations.

In one aspect, the present invention provides a particularly compact and rigid structure formed by the fan 4, the fan housing and the fixed blade assembly 6 based on a coaxial shaft assembly, thereby reducing the clearance between the ends of the fan blades 5 and the fan housing 9. This component can optimize the structure of the propulsion unit of the BLI type, in particular of the BLI360 °, by reducing the necessary clearance between the fan blades 5 and the fan casing 9, and also reduce the dimensions of the structural tension member 26. Furthermore, in the case where the fan casing 9 is mechanically connected to the fixed blade assembly 6, the structural tension member 26 may be eliminated. On the other hand, the insertion of the auxiliary fan 23 between the fan 4 and the fixed-blade assembly 6 makes it possible to increase the propulsive efficiency of the propulsion assembly by increasing the pressure on the propulsive air flow at the base of the fan blades 5 and at the base of the fixed blades 6, thus increasing the propulsive efficiency and reducing the frontal drag produced by the propulsion assembly/aircraft components, in particular of the BLI type.

The combination of advantages obtained by the different aspects of the invention allows to obtain an energy consumption reduction of 2% to 4% for an aircraft equipped as such, compared to the energy consumption of an aircraft equipped with a conventional propeller of the BLI type.

Although in the above description the description of the particular aspects of the invention, in particular the compact rigid coaxial shaft assembly and the auxiliary fan interposed between the fan and the fixed blade assembly, has been made in the context of a propulsion unit of the BLI type, in particular a propulsion unit of the BLI360 ° type, positioned at the rear of the fuselage, they can also be applied in other configurations and in other types of propulsion units.