GAS TURBINE BASICS

GENERAL ELECTRIC

1. What is a Gas Turbine?

  • A gas turbine has three main parts: compressor, combustor, and turbine.

  • Air is compressed, mixed with fuel, and burned. The hot gas spins the turbine.

  • The turbine powers the compressor and may also turn equipment like generators or pumps.

2. How Does It Work? (Brayton Cycle)

  • Compression: Air gets squeezed in the compressor (pressure & temperature rise).

  • Combustion: Fuel is added and burned (very hot gas forms).

  • Expansion: Hot gas pushes through turbine blades (makes power).

  • Exhaust: Gas leaves the engine.

3. Balloon Example (Basic Concept)

  • Imagine a balloon – when air shoots out, it pushes the balloon forward.

  • A gas turbine works the same way: air is accelerated and redirected to spin blades and generate energy.

4. Compressor Design

  • Compressors use rotating blades and stationary vanes to build pressure.

  • Two types:

    • Axial: Air flows straight through.

    • Centrifugal: Air spins outwards like a fan.

5. Inlet Guide Vanes (IGVs)

  • IGVs help guide air into the compressor correctly.

  • Some vanes can adjust to control airflow and pressure based on engine needs.

6. Compressor Stall

  • Happens when airflow is disturbed, like hitting a dent in a blade.

  • Too much or too little air can cause unstable flow (called a stall).

  • Good blade condition and proper air balance prevent this.

7. Combustor Types

  • Three types: Can, Annular, and Can-Annular.

  • Fuel burns inside the combustor to make hot gas.

  • About 18% air is for burning, and 82% is for cooling and flame shaping.

8. Turbine Section

  • Located after the combustor, it extracts energy from hot gas.

  • Spins fast and gets very hot — needs special cooling and materials.

  • Impulse-reaction blades convert gas pressure into rotating power.

9. Shaft Configurations

  • Single Shaft: All parts are connected; stable power – used in generators.

  • Twin Shaft (like LM2500): Power turbine is separate; good for variable speed like pumps.

  • Concentric Shaft: Advanced version used in engines like LM6000.

10. NOx Emissions Control

  • NOx forms when air and fuel burn at high temperatures.

  • Two control methods:

    • Wet method: Inject water or steam to cool the flame.

    • SCR: Add ammonia after combustion to break down NOx.

  • DLE combustors also help lower emissions without water.

GAS TURBINE PACKAGE FAMILIARISATION

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