HYBRID ELECTRIC AIRCRAFT ENERGY REGENERATION

A hybrid electric aircraft powerplant controller for controlling an engine and an electric motor-generator can include an engine recharging module. The engine recharging module can be configured to operate the engine to produce a desired output power to a propulsor and to produce additional power to drive the electric motor-generator to produce electrical output from the electric motor-generator to recharge an electrical storage device during at least one power setting and/or flight phase where the electric motor-generator is not driving the propulsor.

FIELD

This disclosure relates to hybrid electric aircraft, more specifically to energy regeneration in such aircraft.

BACKGROUND

Certain applications of hybrid electric aircraft use electric power over only a portion of the flight envelope (e.g., during take-off and climb). In a parallel hybrid, this electrical energy can be supplied from an onboard battery, for example. The battery may be desired to contain sufficient energy for the initial take-off/climb, plus at least one reserve take-off/climb. Having a battery with sufficient capacity to contain all of this energy at the start of a flight results in a battery of significant size and weight, penalizing the overall hybrid architecture.

Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for hybrid electric aircraft energy regeneration. The present disclosure provides a solution for this need.

SUMMARY

A hybrid electric aircraft powerplant controller for controlling an engine and an electric motor-generator can include an engine recharging module. The engine recharging module can be configured to operate the engine to produce a desired output power to a propulsor and to produce additional power to drive the electric motor-generator to produce electrical output from the electric motor-generator to recharge an electrical storage device during at least one power setting and/or flight phase where the electric motor-generator is not driving the propulsor.

In a certain aircraft flight (e.g., normal aircraft operation), the at least one power setting can include less than a maximum engine power setting. In certain embodiments, the flight phase can include cruise or descent, for example.

The controller can include a windmilling module configured to reduce power from the engine and windmill the propulsor during descent to drive the electric motor-generator at least partially using windmilling. In certain embodiments, the windmilling module can be configured to idle the engine during descent.

A hybrid electric powerplant system can include a propulsor shaft configured to connect to a propulsor, an engine operatively connected to the propulsor shaft to drive the propulsor shaft, and an electric motor-generator operatively connected to the propulsor shaft to drive the propulsor shaft in conjunction with and/or independently of the engine. The powerplant system can include a controller for controlling the engine and the electric motor-generator, e.g., as disclosed herein (e.g., as described above). The propulsor can be a propeller (e.g., fixed pitch or controllable pitch). The powerplant system can include the propeller.

The powerplant system can include a propeller gear box connected to both the engine and the electric motor-generator, and to the propeller shaft (e.g., to provide a geared connection between each of the engine and the electric motor-generator and the propeller). The powerplant system can include the electrical storage device (e.g., a battery).

In certain embodiments, the powerplant system can include power electronics configured to operate bidirectionally to both provide power to the electric motor-generator in motor mode and to receive electric power from the electric motor-generator in generator mode. The controller can be operatively connected to the power electronics to switch the power electronics from motor mode to generator mode when driving the electric motor-generator. In certain embodiments, the power electronics can be configured to switch automatically between motor mode and generator mode.

A method can include charging an electrical storage device by powering an electric motor-generator of a hybrid electric powerplant system with an engine of the hybrid electric powerplant when there is available additional engine power above a desired power output of the engine and the electric motor-generator is not in use to drive a propulsor. Charging with the engine can include charging during cruise and/or descent. Charging with the engine can include only charging during cruise, and the method can include windmilling the propulsor on descent to charge the electrical storage device.

DETAILED DESCRIPTION

Referring toFIG. 1, a hybrid electric aircraft powerplant controller101for controlling an engine103and an electric motor-generator105of a powerplant system100can include an engine recharging module107. The engine recharging module107can be configured to operate the engine103to produce a desired output power (e.g., based on a throttle setting) to a propulsor109and to produce additional power to drive the electric motor-generator105to produce electrical output from the electric motor-generator105to recharge an electrical storage device (e.g., a battery) during at least one power setting and/or flight phase where the electric motor-generator105is not driving the propulsor109.

Referring additionally toFIG. 2, at least one power setting can include less than a maximum engine power setting (e.g., any setting where less than all of the power the engine103can produce is commanded). In certain embodiments, at least one flight phase can include cruise or descent, for example, as shown inFIG. 2. In certain embodiments, for example, the engine103can be sized such that a cruise power setting can require less than all of the power of the engine103to maintain level flight. In such a case, the controller101can cause the engine103to produce more power than commanded (e.g., by a pilot throttle setting) and the additional power can drive the electric motor-generator105.

In certain systems, the controller101can be configured to disengage (e.g., electrically and/or physically) the electric motor-generator105when not being used as a motor (e.g., due to a power setting where electric power is not required). In certain embodiments, the controller101can be configured to engage (e.g., electrically and/or physically) the electric motor-generator105when recharging is desired if the electric motor-generator105is configured to selectively engage and/or disengage based on whether the electric motor-generator105is required to produce a commanded thrust.

Referring additionally toFIGS. 3 and 4, the controller101can include a windmilling module111configured to reduce power from the engine103and windmill the propulsor109during descent to drive the electric motor-generator105at least partially using windmilling. In certain embodiments, e.g., as shown inFIG. 4, the windmilling module111can be configured to idle the engine103during descent, e.g., such that charging is only a function of potential energy recovery. In certain embodiments, it is contemplated that the engine power setting can be above idle (e.g., any suitable setting to descent at a rate and airspeed as desired), and any tendency to increase a speed of the propulsor109(e.g., due to windmilling effect during descent in a fixed pitch propeller) can be converted to electrical energy.

Certain embodiments can control power draw from the engine103and/or windmilling as a function of how much power is desired for certain charge rate, and/or how much power is available. Certain embodiments can combine engine charging and windmilling modules, and the controller101can be configured to compare power output from electric motor-generator105to a power desired for charging. The controller101can be configured to control the engine103as a function of a difference in output generation and desired generation to mix windmilling and engine power output (e.g., while maintaining desired flight characteristics).

As shown, a hybrid electric powerplant system100can include a propulsor shaft113configured to connect to a propulsor109, an engine103operatively connected to the propulsor shaft113to drive the propulsor shaft113, and an electric motor-generator105operatively connected to the propulsor shaft113to drive the propulsor shaft113in conjunction with and/or independently of the engine103. The powerplant system can include a controller101for controlling the engine103and the electric motor-generator105, e.g., any suitable controller101as disclosed herein (e.g., as described above). The propulsor109can be a propeller (e.g., fixed pitch or controllable pitch). The powerplant system100can include the propeller109, in certain embodiments.

The powerplant system100can include a propeller gear box115connected to both the engine103and the electric motor-generator105, and to the propeller shaft113(e.g., to provide a geared connection between each of the engine103and the electric motor-generator105and the propulsor109). The powerplant system100can include the electrical storage device117(e.g., a battery) operatively connected to the electric motor-generator105.

In certain embodiments, the powerplant system100can include power electronics119configured to operate bidirectionally to both provide power from the electrical storage device119to the electric motor-generator105in motor mode and to receive electric power from the electric motor-generator105in generator mode to charge the electrical storage device119. The controller101can be operatively connected to the power electronics119to switch the power electronics119from motor mode to generator mode when driving the electric motor-generator105to charge the electrical storage device117. In certain embodiments, the power electronics119can be configured to switch automatically between motor mode and generator mode.

In accordance with at least one aspect of this disclosure, a method can include charging an electrical storage device by powering an electric motor-generator of a hybrid electric powerplant system with an engine of the hybrid electric powerplant when there is available additional engine power above a desired power output of the engine and the electric motor-generator is not in use to drive a propulsor. Charging with the engine can include charging during cruise and/or descent. Charging with the engine can include only charging during cruise, and the method can include windmilling the propulsor on descent to charge the electrical storage device.

In certain embodiments, an engine can be used exclusively in cruise and/or descent in a hybrid system. Embodiments can power both a propulsor and drive an electric motor-generator to regenerate electricity (e.g., in any scenario where less engine energy is needed than full power). Certain embodiments can reduce a battery size by about 70 kWh and reduce aircraft weight by about 1000 lbs with a minimal increase in carried fuel (e.g., about 20-25 lbs of fuel).

Certain embodiments require no additional power electronics as certain motor drives can be configured to be bidirectional. Certain embodiments need not have additional gear mechanics, clutches, or other different mechanics. Certain embodiments do not need a clutch for engaging or disengaging the electric motor-generator, e.g., where an open circuit stator produces very little horsepower, for example. Certain embodiments can recharge about 20% storage capacity in about a half an hour. For example, certain embodiments can cause an engine to generate about 150 KW of additional engine output to recharge about 70 KWH in about a half hour, which can be about 20% of electric storage capacity in certain embodiments. Embodiments can include an additional mode to windmill the propeller, for example. In this option, at least a portion of the reserve energy is stored as potential energy (weight and altitude) of the aircraft, and the propeller can be used to back-drive the electric motor-generator, generating electricity that is used to recharge the battery, for example.

As appreciated by those having ordinary skill in the art in view of this disclosure, certain embodiments allow hybrid aircraft to include only sufficient battery capacity for an initial take-off and climb, and to use inflight recharging to “refill” the battery for subsequent reserve take-off and climbs. Embodiments provide at least one more operational modes such as conversion of liquid fuel to battery energy and/or conversion of aircraft potential energy to battery energy. Implementation of inflight recharging can allow the batteries to be reduced in size by approximately ⅓, e.g., as described above.