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05/27/16

Overview

The function of the low pressure (LP) turbine section is to change the hot gases into mechanical power. This lets the turbine turn the LP compressor. The turbine section has the exhaust section and the fuel shutoff mechanism.

The turbine section has a two-stage HP turbine and a two-stage LP turbine. The two-stage HP turbine connects to the HP compressor drum through a curvic coupling. The stage-1 and stage-2 HP nozzle guide vanes (NGVs) are installed on the HP turbine case. The two-stage LP turbine is on the LP shaft which connects to the LP compressor. The case contains the two-stage rotor, stubshaft, LP turbine shaft and fuel shut-off mechanism. The exhaust case attaches to the rear flange of the turbine case. The rear support mount of the engine goes around the exhaust case. The turbine exhaust support-struts attach the exhaust case to the engine rear support-mount.

HP Turbine Module

The HP Turbine section includes a two stage HP turbine with a shrouded first stage, and a unshrouded second stage blades. This configuration optimizes the balance between turbine entry temperature (TET) limitations and turbine blade life. The outer casing provides support for the HP stage 1 and 2 Nozzle Guide Vanes (NGVs) and the LP stage 1 NGVs.

The module also includes the rear bearing chamber (RBC). It is supported through a fixed structure inside the LP stage 1 NGVs, and contains the no. 4 bearing for HP turbine support and the outer race of the no. 5 bearing for LP turbine support. Fuel spray nozzles and igniter plugs fitted into the combustion chamber are non-modular. The HP turbine converts a portion of the energy into mechanical energy that drives the HP compressor.

LP Turbine Module

This module provides the motive force to drive the LP compressor (fan), and provides location for the turbine exhaust and rear support nonmodular parts. In addition, the module contains an LP turbine shaft breakage sensing mechanism.

The module comprises a two-stage LP turbine, the LP turbine shaft, an outer casing which supports the second-stage LP NGVs, and the LP turbine (no. 5) bearing. A central signal tube provides a reference signal to the LP turbine shaft breakage sensing mechanism located aft of the bearing chamber.

LP Turbine Blades

There are 100 stage-1 and 59 sets of two-piece stage-2 blades. Firtree roots attach the blades to the disks. There are 100 damper plates between the stage-1 blade roots and the disk. There are 118 damper pins in the roots of the stage-1 blades. Twenty-four retainer plates and four lock plates safety the stage-1 blades to the stage-1 disk. Thirty retainer plates and three lock plates safety the stage-2 blades to the stage-2 disk.

Exhaust Case

The exhaust case is a one-piece forged structure. It has 16 turbine outlet guide-vanes with a diaphragm on the front inner-flange. The vanes are numbered clockwise. Fan air goes through the No.3, No.7, No.11 and No.15 vanes. The air cools the vanes and other components and then mixes with the exhaust air. The air comes out of the vanes through tubes on the external surface.

There are eight mounting bosses on the external surface of the exhaust case. The support struts of the exhaust case attach to the bosses. There are also four connectors on the external surface. These are at the top of the No.3, No.7, No.11 and No.15 vanes. The tubes for the fan air are installed at the connectors.

The front outer flange attaches to the LP turbine case. The rear outer flange holds the exhaust nozzle. The rear inner flange holds the front exhaust cone and the outer air-baffle diaphragm. The inner ring of the diaphragm holds the inner baffle assembly.

Turbine Exhaust Supports

The turbine exhaust supports connect the exhaust case to the rear support mount of the engine. There are eight turbine exhaust supports. One end connects to a mounting boss on the exhaust case, the other end to the engine rear support-mount.

There are four mounting positions on the inner surface of the engine rear support-mount. Each of the mounting positions hold two turbine exhaust supports. A hollow pin attaches the turbine exhaust supports to the support mounts. A bolt, thrust washer and lugged nut safety the pin.

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