FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1.TITLE OF THE INVENTION:
AIRCRAFT TURBOPROP ENGINE PROVIDED WITH AN ELECTRIC MACHINE
2. APPLICANT:
Name: SAFRAN HELICOPTER ENGINES
Nationality: France
Address: 64510 BORDES, France.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it
is to be performed:
2
DESCRIPTION
5
The subject of the invention is an aircraft turboprop engine provided
with an electric machine.
Turboprop engines comprise a propeller, a propeller-carrying shaft and
a gas turbine which is generally connected to the propeller-carrying shaft in order to drive
10 the latter. During a standard flight, the aircraft reproduces five phases: driving on the
ground before take-off or taxiing, take-off, flight, landing then again taxiing. During the
flight, the aircraft moves propelled by the propeller, itself driven in rotation by the gas
turbine. There are, however, other modes of driving the propeller, including that which is
carried out when the gas turbine is inactive and in particular during the taxiing. This mode
15 of moving with the turbine turned off is appreciated because it involves significant fuel
economy. An electric motor is then used to move the aircraft. The aircraft also requires a
constant provision of electricity in order to ensure various services, which include the deicing of the propeller, which can be carried out independently of the operation of the
electric motor. The prior art comprises (GB 584 563 A) turboprop engines provided with
20 electric machines disposed around the propeller-carrying shaft either in order to carry out
the de-icing, or in order to operate or modify the angle of attack of the blades of the
propeller as reversible electricity generators, thus capable of driving the propellercarrying shaft when necessary. A widespread structure (US 2 488 392 A) comprises two
electric machines following one another along the propeller-carrying shaft and which can
25 thus independently ensure these two functions, but it is observed that the arranged is
very complicated and involves a significant increase in mass and footprint. And the known
de-icing devices, based on the use of collectors with brushes in order to transmit a
generally continuous current to a device that is rotating since it is incorporated into the
propeller and into the propeller-carrying shaft, are themselves complex, and subject to
30 wear.
3
The fundamental object of the invention is to provide an electric
machine that is easily integrated into the structure of a turboprop engine and which is
capable of carrying out a plurality of functions of providing energy including the de-icing
of a propeller, with a reduced footprint and mass.
5 The invention relates to a turboprop engine provided with an electric
machine that meets this requirement, and more precisely a turboprop engine, comprising
a propeller, a propeller-carrying shaft and an electric machine around the propellercarrying shaft, characterised in that the electric machine comprises a first machine
formed on a stator and a first rotor, and a second machine formed on the stator and a
10 second rotor corresponding to the propeller-carrying shaft, the stator, the first rotor and
the second rotor being concentric, the first machine and the second machine being
controlled by different electric circuits, the first machine being reversible and the second
electric machine belonging to a circuit for de-icing of the propeller, the second rotor
carrying an induced winding, and the first rotor is connected to the second rotor by a
15 mechanical transmission.
Two electric machines are thus obtained, the operation of which is
independent, but which are integrated one into the other in a compact arrangement with
a simple structure, and which is suitable for occupying a reduced volume and mass in a
turboprop engine and an aircraft: in particular with a reduced axial footprint and very
20 little mechanical-link equipment between the elements of the machine and the other
portions of the turboprop engine. The electrical connections also do not need to be
complicated.
A good integration of the machine of the invention into its turbopropengine environment is achieved. The two machines operate independently, and
25 regardless of the state – rotating or at rest – of the propeller-carrying shaft.
Another aspect of the invention is an aircraft equipped with such a
turboprop engine.
The various aspects, features and advantages of the invention will now
be described by means of the following drawings:
4
- figure 1 schematically illustrates a turboprop engine equipped with the
invention;
- figure 2 illustrates a realisation of the electric machine;
- and figure 3, another realisation of the electric machine.
5 Figure 1 shows the turboprop engine of the invention, comprising a gas turbine 1, a
propeller 2, a propeller-carrying shaft 3, extending towards the gas turbine 1 and capable
of being connected to a turbine shaft 4, which is parallel to it and extends at a short
distance from it, by a known transmission that is not shown. The propeller-carrying shaft
3 is surrounded by a protective casing 5. It is supported in the casing 5 by rolling bearings
10 6 and 7. One of the rolling bearings 6 is close to the propeller 2, and the other of the
rolling bearings 7 is adjacent to a toothed wheel 8 for driving the propeller- carrying shaft
3, which meshes with the transmission mentioned above. An electric machine 9,
characteristic of the invention, is disposed around the propeller-carrying shaft 3, between
the first rolling bearing 6 and the toothed wheel 8, while being surrounded by the casing
15 5 The aircraft of the invention is not otherwise modified and is not therefore shown in its
entirety.
Let us move on to figure 2, which describes the electric machine 9.
In this embodiment, the propeller-carrying shaft 3 is surrounded by a
concentric rotor 10, itself surrounded by a stator ring 11 belonging to the casing 5. The
20 stator ring 11 is provided with a main winding 13 which can be three-phase but more
generally multi-phase. The rotor 10 is provided with a ring of magnetic poles 14. Finally,
the propeller-carrying shaft 3 is provided with a receiver winding 15 axially slightly offset
from the rotor 10 and from the stator ring 11. Other equipment that can be seen in this
figure 2 includes gear teeth 12 disposed at the end of the inner rotor 10 and which are
25 connected to a mechanical transmission in order to transmit a mechanical energy to the
rotor 10 or on the contrary collect this energy according to the operating mode of the
machine; a magnetic bridge 16, comprising a portion 17 connected to the stator 11 and
extending axially and cylindrically, and a portion 18 extending radially and extending from
the former to an end near the propeller-carrying shaft 3, either in front of the receiver
30 winding 15, or side by side, in such a way that the receiver winding 15 thus extends
5
between this portion 18 and the rotor 10; and an electric device 19 connecting the main
winding 13 to a continuous bus 20 and comprising in particular, starting from the latter,
filters 21, a main converter 22, a main circuit 23 composed of at least three wires leading
to the phases of the main winding 13 and an auxiliary circuit 24, provided with an
5 auxiliary converter 25, and leading to the neutral of the main winding 13.
Here is how the device operates. The main winding 13 and the rotor 10
provided with the ring of magnetic poles 14 form a first electric machine capable,
according to the requirements of the moment, of providing electric energy to the aircraft,
or on the contrary mechanical energy allowing to move it, while the gas turbine 1 is
10 stopped. The transmission by which the mechanical energy of the rotor 10 is used can
consist of a train of planetary gears 40 connecting the gear teeth 12 to gear teeth 41 of
the propeller-carrying shaft 3, in order to make the latter rotate, via planets 42, the axis
of which is rigidly connected to the stator (connected to the casing 5). Transmissions of
this type thus allow reversible transmissions of power between the rotor 10 and the
15 propeller-carrying shaft 3.
The receiver winding 15 is an induced winding which, associated with
the main winding 13, forms a second electric machine, operating only as a generator and
which is provided in order to be assigned to the de-icing of the blades of the propeller 2:
an electric circuit 26, rigidly connected to the propeller-carrying shaft 3, connects for this
20 purpose the receiver winding 15 to a thermoelectric heating device 27 contained in the
propeller 2; it can be very simple and be composed in particular of conductive wires. In
general, the invention allows to not use electrical connectors rotating with friction, the
windings linked to the stator are dependent on control equipment rigidly connected to
the stator, and the winding linked to the propeller-carrying shaft serving a piece of
25 equipment disposed on this shaft, or on the propeller which is linked to it.
It is observed that the combined electric machine is easily integrated
into the turboprop engine, by occupying in practice a cavity of the casing 5 that was
empty before, and that its arrangement uses a reduced number of parts and requires few
modifications of the existing structure, and thus the mass and the footprint are reduced.
30 The need to transmit the electricity from a fixed generator to the propeller-carrying shaft
6
2 by a collector with brushes is thus in particular avoided; the grouping of a portion of
each machine on the stator 11 (and, here, in the same main winding 13) is very
economical; and the use of a reversible machine is also very advantageous, while allowing
to combine the de-icing with the taxiing via the second electric machine.
5 Here is how independent operation of the two electric machines is
obtained. The first electric machine has conventional operation and its operation is based
on the electromagnetic interaction between the main winding 13 and the magnetic poles
14 which are concentric to it. The electric energy passes through the main circuit 23. The
second electric machine operates by induction of the receiver winding 15 via a homopolar
10 magnetic flux produced by the main winding 13. The homopolar flux is in the shape of a
loop passing through the magnetic bridge 16, the propeller-carrying shaft 3, the inner
rotor 10 and the stator 11, and thus through the receiver winding 15. The receiver
winding 15, since it is away from the main flux, is thus excited only when this homopolar
component is imposed on the main winding 13, independently of the operation as a
15 motor or generator of the first electric machine. The current provided to the heating
device 27 can be alternating, or made continuous by a rectifier. Finally, the speed of
rotation (or the rest) of the propeller-carrying shaft 3 does not have any effect.
The homopolar flux component can be created by an independent
generator of alternating current, connected between the negative pole of the primary
20 power supply of the main converter 22 and the neutral point of the main winding 13, in
order to superimpose on the main currents a high-frequency homopolar component, by
establishing an imbalance in the phases of the exciter main winding 13, via a modification
of the voltage of the neutral by the circuit 24, with a star configuration of the phases of
the main winding 13. To provide this additional current, the auxiliary converter 25, or the
25 main converter 22 itself, can be used, by using the high-frequency quenching frequency
of the latter by making it so that the instantaneous currents of the windings 13 are
voluntarily unbalanced, their non-zero sum thus forming a homopolar current; the
auxiliary converter 25 would then be omitted.
The control of the two electric machines by two different electric
30 circuits 23 and 24 guarantees the independence of their operation. For convenience, it
7
will be said that the circuit “controls” the reversible machine even if it operates as a
motor.
Another embodiment of the invention will be described by means of
figure 3. The electric machine carries the reference 29. The propeller-carrying shaft 3
5 again comprises a receiver winding 30, and it is surrounded by a stator ring 31 and a rotor
32. The rotor 32 is provided with a ring of magnetic poles 33, like above; however, here it
surrounds the stator ring 31, which thus extends between it and the propeller-carrying
shaft 3. The stator ring 31 carries a main winding 34 and a concentric auxiliary winding 35,
the main winding 34 being on the outside. Moreover, the receiver winding 30 is
10 concentric to the auxiliary winding 35.
The auxiliary winding 35, three-phase, is controlled by an auxiliary
converter 36 to which it is connected by an electric circuit 37 having three wires. The
auxiliary converter 36 is moreover connected to the continuous bus 20 by filters 21, as
was the case for the main converter 22 of the previous realisation. And the main winding
15 34 is controlled by a converter 38 and an electric circuit 39 that are analogous and
independent.
The first electric machine of this device consists of the magnetic poles
33 of the rotor 32 and the main winding 34; this is a reversible machine, the operation of
which is the same as the previous.
20 The second electric machine is composed of the auxiliary winding 35
which is an inductor, and the receiver winding 30 in which a current is induced by the
former. The induction here does not necessarily use a homopolar component introducing
a magnetic flux of a particular shape, but like above, the receiver winding 30 is assigned
to the de-icing of the propeller 2 by a heating device.
25 Here, a mechanical transmission 43, the general description of which is
identical to that of the mechanical transmission 40 already mentioned, also connects the
rotor 32 to the casing 5 and allows them to exchange mechanical power in one direction
or the other, by thus using the reversibility of the first electric machine.
8
The advantages of this embodiment are analogous to the previous one
in terms of good integration of the combined electric machine into the casing 5, its
compactness, its simplicity.
According to certain features:
5 - the stator carries at least one winding 13, 34, 35 of the machine;
- the winding 13 on the stator is connected to each of the electric
circuits;
- the second machine is disposed on the second rotor (the propellercarrying shaft 3) either facing an end of the magnetic bridge adjacent to the second rotor
10 or between said end and a portion of the second rotor that surrounds the stator;
- the second electric machine is connected to a thermoelectric heating
device.
9
WE CLAIM:
1. Turboprop engine, comprising a propeller (2), a propeller-carrying
shaft (3) and an electric machine (9, 29) around the propeller-carrying shaft,
5 characterised in that the electric machine comprises a first machine formed on a stator
(11, 31) and a first rotor (10, 32), and a second machine formed on the stator and a
second rotor (3) corresponding to the propeller-carrying shaft, the stator, the first rotor
and the second rotor being concentric, the first machine and the second machine being
controlled by different electric circuits (23, 24, 37, 39), the first machine being reversible
10 and the second electric machine belonging to a circuit for de-icing of the propeller, the
second rotor (3) carrying an induced winding (15, 30), and the first rotor is connected to
the second rotor by a mechanical transmission.
2. Turboprop engine according to claim 1, characterised in that the
stator carries at least one winding (13, 34, 35), the first rotor carries magnetic poles (14,
15 33).
3. Turboprop engine according to claim 2, characterised in that the
winding (13) on the stator is the only one and shared by the first and the second machine,
and connected to each of the electric circuits.
4. Turboprop engine according to claim 3, characterised in that the
20 winding is multi-phase, the electric circuit (23) of the first machine is connected to the
phases of the winding (13) on the stator, and the electric circuit (24) of the second
machine is connected to a neutral of said winding (13).
5. Turboprop engine according to any one of claims 1 to 4, characterised
in that it comprises a magnetic pole (16) between the stator (11) and the second rotor (3),
25 the second machine being disposed on the second rotor either facing an end of the
magnetic pole adjacent to the second rotor, or between said end and a portion of the
second rotor that surrounds the stator.
6. Turboprop engine according to any one of claims 1 or 2, characterised
in that the first rotor (32) surrounds the stator (31), and the first machine and the second
30 machine comprise concentric windings (34, 35) disposed on the stator.
10
7. Turboprop engine according to claim 6, characterised in that the
winding (35) of the second machine disposed on the stator is concentric to an induced
winding (30) of the second machine disposed on the second rotor.
8. Turboprop engine according to any one of claims 1 to 7, characterised
5 in that the second electric machine is connected to a thermoelectric heating device (27).
9. Aircraft, characterised in that it comprises a turboprop engine
according to any one of the previous claims.