Importance

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Abstract

A gas turbine engine has an engine casing surrounding the turbine section and an internal chamber or jacket which separates the casing from blade tip seals supported by the casing. To maintain an adequate clearance between the turbine blades and the seals during engine startup and acceleration, a portion of the hot combustion gases passing through the turbine blades is bled through the chamber in heat exchange relationship with the casing. The hot gases expand the casing at a faster rate than otherwise to approximate the thermal growth rate of the turbine rotor and maintain a adequate clearance between the turbine blade tips and seals. During steady-state operation relatively cool air bled from the compressor is ducted through the chamber to cool the engine casing and hold the proper clearance between the blades and the seals. A valve connected with the chamber controls the flow of hot combustion gases and cool compressor air through the chamber so that the engine casing can be expanded or contracted to control the blade clearance.

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First Claim