The cooling system supplies a flow of air which decreases the temperature of the blades and the vanes of the turbines. The cooling system supplies the air pressure to pressurize the sump seals and the buffer space. The air comes from:

• The compressor stage 3 bleed (P2.67)
• The compressor stage 4 bleed (P2.7)
• The combustion chamber (P3.0)

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The cooling system provides cooling air from the engine compressor to cool the high and low-pressure turbines inside the hot section of the engine.

The three external tubes that supply the cool air from the compressor are attached to the outside of the compressor case. Each tube provides a path for third stage compressor air to flow into the low-pressure turbine assembly. Check valves are installed in the LPT case at the ends of the three cooling tubes. The check valves will close if a cooling tube breaks to decrease cooling air loss at engine operation.

Compressor discharge air to cool the high-pressure turbines is supplied through internal passages within the engine.

The buffer air system uses low pressure, low temperature compressor air, routed through three tube assemblies to the forward and aft sumps to prevent oil from passing over the carbon seals and to keep the carbon seals cool.

There are no functional components in the cooling system. A series of ducts and holes supply the air to turbine blades and vanes and engine bearing sumps. The restrictor holes control the airflow to give a correct supply of air.

The air from the compressor bleed (P2.7) and from the combustion chamber (P3) decreases the temperature of the high-pressure (HP) turbine blades and vanes. The first-stage HP turbine vanes receive the P3 air through the inner and the outer circumferences of the vanes. The second-stage vanes receive the P3 air through the holes in the pins that go into the outer circumference. The air flows through the trailing edges in two of the stages to decrease the temperature of the turbine blade stage behind it. The air from the second-stage vanes goes through the inner circumference to the space between the two stages of the HP turbine.

The air from the combustion chamber (P3) decreases the temperature of the first-stage turbine blades. The air goes into the feed space and flows through the blades.

The second-stage HP turbine blades receive P2.7 air in the space aft of the turbine wheel. The seal plate on the second-stage turbine wheel has vanes to help move the air to the blades.

The flow of air to the turbine blades is the primary cooling for the turbine wheel.

Three external tubes transmit the air from P2.67 to the LP turbine case. An internal manifold controls the supply of air to a plenum around the interturbine duct. The air flows from the manifold, through the low-pressure (LP) turbine first-stage vane and into a space between the HP and LP turbines. Then the air goes into the holes between each of the LP turbine stages and through the openings in the interstage seal. The air gets to the hot gas stream and makes a layer of cooler air around the blades.

The cooling system has the accessory cooling subsystem.