Patent ID: 12246844

DETAILED DESCRIPTION

The present disclosure relates to architectures of hybrid aircraft power plants and associated methods of operating hybrid aircraft power plants. In some embodiments, the system architectures described herein may facilitate the adaptation of existing gas turbine engine configurations into hybrid power plants. In some embodiments, the system architectures described herein may facilitate the integration of a turboprop gas turbine engine into a hybrid electric aircraft power plant. For example, a bifurcated exhaust duct may be installed on the gas turbine engine to facilitate the installation of an electric motor configured to assist with the propulsion of the aircraft. The electric motor may be mounted directly to the bifurcated exhaust duct to promote a relatively compact system architecture with efficient packaging that does not significantly impact the configuration of the gas turbine engine or the size of the nacelle that encloses the hybrid power plant.

Aspects of various embodiments are described through reference to the drawings.

The terms “connected” or “coupled to” may include both direct connection or coupling (in which two elements contact each other) and indirect connection or coupling (in which at least one additional element is located between the two elements). The term “substantially” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related.

FIG.1is an axial cross-sectional view of hybrid aircraft power plant10(referred hereinafter as “power plant10”) as described herein. Power plant10may be used to propel aircraft12during one or more phases of flight of aircraft12. In some embodiments, aircraft12may be a fixed wing aircraft. In various embodiments, aircraft12may include one or more power plants10for propelling aircraft12. In some embodiments, power plant10may be configured for use on rotary wing aircraft (e.g., helicopter). As illustrated inFIG.1, power plant10may include a turboprop gas turbine engine14(referred hereinafter as “engine14”) however, aspects of the present disclosure may be incorporated into turboshaft gas turbine engines as well. The forward direction shown inFIG.1corresponds to the usual direction of motion of power plant10and of aircraft12when power plant10is propelling aircraft12during flight for example. The aft direction shown Is the axial opposite to the forward direction.

Engine14may be of a type preferably provided for use in subsonic flight. Engine14may be a flow-through gas turbine engine where the flow of air and combustion gas through engine14is generally toward the aft direction (i.e., from a forward portion of engine14to an aft portion of engine14). For example, engine14may include (e.g., radial) air inlet16into which ambient air is received and conveyed toward compressor18. In some embodiments, compressor18may be a multistage compressor that pressurized the air received via air inlet16. Engine14may include combustor20in which the compressed air received from compressor18is mixed with a combustible fuel from fuel tank22and ignited to generate an annular stream of hot combustion gas. Engine14may include a turbine section to extract energy from the combustion gas and convert the energy into motive power to drive an air mover such as propeller24and thereby propel aircraft12. In various embodiments, power plant10may include one or more air movers suitable for propelling aircraft12. In some embodiments, such air mover(s) may include a bladed rotor such as a fan or a variable-pitch propeller for example.

In various embodiments, engine14may be a single spool gas turbine engine or a multi-spool gas turbine engine. For example, engine14may include a high-pressure spool including one or more high-pressure turbines26of the turbine section, high-pressure shaft28and one or more stages of compressor18. High-pressure turbine26may drive the rotation of the high-pressure spool.

Engine14may include a low-pressure spool that is separately rotatable from the high-pressure spool. In other words, the high-pressure spool and the low-pressure spool may be mechanically disconnected to permit one spool to freely rotate relative to the other. The low-pressure spool may include one or more low-pressure turbines30, low-pressure shaft32and optionally one or more stages of compressor18. In some embodiments, high-pressure shaft28and low-pressure shaft32may be coaxial where high-pressure shaft28may be hollow to permit the passage of low-pressure shaft32therethrough. Low-pressure turbine30may be disposed downstream of high-pressure turbine26relative to the gas path conveying combustion gas from combustor20.

Low-pressure turbine30may drive the rotation of the low-pressure spool and may also drive the rotation of propeller24. Low-pressure turbine30may be in torque-transmitting engagement with propeller24via low-pressure shaft32. Low-pressure turbine30and low-pressure shaft32may be rotatable about turbine axis TA. In some embodiments, propeller24may be supported by propeller shaft34, which may be in torque transmitting engagement with low-pressure shaft32via gear train36. Propeller shaft34and propeller24may be rotatable about propeller axis PA, which may be parallel to and offset from turbine axis TA. In other embodiments, propeller24and low-pressure turbine30may be coaxial. In some embodiments, gear train36may be of a speed-reducing type so that the rotational speed of propeller shaft34may be lower than the rotational speed of low-pressure shaft32and of low-pressure turbine30during operation of power plant10. Gear train36may be part of a speed-reducing gear box also known as a reduction gear box (RGB).

Power plant10may include bifurcated exhaust duct38(referred herein after as “exhaust duct”) mounted aft of and downstream from low-pressure turbine30. During operation of engine14, exhaust duct38may receive the annular stream of combustion gas from low-pressure turbine30, split the annular stream into two separate streams and then convey the two separate streams of combustion gas in two different general directions of flow referred herein as directions D1, D2. Directions D1and D2may be different (e.g., divergent, non-parallel). Directions D1and D2may be orientated radially outwardly from turbine axis TA. For example, directions D1and D2may have radially outward and aft vector components. In some embodiments, directions D1and D2may each be oriented at an acute angle from turbine axis TA. In some embodiments, directions D1and D2may each be oriented at an angle of between 30° and 60° from turbine axis TA. In some embodiments, directions D1and D2may each be oriented at an angle of between 40° and 50° from turbine axis TA. In some embodiments, directions D1and D2may each be oriented at an angle of about 45° from turbine axis TA. In some embodiments, exhaust duct38may include first branch40conveying a first portion of the combustion gas toward first direction D1away from turbine axis TA, and second branch42conveying a second portion of the combustion gas toward second direction D2away from turbine axis TA.

In some embodiments, additional duct work such as respective ejector pipes43(only one being shown as an example) may be in fluid communication with first branch40and second branch42of exhaust duct38to optionally ventilate nacelle44and also convey the combustion gas outside of nacelle44. Nacelle44is partially shown inFIG.1and may envelope part of power plant10. For example, in some embodiments, engine14, exhaust duct38and electric machine46may be housed in nacelle44.

Alternatively, first branch40and second branch42may convey the combustion gas directly outside of nacelle44without the use of ejector pipes43. As an example,FIG.1shows alternate nacelle44A in broken lines using reference numeral44A where first branch40and second branch42may convey the combustion gas directly outside of alternate nacelle44A without the use of ejector pipes43. Alternate nacelle44A is partially shown inFIG.1and may envelope part of power plant10. For example, in some embodiments, engine14, some or all of exhaust duct38, and electric machine46may be housed in alternate nacelle44A.

Electric machine46may be mounted to and supported by exhaust duct38. Electric machine46may be disposed aft of low-pressure turbine30. Electric machine46may be drivingly coupled to propeller24via low-pressure turbine30and low-pressure shaft32. In some embodiments, electric machine46may be operable as an electric motor for converting electric energy into torque for driving propeller24. In some embodiments, electric machine46may additionally be operable as an electric generator where mechanical energy (e.g., torque*rotational speed) is converted into electric energy. During a motoring mode of operation, electric machine46may receive electric energy from a suitable electric power source such as battery48. During a generating mode of operation, electric machine46may receive mechanical energy from low-pressure turbine30and generate electric energy for charging battery48or powering one or more other systems of power plant10or of aircraft12.

In various embodiments, engine14and electric machine46may be controlled by one or more controllers so that engine14and electric machine46may be operated either together or separately to drive propeller24. In some embodiments, the operation of engine14and/or electric machine46may be selected based on a phase of flight of aircraft12. For example, during a take-off phase of a fixed-wing aircraft, both engine14and electric machine46may be used to cooperatively drive propeller24. On the other hand, in a leveled cruise phase of flight, only engine14may be used to drive propeller24in some embodiments.

Electric machine46may be mounted to exhaust duct38and be operable to drive (i.e., in torque-transmitting engagement with) propeller24via low-pressure turbine30and low-pressure shaft32and/or via separate torque-transmitting engagement between electric machine46and propeller24. In some embodiments, electric machine46may be selectively or permanently drivingly coupled to low-pressure shaft32via coupling shaft50. Coupling shaft50may be connected to low-pressure shaft32and to electric machine46via suitable splined connections or other means to establish torque transmission between low-pressure shaft32and electric machine46. In embodiments where electric machine46is selectively connectable to low-pressure shaft32, a releasable/engageable clutch may be operatively disposed between electric machine46and low-pressure shaft32.

In some embodiments, electric machine46may be mounted to exhaust duct38at a mounting location between first branch40and second branch42. For example, first branch40and second branch42may extend to opposite sides of electric machine46. In some embodiments, electric machine46may be mounted to be substantially coaxial with low-pressure turbine30and with low-pressure shaft32. In some embodiments, coupling shaft50may be rotatable about turbine axis TA and consequently be substantially coaxial with low-pressure turbine30and low-pressure shaft32.

FIG.2is a perspective view of an exemplary aft portion of power plant10showing exhaust duct38and electric machine46mounted to exhaust duct38. Exhaust duct38may be connected (e.g., fastened) to casing52of engine14as explained below in relation toFIG.4. In various embodiments, exhaust duct38may have a single-walled or a double-walled construction. In an exemplary double-walled embodiment, exhaust duct38may include inner wall54and outer wall56. Inner wall54may interface directly with the combustion gas and cause the annular stream of combustion gas received from low-pressure turbine30to be split and conveyed into first branch40and second branch42. Accordingly, inner wall54may define first branch40and second branch42.

Outer wall56may be dispose over (e.g., radially outwardly of) inner wall54and thereby cover part of inner wall54. In some embodiments, first branch40and second branch42may extend through outer wall56. For example, outer wall56may include first opening58extending therethrough and permitting first branch40to pass through outer wall56and extend from an interior of outer wall56to an exterior of outer wall56. Outer wall56may also include second opening60extending therethrough and permitting second branch42to pass through outer wall56and extend from an interior of outer wall56to an exterior of outer wall56.

Electric machine46may be mounted to outer wall56at mount62. Mount62may be a mounting pad or other suitable surface(s) providing an interface for securing (e.g., fastening) electric machine46to outer wall56. Outer wall56may extend between first branch40and second branch42. Mount62may be defined between first branch40and second branch42. Inner wall54and outer wall56of exhaust duct38may each be connected (e.g., welded) to ring64. Ring64may be an annular member serving as a base of exhaust duct38that may be fastened to casing52of engine14. Accordingly, elements of double-walled exhaust duct38may be assembled together to define a single component.

In some embodiments, inner wall54and outer wall56may be connected together via ring64but may otherwise be disconnected from each other to permit thermal expansion and contraction of inner wall54relative to outer wall56during start-up and shutdown of engine14for example. In other words, outer wall56may be spaced apart from inner wall54and float over inner wall54to define a gap therebetween to accommodate thermal expansion. For example, first branch40of inner wall54and first opening58through outer wall56may be sized to define first gap66between first branch40and a periphery of first opening58. First gap66may extend completely around first branch40. Similarly, second branch42of inner wall54and second opening60through outer wall56may be sized to define second gap68between second branch42and a periphery second opening60. Second gap68may extend completely around second branch42.

Exhaust duct38may be fabricated from a suitable metallic material using known or other sheet metal forming and joining processes. For examples, exhaust duct38may be fabricated from a plurality of separate pieces of sheet metal that are formed to a desired shape and subsequently joined together to define the overall shape of exhaust duct38. In various embodiments, the separate pieces of sheet metal may be welded together or fastened together with rivets for example. In some embodiments, exhaust duct38may be fabricated from stainless steel or a suitable nickel-based alloy for example.

FIG.3is cross-sectional view of the aft portion of power plant10taken along line3-3inFIG.2. In some embodiments, engine14and/or exhaust duct38include one or more vanes70for interacting with the combustion gas received from low-pressure turbine30. Vanes70may serve to redirect (e.g., straighten) the flow of combustion gas. An upstream portion of exhaust duct38may define an annular inlet for receiving the combustion gas. The exhaust duct38may have a geometry that transitions the annular inlet to two separate flows oriented in diverging directions defined by first branch40and second branch42.

Mount62defined by outer wall56may include socket72into which a forward part of electric machine46may be received when electric machine46is mounted to outer wall56. For example, a forward portion of a housing of electric machine46may be received into socket72. When mounted to outer wall56, electric machine46may be coaxial with low-pressure turbine30and low-pressure shaft32. For example, electric machine46may include rotor46A and stator46B. Rotor46A may be rotatable about turbine axis TA. In other words, rotor46A of electric machine46and low-pressure turbine30may have the same rotation axis (i.e., turbine axis TA).

FIG.4is an enlarged view of region4inFIG.3showing exhaust duct38being fastened to casing52of engine14. In some embodiments, exhaust duct38may be connected to casing52via ring64of exhaust duct38. Both inner wall54and outer wall56may be connected (e.g., welded) to ring64. For example, inner wall54and outer wall56may merge together at ring64. Ring64may include duct flange74extending radially outwardly and may be fastened to casing flange76extending radially outwardly from casing52of engine14. Ring64of exhaust duct38may be fastened to casing52via a plurality of fasteners78(e.g., bolts) that extend through and secure duct flange74and casing flange76together. Fasteners78may be angularly distributed around casing52and ring64.

FIG.5is an enlarged view of region5inFIG.3showing electric machine46being fastened to mount62defined by outer wall56of exhaust duct38. Mount62may define a mounting interface including a plurality of fastener holes for receiving respective fasteners80and also socket72for receiving part of electric machine46therein. In some embodiments, socket72may assist in locating electric machine46substantially coaxially with low-pressure turbine30. Electric machine46may be fastened to outer wall56with a plurality of fasteners80(e.g., bolts) that extend through outer wall56and through bosses formed on a housing of electric machine46to secure electric machine46to outer wall56. In some embodiments, mount62of outer wall56may include thickened portions (pads) with threaded holes formed therein so that fasteners80may be threaded directly into the thickened portions. Fasteners80may be angularly distributed around socket72of mount62. In some embodiments, the housing of electric machine46may be in sealing engagement with outer wall56via one or more gaskets or seals such as O-ring73for example.

FIG.6Ais an axial end-on view toward the forward direction of the aft portion of power plant ofFIG.2. In some embodiments, first branch40and second branch42of exhaust duct38may be at diametrically opposed positions relative to turbine axis TA. For example, first flow direction D1of first branch40and second flow direction D2of second branch42may both lie in a (e.g., horizontal) plane including turbine axis TA. In other words, first flow direction D1of first branch40, second flow direction D2of second branch42and turbine axis TA may be substantially co-planar.

In some embodiments, first branch40and second branch42may have the same size to accommodate the same flow rate of combustion gas and may also be symmetric about a vertical plane including turbine axis TA. However, in some embodiments, first branch40and second branch42may have different sizes and be configured to accommodate different flow rates of combustion gases.

FIG.6Bis an axial end-on view toward the forward direction of another exemplary aft portion of a hybrid aircraft power plant.FIG.6Bshows another exemplary bifurcated exhaust duct138including elements of exhaust duct38. Exhaust duct138may be mounted to power plant10to replace exhaust duct38. Like elements are identified using reference numerals that have been incremented by 100. Exhaust duct138may include inner wall154defining first branch140and second branch142. Exhaust duct138may also include outer wall156. In contrast with exhaust duct38, first branch140and second branch142of exhaust duct138may be clocked relative to turbine axis TA to be non-diametrically opposed relative to turbine axis TA. For example, both first branch140and second branch142may be oriented slightly downwardly as well as radially outwardly from turbine axis TA. In other words, first flow direction D1of first branch40, second flow direction D2of second branch42and turbine axis TA may not be co-planar.

FIG.7is a perspective view of another exemplary aft portion of a hybrid aircraft power plant.FIG.7shows another exemplary bifurcated exhaust duct238including elements of exhaust ducts38and138. Exhaust duct238may be mounted to power plant10to replace exhaust duct38. Like elements are identified using reference numerals that have been incremented by 200. Exhaust duct238may have a double-walled construction. Exhaust duct238may include inner wall254defining first branch240and second branch242. Exhaust duct238may also include outer wall256defining mount262to which electric machine46may be mounted. Exhaust duct238may be secured to casing52via ring264. In contrast with exhaust duct38, exhaust duct238may provide additional structural support for electric machine46by including one or more structural engagements/connections between inner wall254and outer wall256in addition to the connections at ring264. For example, support braces may be provided between inner wall254and outer wall256. Alternatively or in addition, inner wall254and outer wall256may be shaped to contact each other and define one or more load transfer paths between inner wall254and outer wall256. In some embodiments, exhaust ducts238may have a stiffer construction than exhaust duct38.

In some embodiments, first branch240of inner wall254may be engaged with outer wall256at first opening258through outer wall256. Similarly, second branch242of inner wall254may be engaged with outer wall256at second opening260through outer wall256. The engagement(s) between inner wall254and outer wall256may include welds and/or other forms of structural engagements. For example, inner wall254and outer wall256may be in direct contact with each other at one or more engagement locations.

Aspects of exhaust duct238may also be applied to exhaust duct138ofFIG.6Bto provide additional structural support in embodiments where first branch140and second branch142are clocked to be non-diametrically opposed.

FIG.8is cross-sectional view of the aft portion of the hybrid aircraft power plant ofFIG.7taken along line8-8inFIG.7.FIG.8shows the engagement(s) between inner wall254and outer wall256at the locations where first branch240passes through outer wall256, and where second branch242passes through outer wall256. The engagements may serve to brace first branch240and second branch242with outer wall256to increase the overall stiffness of exhaust duct238. In some embodiments, the engagements (e.g., contact interfaces) may extend completely around first branch240and second branch242.

FIG.9is a flow diagram of a method1000of operating power plant10or other hybrid aircraft power plants. Method1000may be performed using any one of exhaust ducts38,138and238. Method1000may include elements of power plant10and of exhaust ducts38,138and238. In various embodiments, method1000may include:extracting energy from combustion gas using a turbine such as low-pressure turbine30(block1002);driving an air mover such as propeller24with low-pressure turbine30to propel aircraft12(block1004);receiving the combustion gas from low-pressure turbine30in bifurcated exhaust duct38,138,238(block1006);conveying a first portion of the combustion gas in first branch40,140,240of exhaust duct38,138,238(block1008);conveying a second portion of the combustion gas in a second branch42,142,242of exhaust duct38,138,238(block1010); anddriving propeller24with an electric motor such as electric machine46mounted to exhaust duct38,138,238(block1012).

In some embodiments, electric machine46may be disposed between first branch40and second branch42and axially overlap first branch40and second branch42relative to turbine axis TA. Electric machine46may be coaxial with low-pressure turbine30. In some embodiments, electric machine46may be in torque-transmitting engagement with low-pressure turbine30so that driving propeller24with electric machine46may also include driving low-pressure turbine30with electric machine46.

The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology.