Variable cycle turbine engine

• US 8,943,796 B2
• Filed: 06/28/2011
• Issued: 02/03/2015
• Est. Priority Date: 06/28/2011
• Status: Active Grant

• Current Assignee: Rtx Corporation
• Original Assignee: United Technologies Corporation (Rtx Corporation)
• Inventors: McCaffrey, Michael G.
• Primary Examiner(s): Wongwian, Phutthiwat
• Assistant Examiner(s): SUTHERLAND, STEVEN M
• Application Number:
  US13/170,502
• Publication Number:
  US 20130000314A1
• Time in Patent Office: 1,316 Days
• Field of Search: 602/261, 602/62, 602/63, 608/01
• US Class Current: 60/262
• CPC Class Codes: F01D 13/003 with at least two independent shafts, i.e. cross-compound
• CPC Class Codes: F01D 17/162 for axial flow, i.e. the vanes turning around axes which are essentially perpendicular to the rotor centre line F01D17/167 takes precedence
• CPC Class Codes: F02C 3/13 having variable working fluid interconnections between turbines or compressors or stages of different rotors controlling flow ratio between different flows of multi-flow jet-propulsion plant, e.g. ducted fan F02K3/075
• CPC Class Codes: F02C 7/36 Power transmission arrangements between the different shafts of the gas turbine plant, or between the gas-turbine plant and the power user F02C3/107 - F02C3/13 and F02C7/32 take precedence; couplings for transmitting rotation F16D; gearing in general F16H
• CPC Class Codes: F02C 9/22 by adjusting turbine vanes
• CPC Class Codes: F02C 9/58 with control of a variable-pitch propeller
• CPC Class Codes: F02K 1/06 Varying effective area of jet pipe or nozzle by using fluid jets to influence the jet flow F02K1/30
• CPC Class Codes: F05D 2260/4031 as in toothed gearing
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A gas turbine engine comprises a high spool, a low spool and an intermediate spool. The high spool comprises a high pressure turbine coupled to a high pressure compressor. The intermediate spool comprises an intermediate pressure turbine coupled to a ducted fan. The low spool comprises a low pressure turbine coupled to an open-rotor propeller. A variable area turbine section positioned between the intermediate pressure turbine and the low pressure turbine variable turbine section is configured to vary an expansion ratio across the intermediate pressure turbine to control rotational speeds of the low spool and the intermediate spool.

Claims

1. A gas turbine engine comprising:

a high spool, the high spool comprising a high pressure turbine coupled by a high pressure shaft to a high pressure compressor;

an intermediate spool, the intermediate spool comprising an intermediate pressure turbine disposed axially aft of the high pressure turbine and coupled by an intermediate pressure shaft to a ducted fan disposed axially forward of the high pressure compressor;

a low spool, the low spool comprising a low pressure turbine disposed axially aft of the intermediate pressure turbine and coupled by a low pressure shaft to an open-rotor propeller disposed axially forward of the ducted fan;

a variable area turbine section positioned between the intermediate pressure turbine and the low pressure turbine, wherein the variable area turbine section varies an expansion ratio across the intermediate pressure turbine to control rotational speeds of the low spool and the intermediate spool; and

a fan duct extending from a position just aft of the fan to an exhaust nozzle of the gas turbine engine disposed axially aft of the low pressure turbine, wherein the ducted fan generates thrust by driving bypass flow through the fan duct.

2. The engine of claim 1, wherein the high spool, the intermediate spool and the low spool rotate about a common axis.

3. The engine of claim 2, wherein the open-rotor propeller rotates about the common axis with the high spool, the low spool and the intermediate spool.

4. The engine of claim 1, wherein the variable area turbine section varies the expansion ratio to balance thrust contributions of the open-rotor propeller and the ducted fan based on the rotational speeds of the low spool and the intermediate spool.

5. The engine of claim 4, further comprising a reduction gear coupling the low spool to the open-rotor propeller, wherein the reduction gear reduces a rotational speed of the propeller with respect to the low spool.

6. The engine of claim 4, wherein the propeller comprises a plurality of propeller blades and further comprising a variable pitch mechanism coupled to the propeller blades.

7. The engine of claim 6, wherein the variable pitch mechanism adjusts a pitch of the propeller blades to control loading on the propeller based on airspeed.

8. The engine of claim 1, further comprising a variable vane positioned in the fan duct axially aft of the fan, wherein the variable vane adjusts a flow area of the fan duct to regulate thrust generated by the fan.

9. A variable cycle turbine engine comprising:

a high spool, the high spool comprising a high pressure turbine coupled to a high pressure compressor;

a fan spool coaxial with the high spool, the fan spool comprising an intermediate pressure turbine coupled to a ducted fan;

a propeller spool coaxial with the high spool and the fan spool, the propeller spool comprising a power turbine disposed axially aft of the intermediate pressure turbine and coupled to an open-rotor propeller disposed axially forward of the ducted fan;

a variable area turbine between the intermediate pressure turbine and the power turbine, wherein the variable area turbine varies an expansion ratio of the intermediate pressure turbine to control loading on the fan spool and the propeller spool.

10. The turbine engine of claim 9, further comprising a variable pitch mechanism coupled to the propeller, wherein the variable pitch mechanism varies a pitch angle of the propeller to control loading on the propeller spool;

and a bypass duct coaxial with the fan spool, the bypass duct comprising a variable fan nozzle downstream of the ducted fan.

11. The turbine engine of claim 9, wherein the variable fan nozzle varies a flow area of the bypass duct to control a bypass ratio of the turbine engine.

12. The turbine engine of claim 9, further comprising a reduction gearbox coupling the propeller to the propeller spool.

13. The turbine engine of claim 12, wherein the reduction gearbox coaxially couples the propeller to the propeller spool, such that the propeller shares a rotational axis with the propeller spool and the fan spool.

14. A method of turbine operation, the method comprising:

rotating a fan spool about an axis, the fan spool comprising an intermediate pressure turbine coupled to a ducted fan that drives a bypass flow through a fan duct

counter-rotating a propeller spool about the axis, the propeller spool comprising a power turbine disposed aft of the intermediate pressure turbine and coupled via a reduction gearbox to an open-rotor propeller disposed axially forward of the ducted fan;

controlling an expansion ratio across the fan spool by actuating a variable area turbine section disposed between the intermediate pressure turbine and the power turbine; and

shifting power between the fan spool and the propeller spool, based on the expansion ratio.

15. The method of claim 14, further comprising adjusting the variable area turbine section and setting a pitch angle of the propeller to load the propeller spool for takeoff.

16. The method of claim 14, further comprising opening the variable area turbine section to load the fan spool for climbing.

17. The method of claim 16, further comprising increasing a pitch angle to reduce loading on the propeller for cruising.

18. The method of claim 17, further comprising closing a variable fan nozzle to reduce bypass flow during cruising.