POWPLANT 2 - QUIZ 3 Reviewer

Turbine

transforms a portion of the kinetic energy in the hot exhaust gases into mechanical energy to drive the compressor and accessories.

60 to 80%

In a turbojet engine, the turbine absorbs approximately ________ to _________ of the total pressure energy from the exhaust gases.

What are the 4 turbine tasks?

Provides power to drive the compressor and accessories.

Provides shaft power for a propeller or rotor.

Extracts energy from the hot gases.

Expands gases to a lower pressure and temperature.

What are the four basic elements of turbine?

Case, Stator, Shroud, Rotor

Turbine Case

-Encloses the turbine rotor and stator assembly.

- Provides either direct or indirect support to the stator elements.

- Typical case includes flanges for attaching the turbine section to the combustion section and exhaust assembly.

Turbine Stator

- Also referred to as the turbine inlet nozzle, inlet guide vanes, or nozzle diaphragm.

- Positioned between the combustion section and turbine wheel.

- Collects high-energy airflow and directs it to the turbine rotor at the correct angle.

- Converts pressure energy to velocity energy via converging nozzles.

Turbine Shroud

- Composed of inner and outer shrouds that retain and surround the nozzle vanes.

- Allows thermal expansion through

1. Loose assembly of vane shrouds in contoured slots.

2. Welded or riveted vanes with segmented shroud rings to manage expansion.

Turbine Blades

- Composed of a shaft and a rotating disk.

- Anchored to the disk, transferring extracted energy to the rotor shaft.

- May be forged or cast, often as single crystals for improved heat resistance.

- Heat barrier coatings and air flow cooling increase efficiency.

Impulse Turbine

Changes airflow direction without altering pressure or velocity. The turbine wheel simply absorbs the force required to change the direction of airflow and converts it to rotary motion.

Reaction Turbine

Forms converging ducts, increasing gas velocity and reducing pressure.

Impulse-Reaction Turbine

Combines impulse-shaped blade bases with reaction-shaped tips for uniform performance.

Single-Stage Rotor Turbine

One rotor drives all engine parts. This is the simplest version of the pure turbojet engine.

Multiple Spool Engines

Each spool has its own turbine stage, driving specific compressors. Most turbofan engines have two spools: low pressure (fan shaft a few stages of compression and the turbine to drive it) and high pressure (high pressure compressor shaft and high pressure turbine).

Exhaust Section

Directs hot gases rearward to prevent turbulence and ensure high exit velocity.

Exhaust Cone

Aligns and supports inner and outer sections.

Tail Pipe

Extends the exhaust section and protects the fuselage.

Exhaust Nozzle

Boosts velocity with designs like

Converging - Diameter decreases from front to back for venturi effect.

Converging-Diverging - Diameter decreases, then increases from front to back. Increases gas speed above supersonic levels.

Converging

Diameter decreases from front to back for venturi effect.

Converging-Diverging

Diameter decreases, then increases from front to back. Increases gas speed above supersonic levels.

Accessory Section

- Powers engine and aircraft accessories (e.g., generators, pumps).

- Secondary functions include acting as an oil sump and housing drive gears.

- Located to streamline the engine profile, often at the midsection, front, or rear.

- power is drawn from the engine's main power shaft.

Turbine Section

Located downstream of the combustion section.

Turbine wheel

is a dynamically balanced unit consisting of blades attached to a rotating disk.

Turbine disk

referred to as such without blades.

500 hp

Large high-bypass engines may require up to __________ for the accessory drive system.