Durable turbine nozzle

Abstract

A turbine nozzle includes a plurality of vanes joined at opposite ends to outer and inner bands. The inner band has a forward hook which is segmented to reduce thermal mismatch. And, in additional embodiments the vane includes an impingement baffle having preferential cooling.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates generally to gas turbine engines, and, more specifically, to turbine nozzles therein.[0002]In a gas turbine engine, air is pressurized in a compressor and mixed with fuel and ignited in a combustor for generating hot combustion gases. Energy is extracted from the gases in corresponding turbine stages which power the compressor and produce useful work, such as powering a fan in a turbofan engine for propelling an aircraft in flight, for example.[0003]Since the turbines are bathed in the hot combustion gases during operation, they must be suitably cooled which is typically accomplished by bleeding a portion of the pressurized air from the compressor and channeling it through the turbine components.[0004]A high pressure turbine directly receives gases from the combustor and includes a stator nozzle and a corresponding first stage rotor having a plurality of rotor blades extending radially outwardly from a supporting disk. A...

AI Technical Summary

Benefits of technology

[0010]A turbine nozzle includes a plurality of vanes joined at opposite ends to outer and inner bands. The inner band has a forward hook which is segmented to reduce thermal mismatch. And, in additional embodiments the vane includes an impingement baffle having preferential cooling.

Problems solved by technology

Such extended life is difficult to achieve since the nozzles are subject to various differential temperatures during operation which create thermal loads and stress therefrom.

And, temperature distributions and heat transfer coefficients of the combustion gases channeled through the nozzle vary significantly and increase the complexity of providing corresponding cooling.

However, these nozzles are beginning to experience distress at high cycle operation which may require their replacement prior to their expected useful life.

Nozzle distress is caused by locally high heat transfer coefficients in different regions of the nozzle at which corresponding cooling is limited.

Thermal gradients lead to thermal stress, which adversely affect the useful life of the nozzle.

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