Gas Turbine Compressor Section

General Description
The axial-flow compressor section consists of the compressor rotor and the inclosing casing. Included within the compressor casing are the inlet guide vanes, the 17 stages of rotor and stator blading and the exit guide vanes.

In the compressor, air is confined to the space between the rotor and stator blading where it is compressed in stages by a series of alternate rotating (rotor) and stationary (stator) airfoil shaped blades. The rotor blades supply the force needed to compress the air in each stage and the stator blades guide the air so that it enters in the following rotor stage at the proper angle. The compressed air exits through the compressor discharge casing to the combustion chambers. Air is extracted from the compressor for turbine cooling, for bearing sealing, and during startup for pulsation control.

Since minimum clearance between rotor and stator provides best performance in a compressor, parts have to be made and assembled very accurately.

Compressor Rotor

The compressor rotor is an assembly of 15 individual wheels, two stub-shafts, each with an integral wheel, a speed ring, tie bolts, and the compressor rotor blades. Each wheel and the wheel portion of each stub-shaft has slots broached around its periphery. The rotor blades and spacers are inserted into these slots and are held in axial position by staking at each end of the slot. The wheels and stub-shafts are assembled to each other with mating rabbets for concentricity control and are held together with tie bolts. Selective positioning of the wheels is made during assembly to reduce balance correction. After assembly, the rotor is dynamically balanced to a fine limit.

The forward stub-shaft is machined to provide the forward and aft thrust faces and the journal for the n° 1 bearing, as well as the sealing surfaces for the nø 1 bearing oil seals and the compressor low pressure air seals.

Compressor Stator
The stator (casing) area of the compressor section is composed of four major sections :
  • Inlet casing forward compressor casing
  • Aft compressor casing
  • Compressor discharge casing
These sections, in conjunction with the turbine shell and exhaust frame form the primary structure of the gas turbine. They support the rotor at the bearing points and constitute the outer wall of the gas path annulus.

The casing bore is maintained to close tolerances with respect to the rotor blade tips for maximum efficiency.


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