Gas Turbine Components & Systems – Vocabulary Review

This set of vocabulary flashcards covers major gas-turbine components, operating principles, supporting systems, and performance-improvement methods discussed in the lecture notes. Use them to reinforce terminology and core concepts before the exam.

Gas Turbine

A self-contained prime mover that compresses air, adds heat in a combustor, and expands the hot gas through a turbine to produce mechanical power.

Compressor

Front-end section of a gas turbine that raises inlet-air pressure; may be centrifugal or axial in design.

Centrifugal Compressor

Single- or two-stage unit that accelerates air outward with an impeller and converts velocity to pressure in a diffuser.

Axial Compressor

Multi-stage compressor with alternating rows of rotor blades and stator vanes that raise pressure while air flows parallel to the shaft.

Impeller

Rotating wheel in a centrifugal compressor that imparts high velocity and partial pressure rise to incoming air.

Diffuser (Compressor)

Ring of divergent passages that convert the impeller’s kinetic energy into static pressure.

Rotor Blades

Moving blades in an axial compressor stage that accelerate the airflow rearward.

Stator Vanes

Stationary vanes in an axial compressor that diffuse the air and redirect it onto the next rotor row.

Pressure Ratio

Ratio of compressor outlet pressure to inlet pressure; a key measure of compressor performance.

Mass Flow

Quantity of air passing through the engine per unit time; higher mass flow enables greater thrust.

Variable Stator Vanes

Movable compressor stators that adjust airflow angles for efficient operation at off-design speeds.

Single-Spool Compressor

Compressor with one rotor assembly driven by a single turbine stage on a common shaft.

Multi-Spool Compressor

Compressor arrangement with two or more independently driven rotors to optimize speed and pressure ratio.

Combustion Chamber (Combustor)

Engine section where fuel mixes with high-pressure air and burns, producing hot gases for the turbine.

Combustor Requirements

High efficiency, stable flame, low pressure loss, uniform outlet temperature, durability, low emissions.

Tubular Combustor

Multiple individual flame tubes arranged around the engine; robust but bulky and high in pressure loss.

Tuboannular (Can-Annular) Combustor

Cylindrical liners inside a common annular casing, combining compactness with tubular robustness.

Annular Combustor

Single continuous flame tube forming a ring; shortest, lightest, and lowest pressure loss of combustor types.

Primary Combustion Zone

Front section of a combustor where approximately 20–40 % of the air mixes with fuel for main burning at near 15:1 air-fuel ratio.

Dilution Zone

Region downstream of primary zone where additional air mixes to reduce gas temperature before turbine entry.

Flame Tube

Inner liner of a combustor that contains the flame and directs airflow patterns; requires intensive cooling.

Nozzle Guide Vane (NGV)

Stationary aerofoil at turbine inlet that directs, accelerates, and conditions hot gas onto the first turbine blades.

Turbine Disc

Rotating hub that carries turbine blades; made from nickel alloys and cooled to resist fatigue and thermal stress.

Turbine Inlet Temperature (TIT)

Gas temperature entering the first turbine stage; higher TIT improves efficiency but demands advanced cooling.

Turbine Cooling

Internal convection and external film or transpiration methods that allow blades and vanes to survive temperatures above alloy melting points.

Accessory Gearbox

Internal–external gear system that powers pumps, generators, and starters from an engine shaft.

Accessory Drive

Mechanical take-off that supplies power to hydraulic, pneumatic, and electrical accessories using gearbox outputs.

Fuel System

Components that filter, meter, and deliver gas or liquid fuel to the combustor in the required quantity and condition.

Fuel Manifold

Ring or distribution pipe that supplies metered fuel evenly to each injector or nozzle.

Fuel Injector / Nozzle

Device that atomizes and sprays fuel into the combustor to ensure complete, stable combustion.

Fuel Control and Metering

Governor-based system regulating fuel flow for start, acceleration, load rejection, and steady-state power.

Natural-Gas Fuel System

Simpler system using filters, shut-off and throttle valves, pressure regulator, manifold, and injectors; no atomization needed.

Liquid Fuel System

Complex system with boost pump, main positive-displacement pump, filters, throttle and bypass valves to supply pressurized fuel for atomization.

Boost (Supply) Pump

Centrifugal or radial pump that moves fuel from storage to the main pump, overcoming inlet losses.

Main Fuel Pump

Engine- or motor-driven positive-displacement pump that delivers high-pressure fuel to injectors across the operating range.

Filtration (Fuel)

Removal of solid and liquid contaminants to protect valves, pumps, and nozzles from wear and sticking.

Lube Oil System

Self-contained system providing pressurized, cooled, and filtered oil to bearings, gears, and control devices.

Magnetic Plug

Magnet inserted in oil return flow to collect ferrous debris for condition monitoring.

Chip Detector

Sensor that triggers a warning when metallic particles appear in scavenged oil, indicating wear or failure.

Synthetic Lubricant

Heat-resistant oil used in some rolling-element bearing engines; incompatible with certain standard seals and gaskets.

Air Starter

Pneumatic device that spins the gas turbine compressor to self-sustaining speed during start-up.

Electric Starter

Motor-driven system providing initial rotor acceleration until fuel ignition and engine self-acceleration.

Convergent Duct

Passage that decreases area to convert pressure energy into velocity (e.g., turbine nozzles).

Divergent Duct

Passage that increases area to convert velocity into pressure (e.g., compressor diffusers).

Cooling Air Film

Thin layer of cooler compressor air bled onto hot-gas surfaces to protect combustor liners or turbine components.

Reheating (Gas Turbine)

Addition of a second combustor between turbine stages to raise gas temperature, increasing shaft work but slightly lowering efficiency.

Regeneration (Recuperation)

Heat exchanger process that transfers exhaust heat to compressor discharge air, reducing required fuel and raising efficiency ~5-6 %.

Intercooling

Cooling of compressed air between LP and HP compressor stages to reduce compression work and raise output power.

CODOG

Combined Diesel Or Gas-turbine propulsion where either the diesel (cruise) or GT (high speed) drives each shaft individually.

CODAG

Combined Diesel And Gas-turbine system allowing simultaneous or separate operation via multi-speed gearboxes for higher speed range.

COGAG

Combined Gas-turbine And Gas-turbine configuration with two GTs per shaft, offering flexible full-load efficiency but lower cruise efficiency.

High Pressure Ratio per Stage

Characteristic advantage of centrifugal compressors achieving large pressure rise in one stage compared with axial.

Stable Operating Range

Compressor ability to avoid stall or surge across varying speeds and loads.

Film-Cooled Turbine Blade

Blade with rows of small holes that form a protective air layer over its surface to survive high TIT.