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1.General.
The first stage high pressure nozzle is air cooled by convection and film cooling. The purpose of the nozzle is to direct high pressure gases from the combustor onto the first stage high pressure turbine blades at the proper angle and velocity.
The major components of the nozzle assembly (Figure 1) are the nozzle support, vanes and inner and outer seals.
The nozzle is bolted at its inner diameter to the first stage support and receives axial support at its outer diameter from the second stage nozzle support.
2.First Stage Nozzle Support.
This component is a sheet metal and machined ring weldment. In addition to supporting the first stage nozzle it forms the inner flow path wall from the compressor rear frame to the nozzle.
3.Vanes.
The first stage vanes are coated to improve erosion and oxidation resistance. The vanes are cast individually and welded into pairs to decrease the number of gas leakage paths. The vanes are cooled by compressor discharge air which flows through a series of leading edge holes and gill holes on each side located close to the leading edge (Figure 2). Air flowing from these holes forms a thin film of cool air over the length of the vane. Internally the vane is divided into two cavities and air flowing into the aft cavity is discharged through trailing edge slots.
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Figure 1 First-Stage HP Turbine Nozzle
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Figure 2 First Stage HPT Nozzle Cooling Air Flow