apu and turbine lecture

Turbine Engine Main Sections

• Compression

  • Process of compressing incoming air for increased efficiency and pressure.

• Aircraft

  • Refers to the interaction between the turbine engine and aircraft components.

• Exhaust

  • Where spent gases exit the engine, affecting thrust and performance.

• Accessories

  • Additional components contributing to engine functionality (e.g. fuel pumps, ignition systems).

• Ground Power Unit (GPU)

  • Provides electrical power for starting the APU and other systems.

• Starter Motor

  • Key component that initiates engine rotation when powered by the GPU.

APU (Auxiliary Power Unit) Operation

• Electrical Power to Starter Motor

  • The GPU supplies power to the APU's starter motor.

  • Starts the accessory section, rotating essential components.

• Components powered by Starter Motor

  • Rotates:

    • Cooling fan

    • AC Generator

    • Lubrication System

    • Fuel System

• AC Generator

  • Activated by the starter, it sends power to the ignition system.

• Drive Shaft Rotation

  • As the drive shaft spins, it powers:

    • Loading Compressor

    • Power Compressor

    • Turbine

    • Power Turbine

• Compressor Function

  • The load compressor increases the air pressure before it reaches various systems including:

    • Pneumatic System

    • Bleed Control Valve

Air Compression and Mixing

• Airflow Process

  • Air flows from the APU to the compressor, then to:

    • Diffuser (increases pressure, decreases velocity)

    • Manifold (directs air to mixed zones)

• Fuel Mixing

  • Mixes compressed air with fuel in the combustion zone; fuel is dosed via fuel control units.

  • Types of fuel nozzles are Simplex or Duplex.

• Ignition Process

  • The igniter plugs produce sparks igniting the fuel-air mixture.

Turbine Operations

• High-Pressure Combustion

  • High velocity, high temperature air from combustion drives the turbines.

  • Turbines rotate blades for energy extraction and compressor work.

• Turbine Blade Design

  • Shrouded blades with impulse and reaction types.

• Turbine Temperature Monitoring

  • Thermocouples measure temperature at the turbine inlet (TIT) and guide fuel flow control.

• Exhaust Section

  • Convergent and divergent nozzles regulate airflow for optimal thrust.

  • EGT (Exhaust Gas Temperature) sensors monitor exhaust conditions.

Airflow and Engine Efficiency

• Bypass Ratio

  • Represents the ratio of secondary (bypass) airflow to core airflow in high bypass turbofans:

    • Low: < 2:1

    • Medium: 2-4:1

    • High: 5-6:1

    • Ultra High: > 7:1

• Engine Cooling

  • Bypass airflow contributes to cooling and overall thrust generation.