Seal clearance control system for a gas turbine

Claim 1

In a gas turbine engine having a compressor defining a flow path from which a fluid-working medium is discharged at an elevated pressure, a combustion section receiving the working medium discharged from the compressor and combining the medium with a fuel in a combustion process to generate a high-velocity stream of combustion gases, a turbine section having a turbine including a plurality of peripheral turbine blades situated in a gas flow path carrying the high-velocity combustion gases from the combustion section through the turbine to drive the turbine, an engine casing enclosing the turbine and turbine seal means supported from the casing closely adjacent the tips of the turbine blades in the gas flow path, an improved seal clearance control system comprising: heat exchanging means for controlling thermal expansion of the engine casing and the seal means and including fluid conduit means extending into the turbine section in heat exchange relationship with the engine casing, the fluid conduit means having a fluid connection at an upstream end with the compressor to receive a portion of the relatively cool working medium from the compressor and another upstream connection with the gas flow path in the turbine section to receive the relatively hot combustion gases and also having a downstream end from which the working medium and the hot combustion gases are discharged, the intermediate portion of the conduit between the upstream connection and the downstream end being in heat exchange relationship with the engine casing supporting the turbine seal means; and flow control means associated with the heat exchanging means for regulating the flow of both the relatively cool working medium and the hot combustion gases through the conduit means in heat exchange relationship with the casing whereby expansion and contraction of the engine casing and the clearance between the seal means and the blade tips in the turbine may be controlled, the flow control means including vent valve means connected with the fluid conduit means between the upstream and downstream ends for controlling pressure within the fluid conduit means and the resulting flow of the relatively cool working medium and hot combustion gases through the conduit means in heat exchange relation with the engine casing.