Contra-Rotating Open Rotor Distributed Propulsion System

(19) TZZ ¥Z___T

(11) EP 2 930 114 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.: 14.10.2015 Bulletin 2015/42 B64D 27/14 (2006.01)

(21) Application number: 15150203.6

(22) Date of filing: 06.01.2015

(84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • Veilleux, Jr., Leo J. GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Wethersfield, CT 06109 (US) PL PT RO RS SE SI SK SM TR • Ribarov, Lubomir A. Designated Extension States: West Hartford, CT 06107 (US) BA ME (74) Representative: Leckey, David Herbert (30) Priority: 06.01.2014 US 201461924142 P Dehns St Bride’s House (71) Applicant: United Technologies Corporation 10 Salisbury Square Hartford, CT 06109 (US) London EC4Y 8JD (GB)

(54) Contra-rotating open rotor distributed propulsion system

(57) An aircraft propulsion system includes a gas tur- outside of the aircraft fuselage (12) separately from the bine engine (30) supported within an aircraft fuselage gas turbine engine (30). A secondary drive (56A, 56B) (12), a main drive (52) driven by the gas turbine engine that is driven by the main drive (52) drives the open rotor (30) and an open rotor propeller system (14) supported propeller system (14). EP 2 930 114 A1

Printed by Jouve, 75001 PARIS (FR) 1 EP 2 930 114 A1 2

Description en through a mechanical coupling to the turbine engine. [0008] In a further embodiment of any of the foregoing BACKGROUND aircraft propulsion systems, the turbine engine includes a first turbine engine and second turbine engine support- [0001] A contra-rotating open rotor (CROR) propulsion 5 ed within the aircraft fuselage and each of the first and system for an aircraft typically includes two engines second turbine engines are coupled to drive the main mounted on either side of an aft portion of the aircraft gearbox. The first and second turbine engines may be fuselage. Each engine powers contra-rotating rotors that aligned along a common longitudinal axis. each includes a plurality of blades. Typically small turbine [0009] In a further embodiment of any of the foregoing engines are utilized to drive a contra-rotating gearbox 10 aircraft propulsion systems, the main drive includes a that provides the opposite rotation of the open rotors. main electric generator generating electrical power and Propulsive efficiency is provided by the large bypass flow the secondary drive includes an electric motor driven by at relatively low velocities. The large bypass volumes the main electric generator. along with the lower velocities also provide favorable [0010] In a further embodiment of any of the foregoing noise properties. Although smaller turbine engines are 15 aircraft propulsion systems, the propeller system in- often utilized, the radial cross-section of the engine re- cludes a first propeller system mounted on a first side of duces the effective area of the open rotors and thereby the aircraft fuselage and a second propeller system can reduce overall propulsive efficiency. The turbine en- mounted on a second side of the aircraft fuselage and gines’ radial cross-section also causes increased resist- the secondary drive includes first and second electric mo- ance thus affecting adversely the aircraft’s overall effi- 20 tors driven by the main electric generator for driving a ciency. Moreover, the support structure required for sup- correspondingone of thefirst and second electric motors. porting the weight of the gas turbine engine away from [0011] In a further embodiment of any of the foregoing the aircraft can limit the overall size of the contra-rotating aircraft propulsion systems, the first and second electric open rotors and thereby overall propulsive efficiency. motors are mounted within the aircraft fuselage and drive [0002] Accordingly, improvements in contra-rotating 25 gearboxes mounted within a corresponding one of the propulsion systems are part of continued efforts by en- first and second propeller systems. gine and aircraft manufacturers to improve engine per- [0012] In a further embodiment of any of the foregoing formance and propulsive efficiencies. aircraft propulsion systems, the turbine engine includes first and second turbine engines and the main generator SUMMARY 30 includes first and second generators driven by a corresponding one of the first and second turbine engines. [0003] A aircraft propulsion system according to an ex- Each of the first and second generators drives a corre- emplary embodiment of this disclosure, among other sponding one of the first and second electric motors. possible things includes a turbine engine supported with- [0013] A further embodiment of any of the foregoing in an aircraft fuselage, a main drive driven by the turbine 35 aircraft propulsion systems may include a nacelle assem- engine, an open propeller system supported outside of bly spacedapart fromthe aircraft fuselage, thesecondary the aircraft fuselage separately from the turbine engine, drive being disposed within nacelle assembly. and a secondary drive driven by the main drive for driving [0014] An aircraft propulsion assembly according to an the open propeller system. exemplary embodiment of this disclosure, among other [0004] In an embodiment of the foregoing aircraft pro- 40 possible things includes a first contra-rotating open rotor pulsion system, the propeller system includes a contra- propeller system supported on a first side of an aircraft rotating open rotor propeller system. fuselage. A second contra-rotating open rotor propeller [0005] In a further embodiment of any of the foregoing system is supported on a second side of the aircraft fu- aircraft propulsion systems, the contra-rotating open ro- selage. A turbine engine is supported within the aircraft tor propeller system includes a forward propeller assem- 45 fuselage. A main power transfer system is mechanically bly and an aft propeller assembly having an outer diam- coupled to the turbine engine and supported within the eter larger than the forward propeller assembly. aircraft fuselage. A first drive is driven by the main power [0006] In a further embodiment of any of the foregoing transfer system for driving the first contra-rotating open aircraft propulsion systems, the contra-rotating propeller rotor propeller system. A second drive is driven by the system includes a gearbox for generating contra rotation 50 main power transfer system for driving the second contra- of a forward propeller assembly and an aft propeller as- rotating open rotor propeller system. sembly about a common axis of rotation. [0015] In an embodiment of the foregoing aircraft pro- [0007] In a further embodiment of any of the foregoing pulsion assembly, the main power transfer system in- aircraft propulsion systems, the main drive includes a cludes a main gearbox driven by the turbine engine main gearbox and the secondary drive includes a pro- 55 through a main shaft. peller gearbox and the main gearbox is mechanically [0016] In a further embodiment of any of the foregoing coupled to drive the propeller gearbox. The main gearbox aircraft propulsion assemblies, the first drive and the sec- may be supported within the aircraft fuselage and be driv- ond drive include gearboxes mechanically coupled to the

2 3 EP 2 930 114 A1 4 main gearbox and configured to generate for counter ro- cally coupledto drive first and second CROR system. tation of the corresponding first contra-rotating open rotor Figure 7 is a schematic view of another example dis- propeller assembly and the second contra-rotating open closed distributed propulsion system. rotor propeller assembly. Figure 8 is a schematic view of an example disclosed [0017] In a further embodiment of any of the foregoing 5 distributed propulsion system including first and sec- aircraft propulsion assemblies, the main power transfer ond turbine engines driving corresponding electric system includes a main generator and the first drive and generators electrically coupled to drive first and sec- the second drive include first and second electric motors ond CROR systems. electrically coupled to the main generator. Figure 9 is a schematic view of windmill operation of [0018] In a further embodiment of any of the foregoing 10 the example distributed propulsion system of Figure aircraft propulsion assemblies, the turbine engine in- 8. cludes a first turbine engine and a second turbine engine Figure 10 is a schematic view of another mounting and the main generator includes a first generator driven location for a disclosed CROR system. by the first turbine engine and a second generator driven Figure 11 is a schematic view of another mounting by the second turbine engine. 15 location for a disclosed CROR system. [0019] In a further embodiment of any of the foregoing Figure 12 is a schematic view of an example reverse aircraft propulsion assemblies, the turbine engine in- flow mounting configuration of a gas turbine engine. cludes a reverse flow turbine engine with a compressor communicating compressed air forward to a combustor DETAILED DESCRIPTION to generate high energy exhaust gases forward to a tur- 20 bine that is configured to drive the compressor. [0024] Referring to Figures 1 and 2, an aircraft 10 is [0020] A further embodiment of any of the foregoing schematically shown and includes contra-rotating open aircraft propulsion assemblies includes a recuperator in rotors (CROR) 14 mounted to pylon 18 on each side of communication with incoming airflow and outgoing ex- the aircraft fuselage 12. A wing 15 extends outward from haust gas flow. 25 each side of the fuselage 12 and a vertical T-tail stabilizer [0021] Although the different examples have the spe- (and rudder(s)) 82 extends upward. In the T-tail horizon- cific components shown in the illustrations, embodiments tal stabilizer configuration, the horizontal stabilizer (and of this disclosure are not limited to those particular com- elevators) is mounted on top of the vertical stabilizer away binations. It is possible to use some of the components from the engine’s exhaust and propellers’ turbulent wake. or features from one of the examples in combination with 30 T-tail configurations are common for rear fuselage (i.e., features or components from another one of the exam- empennage)-mounted engines as shown in Figure 1 and ples. 2. The CROR 14 includes two rotors, a forward rotor 20 [0022] These and other features disclosed herein can and an aft rotor 22. The first rotor 20 includes a first plu- be best understood from the following specification and rality of propeller blades 24 and the second rotor includes drawings, the following of which is a brief description. 35 a second plurality of propeller blades 26. Each of the rotors 20, 22 rotate about a common longitudinal axis A. BRIEF DESCRIPTION OF THE DRAWINGS One of the rotors 20, 22 is configured to rotate clockwise and the other is configured to rotate counterclockwise. [0023] [0025] In this example, the forward rotor 20 rotates in 40 a clockwise direction and the aft rotor 22 rotates in a Figure 1 is a schematic front view of an example counter-clockwise direction. The disclosed example pro- contra-rotating open rotor (CROR) propulsion sys- peller blades 24, 26 are highly swept "Scimitar"-style tem. "pusher" propeller blades. It should be understood, that Figure 2 is a schematic view of a prior art CROR other propeller shapes and configurations are within the propulsion system. 45 contemplation of this disclosure. Moreover, although a Figure 3 is a schematic view of a disclosed example pusher propeller system is disclosed, a "pull" propeller CROR propulsion system. system is also within the contemplation of this disclosure. Figure 4 is a schematic view of an example disclosed [0026] In this disclosure, the term contra-rotation is uti- distributed propulsion system including a gas turbine lized to describe a propulsion system where different ro- engine mechanically coupled to drive first and sec- 50 tors rotate about a common axis in different directions. ond CROR assemblies. The term counter-rotating is utilized in this disclosure to Figure 5 is schematic view of another example dis- describe a propulsion system where propeller rotors on closed distributed propulsion system including first opposite sides of the aircraft fuselage 12 rotate in oppo- and second gas turbine engines mechanically cou- site directions. pled to drive a common main gearbox. 55 [0027] The example aircraft propulsion system in- Figure 6 is a schematic view of another example dis- cludes a pusher CROR 14 mounted within a nacelle 16 closed distributed propulsion system including a gas supported by a pylon 18 on either side of the aircraft turbine engine driving an electric generator electri- fuselage 12. The CROR 14 may be counter-rotated with

3 5 EP 2 930 114 A1 6 respect to the CROR 14 on the opposite side of the air- ically shown, the high pressure compressor 36 is coupled craft 10, but may also be rotated in common directions to the high pressure turbine 42 through a second outer regardless of the side of the aircraft 10 on which it is shaft (not shown) as is known. Although not shown in mounted. Both configurations are within the contempla- Fig. 4, a three-shaft (spool) gas turbine engine is also tion of this disclosure. The nacelle 16 is spaced apart 5 within the contemplated possibilities of this disclosure. A from the fuselage 12 by the pylon 18. typical three-shaft turbine engine adds an intermediate [0028] Referring to Figure 2, a prior art contra-rotating shaft nestled concentrically between the high-pressure open rotor system 214 is shown and includes a turbine shaft and the low-pressure shaft. The intermediate shaft engine 230 supported within a nacelle 216 spaced apart connects the intermediate-pressure turbine with the in- from the aircraft fuselage 212 by a pylon 218. The turbine 10 termediate-pressure compressor. engine 230 drives a forward rotor 220 including a forward [0032] The shaft 46 is supported by bearing assembly plurality of propeller blades 224 and an aft rotor 222 in- 48 and output is transmitted to a main drive 52 that in cluding an aft plurality of propeller blades 226. turn drives secondary drives 56A and 56B. In this exam- [0029] The turbine engine 230 is of a significant weight ple the main drive is a main differential gearbox 52 and and provides a large radial cross-section. The pylon 218 15 the secondary drives are CROR engine gearboxes 56A, is required to be of sufficient structural strength to support 56B. Intermediate shafts 54A and 54B supported by the weight and structure of the turbine engine 230. The bearing assemblies 50 extend from the main differential required pylon structure can constrain the amount of gearbox 52 and the drive smaller CROR engine gear- spacing form the aircraft fuselage 212 and thereby limit boxes 56A, 56B for each of the first and second CROR the diameter of the propeller blades 224, 226. Addition- 20 systems 14A, 14B. Each of the CROR gearboxes 56A, ally, the radial cross-section of the turbine engine 230 56B drive a corresponding contra-rotating shaft system can reducethe efficiencyof thepropeller blades 224, 226. 64A, 64B supported by bearing assemblies 58 within the [0030] Referring to Figures 3 and 4, a disclosed dis- nacelle 16A, 16B. The forward and aft rotors 20, 22 of tributed propulsion system 28 includes the CROR 14 that the corresponding CROR system 14A, 14B are driven is driven by a turbine engine 30 (as shown in Figure 4) 25 through the corresponding gearbox 56A, 56B by the con- supported within the aircraft fuselage 12. The distributed centric contra-rotating drive shaft system 64A, 64B. propulsion system 28 includes a highly-efficient turbine [0033] Because the turbine engine 30 is mounted with- engine 30 located along the aircraft longitudinal axis C in the aircraft fuselage 12 and not within each nacelle inside the aircraft fuselage 12 near its tail cone 17. The 16A, 16B, each of the nacelles 16A, 16B supporting the highly-efficient gas turbine engine can be of any of the 30 corresponding CROR systems 14A, 14B can be very architectures such as but not limited to: turboshaft, tur- small with a minimal front cross section. In fact, the na- bojet, low-bypass turbofan, high-bypass turbofan, celles 16A, 16B need only be large enough to support geared turbofan (GTF), etc. The turbine engine 30 drives the corresponding gearbox 56A, 56B and the drive shaft a first CROR system 14A and a second CROR system system 64A, 64B. 14B mounted within corresponding nacelles 16A, 16B on 35 [0034] The example propulsion system 28 enables either side of the aircraft fuselage 12. In this example, mounting of the CROR systems 14A, 14B further aft on the first CROR system 14A rotates in a first direction 60 the aircraft fuselage in a position aft of aircraft wakes that and the second CROR system 14B rotates in a second reduces noise and increases propulsive efficiency. More- direction 62 opposite the first direction 60 about CROR over, because the turbine engine 30 powering the CROR axes A1 and A2, respectively. As appreciated, each of 40 systems 14A, 14B is mounted within the aircraft fuselage the first and second CROR systems 14A, 14B are contra- 12 instead of within the nacelle 16A, 16B, a smaller na- rotating, however, rotation of the forward and aft rotors celle 16A, 16B and therefore a smaller pylon support 20, 22 can be counter-rotating relative to the CROR sys- structure 18 can be utilized. The nacelles 16A, 16B and tem mounted to on the opposite side of the aircraft fuse- pylon 18 need be only large enough to contain the CROR lage 12. Moreover, while the disclosed examples are 45 drive system including the CROR gearbox 56A, 56B, CROR systems, it is within the contemplation of this dis- shaft system 64A, 64B, bearing assemblies 58 and rotors closure to utilize a single propeller rotor rotating about a 20, 22. Furthermore, the nacelles 16A, 16B may be common axis. spaced further away from the fuselage 12 to enable the [0031] The example turbine engine 30 includes a com- use of larger diameter propellers 24, 26 and thereby an pressor section 32 that feeds compressed air to combus- 50 increased production of propulsive thrust for the same tor 38 where fuel is mixed with the air and ignited to gen- engine power input. erate a high energy gas flow. The high energy gas flow [0035] Referring to Figure 5 another example propul- expands through at turbine section 40. The turbine sec- sion system 25 includes two turbine engines 30A, 30B tion 40 includes a high pressure turbine 42 and a low that are disposed along the aircraft longitudinal axis C pressure turbine 44. The high pressure turbine 42 is cou- 55 and turning in directions 27 and 29, respectively. Each pled to a high pressure compressor 36. The low pressure of the turbine engines 30A, 30B drives a corresponding turbine 44 is coupled to a low pressure compressor 34 shaft 46A, 46B coupled to drive a main drive 51. In this through shaft 46. Although a single shaft 46 is schemat- example, the main drive 51 is a differential gearbox 51

4 7 EP 2 930 114 A1 8 receiving driving input from each of the first and second directions. Each of the electric motors 72A, 72B can be turbine engines 30A, 30B. The two gas turbine engines placed either in the CROR’s nacelles 16A, 16B (as shown 30A, 30B provide a desired redundancy within the pro- in Fig. 8), or inside the aircraft fuselage 12 in an archi- pulsion system 28. The gas turbine engines 30A, 30B tecture similar to the one shown in Fig. 7). Mounting the are placed in series for driving each of the CROR systems 5 electric motors 72A, 72B within the aircraft fuselage 12 14A, 14B through the same main differential gearbox 51. provides for a very small cross-section of the nacelles [0036] Referring to Figure 6, another example propul- 16A, 16B. sion system 66 is shown where the main drive is a gen- [0039] The example propulsion system 75 provides im- erator 68 driven by a gas turbine engine 30 that produces proved system redundancy and finer speed control by electric power and communicates that electric power to 10 the electric motors 72A, 72B. This capability can improve secondary drives that are electric motors 72A, 72B the overall operational efficiency and capability of the air- mounted within corresponding nacelles 16A, 16B to pow- craft. er the corresponding CROR system 74A, 74B. Electric [0040] Referring to Figure 9, the example propulsion power is communicated through cables 70 to each cor- systems enable windmilling of the CROR propellers 24, responding electric motor 72A, 72B. The use of electric 15 26 if the turbine engines 30A/30B fail in flight. Windmilling cables 70 to transmit power reduces complexity and of the propellers 24, 26 can turn the electric motors 72A, overall system weight. The electric motors 72A, 72B can 72B into generators to perform the function of a Ram Air either drive a corresponding gearbox that provides the Turbine (commonly referred to as a "RAT") to generate desired contra-rotation of the rotors 20, 22, or may be electric power. The multi-bladed CROR systems 77A, configured to drive different shafts corresponding to the 20 77B improve efficiency of extracting power from the air different rotors 20, 22. The two different motors can drive slip-stream while the redundancy improves safety. Be- either of the gearboxes to provide operational redundan- cause each of the CROR systems 77A, 77B includes two cy. Moreover, each of the different motors drives a sep- independently rotatable rotors 20, 22, each rotor will turn arate shaft to provide improved electrical speed control the corresponding electric motor 72A, 72B and thereby of the shafts. Additionally, the contra-rotating "twin" shaft 25 improve operation and efficiency of power generation. can be geared off of the first shaft. [0041] During windmilling operation, the propellers 24, [0037] Referring to Figure 7 another example propul- 26 will drive the shaft systems 64A, 64B to drive the cor- sion system 65 is shown where the main drive is a gen- responding electric motor 72A, 72B. The two contra-ro- erator 68 driven by a gas turbine engine 30 that produces tating rotors provide an increased efficiency in power electric power and communicates that electric power to 30 generation as compared to a single-axle, two-bladed electric motors 67A, 67B mounted within aircraft fuselage "conventional" RAT. The example CROR system 77A, 12.The electric motors 67A,67B in turn drive correspond- 77B enable decoupling of the concentric shaft systems ing CROR gearboxes 69A, 69B that are mounted within 64A, 64B so that one or two, or three or all four propellers corresponding nacelles 16A, 16B through shafts 71A, 24, 26 can independently extract kinematic energy from and 71B. The gearboxes 69A, 69B drive the correspond- 35 the slipstream by turning their respective shafts thus in ing CROR system 63A, 63B. Electric power is commu- turn powering the on-board electric generators 68A, 68B, nicated through cables 70 to each corresponding electric respectively. The independent power generation is sche- motor 67A, 67B. The electric motors 67A, 67B drive the matically indicated by solid line 76 and dashed line 78. corresponding gearbox 69A, 69B that provides the de- The solid line 76 represents power generation from the sired contra-rotation of the rotors 20, 22. Mounting of the 40 forward rotor 20 and propeller 24, and the dashed line electric motors 67A, 67B within the aircraft fuselage 12 78 represents power generation from the aft rotor 22 and provides for a very small cross-section of the nacelles propeller 26. 16A, 16B. [0042] Referring to Figures 10 and 11, an aircraft 10 [0038] Referring to Figure 8, another example propul- including the distributive propulsion systems 66 and 75 sion system 75 includes two smaller compact turbine en- 45 shown in Figures 6 and 8 respectively, provide for alter- gines 30A, 30B positioned axially side-by-side in the rear nate positioning of the CROR system 14. Because power fuselage 12 and rotating about longitudinal axes B1 and is transmitted through cables 70 additional optional B2, respectively. Both axes B1 and B2 are equidistant mounting locations of the example CROR systems be- from the main central axis C. The axis B1 is on the star- come possible. Because the motors 72 are not mechan- board side, while the axis B2 is in the port side of the50 ically coupled to the turbine engine 30, or a main gearbox, aircraft fuselage 12. Each of the turbine engines 30A, the CROR systems can be located further away from the 30B drives a separate main drive that in turn drives a fuselage 12. In one example shown in Figure 10, the secondary drive. In this example the main drives are sep- CROR system is mounted on a top surface of the aircraft arate electric generator 68A, 68B that in turn drives the wing 15. In another example shown in Figure 11, the electric motor 72A, 72B for the corresponding CROR sys- 55 CROR system is mounted below the aircraft wing 15. tem 77A,77B. Eachof the electric motors 72A, 72B drives Additionally, the CROR system enables lighter more ef- the corresponding concentric contra-rotating shaft sys- ficient support structures because support is only re- tems 64A, 64B for driving the rotors 20, 22 in opposing quired for the structures required to rotate the CROR

5 9 EP 2 930 114 A1 10 system and not for the entire turbine engine. work done on the inlet air by the compressor section 32. [0043] Figure 10 includes a horizontal stabilizer (with In addition, the preheated air entering the combustor 38 elevators) 85 that is modified to accommodate the mount- facilitates the liquid fuel break-up and droplet atomization ing position of the CROR system 14. In this example, the for improved combustor light-off, stability, and operation- horizontal stabilizer (with elevators) 85 is shortened and 5 aleconomy. Therecuperator also lowers thetemperature slightly angled upward such that is remains out of the of the exhaust gas exiting through the outlet 86, thus airflow generated by the CROR system 14 toward the aft making the cooler exhaust less detectable by enemy portion of the aircraft 10. The vertical stabilizer (with rud- heat-seeking infra-red (IR) missiles. Although a T-tail der(s)) 82 and the horizontal stabilizer (with elevators) configuration is shown with vertical stabilizer 82 in Fig. 85 can be either of the conventional tail configuration or 10 12, other tail architectures (i.e., such as the ones shown of the cruciform tail with no loss of functionality to the in Figures 10 and 11, etc.) are also contemplated. In fact, disclosed invention.In the conventionaltail configuration, since the main engine is inside the fuselage, the choice the horizontal stabilizer is mounted directly to the em- of tail configurations will depend on the actual placement pennage (i.e., the rear fuselage). In the cruciform tail con- of the CROR propulsion systems around the aircraft’s figuration, the horizontal stabilizer intersects the vertical 15 fuselage 12. stabilizer somewhere in the middle of the vertical stabi- [0047] Although an example embodiment has been lizer in a "cross"-like formation. disclosed, a worker of ordinary skill in this art would rec- [0044] Figure 11 includes a horizontal stabilizer 87 ognize that certain modifications would come within the (with elevators) that is mounted directly to the aircraft scope of this disclosure. For that reason, the following fuselage 12 rear portion (empennage) in a conventional 20 claims should be studied to determine the scope and tail configuration including a vertical stabilizer (with rud- content of this disclosure. der(s)) 82. The indicated location of the horizontal stabilizer (with elevators) 87 is such that it is spaced away from airflow and prop wash generated by the CROR sys- Claims tem 14 mounted below the wing of the aircraft 10. 25 [0045] Referring to Figure 12, decoupling the gas gen- 1. An aircraft propulsion system (14) comprising: eratorfrom the CRORsystem enablesadditional optional engine mounting arrangements that can improve effi- a turbine engine (30) supported within an aircraft ciency. An example engine mounting system 80 can be fuselage (12); utilized with any of the example propulsion systems to 30 a main drive (52; 51; 68; 68A, 68B) driven by thermodynamically improve operation. In the example the turbine engine (30); engine mounting system 80 the turbine engine 30 is be an open propeller system supported outside of mounted and operated in a "reverse flow" engine config- the aircraft fuselage (12) separately from the tur- uration. In the illustrated reverse flow engine configura- bine engine (30); and tion, the compressor section 32 is mounted aft of the35 a secondary drive (56A, 56B; 72A, 72B) driven turbine section 40. Accordingly, the compressor section by the main drive for driving the open propeller 32 faces aft, the turbine section 40 faces forward and the system. power shaft 46 extends forward from the turbine section 40. Airflow is communicated through an intake 84 near 2. The aircraft propulsion system as recited in claim 1, the base/root of the aircraft vertical stabilizer (with rud- 40 wherein the propeller system comprises a contra- der(s)) 82 to the aft facing compressor section 32, which rotating open rotor propeller system, wherein, op- moves forward, consecutively, through the combustor tionally, the contra-rotating open rotor propeller sys- and turbine, and exhaust gases from the turbine section tem includes a forward propeller assembly (20) and 40 are turned aft, and directed back through an outlet 86 an aft propeller assembly (22) having an outer diam- past the incoming airflow. 45 eter larger than the forward propeller assembly (20). [0046] An air intake passage 98 directs incoming air from the inlet 84 to the compressor section 32 and an 3. The aircraft propulsion system as recited in claim 2, exhaust gas duct 100 directs exhaust gases to the up- wherein the contra-rotating propeller system in- ward-directed/oriented outlet 86. Each of the intake pas- cludes a gearbox for generating contra rotation of a sage 98 and exhaust passage are "S"-shaped to enable 50 or the forward propeller assembly (20) and an or the crossing flow through a recuperator 90. The recuperator aft propeller assembly (22) about a common axis of 90 utilizes the thermal difference between the hot engine rotation. exhaust gas and the cold inlet air flow. The recuperator 90 utilizes the engine exhaust flow to preheat airflow to 4. The aircraft propulsion system as recited in any pre- the combustor 38. Accordingly, inlet airflow to the com- 55 ceding claim, wherein the main drive comprises a bustor 38 is preheated by the hot exhaust. The preheated main gearbox (52, 51) and the secondary drive com- inlet air to the combustor 38 improves the engine’s overall prises a propeller gearbox (56A, 56B) and the main thermodynamic efficiency by decreasing the required gearbox (52, 51) is mechanically coupled to drive

6 11 EP 2 930 114 A1 12

the propeller gearbox (56A, 56B). 13. An aircraft propulsion assembly comprising:

5. The aircraft propulsion system as recited in claim 4, a first contra-rotating open rotor propeller sys- wherein the main gearbox (52, 51) is supported with- tem (14A) supported on a first side of an aircraft in the aircraft fuselage (12) and is driven through a 5 fuselage (12); mechanical coupling to the turbine engine (30). a second contra-rotating open rotor propeller system (14B) supported on a second side of the 6. The aircraft propulsion system as recited in claim 4 aircraft fuselage (12); or 5, wherein the turbine engine comprises a first a turbine engine (30) supported within the air- turbine engine (30A) and second turbine engine10 craft fuselage; (30B) supportedwithin the aircraftfuselage and each a main power transfer system mechanically cou- of the first and second turbine engines are coupled pled to the turbine engine (30) and supported to drive the main gearbox (51). within the aircraft fuselage (12); a first drive driven by the main power transfer 7. The aircraft propulsion system as recited in claim 6, 15 system for driving the first contra-rotating open wherein the first and second turbine engines (30A, rotor propeller system (14A); and 30B) are aligned along a common longitudinal axis. a second drive driven by the main power transfer system for driving the second contra-rotating 8. The aircraft propulsion system as recited in any pre- open rotor propeller system (14B); wherein, op- ceding claim, wherein the main drive comprises a 20 tionally, the main power transfer system com- main electric generator (68) generating electrical prises a main gearbox (51; 52) driven by the power and the secondary drive comprises an electric turbine engine (30) through a main shaft, and/or motor (72) driven by the main electric generator. wherein, optionally, the first drive and the second drive comprise gearboxes mechanically 9. The aircraft propulsion system as recited in claim 8, 25 coupled to the or a main gearbox (51, 52) and wherein the propeller system comprises a first pro- configured to generate for counter rotation of the peller system (14A) mounted on a first side of the corresponding first contra-rotating open rotor aircraft fuselage (12) and a second propeller system propeller assembly and the second contra-ro- (14B) mounted on a second side of the aircraft fuse- tating open rotor propeller assembly. lage (12) and the secondary drive comprises first 30 and second electric motors (72A, 72B) driven by the 14. The aircraft propulsion system as recited in claim 13, main electric generator (68) for driving a correspond- wherein the main power transfer system comprises ing one of the first and second electric motors (72A, a main generator (68) and the first drive and the sec- 72B; 67A, 67B). ond drive comprise first and second electric motors 35 (72A, 72B) electrically coupled to the main generator 10. The aircraft propulsion system as recited in claim 9, (68), and wherein, optionally, the turbine engine wherein the first and second electric motors (67A, comprises a first turbine engine (30A) and a second 67B) are mounted within the aircraft fuselage (12) turbine engine (30B) and the main generator (68) and drive gearboxes (69A, 69B) mounted within a comprises a first generator (68A) driven by the first corresponding one of the first and second propeller 40 turbine engine (30A) and a second generator (30B) systems (14A, 14B). driven by the second turbine engine (30B).

11. The aircraft propulsion system as recited in claim 9 15. The aircraft propulsion system as recited in claim 13 or 10, wherein the turbine engine comprises first and or 14, wherein the turbine engine comprises a re- second turbine engines (30A, 30B) and the main 45 verse flow turbine engine with a compressor (32) generator comprises first and second generators communicating compressed air forward to a com- (68A, 68B) driven by a corresponding one of the first bustor (38) to generate high energy exhaust gases and second turbine engines (30A, 30B), wherein forward to a turbine (40) that is configured to drive each of the first and second generators (68A, 68B) the compressor, and optionally including a recuper- drives a corresponding one of the first and second 50 ator (90) in communication with incoming airflow and electric motors (72A, 72B; 67A, 67B). outgoing exhaust gas flow.

12. The aircraft propulsion system as recited in any pre- ceding claim, including a nacelle assembly (16) spaced apart from the aircraft fuselage (12), wherein 55 the secondary drive (56A, 56B; 72A, 72B) is disposed within nacelle assembly (16).

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8 EP 2 930 114 A1

9 EP 2 930 114 A1

10 EP 2 930 114 A1

11 EP 2 930 114 A1

12 EP 2 930 114 A1

13 EP 2 930 114 A1

14 EP 2 930 114 A1

15 EP 2 930 114 A1

16 EP 2 930 114 A1

17 EP 2 930 114 A1

18 EP 2 930 114 A1

19 EP 2 930 114 A1