Thursday, December 4, 2008

High Pressure Compressor

The LM6000 high pressure compressor (HPC) is a 14-stage, axial flow compressor, which incorporate variable inlet guide vanes (VIGV) and variable stators in stages 0-5 to provide stall-free operation and high efficiency throughout the starting and operating range. Provisions for bleed-air are available at stage 8 and at the compressor discharge. On earlier model turbines the seventh and eleventh stages bleed air is utilized, while, while later version use eighth and eleventh stage bleed air. Compressor discharge air is extracted for cooling and pressurization of the engine components.

The high pressure compressor rotor is a bolted assembly of major structural elements consisting of a stage 1 disk, a stage 2 disk with an integral forward shaft, stage 3-9 spool, a stage 10 disk, and stages 11-14 spool with an integral rear shaft. These structural elements are connected through fully rabbeted joints at stage 2 and stage 10. On newer model high pressure compressor there are only four major structural elements. In these versions the tenth stage disk has been eliminated and added as integral component of the 10-14 spool assembly.

Stages 1 and 2 blades are individually retained in axially dovetail slots, and the remaining blades are held in circumferencial dovetail slots. These features allow individual stage 1 blade replacement without disassembly of the rotor. Stage 1 blades are shrouded at mid span for the purpose of reducing vibratory stress. All other blades are cantilever from the rotor structure.

The high pressure compressor stator consists of a cast stator case that contains the compressor stator vanes. The inlet guide vanes (IGV) and the stages 1-5 vanes can be rotated about the axis of their mounting trunnions to vary the pitch of the airfoils in the compressor flow path. Vane airfoils in the remaining stages are stationary. All fixed and variable blades are non-interchangeable with other stages to prevent incorrect assembly. The casing is split along the horizontal split line for ease of assembly and maintenance. The inlet guide vanes and the stages 1-2 vane shrouds also support interstage rotor seals. The shrouds are designed to allow the removal of either half of the compressor casing. There are 14 axial stations provided for borescope inspection of blades and vanes.