Turbo machine shroud-to-rotor blade dynamic clearance control

• US 5,601,402 A
• Filed: 06/06/1986
• Issued: 02/11/1997
• Est. Priority Date: 06/06/1986
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Corsmeier, Robert J., Wakeman, Thomas G.
• Primary Examiner(s): Carone, Michael
• Application Number:
  US06/874,201
• Time in Patent Office: 3,903 Days
• Field of Search: 415/113, 415/116, 415/171, 415/174, 415/178, 415/170 R, 415/170 B, 415/173 R, 415/170.1, 415/173.1, 415/174.1-174.5, 415/178, 415/171.1, 415/47 , 415/173.2, 60/39.32, 60/223
• US Class Current: 415/173.2
• CPC Class Codes: F01D 11/22 by mechanically actuating the stator or rotor components, e.g. moving shroud sections relative to the rotor

Abstract

A clearance control arrangement for the rotor blade-to-stator shroud clearance in an aircraft engine or other turbo machine. The disclosed arrangements use large area piston-like structures located circumferential to the turbo machine and capable of operation from pressures developed within the machine. One disclosed arrangement incorporates static adjustment capability that can be disposed to provide symmetrical or asymmetrical clearances. The disclosed clearance control can be used as a fast-acting supplement or in lieu of other clearance control arrangements and is arranged to be actuated upon sensing the onset of rotor-to-stator collision pinch point conditions in the turbo machine.

Claims

1. A method for operating a low leakage, close radial clearance turbomachine comprising the steps of:

selecting for said turbomachine a static rotor-to-stator shroud radial clearance value selected to produce rotor-on-stator rubbing collision during worst case transient operation thereof;

determining the turbomachine transient operating conditions capable of inducing said rotor-on-stator rubbing collision;

sensing the onset of turbomachine operating conditions approaching said rotor-on-stator rubbing collision conditions;

increasing said rotor-to-stator shroud radial clearance from a first predetermined low leakage value to a second, higher leakage, collision avoidance, predetermined value for the duration of said transient rubbing collision inducing operating conditions;

returning said radial clearance to a close, predetermined low leakage value following cessation of said transient rubbing collision inducing operating conditions; and

maintaining said rotor-to-stator shroud clearance in a dynamically corrected partially rubbing free condition using a predetermined analog algorithm response to turbomachine operating conditions whereby said sensing, increasing and returning sequence radial clearance is supplementary to said analog algorithm radial clearance.

2. The method of claim 1 wherein said predetermined values of clearance are determined by said analog algorithm.

3. The method of claim 1 wherein said sensing the onset step includes monitoring the operating temperature of an element in said turbomachine.

4. The method of claim 1 wherein said sensing the onset step includes monitoring the operating pressure adjacent an element in said turbomachine.

5. The method of claim 1 wherein said sensing the onset step includes monitoring the flow rate of a fluid communicating with said turbomachine.

6. The method of claim 1 wherein said selecting step includes adjusting said rotor-to-stator shroud clearance statically at segments of said stator shroud disposed around the periphery of said rotor.

7. The method of claim 6 wherein said adjusting step includes imparting differing values of rotor-to-stator shroud static radial clearance at different circumferential points around said turbomachine rotor in response to expected g force loading of said turbomachine.

8. In a jet engine having an air compressor stage, a fuel supply system and a fuel combustion products energized bladed turbine stage, the method of controlling rotor-to-stator shroud running clearance at the blade periphery of the turbine stage comprising the steps of:

segmenting the rotor facing surface of said shroud to enable expansive radial movement thereof with respect to the blade ends of said turbine;

actuating said shroud segmented surfaces from an annularly disposed radially expansible chamber having actuation surface area selected according to the force required in radially moving said shroud surfaces inward against engine flowpath pressures;

inflating said expansible chamber and moving said shroud segmented surfaces inward toward said blade ends using pressurized bleed air from said engine compressor stage; and

controlling inflation movement of said expansible chamber and said shroud surfaces between first short radius small rotor clearance and second longer radius large rotor clearance positions in response to a predetermined algorithm for averting blade end to shroud segment surface pinch point rubbing.

9. The method of claim 8 wherein said controlling step also includes selectively venting said expansible chamber to a low pressure region thereby enabling outward increased rotor clearance movement of said shroud surfaces in response to said engine flow pressure.

10. Rotor-to-stator shroud radial clearance control apparatus for a low leakage close clearance turbomachine apparatus comprising:

means for sensing the onset of turbomachine operating conditions approaching rotor-on-stator rubbing collision;

means for stepwise increasing said rotor-to-stator shroud radial clearance from a first predetermined low leakage value to a second, higher leakage collision avoidance predetermined value for the duration of said rubbing collision operating conditions; and

means for returning said radial clearance to a close, predetermined low leakage value following termination of said rubbing collision inducing operating conditions.

11. The apparatus of claim 10 further including means for maintaining said rotor-to-stator shroud radial clearance in a dynamically corrected partially collision rubbing free condition including a predetermined algorithm responsive to turbomachine operating conditions.

12. The apparatus of claim 10 wherein said means for stepwise increasing is fluid pressure actuated.

13. The apparatus of claim 10 wherein said turbomachine is a jet engine and wherein said operating conditions approaching rotor-on-stator rubbing collision include transient thermal conditions responsive to engine power setting changes.

14. The apparatus of claim 13 wherein said fluid pressure is comprised of fluid pressurized in the course of normal operation of said turbomachine.

15. The apparatus of claim 14 wherein said means for stepwise increasing includes a pressurized fluid expansible chamber member disposed surrounding a substantial portion of a rotor member in said turbomachine.

16. The apparatus of claim 15 wherein said stator shroud member is disposed intermediate said rotor member and said expansible chamber member.

17. The apparatus of claim 15 wherein said turbomachine is a jet aircraft engine and said pressurized fluid is compressor discharge pressure air from the compressor stage of said jet engine.

18. The apparatus of claim 17 wherein said expansible chamber member includes an actuation surface area size selected in accordance with the force required to move said shroud inward toward said rotor member against engine combustion flow pressure.

19. The apparatus of claim 18 wherein said means for returning includes release means for enabling escape of said pressurized fluid from said expansible chamber member to a region of lower pressure.

20. The apparatus of claim 19 wherein said means for stepwise increasing said rotor-to-stator shroud radial clearance includes clearance limit determining elements movably responsive to said predetermined algorithm;

whereby said stepwise clearance increase is additive to said algorithm clearance maintenance.

21. The apparatus of claim 20 wherein said predetermined algorithm is an analog algorithm.

22. The apparatus of claim 21 wherein said algorithm includes a thermal response to engine operating parameters.

23. The apparatus of claim 22 wherein said clearance control shroud actuation surface area includes a length dimension, measured along the length axis of said engine, substantially equal to the axial projected component of turbine blade end length.

24. Clearance adjustment apparatus for the stator-to-bladed rotor clearance gap of an aircraft engine turbomachine comprising:

an engine housing of substantially circular cross section;

a circularly disposed azimuthally segmented rub strip assembly located within said housing surrounding said bladed rotor ends and separated therefrom by said clearance gap;

a circularly disposed azimuthally segmented rub strip support structure located between said rub strip assembly and said housing, said support structure including annularly disposed pneumatically expansible chamber means for moving said rub strip segments radially inward and outward with respect to said rotor blade ends;

a plurality of thread adjustable radially disposed shank means periodically located around said housing and support structure and connected with said housing at the outward ends thereof, said shank means being also connected at the inward ends thereof with the outward facing portion of said support structure pneumatically expansible chamber means, for statically adjusting said rub strip to blade end clearance gap in circumferential periodic segments; and

means including a binary modulation control for selectably supplying ambient pressure air and pressurized air from the compressor stage of said engine to said expansible chamber means.

25. The apparatus of claim 24 wherein said shank means is comprised of shank members passing radially through said engine housing.

26. The apparatus of claim 25 wherein a thread adjustable portion of said thread adjustable shank means is located external of said engine housing.

27. The apparatus of claim 26 wherein said thread adjustable portion includes a threaded shank member.

28. The apparatus of claim 27 wherein said thread adjustable portion also includes a threaded nut member.

29. The apparatus of claim 28 wherein said thread adjustable portion includes also resilient sealing means for inhibiting the flow of pressurized fluid between the interior and exterior of said housing.

30. The apparatus of claim 28 wherein a plurality of rub strip segments of said segmented rub strip assembly are received on each segment of said segmented support structure.

31. The apparatus of claim 24 wherein said segmented rub strip assembly includes a plurality of circumferentially expansible gas seal members located circumferentially intermediate adjacent segment ends of said rub strip assembly.

32. The apparatus of claim 24 wherein said plurality of shank means is comprised of at least four shank members disposed in quadrature about said engine circumference;

whereby asymmetric static adjustment of said rotor blade end to stator rub strip clearance gap in accommodation of expected asymmetric g force loading of said engine is enabled.

33. The apparatus of claim 24 wherein the combination of said rub strip and rub strip support structure further includes engine operating condition responsive means for controlling said rotor blade end to stator rub strip clearance gap and wherein said pneumatically expansible chamber means movement of said rub strip segments is mathematically supplemental to said operating condition responsive gap clearance control.