ARCHITECTURE OF A MULTIPLE-ENGINE HELICOPTER PROPULSION SYSTEM, AND CORRESPONDING HELICOPTER

Abstract

An architecture of a propulsion system of a multi-engine helicopter is disclosed, comprising turboshaft engines that are connected to a power transmission gearbox. It comprises: a hybrid turboshaft engine that is capable of operating in at least one standby mode during a stable flight of the helicopter; a pack for quickly restarting said hybrid turboshaft engine in order to bring said engine out of said standby mode and to reach a nominal operating mode; an auxiliary power unit that is connected to said electrotechnical restart pack by means of a first AC/DC converter and is capable of providing said restart pack, on demand, with power required for bringing said hybrid turboshaft engine out of said standby mode.

Claims

1. Architecture of a propulsion system of a multi-engine helicopter, comprising turboshaft engines that are connected to a power transmission gearbox, wherein the architecture comprises: at least one hybrid turboshaft engine among said turboshaft engines, which is capable of operating in at least one standby mode during a stable flight of the helicopter, the other turboshaft engines operating alone during this stable flight; at least one restart pack for quickly restarting a hybrid turboshaft engine in order to bring said engine out of said standby mode and to reach a nominal operating mode; at least one auxiliary power unit that is connected to the at least one restart pack and is capable of providing said restart pack, on demand, with power required for bringing said corresponding hybrid turboshaft engine out of said standby mode.

2. Architecture according to claim 1, wherein it comprises: just one hybrid turboshaft engine capable of operating in at least one standby mode during a stable flight of the helicopter, the other turboshaft engines operating alone during this stable flight, just one restart pack for quickly restarting said hybrid turboshaft engine in order to bring said engine out of said standby mode and to reach a nominal operating mode, just one auxiliary power unit that is connected to said just one restart pack and is capable of providing said restart pack, on demand, with power necessary for bringing said hybrid turboshaft engine out of said standby mode.

3. Architecture according to claim 2, wherein it comprises: a low DC voltage onboard network for supplying power to helicopter equipment during flight, at least one source of electrical power for said onboard network, wherein said auxiliary power unit is connected to said onboard network by an AC/DC converter.

4. Architecture according to claim 3, wherein it comprises a contact switch that is arranged between said auxiliary unit and said onboard network and is controlled such as to decouple said auxiliary power unit from said onboard network when said hybrid turboshaft engine is restarted in an emergency.

5. Architecture according to claim 3, wherein said electrical power source of said onboard network is selected from the group consisting of: at least one current generator that is arranged between said power transmission gearbox and said onboard network and is associated with an AC-DC converter, and a starter-generator that is arranged between a non-hybrid turboshaft engine and said onboard network.

6. Architecture according to claim 5, wherein said generator is capable of providing an AC voltage of 115 volts and wherein said associated converter is capable of providing a DC voltage of 28 volts.

7. Architecture according to claim 1, wherein at least one quick restart pack comprises an electrical machine that is capable of restarting at least one hybrid turboshaft engine when leaving standby in normal conditions, and a device for leaving standby in an emergency that is capable of restarting said hybrid turboshaft engine when leaving standby in emergency conditions.

8. Architecture according to claim 7, wherein said device for leaving standby in an emergency can be an electrotechnical, pyrotechnic, pneumatic or hydraulic device.

9. Architecture according to claim 1, wherein at least one auxiliary power unit is connected to a restart pack by an AC/DC converter.

10. Helicopter comprising a propulsion system, wherein said propulsion system has an architecture according to claim 1.

Description

6. DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

[0052] FIG. 1 is a schematic view of an architecture of a propulsion system of a twin-engine helicopter according to an embodiment of the invention. This architecture comprises two turboshaft engines 1, 2 that are connected to a power transmission gearbox 3. Each turboshaft engine 1, 2 is controlled by its own inspection-control device, which is not shown in the FIGURE for reasons of clarity.

[0053] As is known, each turboshaft engine further comprises a gas generator and a free turbine that is rigidly connected to an output shaft rotated by the gas generator. The output shaft of each free turbine is suitable for inducing the movement of the power transmission gearbox 3 (referred to in the following by the abbreviation PTG), which itself drives the rotor of the helicopter which is equipped with blades having a variable pitch.

[0054] According to the invention, the turboshaft engine 1 is a hybrid turboshaft engine that is capable of operating in at least one standby mode during a stable flight of the helicopter.

[0055] This standby mode is preferably selected from the following operating modes: [0056] a standby mode referred to as normal idling, in which the combustion chamber is ignited and the shaft of the gas generator rotates at a speed of between 60 and 80% of the nominal speed, [0057] a standby mode referred to as normal super-idling mode, in which the combustion chamber is ignited and the shaft of the gas generator rotates at a speed of between 20 and 60% of the nominal speed, [0058] a standby mode referred to as assisted super idling, in which the combustion chamber is ignited and the shaft of the gas generator rotates, with mechanical assistance, at a speed of between 20 and 60% of the nominal speed, [0059] a standby mode referred to as turning, in which the combustion chamber is extinguished and the shaft of the gas generator rotates, with mechanical assistance, at a speed of between 5 and 20% of the nominal speed, [0060] a standby mode referred to as shutdown, in which the combustion chamber is extinguished and the shaft of the gas generator is at a complete stop.

[0061] The architecture further comprises an electrotechnical pack 5, 6 for quickly restarting the hybrid turboshaft engine 1 in order to bring it out of the standby mode and to reach a nominal operating mode.

[0062] This restart pack 5, 6 is supplied with electricity by an auxiliary power unit 11 (referred to in the following by the abbreviation APU) by means of an AC/DC converter 10. This auxiliary engine provides non-propulsive power to the electrotechnical pack 5, 6 on demand to allow said pack to bring the hybrid turboshaft engine 1 out of its standby mode.

[0063] This APU 11 can, for example, comprise a thermal engine (such as a connected gas power turbine or a two-stroke or four-stroke petrol or diesel engine) and a starter-generator capable of restarting the combustion of the APU and of providing the necessary electrical power to the electrotechnical pack. Preferably, the APU provides an AC voltage of 115 volts.

[0064] The AC/DC converter 10 enables the high AC voltage of 115 volts supplied by the APU 11 to be converted into high DC voltage required for restarting the turboshaft engine 1. According to other embodiments, the APU directly provides a DC voltage, and so there is no need for a voltage converter 10.

[0065] The architecture further comprises a low-voltage onboard network 7, preferably of 28 volts (referred to in the following by the abbreviation OBN), for supplying power to helicopter equipment during flight.

[0066] This OBN 7 is supplied with current by the APU 11 by means of a high AC/low DC voltage converter, and by a starter-generator 4 that is connected to the turboshaft engine 2 and directly provides low DC voltage. The OBN 7 further supplies power to a battery 8 for storing 28 volt energy. According to another variant (not shown in the FIGURE), the OBN 7 is supplied with power by a generator installed on the PTG 3.

[0067] To prevent the restart of the turboshaft engine 1 being disrupted, a contact switch 12 is arranged between the OBN 7 and the APU 11 to decouple the OBN 7 and the APU 11 when all the electrical power in the APU 11 is required to bring the turboshaft engine 1 out of the standby mode.

[0068] Preferably, the APU provides an AC voltage of 115 volts and the OBN 7 is a 28 DC volt network. This APU 11 can also directly supply power to specific equipment 9 of the helicopter.

[0069] According to the embodiment in FIG. 1, the quick restart pack comprises an electrical machine 5 that is capable of restarting the hybrid turboshaft engine 1 when leaving standby in normal conditions, and a device 6 for leaving standby in an emergency that is capable of restarting the turboshaft engine 1 when leaving standby in emergency conditions.

[0070] This device 6 for leaving standby in an emergency is, for example, an electrical, pyrotechnic, pneumatic or hydraulic device.

[0071] According to another embodiment of the invention (not shown in the FIGURE), the APU is designed to provide a DC voltage and the electrical machine is designed to operate using alternating current. In this case, an inverter is arranged between the APU and the electrical machine to rectify the current and to power the electrical machine by means of the energy produced by the APU.

[0072] The invention is not limited to the described embodiments only. In particular, the architecture can comprise three turboshaft engines for the equipment of a three-engine helicopter.