Turbo machine shroud-to-rotor blade dynamic clearance control
First Claim
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.
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Accused Products
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.
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Citations
33 Claims
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1. A method for operating a low leakage, close radial clearance turbomachine comprising the steps of:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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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:
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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. - View Dependent Claims (9)
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10. Rotor-to-stator shroud radial clearance control apparatus for a low leakage close clearance turbomachine apparatus comprising:
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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. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. Clearance adjustment apparatus for the stator-to-bladed rotor clearance gap of an aircraft engine turbomachine comprising:
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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. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification