Patent Description:
Hybrid power plants employ two or more different types of energy sources to provide propulsive power to an aircraft. Compared to more conventional, single engine, designs, hybrid power plants provide additional flexibility with respect to how the required power is generated, by selecting an appropriate work split ratio between the engine types. This work split ratio may, for example, be selected in view of operating conditions, power requirements, fuel economy, and/or other considerations. Much like single engine aircraft power plants, hybrid power plants remain subject to noise regulations, for instance when operating near airports and/or near populated areas. For certain airports close to populated areas, noise regulations may be even more restrictive. Improvements are therefore sought to minimize the noise of such hybrid power plants on an aircraft.

<CIT> discloses a prior art hybrid turbine engine and a controller configured to reduce a rotational speed of the gas turbine engine core to reduce noise generated by the hybrid turbine engine in response to receiving a signal indicating that a noise level generated by the hybrid turbine engine is above a predetermined noise threshold.

<CIT> discloses a prior art hybrid propulsion system and method of management thereof.

<CIT> discloses a prior art hybrid electric powerplant control architecture.

<CIT> discloses a prior art aircraft hybrid propulsion system.

<CIT> discloses a prior art operations support system for an engine.

In one aspect of the present invention, there is provided a method of reducing acoustic noise produced by a hybrid power plant having a thermal engine and an electrical motor according to claim <NUM>.

In certain embodiments, the method as defined above and described herein includes one or more of the following features, in whole or in part, and in any combination.

Optionally, and in accordance with the above, the determining of the work split ratio includes determining the work split ratio from a database correlating noise signatures with work split ratios and power levels.

Optionally, and in accordance with any of the above, the determining of the work split ratio from the database includes: determining, from the database, a second work split ratio at which a second noise signature generated by the hybrid power plant is minimal for the power level; determining that the initial work split ratio is different than the second work split ratio; and selecting the work split ratio for which the noise signature is at or below the target noise signature and at or above the second noise signature.

Optionally, and in accordance with any of the above, the selecting of the work split ratio includes selecting the work split ratio corresponding to the second work split ratio, and the operating of the hybrid power plant at the work split ratio includes operating the hybrid power plant at the second work split ratio.

Optionally, and in accordance with any of the above, the target noise signature is a maximum target noise of a target noise signature range, and the determining of the work split ratio includes determining the work split ratio within the target noise signature range.

Optionally, and in accordance with any of the above, the receiving of the signal from the one or more sensors includes receiving data about the initial noise signature, the data including one or more of an overall sound pressure level, a frequency composition, and a tonal amplitude of peak tonal noises of the hybrid power plant.

Optionally, and in accordance with any of the above, the method includes storing the initial noise signature.

In another aspect of the present invention, there is provided a hybrid power plant according to claim <NUM>.

In certain embodiments, the hybrid power plant as defined above and described herein includes one or more of the following features, in whole or in part, and in any combination.

Optionally, and in accordance with any of the above, the modulating of the work split ratio includes determining the work split ratio from a database correlating noise signatures with work split ratios and power levels.

Optionally, and in accordance with any of the above, the determining of the work split ratio from the database includes: determining, from the database, a second work split ratio at which a second noise signature generated by the hybrid power plant is minimal for the power level; determining that the initial work split ratio is different than the second work split ratio; and selecting the work split ratio for which the noise signature is within the target deviation range.

Optionally, and in accordance with any of the above, the selecting of the work split ratio includes selecting the work split ratio corresponding to the second work split ratio.

Optionally, and in accordance with any of the above, the target noise signature is a maximum target noise of a target noise signature range, and the determining of the work split ratio includes determining the work split ratio is within the target noise signature range.

Referring to <FIG>, an aircraft is shown generally at <NUM>. The aircraft <NUM> includes a fuselage <NUM> enclosing a cabin for passengers, wings <NUM> mounted to the fuselage <NUM>, a horizontal stabilizer <NUM> mounted to a rear end of the fuselage <NUM>, a vertical stabilizer <NUM> mounted to the rear end of the fuselage <NUM>. The aircraft <NUM> is equipped with two hybrid power plants <NUM>, although the aircraft <NUM> may be equipped with more than two hybrid power plants <NUM> or only one hybrid power plant <NUM>. A controller <NUM> is operatively connected to the hybrid power plant(s) <NUM> via suitable communication links. The controller <NUM> may be a controller of the aircraft <NUM>. These communication links may be hard wires, wireless links, or any combination thereof. In the embodiment shown, the two hybrid power plants <NUM> include each a propulsor <NUM>. As depicted, the propulsor <NUM> may be a propeller or, any other means operable to generate a thrust for propelling the aircraft <NUM>. For instance, the propulsor <NUM> may be a fan, a rotor, and so on.

Referring more particularly to <FIG>, one of the two hybrid power plants <NUM> is shown and described in greater detail. The description below uses the singular form, but it may apply to each of the hybrid power plants <NUM> of the aircraft <NUM> (<FIG>). In the embodiment shown, the hybrid power plant <NUM> includes a thermal engine <NUM> that is drivingly engageable to the propulsor <NUM> via a gearbox <NUM>. The thermal engine <NUM> is fluidly connected to a tank <NUM> that contains a fuel. The thermal engine <NUM> may be any engine that relies on combustion for its operation. For instance, the thermal engine <NUM> may be an internal combustion engine such as a piston engine, a rotary engine, or any engine having a combustion chamber of varying volume. The thermal engine <NUM> may be a gas turbine engine comprising a compressor, a combustor, and a turbine. The hybrid power plant <NUM> further includes an electrical motor <NUM> that is drivingly engageable to the propulsor <NUM> via the gearbox <NUM>. The electrical motor <NUM> may be operatively connected to a power source <NUM>, such as a battery, via a converter <NUM>. The power source <NUM> may alternatively be a generator. The converter <NUM> may be used to transform a direct current from the power source <NUM> to an alternating current supplied to the electrical motor <NUM>. Any suitable electrical motor <NUM> may be used.

The gearbox <NUM> is operable to combine inputs of both of the thermal engine <NUM> and the electrical motor <NUM> to deliver a common output to drive a common load, which herein corresponds to the propulsor <NUM>. Stated differently, the gearbox <NUM> is drivingly engaged by an output shaft <NUM> of the thermal engine <NUM> and by an output shaft <NUM> of the electrical motor <NUM>. The gearbox <NUM> may include clutches to selectively engage and disengage the thermal engine <NUM> and the electrical motor <NUM> from the propulsor <NUM>. For instance, the clutches may disengage one of the thermal engine <NUM> and the electrical motor <NUM> if a thrust requirement of the aircraft <NUM> is such that only power generated by the other of the thermal engine <NUM> and the electrical motor <NUM> is required. These clutches may be one-way clutches, friction clutches, and so on.

In some embodiments, the hybrid power plant <NUM> may include a second electrical motor <NUM> drivingly engageable to the propulsor <NUM> via the gearbox <NUM>. In some embodiments, the hybrid power plant <NUM> may include a second thermal engine (not shown). In some embodiments, the hybrid power plant may include two or more thermal engines drivingly engaged to the propulsor <NUM>, or two or more electrical motors drivingly engaged to the propulsor <NUM>. The two thermal engines may be of a same model. Alternatively, the two thermal engines may be have different power ratings. The two electrical motors may be of a same model. Alternatively, the two electrical motors may have different power ratings. The hybrid power plant <NUM> may include a first power generator and a second power generator. The first power generator may be a thermal engine, an electrical motor, or any other suitable machine operable to generate power (e.g., torque, propulsive power). The second power generator may be a thermal engine, an electrical motor, or any other suitable machine operable to generate power. Therefore, the expression "hybrid" may include any power plant including two or more machines able to generate power. Hence, the hybrid power plant <NUM> may include two or more thermal engines, two or more electrical motors, or any combinations of thermal engines, electrical motors, and other machines.

In use, the hybrid power plant <NUM> generates a noise signature. This noise signature may be caused by a combination of respective noise signatures of the thermal engine <NUM> and the electrical motor <NUM>. Acoustic sensors, herein after simply "sensors", <NUM> are disposed at a plurality of locations to measure the noise signature of the hybrid power plant <NUM>. For instance, the hybrid power plant <NUM> may include a nacelle 20A, an inlet 20B, and an exhaust 20C. The sensors <NUM> may be located at any location within the nacelle 20A, inlet 20B, and exhaust 20C. The sensors <NUM> may be pressure transducers, microphones, or any suitable acoustic sensors. The sensors <NUM> may generate real-time acoustic measurements.

The noise signature of the hybrid power plant <NUM> may include data about one or more of an overall sound pressure level, a frequency composition, and a tonal amplitude of peak tonal noises of the hybrid power plant <NUM>. The noise signature may vary with a power level of the hybrid power plant <NUM>. The power level may be considered to be a power (e.g., torque) provided by the hybrid power plant <NUM> to the propulsor <NUM>. The hybrid power plant <NUM> may vary its power level to vary a thrust generated by the propulsor <NUM>. The noise signature of the hybrid power plant <NUM> may also be influenced by a work split ratio between the thermal engine <NUM> and the electrical motor <NUM>. The work split ratio corresponds a power provided by the thermal engine <NUM> divided by a power provided by the electrical motor <NUM>. The hybrid power plant <NUM> may be operated at more than one engine split ratios to provide substantially the same power level. For instance, a same power may be provided to the propulsor <NUM> if the work split ratio is <NUM>% for the electrical motor <NUM> and <NUM>% for the thermal engine <NUM> and if the work split ratio is <NUM>% for the electrical motor <NUM> and <NUM>% of the thermal engine <NUM>. These two different work split ratios may provide the same power to the propulsor <NUM>. However, even if the same power is delivered to the propulsor <NUM> for these work split ratios, an efficiency of the hybrid power plant <NUM> and the noise signature of the hybrid power plant <NUM> may vary. For instance, more noise may be generated by the thermal engine <NUM> than by the electrical motor <NUM>. Hence, using a work split ratio favoring the thermal engine <NUM> may generate more noise.

It may be desirable to minimize the noise signature generated by the hybrid power plant <NUM> in some flight phases of the aircraft <NUM>. For instance, during take-off, climb, descend, and landing, the noise generated by the aircraft <NUM>, and by its hybrid power plant(s) <NUM> may be subjected to some regulations to limit disturbances to surrounding populations. During cruise, it may be desired to minimise the noise for passenger comfort.

In the embodiment shown, the sensors <NUM> are used to measure the noise signature of the hybrid power plant(s) <NUM>. This may be done by combining noise signatures measured by the plurality of sensors <NUM> each disposed in the vicinity of a respective component of the hybrid power plant <NUM>. For instance, noise signatures generated at the inlet 20B, within the nacelle 20A, at the exhaust 20C, proximate the thermal engine <NUM>, and proximate the electrical motor <NUM> may be combined to yield an overall noise signature of the hybrid power plant <NUM>. In some other embodiments, only one sensor <NUM> may be used. This sensor <NUM> may be located at any suitable location permitting the sensor <NUM> to capture the overall noise signature of the hybrid power plant <NUM>. For instance, this sensor <NUM> may be located outside the nacelle 20A, proximate the hybrid power plant <NUM>. In some embodiments, this sensor <NUM> may be located on the wing <NUM>.

Once the noise signature of the hybrid power plant <NUM> is known, it may be possible to determine that the noise signature is above a target noise signature threshold of the hybrid power plant <NUM>. This threshold may be imposed by regulations (e.g., for flight phases where the aircraft <NUM> is close to the ground) or may be set in accordance with preferences for passenger comfort (e.g., during cruise). At which point, another work split ratio may be determined. The hybrid power plant <NUM> may output substantially the same power at this other work split ratio, but may generate a noise signature at or below the target noise signature. Then, the hybrid power plant <NUM> is operated at this other work split ratio.

Referring now to <FIG>, a method of reducing the noise of the hybrid power plant <NUM> is shown at <NUM>. The method <NUM> includes driving the propulsor <NUM> with the hybrid power plant <NUM> operated at an initial work split ratio and at a power level at <NUM>; receiving a signal from the one or more acoustic sensors <NUM>, the signal indicative of an initial noise signature generated by the hybrid power plant <NUM> operated at the initial work split ratio and the power level at <NUM>; determining that the initial noise signature generated by the hybrid power plant <NUM> is above a target noise signature of the hybrid power plant at <NUM>; determining a work split ratio which will generate a noise signature of the hybrid power plant <NUM> is at or below the target noise signature at <NUM>; and operating the hybrid power plant <NUM> at the work split ratio at <NUM>.

In the embodiment shown, the receiving of the signal at <NUM> includes receiving data about the initial noise signature, the data including one or more of an overall sound pressure level, a frequency composition, and a tonal amplitude of peak tonal noises of the hybrid power plant.

In the present embodiment, the determining of the work split ratio at <NUM> includes determining the work split ratio from a database <NUM> (<FIG>) correlating noise signatures with work split ratios and power levels of the hybrid power plant <NUM>. The determining of the work split ratio from the database may include determining, from the database <NUM>, a second work split ratio at which a second noise signature generated by the hybrid power plant is minimal for the power level; determining that the initial work split ratio is different than the second work split ratio; and selecting the work split ratio for which the noise signature is at or below the target noise signature and at or above the second noise signature. The selecting of the work split ratio may include selecting the work split ratio corresponding to the second work split ratio, and the operating of the hybrid power plant <NUM> at the work split ratio at <NUM> may include operating the hybrid power plant <NUM> at the second work split ratio. In the embodiment shown, the target noise signature is a maximum target noise of a target noise signature range, the determining of the work split ratio includes determining the work split ratio within the target noise signature range.

As explained below, the target noise signature varies as a function of a flight phase of the aircraft <NUM>. Hence, the method <NUM> includes determining the target noise signature as a function of the flight phase. More specifically, not according to the claims, the method <NUM> may include determining that the flight phase is one of take-off, landing, descend, and climb. Then, not according to the claims, the determining of the target noise signature may include determining a target far-field noise signature corresponding to a ground noise signature of the hybrid power plant perceived on the ground. In other words, the noise signature of the hybrid power plant <NUM> may differ from in the vicinity of the hybrid power plant <NUM> and on the ground. The database <NUM> may therefore contain data correlating the far-field noise signature of the hybrid power plant <NUM> with work split ratios and power levels.

The method <NUM> includes determining that the flight phase is cruise. Then, the determining of the target noise signature includes determining a target cabin noise signature corresponding to a cabin noise signature of the hybrid power plant perceived within a cabin of the aircraft <NUM>. In other words, the noise signature of the hybrid power plant <NUM> may differ from in the vicinity of the hybrid power plant <NUM> and inside the cabin. The database <NUM> may therefore contain data correlating the cabin noise signature of the hybrid power plant <NUM> with work split ratios and power levels.

The disclosed method <NUM> may include collecting instantaneous engine noise signatures; dynamically adjusting the engine work split ratio between the thermal engine <NUM> and the electrical motor <NUM> to minimize the far-field or targeted noise level in various situations; and storing instantaneous engine noise data to refine future engine operation strategy and identify potential engine problems and maintenance need.

Referring now to <FIG>, a method of reducing the noise of the hybrid power plant <NUM> is shown at <NUM>. The method <NUM> includes receiving a signal from the one or more sensors <NUM> at <NUM>, the signal indicative of an initial noise signature generated by the hybrid power plant <NUM>; determining when the initial noise signature deviates from a target noise signature of the hybrid power plant by more than a target deviation range at <NUM>; and in response to the determining when the initial noise signature deviates from the target noise signature by more than the target deviation range, modulating the noise signature by modulating a work split ratio between the thermal engine <NUM> and the electrical motor <NUM> until the noise signature is within the target deviation range at <NUM>.

In the embodiment shown, the modulating of the work split ratio at <NUM> includes determining the work split ratio from a database correlating noise signatures with work split ratios and power levels. The determining of the work split ratio from the database may include determining, from the database, a second work split ratio at which a second noise signature generated by the hybrid power plant is minimal for the power level; determining that the initial work split ratio is different than the second work split ratio; and selecting the work split ratio for which the noise signature is within the target deviation range. The selecting of the work split ratio may include selecting the work split ratio corresponding to the second work split ratio.

In another embodiment, the hybrid power plant <NUM> may have a standard operation mode and a whisper mode for each power level. The standard operation mode may provide a better energy efficiency of the hybrid power plant <NUM> than the whisper mode, or may be more desirable for other considerations (e.g., fuel consumption, battery usage, cold or hot temperatures, etc). However, the hybrid power plant <NUM> may generate less noise in the whisper mode, but with efficiency and/or other penalties. During use of the aircraft <NUM>, it may be determined that the aircraft is subjected to noise regulations. At which point, the work split ratio of the hybrid power plant <NUM> may be varied to switch the hybrid power plant <NUM> from the standard operation mode to the whisper mode to decrease the noise below an acceptable level. In some embodiments, the determining that the aircraft <NUM> is subjected to noise regulations may be achieved by determining that an altitude of the aircraft <NUM> is below a first threshold for take-off, climb, descend, and landing phases and above a second threshold for cruise. When the altitude is below the first threshold, the far-field noise signature is to be minimized for surrounding populations on the ground whereas, when the altitude is above the second threshold, the cabin noise signature is to be minimized for passenger comfort.

Referring to <FIG>, a method of operating the aircraft is shown at <NUM>, the method <NUM> includes driving the propulsor(s) <NUM> of the aircraft with the hybrid power plant(s) <NUM> operated in a standard operation mode associated with a standard operation work split ratio at <NUM>; determining that the aircraft <NUM> is subjected to noise restrictions at <NUM>; and operating the hybrid power plant(s) <NUM> of the aircraft <NUM> in a whisper mode associated with a whisper work split ratio different than the standard operation work split ratio at <NUM>. A whisper noise signature of the hybrid power plant at the whisper work split ratio is less than a standard operation noise signature of the hybrid power plant at the standard operation work split ratio.

The determining that the aircraft <NUM> is in the flight phase subjected to noise restrictions at <NUM> includes determining that the flight phase is cruise.

In the depicted embodiment, the operating of the hybrid power plant(s) <NUM> in the whisper mode at <NUM> includes determining the whisper work split ratio by selecting, from the database <NUM> correlating noise signatures with work split ratios, a work split ratio at which a noise signature of the hybrid power plant(s) <NUM> is at or below a target noise signature.

In some embodiments, a pilot of the aircraft <NUM> may actuate the whisper mode with a switch. The determining that the aircraft is in a flight phase subjected to noise restrictions at <NUM> may include receiving a signal from the switch; the signal indicative that the hybrid power plant(s) <NUM> is to be operated with a work split ratio generating noise at or below a target noise signature.

With reference to <FIG>, an example of a computing device <NUM> is illustrated. For simplicity only one computing device <NUM> is shown but the system may include more computing devices <NUM> operable to exchange data. The computing devices <NUM> may be the same or different types of devices. The controller <NUM> may be implemented with one or more computing devices <NUM>. Note that the controller <NUM> can be implemented as part of a full-authority digital engine controls (FADEC) or other similar device, including electronic engine control (EEC), engine control unit (ECU), electronic propeller control, propeller control unit, and the like. In some embodiments, the controller <NUM> is implemented as a Flight Data Acquisition Storage and Transmission system, such as a FAST™ system. The controller <NUM> may be implemented in part in the FAST™ system and in part in the EEC. Other embodiments may also apply.

The memory <NUM> may include a suitable combination of any type of computer memory that is located either internally or externally to device, for example random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like.

The methods and systems for reducing noise of an hybrid power plant described herein may be implemented in a high level procedural or object oriented programming or scripting language, or a combination thereof, to communicate with or assist in the operation of a computer system, for example the computing device <NUM>. Alternatively, the methods and systems for reducing noise of an hybrid power plant may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems for reducing noise of an hybrid power plant may be stored on a storage media or a device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the methods and systems for reducing noise of an hybrid power plant may also be considered to be implemented by way of a non-transitory computer-readable storage medium having a computer program stored thereon. The computer program may comprise computer-readable instructions which cause a computer, or more specifically the processing unit <NUM> of the computing device <NUM>, to operate in a specific and predefined manner to perform the functions described herein, for example those described in the method <NUM>.

The targeted acoustic noise reduction is in the cabin and may be, not according to the claims, in the far-field, in the vicinity of the aircraft or anywhere else deemed appropriate. The disclosed methods <NUM>, <NUM> are applicable for two, or any larger number of engines coupled with one another. The methods <NUM>, <NUM> are applicable for engines of any type (electric, thermodynamic, or other). The quantity of acoustic measurement(s) may be any deemed necessary. The acoustic measurement(s) may be located anywhere in the aircraft deemed necessary, inside the nacelle or elsewhere. The acoustic measurement(s) may be of any type deemed necessary.

Claim 1:
A method (<NUM>) of reducing acoustic noise produced by a hybrid power plant (<NUM>) having a thermal engine (<NUM>) and an electrical motor (<NUM>), the method comprising:
driving (<NUM>) a propulsor (<NUM>) with the hybrid power plant (<NUM>) operated at an initial work split ratio and at a power level, the initial work split ratio corresponding to a power provided by the thermal engine (<NUM>) divided by a power provided by the electrical motor (<NUM>);
receiving (<NUM>) a signal from one or more sensors (<NUM>), the signal indicative of an initial noise signature generated by the hybrid power plant (<NUM>) operated at the initial work split ratio and the power level;
determining (<NUM>) that the initial noise signature generated by the hybrid power plant (<NUM>) is above a target noise signature of the hybrid power plant (<NUM>);
determining (<NUM>) a work split ratio of the hybrid power plant (<NUM>) which will generate a noise signature that is at or below the target noise signature; and
operating (<NUM>) the hybrid power plant (<NUM>) at the work split ratio, wherein the determining (<NUM>) that the initial noise signature is above the target noise signature includes determining the target noise signature as a function of a flight phase,
wherein
the determining of the target noise signature as a function of the flight phase includes determining that the flight phase is cruise; and characterised in that
the determining of the target noise signature includes determining a target cabin noise signature corresponding to a cabin noise signature of the hybrid power plant (<NUM>) perceived from within a cabin of an aircraft (<NUM>) equipped with the hybrid power plant (<NUM>).