The compressor section includes the axial compressor case, diffuser case, and high-pressure (HP) compressors. The HP compressors are axial and centrifugal compressors. The diffuser case holds the impeller shroud, radial diffuser, and deswirl that send the flow to the combustion section at the correct pressure. The core airflow goes through the compressors, which give a total 16:1 pressure ratio.

The inlet air from the fan section moves through the compressor section. Primarily, the compressor section increases air pressure and temperature before the air goes to the combustion section.

The secondary functions of the compressor section are to supply:

• Buffer air to pressurize bearing seals and cooling air from the low-pressure (LP) turbine
• Hot air for airframe and nacelle anti-icing
• Clean air for aircraft cabin pressurization, air-conditioning and pneumatic starting

The high-pressure compressors increase airflow pressure for the combustion section. The HP compressors have an axial compressor assembly and centrifugal compressor. The variable vanes, stator vanes, compressor case, and diffuser case do not turn. The air flows through the five vane assemblies and four blisk assemblies of the axial compressor, and into the centrifugal compressor. The compressor rotors operate from the high-pressure turbine spool.

The HP compressors have the following components:

Axial Compressor Case

The axial compressor case supports the inlet guide vanes, compressor variable vanes, and stator vanes. The axial compressor case contains the blades if a blade failure occurs.

Axial Compressor Rotor

The axial compressor supplies air to the centrifugal compressor at the desired pressure. The axial compressor rotor contains four blisks and their spacers. A blisk is a single component which comprises the disk and the blades. The rotors connect through the curvic couplings. The axial compressor rotor produces a 6.4:1 pressure ratio.

Variable Vanes

The first two vane stages of the axial compressor are the variable vanes, which comprise the inlet guide vanes and the compressor variable vanes. Two unison rings around the compressor case are attached to the inlet guide vane and variable vane assemblies. An external lever is attached to the unison rings and compressor variable geometry (CVG) actuator. The full authority digital engine control (FADEC) system sends a signal to the engine fuel control for pressurized fuel which goes to the CVG. The CVG moves the lever which moves the unison rings to set each vane to the optimal vane setting angle. This gives the most satisfactory airflow conditions at all ranges of engine operation.

Stator Vanes

The compressor stator vanes are the third-, fourth and fifth-stage fixed vanes. The vanes are fixed-position airfoils that are part of the case. The stators have inner and outer bands that are the axial rotor blade path guides. The bands give the case structural component strength. The rotor blade path for each axial stage has an abradable surface. The rotor blade tips can contact the case and not decrease the blade performance. This restricts reverse airflow leakage between the compressor stages.

Vortex Spoiler

The vortex spoiler connects the centrifugal compressor impeller to the axial compressor blisks and transmits the torque necessary for the axial compressor to operate. The vortex spoiler has a labyrinth seal that prevents airflow from the impeller back to the axial compressor.

Centrifugal Compressor

The centrifugal compressor rotor has a one-stage impeller with 19 primary and splitter airfoils. This rotor has a 2.5:1 pressure ratio.

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