Electric ducted fan propulsor

Abstract

A propulsion system for an aircraft having a two stage contra-rotating fan system to generate thrust. The contra-rotating fan system is surrounded by an aerodynamic duct, having the power train within the duct.

Claims

1. An electric ducted fan propulsion system for an aircraft characterised in having a two stage contra-rotating fan system comprising an aerodynamic duct surrounding contra-rotating fan stages providing contra-rotating fans to generate thrust, the aerodynamic duct defining an internal annular volume between inner and outer walls of the aerodynamic duct; the internal annular volume housing a power train within the internal annular volume, in which: the two stage contra-rotating fan system comprises a rim-driven motor system to drive the contra-rotating fans; the rim-driven motor system comprising: a pair of rings that form outer tips of the contra-rotating fans; each ring bearing embedded rotors for cooperating with respective stators located within the internal annular volume of the aerodynamic duct; the pair of rings and the embedded rotors both being housed within the internal annular volume of the aerodynamic duct; the power train comprises energy storage, electric motor drive and inverter, engine control unit, power distribution unit, and thermal management system.

2. The propulsion system according to claim 1 characterised in that the power train comprises two motors each comprising an annular stator supplied from an energy storage means in said aerodynamic duct and the embedded rotors of each motor comprising permanent magnets disposed in a ring around the outer tips of each fan stage, energy being supplied to the stator through the electric motor drive and inverter.

3. The propulsion system according to claim 2 characterised in that each motor is supplied from a respective energy storage means of the energy storage means that is independent of an energy storage means of the energy storage means of the other motor.

4. The propulsion system according to claim 1, characterised in that a length to diameter ratio of the duct is between 0.6 to 1.4.

5. The propulsion system according to claim 1 in which the contra-rotating fan stages are independently mounted on bearing housings in a central hub.

6. The propulsion system according to claim 1 characterised in that each fan stage may operate independently of the other fan stage in the event of failure of the other fan stage.

7. The propulsion system according to claim 1 having a thermal circuit, said thermal circuit taking heat generated in the power train and imparting the heat to air flow in the aerodynamic duct down-stream of the contra-rotating fans through a heat exchanger.

8. The propulsion system according to claim 7 in which the heat exchanger is disposed annularly around an inside of the aerodynamic duct downstream of the contra-rotating fans.

9. The propulsion system according to claim 8 in which the heat exchanger is serrated on a surface of the heat exchanger facing air flow downstream of the aerodynamic duct.

10. The propulsion system according to claim 1 characterised in that heat taken from the powertrain expands a downstream flow from the contra-rotating fans increasing thrust.

11. The propulsion system according to claim 1 characterised in that heat taken from the powertrain is utilised for de-icing functions on aerodynamic surfaces.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic plan view of an example electric ducted fan propulsor according to the invention;

(2) FIGS. 2A, 2B and 2C show perspective half left, front, and side views of the electric ducted fan propulsor of FIG. 1;

(3) FIGS. 3A, 3B and 3C are schematic half left, top and front view an aircraft having two of the electric ducted fan propulsors of FIG. 1;

(4) FIG. 4 is a block diagram for an engine control unit for an electric ducted fan propulsor of FIG. 1;

(5) FIG. 5 is a block diagram of the thermal management system of the propulsor;

(6) FIG. 6 shows the annular heat exchanger of the ducted electric fan propulsor of FIG. 1 seen from the rear of the duct of the ducted fan propulsor; and

(7) FIG. 7 shows a further enhancement of the annular heat exchanger of FIG. 6 having serrations on its surface to improving thermal performance and reduce noise.

DESCRIPTION OF EMBODIMENTS

(8) In FIGS. 1 and 2, an electric ducted fan propulsor 10 has a central hub 11, forming a static structure to hold bearing housings 22 and 23 and the contra-rotating fan stages 18 and 24. The central hub forms part of the load path for the load transfer of thrust from the fan stages into the duct and the aircraft.

(9) Around the central hub 11 is disposed the duct 13, held in position by inlet guide vanes 12. The inlet guide vanes hold the central hub in position and enable the transfer of loads from the central hub into the duct structure and further on into the aircraft. The inlet guide vanes 12 also direct the flow into the propulsor and help reduce the impact of cross flows/inlet turbulence on thrust generation.

(10) The duct 13, itself, acts as an aerodynamic surface augmenting the thrust from the fan stages. It houses the entire powertrain-motor, inverter, battery, thermal management system, the engine control unit, and other propulsion associated systems (such as sensors, data loggers, actuators). Additionally, it acts as a protective shroud against fan blade-off events and attenuates some of the noise from the fan stages. Furthermore, it acts as a protective shroud in the event of blade failure, provides a secondary source of thrust apart from the fan blades. Normally, the length to diameter ratio of the duct 13 is between 0.6 to 1.4.

(11) The circular battery packs 14 and 25 are located towards the front of the shroud. These comprise contains electrochemical cells in a cylindrical format, (although prismatic cells could be used); lithium-ion cells are a preferred choice for these cells. The cells are arranged to achieve the highest capacity in the available space. The battery packs use dielectric liquid cooling which is shared between the motor and inverter. Each propulsor has two battery packs 14, 25, one pack 14 powering one fan stage 18 of the contra-rotating fan system, the other pack 25 powering the other fan stage 24. The waste heat generated by the battery packs is removed by the thermal management system described with reference to FIG. 5 and used to boost thrust.

(12) Two motors with associated power inverters 17 and 26 convert the electrical power from the battery packs 14 and 25 to mechanical power that is harnessed by the contra-rotating fan stages 18 and 24 to generate thrust. Each motor independently providing mechanical power to each stage of the contra-rotating fan systems and comprises a stator 15 and 27 lying in the annulus of the duct and a rotor 16 and 28 for each motor consisting of permanent magnets arranged in a Hallbach array embedded onto the outer in ring of the contra rotating fan stages.

(13) The contra rotating fan system comprises a first stage 18 and a second stage 24. Each stage consists of several fan blades attached to and inner ring attached to the bearing housings 22 (first stage 18) or 23 (second stage 24) and an outer ring comprising the electric motor rotors 16 and 28. The torque induced in the fan stage by electro-magnetic forces acting on the permanent magnets accelerate airflow through the contrarotating fans to produce thrust. Having a two stage contra-rotating fan system enables thrust production even after failure of a single fan stage or its associated energy/power source.

(14) The central hub 11 also contains a variable pitch mechanism for the contra-rotating fan stages 18 and 24 to enable optimisation of the aerodynamic performance for different flight regimes of an aircraft to which the ducted propulsor is fitted.

(15) Around the duct 13, adjoining the downstream flow from the fans 18 and 24 is an annular heat exchanger 19, discussed further in relation to FIGS. 4, 5 and 6. This is connected to the thermal management unit 20 consisting of pipes, coolant, and pumps.

(16) Toward the read of the duct 13, are exit vanes 21 between the duct 13 and hub 1. The exit vanes 21 may have control surfaces that deflect the flow to achieve aircraft control during certain flight regimes such as hover and transition.

(17) FIGS. 3A, 3B and 3C show two electric ducted fan propulsor 10 as described in relation to FIGS. 1 and 2 mounted beneath the wings 41 of an aircraft 40.

(18) FIG. 4 illustrates a control system 51 for an aircraft incorporating an electric ducted fan propulsor according to the invention. The engine control system 51 includes electronics and algorithms that commands the various sub-systems of the propulsor, and also aggregates all the sensor input from various sub-systems and other parts of the propulsor to monitor health and usage in one location. The engine control system 51 communicates key information about the propulsor's health and usage to the aircraft flight computer 50 and receives key information from the aircraft flight computer 50 to command the various sub-systems.

(19) FIG. 5 is a block diagram showing the thermal management system. The heat exchanger 19 is disposed around the inside of duct 13 (as seen in FIGS. 1 and 6). The heat exchanger imparts heat to the downstream flow from the contrarotating fans 18 and 24. A circuit of dielectric liquid 31, passes through a reservoir 29 and pump 30 to cool the electrochemical cell batteries 14 and 26, the motor stators 15 and 27, and invertors 17 and 26. improving the efficiency of these, to lose the heat gained through the heat exchanger 19 to the downstream flow. As described the dielectric fluid collects the waste heat from each sub-system and is pumped into the annular heat exchanger 19 from where the waste heat is transferred into the downstream flow from the contrarotating fans to produce additional thrust.

(20) In addition to being used in producing the additional thrust as described in the preceding paragraph, heat taken from the powertrain can also be utilised for de-icing functions on the critical aerodynamic surfaces. In order to do this, the dielectric heated flow pass under the surfaces concerned. The flow to those surfaces would be controlled by a valve, so that the flow would only occur when de-icing was required, but not at other times, when the waste heat would be passed entirely to the heat exchanger 19.

(21) FIG. 6 shows more detail of the annular heat exchanger 19 around the inside of the duct 3, adjacent to the downstream flow 32 from the contra rotating fans 18 and 24. Extending between the central hub 13 and the duct 11, are exit vanes 21, with control surfaces 33 which can deflect flow, to enable the aircraft to be maneuvered or controlled during certain flight regimes, such as hovering and transition.

(22) FIG. 7 show a further development of the arrangement shown in FIG. 6, in FIG. 6, in FIG. 7 the surface of the heat exchangers 19 facing the downstream flow 32 has serrations 34 across the width of the heat exchanger. This has two benefits, as it increases the surface available for heat transfer and it reduces noise. As a further development the serrations 34 extend to the trailing edge 35 of the duct 13, further reducing noise.