Hybrid propulsive architecture for an aircraft comprising an engine with a reversible electric machine mounted on two shafts

Abstract

The aircraft motor architecture comprises two reversible electric machines (3, 4), the rotors (10) of which are linked both to the low pressure shaft (1) and to the high pressure shaft (2) by transmissions (11, 12, 13, 14) alternately disengaged depending on the direction of rotation of the rotor (10), the transmissions comprising passive one-way clutches (15, 16, 17, 18), the engagement directions of which are opposed. Independent modes of operation of the machines, as a starter or as an electric generator of each of the shafts, are thus provided.

Claims

1. An architecture of a hybrid propulsive system for an aircraft, comprising an engine comprising at least two shafts rotating independently of one another, two reversible electric machines connected to a distribution network, and a control system for the two reversible electric machines, wherein: a rotor of each of the two reversible electric machines is respectively connected to each of the at least two shafts by a respective transmission, the at least two shafts rotating independently have either reversed directions of rotation, or identical directions of rotation, one of the transmissions then including a direction of rotation reversed, each of the transmissions comprising a disengaging coupling, wherein the disengaging couplings are passive one-way clutches, and the passive one-way clutches of each reversible electric machine couple the rotor of a respective reversible electric machine with a respective and single one of the at least two shafts for opposite directions of rotation of the rotor of the respective reversible electric machine, the control system for the two reversible electric machines enables: a control of the two reversible electric machines in a motor mode and in a generator mode in both directions of rotation of their rotor, a driving of at least one of the at least two shafts by both reversible electric machines, and also a generation of electricity from one of the at least two shafts by a first reversible electric machine, simultaneously to driving another of both shafts by a second reversible electric machine.

2. The architecture of a hybrid propulsive system for an aircraft according to claim 1, wherein the control system enables electricity to be generated from one of the at least two shafts, by at least one of the two reversible electric machines.

3. The architecture of a hybrid propulsive system for an aircraft according to claim 1, wherein the transmissions comprise unequal rotating speed reducing ratios between the rotor of at least one of the two reversible machines and the at least two shafts of the engine.

4. An aircraft, comprising: a plurality of engines each being provided with an architecture for a hybrid propulsion and comprising at least two shafts rotating independently of one another, the architecture further comprising two reversible electric machines connected to a distribution network, wherein a rotor of each reversible electric machine is respectively connected to each of the at least two shafts by a respective transmission, each of the transmissions comprising a disengaging coupling, the disengaging couplings are passive one-way clutches, and the passive one-way clutches of each reversible electric machine couple the rotor of a respective reversible electric machine with a respective and single one of the at least two shafts for opposite directions of rotation of the rotor of the respective reversible electric machine, the at least two shafts rotating independently have either reversed directions of rotation, or identical directions of rotation, one of the transmissions then including a direction of rotation reversed, and further comprising a system for controlling the two reversible electric machines in a motor mode and in a generator mode in both directions of rotation of their rotor, the system further enabling at least one of the at least two shafts to be driven by both reversible electric machines, and also enabling electricity to be generated from one of the at least two shafts by a first reversible electric machine, simultaneously to driving another of the at least two shafts by a second reversible electric machine, and the two reversible electric machines of each of the plurality of engines are connected to an energy supplying device.

5. The aircraft according to claim 4, further comprising a control system enabling a first one of the engines to be driven by another one of the engines via the two reversible electric machines, the two reversible electric machines of the first one of the engines operating in an engine mode and the two reversible electric machines of another one of the engines operating in a generator mode.

6. The aircraft according to claim 4, further comprising an energy supplying device, connected to the two reversible electric machines, and which comprises a turbogenerator and/or an energy storing device.

7. An architecture of a hybrid propulsive system for an aircraft, comprising an engine comprising a low pressure shaft and a high pressure shaft rotating independently of one another, two reversible electric machines connected to a distribution network, and a control system for the two reversible electric machines, wherein: a rotor of each of the two reversible electric machines is connected to the low pressure shaft and to the high pressure shaft by a respective transmission, each of the transmissions comprising a disengaging coupling, wherein the disengaging couplings are passive one-way clutches, and the passive one-way clutches of each of the two reversible electric machines couple the rotor of a respective reversible electric machine with a respective and single one of the low pressure shaft and the high pressure shaft for opposite directions of rotation of the rotor of the respective reversible electric machine, the control system for the two reversible electric machines enables: a control of the two reversible electric machines in a motor mode and in a generator mode in both directions of rotation of their rotor, a driving of at least one of the low pressure shaft and high pressure shaft by both reversible electric machines, and also a generation of electricity from one of the low pressure shaft and the high pressure shaft by a first reversible electric machine, simultaneously to driving another of the low pressure shaft and the high pressure shaft by a second reversible electric machine.

8. The architecture of a hybrid propulsive system for an aircraft according to claim 7, wherein the control system enables electricity to be generated from one of the low pressure shaft and high pressure shaft, by one or two reversible electric machines.

9. The architecture of a hybrid propulsive system for an aircraft according to claim 7, wherein the transmissions comprise unequal rotating speed reducing ratios between the rotor of at least one of the two reversible electric machines and the low pressure shaft and the high pressure shaft of the engine.

Description

(1) Different aspects, characteristics and advantages of the invention will be now described in relation to the following figures, which depict in a detailed way a purely illustrative implementation thereof:

(2) FIGS. 1 to 6 show an implementation of the invention and its different operating modes, and

(3) FIG. 7 shows the complete arrangement disposed on an aircraft.

(4) The description is first about FIGS. 1 and 7. An aircraft engine comprises a low pressure shaft 1 and a high pressure shaft 2 which are coaxial and concentric, as is usual. It is associated with two reversible electric machines 3 and 4 each of which comprises a stator 5 connected by electric cables from a distribution network 6 to a control system 7, and through the latter to a battery or another electric energy storing device 8. FIG. 7 shows that the control system 7 is connected to all the electric machines characterising the invention, which is here advantageously applied to each of both engines 21 and 22 of the aircraft. The control system 7 interacts with the power electronics necessary to control the electric machines 3 and 4. The architecture can also have a turbogenerator 9 which supplies among other things, the electric distribution network 6 and/or an energy storing device as systems of batteries.

(5) The electric machines 3 and 4 each comprise a rotor 10, which is connected to each of the low pressure 1 and high pressure 2 shafts by a transmission, respectively 11 and 12 for the electric machine 3 and 13 and 14 for the electric machine 4. Each of the transmissions 11, 12, 13 and 14 comprises actual transmission elements such as rotor elements, intermediate shafts, gears, etc., of any types and also a one-way coupling, respectively 15, 16, 17 and 18, that can advantageously be a passive element as a coupling with an overrunning clutch. The one-way couplings 15 to 18 can be directly mounted on the rotors 10 as shown here, or elsewhere on the transmissions 11 to 14.

(6) It is essential to notice that the coupling directions of the overrunning clutches 15 and 16 are opposite, in the same way as those of the overrunning clutches 17 and 18, resulting in each of the rotors 10 being coupled with either of the low pressure 1 and high pressure 2 shafts, through either of the transmissions 11 and 12, or 13 and 14, and only one of them, according to its direction of rotation.

(7) The different possible operating modes, governed by the control system 7, will now be detailed. These operating modes are chosen and set by the control system 7, which acts on the controls of the electric machines 3 and 4 and the check of the engine; the one-way couplings 15 to 18 do not need any control mechanism if they are passive, which is a considerable advantage increasing the reliability of the architecture.

(8) The embodiment of FIG. 1 is an embodiment where the rotors 10 of both electric machines 3 and 4 rotate in a direction of rotation which will be denoted positive (R3+ and R4+) which induces the coupling of the overrunning clutches 15 and 17. The engagement of both rotors 10 and of the low pressure shaft 1 is made by the transmissions 11 and 13. Moreover, the energy storing device 8 supplies the necessary electric power to the electric machines 3 and 4. This situation may correspond to a turned off engine 21 or 22 and to the taxiing mode or ground driving mode by a propeller or a fan 23 (FIG. 7) at the end of the low pressure shaft 1, or to the transient or continuous additional power supply exclusively on the low pressure shaft 1, which can be established during the different flight phases. In this operating mode as in all those where the electric machines 3 and 4 (or only one of them) work in engine mode, the electric energy which supplies them may also come from other pieces of equipment which are connected to them by the distribution network 6, as from the turbogenerator 9 or the other of the engines 22 or 21, by the electric machines 3 and 4 of the latter. The invention can therefore allow operating modes where one of the engines starts or accelerates the other, which is particularly appreciated in case of failure, the turned off engine then continuing operating through its low pressure shaft 1, which here further drives a propeller or the fan 23.

(9) The embodiment of FIG. 2 is similar to the one of FIG. 1 and is especially based on the rotation of both rotors 10 in the positive direction R3+ and R4+, except that the electric machines 3 and 4 both work as an electric power generator thanks to their power electronics. This mode enables the mechanical power to be withdrawn from the low pressure shaft 1 to supply non-propulsive energy, charge the energy storing device 8 or brake the low pressure shaft 1.

(10) The embodiment of FIG. 3 can be distinguished from the previous embodiments by a reverse of the directions of rotation of the rotors 10, that is they rotate in the so-called negative directions R3− and R4−. The transmissions 11 and 13 leading to the low pressure shaft 1 then become inactive, and reciprocally the transmissions 12 and 14 leading to the high pressure shaft 2 transmit power. In this embodiment, power is supplied by the energy storing device 8, or the turbogenerator 9, or the second engine 22 or 21 to the high pressure shaft 2 by both electric machines 3 and 4. That can be used for starting the engine 21 or 22 or a transient or continuous power assist of the high pressure shaft 2, which can be established during the different flight phases. Here also, the presence of both electric machines 3 and 4 that can be independently controlled offers a greater design freedom.

(11) In the embodiment of FIG. 4, there are again the same negative directions of rotation R3− and R4− of the rotors 10, but the power transmission direction is reversed, that is the electric machines 3 and 4 work in generator mode. This operating mode could be usual to supply non-propulsive energy, charge the energy storing device 8 or brake the high pressure shaft 2.

(12) In the operating mode of FIG. 5, the rotation in the positive direction R3+ of the first electric machine 3 is associated with the negative direction of rotation R4− of the second electric machine 4. It is then possible to withdraw the mechanical power from one of the shafts and to supply the mechanical power to the other, with an electric power supply or draining balance on the distribution network 6 that can be zero. Here, the first electric machine 3 helps to drive the low pressure shaft 1 by the transmission 11, and the high pressure shaft 2 operates the second electric machine 4 in electricity generator mode. Such an operating mode can be of interest for example in the transient phases of the engine 21 or 22, by accelerating the low pressure shaft 1 and decelerating the high pressure shaft 2.

(13) FIG. 6 shows that the opposite operation is possible, the first electric machine 3 supplying energy to the high pressure shaft 2, with the negative direction of rotation R3−, and the low pressure shaft 1 operating the second electric machine 4 as a generator by means of rotating its rotor 10 in the positive direction R4+. Such an operating mode can be of interest for example in the transient phases of the engine 21 or 22, by accelerating the high pressure shaft 2 and decelerating the low pressure shaft 1.

(14) Switching between the different operating modes can be made easier, as well as the dimensioning of the electric machines 3 and 4, if the reducing ratios of the transmissions 11 and 12, and 13 and 14 leading to each of the rotors 10 are unequal, so that the load intervals of the low pressure shaft 1 and of the high pressure shaft 2 correspond to speed intervals close on the rotor 10 to each of the electric machines 3 and 4, which can be obtained by rotation amplifiers or reducers (not shown, which can consist of gears) on the transmissions 11 to 14 of each of the electric machines 3 and 4.