industrial gas turbine (combustion chamber) - 1st

8/2/2019 Industrial Gas Turbine (Combustion Chamber) - 1st

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Industrial Gas TurbineUnit 303 - Combustion Section and Fuels

Topic C:

3.1Combustion Section

3.3Operation of Combustion Chamber3.4Inspection of Combustion liners

3.5Typical fault in Combustion Liners


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Learning Aim and Objective

Aim:

To demonstrate an understanding of theconstruction, maintenance and operation of

the combustion section.


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Learning Aim and Objective

Objective:

At the end of this lesson, you should be able to:

State the combustion sections.

Explain the operation of Combustion Chamber.

Describe a typical inspection procedure for

combustion linear and cross fire tubes.

Identify the typical faults in Combustion Liners.


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Air Inlet from Compressor

Combustion Section

Combustion section consist of:Spark Plug

Combustion Liner

Dual Fuel Nozzle

Transition Piece


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Combustion Section

Combustion section consist of:2 Spark Plug

4 Ultraviolet Flame Sensor

Mounting Adapters

Crossfire Tubes

Back


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Combustion Chamber

Construction

Between Compressor &Turbine Section.

Chamber must be in a through-flow position.

Its design such that the air near the nozzle staysclose to the front wall of the liner. Why?

Function of Air flow through Combustion Chamber:

To oxidize the fuel.To cool the metal parts.

To control the combustion products.


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Ultraviolet Flame Detectors

Purpose

To indicate the present or absence of flame.

Operation A flame Sensor (gas filled detector)

Sensitive to the present of Ultraviolet radiation

(emitted by a Hydrocarbon flame).

Failure to detect flame will inhibit further

progress of the sequence.


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Ultraviolet Flame Detectors


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Spark Plugs

Purpose

- To provide a place for an electric spark that is hot

enough to ignite the mixture of air & fuel inside the

combustion chamber of gas turbine.

Operation

Electrode Type spark plugs.

Supply High voltage current arcing across a gap on

the spark plug. Received power from Ignition Transformer.

Two are installed.


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Spark Plugs

Core Assembly

Spark Plug

Retainer

Spark Plug Retainer


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Cross Fire Tube

Purpose

Enable flame from the fired chamber to propagate

to the unfired chambers. (FIG.2Combustion CamberArrangement.)


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Fuel Nozzle

Purpose

To control the amount of fuel into

combustion chamber.Fitted on each combustion chamber.


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Fuel NozzleOperation

Fuel get through Central Tube.

Air pass through annular space.

The mixing of Fuel and Air at passage K.

Final mixing and atomization at circular slot L.


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Transition Pieces

Purpose

- To link the hot gas path between combustion

chambers and first stage nozzle.

Construction

Clamped to the forward side of nozzle assembly.

The Nozzle assembly sealed at both outer and

inner periphery.Why?


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Transition Pieces


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3.3 - Operation of Combustion Chamber

Purpose

- To burn the mixture of air and fuel inside

combustion chamber so that the expanded gas

can be used to spin the turbine.

Operation

Fuel is introduced at the front end of the burner.

Air flows around the fuel nozzle and through thefirst row of combustion air holes in the liner.


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The air entering through opposing liner holes

mixes rapidly with the fuel to form a combustiblemixture.


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Air entering the forward section of the liner re-

circulate & move upstream against the fuel spray.Why?


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Air entering the downstream part of the liner

provides the correct mixture for combustion andcreates turbulence for mixing the fuel & air.Why?


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After ignition, the flame spreads to the primary

zone (combustion zone).

Only 20% - 25% of the air takes parts in the

combustible process.Why?

75% - 80% used to form an air blanket aroundthe burning gases and to dilute the temperature.


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The gases then spin the turbine and gain its

speed.

The gases from combustion process having

temperatures of 3500F (1900C).

Before entering the turbine, the gases must becooled to approximately half of the value. How?


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How?

Cooling is done by diluting the hot gases with thesecondary air.


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3.4Inspection of Combustion Liner

Periodic maintenance and inspection important.Why?

Inspection carried out according to the amount

of running hours specified by the manufacturersof the Gas Turbine.

Inspection can be carried out even without

removing the chamber out from its outer

casing. How?


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Inspection using Borescope

Removed Fuel Injector

Insert tube of Borescope through the

hole, where the fuel injector is situated.

Check combustion liner on the outsideand inside. Look for what?


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3.5Combustion Liner fault

Combustion liners exposed to open flame,therefore subjected to Stress. It is important to

check for:

Cracks result from continuous full capacityapplication of gas turbine i.e. high speed equal to

high temp in combustion chamber.

Blocked cooling holes result from burnt rice

(dry seed).


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Recap

State the component attached onthe combustion sections.

Describe the operation of

Combustion Chamber.Describe a typical inspection

procedure for combustion linear.

Identify the typical faults inCombustion Liners.


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Overview of Next Lesson

Section E Cooling System

Topic: Cooling air system & sealing air

Thank you for your Attention

industrial gas turbine (combustion chamber) - 1st

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