Industrial Gas Turbines: Principles and Configurations

Gas Turbine Advantages

  • Power Output: Capable of producing up to 400 MW400\,MW.

  • Power-to-Weight Ratio: High ratio, optimal for weight-sensitive applications like offshore rigs.

  • Fuel Versatility: Compatible with various liquid and gaseous fuels.

  • Operational Efficiency: Rapid start-up for backup use, high availability, and remote operation capability.

  • Design: Compact and simple auxiliary systems with quick replacement options for major failures.

Gas Turbine Disadvantages

  • Cost and Complexity: High manufacturing costs and requires additional components (intercoolers, regenerators, reheaters) to match gasoline engine efficiency.

  • Performance: Slow response to throttle changes and decreased efficiency at low power or partial throttle.

  • Applications: Limited automotive use due to design and cost constraints.

Types of Industrial Gas Turbines

  1. Aero-derivative: Derived from jet engines with thrust components replaced by power turbines.

  2. Heavy-duty: Specifically designed for land-based applications.

Industrial and Commercial Gas Turbines

  • Applications: Power generation, driving pumps, and compressors.

  • Generation Modes:

    • Base load: Steady, ongoing electricity production.

    • Peak power: Generated during distribution network overloads.

    • Emergency: Provides back-up power.

Core Components and Operating Principles

  • Compressor: Supplies high-pressure air (1100−3000 kPa1100 - 3000\,kPa).

  • Combustor: Burns fuel (natural gas or oil) continuously. Flame temperature reaches high values (≈2,100∘C\approx 2,100^{\circ}C), reduced to 1,000−1,500∘C1,000 - 1,500^{\circ}C at the exit for material protection.

  • Turbine: Converts combustion gases into rotational energy to drive the compressor and generator. Gases exit at near atmospheric pressure between 500−640∘C500 - 640^{\circ}C.

Single Shaft Gas Turbine

  • Configuration: Compressor, turbine, and load share a single shaft and rotate at the same speed.

  • Pros/Cons: Mechanically simpler but requires a larger starting motor and offers less operating flexibility.

  • Best Use: Constant speed requirements like power generation.

Dual Shaft Gas Turbine

  • Configuration: A High-Pressure (HP) turbine drives the compressor on one shaft, while a Low-Pressure (LP) power turbine drives the load on a separate shaft without mechanical linkage.

  • Advantages: Higher flexibility (variable load/compressor speeds) and uses a smaller starting motor as it only rotates the compressor and HP turbine.

Open and Closed Cycle Operations

  • Open Cycle: Draws air from the atmosphere and exhausts it back after processing. Valued for its simplicity.

  • Closed Cycle: Recirculates working fluids (e.g., nitrogennitrogen, heliumhelium, or argonargon). Fluid is pressurized, preheated via a regenerator, heated by an external source, expanded in the turbine, and cooled before re-compression.