Variable cycle propulsion system with gas tapping for a supersonic airplane, and a method of operation
View Patent ↗A variable cycle propulsion system for a supersonic airplane, the system comprising at least one engine having means for producing exhaust gas and a gas exhaust nozzle for generating thrust for supersonic flight speeds, and at least one separate auxiliary propulsion assembly dissociated from said engine, having no gas generator, and capable of generating thrust for takeoff, landing, and subsonic flight speeds. The system further comprises gas flow tapping means movable between a position in which they tap off at least a fraction of the exhaust gas produced by said engine and feed it to said propulsion assembly to enable it to generate thrust for takeoff, landing, and subsonic cruising flight, and a position in which the gas produced by the engine is directed solely to the engine nozzle for supersonic cruising flight.
1. A method of operating a variable cycle propulsion system for a supersonic aircraft, the method comprising:
providing at least two engines, each engine being configured to produce exhaust gas and provided with a nozzle for generating thrust for supersonic flight speeds,
providing at least one separate propulsion assembly dissociated from said at least two engines, said propulsion assembly being configured to generate thrust for takeoff, landing, and subsonic flight speeds and comprising a turbine having a hub with blades and a fan having a hub with blades, the fan connected to said turbine;
tapping off, at least during takeoff and landing, at least a fraction of the exhaust gas produced by said at least two engines;
feeding said fraction of the exhaust gas to said propulsion assembly;
driving said turbine of said propulsion assembly with said fraction of the exhaust gas thereby slowing down said exhaust gas;
driving said fan with said turbine; and
exhausting air with said fan thereby generating additional thrust from said fan for takeoff and landing.
2. A method according to claim 1 , further comprising the step of interrupting, during supersonic cruising flight, the tapping off the exhaust gas for the propulsion assembly, with the engine alone providing propulsion.
3. A method according to claim 2 , further comprising the step of closing off, at least in part, during take-off and landing, an outlet through the nozzle for the exhaust gas produced by the at least two engines.
4. A method according to claim 3 , further comprising the step of opening, during acceleration and subsonic cruising flight, the exhaust gas outlet from said at least two engines.
5. A method according to claim 4 , further comprising the step of closing off progressively the tapping off of combustion gas produced by the at least two engines and the feeding to the propulsion assembly in order to change over to supersonic cruising flight.
6. A method according to claim 4 , wherein the step of opening is performed in order to reduce base drag of said at least two engines.
7. A method according to claim 5 , further comprising the step of opening progressively the outlet for exhaust gas through the nozzle.
8. A method according to claim 1 , wherein said at least two engines comprises at least three engines configured to feed the propulsion assembly.
9. A method according to claim 1 , wherein said turbine and said fan are coaxial with each other and offset from axes of said two engines.
10. A method according to claim 1 , further comprising providing said fan upstream from said turbine.
11. A method according to claim 1 , wherein said feeding of said fraction of the exhaust gas is performed with ducts between said engines and said turbines.
12. A method according to claim 11 , further comprising providing said fan upstream from locations where said ducts open into said turbine.
13. A method according to claim 12 , further comprising providing said nozzles downstream from locations where said ducts open into said engines.
14. A method according to claim 13 , further comprising shutting off said nozzles during take off while maintaining said feeding of said fraction of the exhaust gas to said propulsion assembly.
15. A method according to claim 1 , further comprising integrating said propulsion assembly within the fuselage of the aircraft.
16. A method according to claim 1 , further comprising generating horizontal thrust during take off.
17. A method of operating a propulsion system, for an aircraft having a fuselage said method comprising the steps of:
generating an exhaust gas with at least two engines;
directing said exhaust gas toward nozzles of the at least two engines;
redirecting a portion of said exhaust gas to a propulsion assembly under a set of conditions, said portion of the exhaust gas being otherwise directed to said nozzles of the at least two engines;
generating thrust with said propulsion assembly under said set of conditions; and
integrating said propulsion assembly within the fuselage of the aircraft.
18. A method of operating a propulsion system according to claim 17 , wherein the set of conditions comprises at least one of take-off, landing, and subsonic flight.
19. A method of operating a propulsion system according to claim 18 , wherein the set conditions comprises take-off, landing, and subsonic flight.
20. A method of operating a propulsion system according to claim 17 , further comprising the steps of:
interrupting said redirecting step; and
directing all the exhaust gas from the at least two engines to said nozzles during supersonic flight.
21. A method according to claim 17 , further comprising providing said propulsion assembly with a turbine and a fan.
22. A method according to claim 21 , wherein said turbine and said fan are coaxial with each other and offset from axes of said two engines.
23. A method according to claim 21 , further comprising:
driving said turbine with said portion of said exhaust gas thereby slowing down said exhaust gas;
driving said fan with said turbine; and
exhausting air with said fan thereby generating an additional thrust from said propulsion assembly.
24. A method according to claim 21 , further comprising providing said fan upstream from said turbine.
25. A method according to claim 24 , wherein said feeding of said fraction of the exhaust gas is performed with ducts between said engines and said turbines.
26. A method according to claim 25 , further comprising providing said fan upstream from locations where said ducts open into said turbine.
27. A method according to claim 26 , further comprising providing said nozzles downstream from locations where said ducts open into said engines.
28. A method according to claim 27 , further comprising shutting off said nozzles during take off while maintaining said feeding of said fraction of the exhaust gas to said propulsion assembly.
29. A method according to claim 17 , further comprising generating horizontal thrust during take off.