ELECTRICALLY DRIVEN DUCTED FAN ENGINE

Abstract

Disclosed is an electrically driven ducted fan engine, comprising a housing with an inner housing wall, defining a substantially cylindrical inner space and a longitudinal axis, an inlet opening, a rotor with a multitude of rotor blades positioned in the inner space of the housing downstream of the inlet opening, a stator assembly with a multitude of guide vanes extending from a radially central region of the inner space to the inner wall of the housing, and an exhaust opening provided in the housing downstream of the stator assembly, an interstage region defined between the rotor and the stator assembly, a guide vane region defined in which guide vanes extend to the inner wall of the housing and an exhaust section, wherein in at least one of the interstage region, the guide vane region and the exhaust region, acoustic liners are provided to the housing.

Claims

1. An electrically driven ducted fan engine, comprising: a housing with an inner housing wall, defining a substantially cylindrical inner space and a longitudinal axis; an inlet opening provided in the housing; a rotor with a multitude of rotor blades which is arranged to be driven in rotation by means of an electrical motor and positioned in the inner space of the housing downstream of the inlet opening with respect to the longitudinal axis of the engine; a stator assembly with a multitude of guide vanes extending from a radially central region of the inner space to the inner wall of the housing, which is fixedly arranged in the inner space of the housing downstream of the rotor with respect to the longitudinal axis of the engine; and an exhaust opening provided in the housing downstream of the stator assembly with respect to the longitudinal axis of the engine; wherein with respect to the longitudinal axis of the engine, an interstage region is defined between the rotor and the stator assembly, a guide vane region is defined in the longitudinal section in which the guide vanes extend to the inner wall of the housing and an exhaust section is defined between the stator assembly and the exhaust opening, wherein in at least one of the interstage region, the guide vane region and the exhaust region, acoustic liners are provided to the housing.

2. The electrically driven ducted fan engine according to claim 1, wherein in all of the interstage region, the guide vane region and the exhaust region, acoustic liners are provided to the housing.

3. The electrically driven ducted fan engine according to claim 1, wherein the longitudinal section of the housing upstream of the rotor is devoid of acoustic liner.

4. The electrically driven ducted fan engine according to claim 1, wherein the acoustic liners are tuned to at least one wavelength, λ, which is preferably calculated depending on at least one of the number of rotor blades, the number of guide vanes and a number of poles of the electric motor driving the rotor.

5. The electrically driven ducted fan engine according to claim 1, wherein the acoustic liner comprises porous liner material.

6. The electrically driven ducted fan engine according to claim 5, wherein the porous liner material is tuned with respect to its porosity, cavity thickness, flow resistivity and/or tortuosity.

7. The electrically driven ducted fan engine according to claim 6, wherein the porosity of the porous liner material is in the range of 80 to 99% and/or its cavity thickness is approximately λ/4.

8. The electrically driven ducted fan engine according to claim 1, wherein the acoustic liner comprises Helmholtz liners.

9. The electrically driven ducted fan engine according to claim 8, wherein the Helmholtz liners are tuned with respect to their thickness, porosity, plate thickness, hole diameter and/or cavity depth.

10. The electrically driven ducted fan engine according to claim 9, wherein the hole diameter is in the range of 0.1 to 5 mm, the cavity thickness is in the range of λ/20 to λ/4 and/or the porosity is in the range of 2 to 10%.

11. The electrically driven ducted fan engine according to claim 1, wherein the engine has a diameter of 28 to 38 cm.

12. An aircraft with a fuselage and at least one pair of wings, further provided with at least one electrically driven ducted fan engine according to claim 1, wherein the ducted fan engine is pivotably mounted to one of the wings.

Description

[0025] Further features and advantages of the present invention will become even clearer from the following description of an embodiment thereof, when taken together with the accompanying drawings. These drawings in particular show:

[0026] FIG. 1 a cross-sectional view of an electrically driven ducted fan engine according to the present invention;

[0027] FIG. 2 a schematic cross-sectional view of the engine of FIG. 1 with its housing removed; and

[0028] FIG. 3 a schematic top view of an aircraft provided with a plurality of engines as shown in FIGS. 1 and 2.

[0029] In FIG. 1, an electrically driven ducted fan engine is shown in cross-sectional view and generally denoted by reference numeral 10. Said engine comprises a housing 12 with an inner housing wall 12a defining a substantially cylindrical inner space 14 and a longitudinal axis L. It is obvious from FIG. 1 that the substantially cylindrical inner shape may also encompass regions, in which it is at least slightly conical such as towards its outlet.

[0030] On the upstream end of the engine 10 with respect to the longitudinal axis L, an inlet opening 16 is provided in the housing 12 through which air can be taken in which will subsequently be compressed and ejected for providing thrust for the propulsion of the aircraft to which the engine 10 is mounted. For an overview of such an aircraft, it is referred to FIG. 3, which will be discussed below.

[0031] In order to install the engine 10 on a wing or canard of the aircraft 100 of FIG. 3, a connection section 18 is provided in the front part of the engine housing 12, which may allow for a tilting of the engine 10 with respect to the wing or canard around an axis which substantially extends along the longitudinal direction of the respective wing 104 or canard 106, such that the aircraft is capable of vertical take-off and landing by means of respective tilting strategies of its engines.

[0032] Inside the inner space 14 of the housing 12, a rotor 20 with a multitude of rotor blades 20a is provided, which is arranged to be driven in rotation by means of an electric motor 22 with a stator and a plurality of rotating poles. Further downstream of the rotor 20, a stator assembly 24 with a multitude of guide vanes 24a is provided, wherein the guide vanes 24a extend from a radially central region of the inner space 14 to the inner wall 12a of the housing. Said static guide vanes serve the purpose of directing the transverse impulse in the driven air stream of the rotor 20 in a suitable manner substantially in the longitudinal direction L and avoiding the formation of cross-flows. Thus, the guide vanes 24A effectively act as baffle plates.

[0033] Even further downstream of the stator assembly 24, an exhaust opening 26 is provided in the housing 12 through which the air compressed by the rotor 12 will finally exit the engine 10 and provide thrust to the aircraft along the longitudinal axis L of the engine 10.

[0034] Taking into account the above-described components of the engine 10, with respect to the longitudinal axis L of the engine 10, several regions can be defined, namely an inlet section 28 upstream of the rotor 20, an interstage region 30 between the rotor 20 and the stator assembly 24, a guide vane region 32 in which the guide vanes 24a extend to the inner wall 12a and finally an exhaust section 34 between the stator assembly 24 and the exhaust opening 26 of the engine 10.

[0035] In order to reduce the emission of operating noise of the engine 10, according to the present invention, acoustic liner is provided to the housing in at least one of the interstage region 30, the guide vane region 32 and the exhaust region 34 as can be seen in particular in FIG. 2, in which for better visibility the housing 10 has been removed.

[0036] In said FIG. 2, the respective acoustic liners are denoted with 30a, 32a and 34a referring to the liners provided in the interstage region 30, the guide vane region 32 and the exhaust region 34, respectively. Said acoustic liners 30a to 34a may comprise a porous liner material and/or Helmholtz liners which can be tuned according to the acoustic properties of the engine 10 in its operation and a substantial reduction of noise emitted can be achieved, in particular with respect to the ground, especially when taking into account the tiltable connection of the engine 10 to the corresponding wing 104 or canard 106 of the aircraft 100 as discussed below.

[0037] Said aircraft 100 is shown in FIG. 3 in a schematic manner and it comprises a fuselage 102, a pair of wings 104 and a pair of canards 106 positioned in front of the wings 106 with respect to the main flying direction of the aircraft 100. To each of the wings 104 and canards 106, a plurality of engines 10 as shown in FIGS. 1 and 2 are mounted in a tiltable manner by means of their respective connection sections 18, such that the engines are tiltable with respect to axes with substantially extend along the longitudinal directions L104 and L106 of the wings 104 and canards 106, respectively. By employing suitable strategies for tilting the engines 10 with respect to their respective wing 104 or canard 106, the aircraft is capable of vertical take-off and landing.