gas turbine 1

GLOSSARY OF GAS TURBINE The following definitions and nomenclature provide to familiarize with gas turbine terminology

Terms

Definitions

Gas turbine

A rotary prime mover in which the working medium, air or gas, is compressed, heated and expanded to produce useful power.

Open cycle

One in which the working medium enters the gas turbine from the atmosphere and discharges to the atmosphere.

Simple cycle

One in which the working medium passes successively through the compressor, combustor and turbine (s).

Regenerative cycle

One in which the working medium passes successively through the compressor, regenerator, combustor, turbine (s) and regenerator.

Single shaft

The arrangement in which the rotating components are mechanically coupled together on a common axis.

Two shaft

The arrangement in which the rotating components are arranged on two separate shafts. The shaft which is connected to the load is known as the output or power shaft, the other shaft is known as the compressor shaft.

Direction of rotation

Direction of rotation of a gas turbine is the clockwise direction or C.C. rotation, determined by looking at the face of the gas turbine output shaft coupling.

Ignition speed

The speed of the compressor shaft at which ignition and fuels are applied.

Self-sustaining speed

The minimum speed of the compressor shaft at which the turbine will continue to operate at no-load without cranking power.

Idling speed

The specified operating speed of the compressor shaft for no-load operation.

Rated speed

The speed of a designated shaft at which rated power is developed.

Terms MODULE 1 GAS TURBINE AND DIESEL ENGINE

Definitions SPECIFIC COURSE FOR ENGINEERS GLOSSARY, PAGE 1

Trip speed

The speed at which the over speeds protective device operates.

Cranking power

The external power which is required to accelerate the compressor, its turbine, and any connected load to self-sustaining speed in a specified time.

Protective device

One which, alone or as part of a system, controls or signals in some predetermined manner, abnormal conditions which may occur during the operation of the unit or system to which it is connected.

Controlling device

One which automatically initiates action of a system which controls conditions during the normal operation of the gas turbine.

Warning device

One which by visible or audible means, or both, indicates that an abnormal operating condition exists.

NOMENCLATURE Terms

Definitions

Turbine

A mechanical component in which the thermal energy of the working medium is converted to mechanical energy by kinetic action on a rotary element.

Compressor turbine

The mechanical component in which a portion of the thermal energy of the working medium is converted to mechanical energy and utilized to drive the axial compressor.

Power turbine

The mechanical component in which a portion of the thermal energy of the working medium is converted to mechanical energy and utilized to drive the connected load.

Turbine blades

Curved vane elements mounted on a rotating wheel and proportioned to transfer energy from the working medium to the turbine rotor.

Turbine diaphragm

A stationary element used to expand the working medium and direct it against the rotating blades.

Axial compressor

The mechanical component in which the pressure of the working medium is increased.

Terms SPECIFIC COURSE FOR ENGINEERS GLOSSARY, PAGE 2

Definitions MODULE 1 GAS TURBINE AND DIESEL ENGINE

Compressor blades

Airfoil sections mounted on a rotating disc and proportioned to compress the working medium through each successive row of compressor diaphragms.

Compressor diaphragm

A stationary element containing a set of stator blades used to compress the working medium and direct it against the rotating blades.

Combustor basket

That mechanical component of the combustion system in which the fuel is burned to increase the temperature of the working medium.

Transition piece

Mechanical component which directs the hot gases from each combustor basket to the segmental opening leading to the turbine inlet.

Fuel nozzle

That component of the combustion system which meters the fuel to the combustor basket with the proper dispersion pattern.

Igniter

That component of the combustion system, which at a predetermined point is energized to provide the spark for igniting the fuel in the combustor basket.

Cross flame tube

A mechanical interconnection between combustor baskets for the purpose of carrying the flame from a fired to an unfired combustor basket.

Interstage seals

Mechanical device used to restrict the leakage of the working medium between stages.

Compressor bleed

An open-close bleed line used to bleed off a portion of the working medium during a start-up or a stop period.

Bearing housing

An enclosure used to contain and support the shaft bearings and may be of the bracket or pedestal type.

Shaft-bearing

Journal bearing used to support the rotating elements.

Thrust bearing

A thrust bearing transmits the residual axial thrust of the rotor to the bearing housing and maintains the axial position of the rotor in respect of the stator.

Turbine stage

Consists of a set of stationary nozzles and one row of moving blades, which are mounted, on one wheel. The working medium expands through the stationary nozzles to a lower pressure, thus releasing kinetic energy, which is absorbed by the moving blades.

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Terms

Definitions

Rotor assembly

This is the rotating element of the gas turbine, which includes all parts attached to the shaft, and has provision for coupling.

Discs (wheels)

Wheels are discs, which are, part of or fixed to the gas turbine shaft and on which the blades are mounted.

Shroud

A strip attached to or adjacent to the blade tips to limit leakage.

Speed governing system

A system of control elements and devices for the control of the speed or power output of a gas turbine and including a speed governor, speed changer, fuel control mechanism, and other devices and control elements required to actuate the fuel control valve.

Speed governor

The primary speed-sensitive element which is directly responsive to speed and which positions or influences the action of other control elements.

Fuel control mechanism

This mechanism controls the flow of fuel to the gas turbine.

Servomotor

Fuel controls mechanism, which positions the fuel throttle valve.

Speed changer

Used to change the setting of the speed governing system for the purpose of adjusting the speed and / or load of the gas turbine during operation.

External control device

An element, which is responsive to, signals that are external to the gas turbine. It may be pneumatically, hydraulically or electrically actuated from the signal source and acts to control the energy input to the gas turbine.

Control panel

A component on which are mounted the devices used to initiate, regulate and monitor the necessary functions for safe operation of the gas turbine.

Inlet silencer

An inlet silencer attenuates the sound power level transmitted through the working medium at the inlet of the compressor.

Exhaust silencer

An exhaust silencer attenuates the sound power level transmitted through the working medium leaving the gas turbine.

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MODULE 1 GAS TURBINE AND DIESEL ENGINE

Terms

Definitions

Main gear

Converts the speed of the gas turbine output shaft to the required operating speed of the driven apparatus.

Auxiliary gear

Converts the gas turbine speed to the speed required by the auxiliary equipment.

Baseplate (bedplate)

A structural metal frame for supporting the gas turbine and its auxiliaries as a unit.

Exhaust heat boiler

Used to recover and transfer heat from the working medium leaving the gas turbine to generate steam or hot water.

Barring gear

It is used :1.

To rotate the gas turbine rotor at low speed prior to starting to facilitate rotor acceleration.

2.

During the cooling period, immediately after a shutdown, to prevent excess temperature gradients across the machine (to assure uniform temperature distribution in the rotor).

Turbine temperature detector

That component of the control system which senses the temperature of the working medium and provides the signal to limit the fuel input to the combustor baskets when maximum temperature is reached.

Accessories

Apparatus deemed necessary for the proper functioning and safety of operation of the gas turbine.

Starting equipment

The starting equipment shall be capable of bringing the gas turbine up through the normal starting cycle to self-sustaining speed.

Governing system

Includes but is not limited to :1.

Speed governor on the load shaft with load setting device for manual operation at the machine and / or control panel.

2.

Overriding control.

3.

Emergency overspeeds governor on the load shaft (also on the compressor shaft for a twoshaft machine).

Terms

MODULE 1 GAS TURBINE AND DIESEL ENGINE

maximum

turbine

temperature

Definitions

SPECIFIC COURSE FOR ENGINEERS GLOSSARY, PAGE 5

Lubricating system

Supervisory instrumentation

A closed forced-feed system including the following :1.

Oil reservoir of sufficient capacity and oil piping.

2.

Main oil pump-sized to supply oil requirements for the complete gas turbine unit during normal operation.

3.

Auxiliary and / or emergency lube oil pump (s) with means for testing their operation.

4.

Lube oil coolers.

5.

Reservoir oil level indicator.

6.

Temperature measuring device in the oil feed header.

7.

Means for automatically activating emergency lube oil pump.

8.

Oil feed header pressure gauge.

9.

Relief valves.

Provided for adequately checking and monitoring the performance of the machine. 1.

Master control switch for semi-automatic start and for stopping the gas turbine.

2.

Means for controlling power operated speed changer.

3.

Relays to provide the necessary functions for the control and protective operation of the gas turbine.

4.

Starting and sequence indicating lights.

5.

Temperature indicator for the turbine exhaust temperature.

6.

Speed indicator for out put shaft compressor shaft for two-shaft machine.

7.

Loss of flame indication.

Terms

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and

Definitions

MODULE 1 GAS TURBINE AND DIESEL ENGINE

Temperature control system

8.

Annunciator with audible alarm and individual malfunction indicators for overspeed, flameout, low lube pressure, high bearing oil temperature, and high turbine cooling temperature.

9.

Pressure gauges for measuring lube oil header pressure, fuel pressure, overspeed oil pressure and control air pressure.

Under any normal conditions of operation, shall limit fuel input as necessary to prevent the temperatures in the turbine from exceeding allowable limits.

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