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III A

One of the significant internal combustion engines type are the gas turbine engines that

can be seen in aircraft engines. The gas turbine engines are basically classified in three main

components; compressors, combustors and turbines. The first of these component is

compressors. Giampaolo explains that the compressors generate the high pressure air. Power

output is created by high pressure air which is heated and expended by compressors (2009,

p.52). This clearly show that which purpose compressors use in gas turbine engines.

Giampaolo reports that compressors which are used today include two type namely axial and

centrifugal compressors. Medium and high horsepower applications utilize the axial

compressors but low horsepower applications use the centrifugal compressors (2009,

p.53).This clearly show that when the compressors are going to be chosen, the horsepower

must keep in view. The second component of gas turbine engines is combustors. According to

Boyce, although there are different types of gas turbine combustors, they apply same task.

Gas turbine combustors consume ten percent of air for processing of combustion. Ninety

percent of air is utilized for cooling and mixing. Steam is included in the circulation for

cooling in new combustors (2006, p.33). This makes it clear that combustion area is

significant part of gas turbine engine, because combustors rise the temperature of high

pressure gas. Lefebvre express that combustor type and layout which will be used in the most

suitable engine is chosen all of the engine design. This engine must be available for necessity

combustors which are divided two type; tubular and annular. Tubuannular (can-annular) is

also combustor between tubular and annular. Tubuannular is the combine of annular and

tubular. Thus, there are three combustors type (2010, p.10). This shows that combustion type

should be chosen for gas turbine. The chosen combustion type should be available as

efficaciously as possible for gas turbines. The last component of gas turbine engines is

turbines. Giampaolo reports that kinetic energy is gained from the expanding cases which

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strain from the combustion chamber by the turbine. This energy is transformed into Shafter

horsepower to drive the compressors and output turbine (2009, p.73). Obviously, turbines

produce the kinetic energy in order to rotate compressors. Boyce states that axial flow and

radial flow are two types of turbines that are used in gas turbines. More than ninety five

percent of application use axial-flow turbines. Axial flow and radial-inflow turbines include

units which are called impulse and reaction. Although reaction turbines get derivative

enthalpy that fall through both the nozzles and the impeller blades. All of the enthalpy is taken

by impulse turbines (2006, p.43). This implies that axial-flow turbines are used more than

radial-inflow turbines. As a result, combination of compressors, combustors and turbines

create the gas turbine engines.

III B

Gas turbine working principles are analyzed in three main parts; compressors,

combustion area and turbines. The first part is the compressor. According to Boyce there are

two kinds of compressors that are used in gas turbine technology axial and centrifugal.

Almost whole gas turbine manufacturing over 5MW have axial-flow compressors. Some of

them are combined axial and centrifugal which follow the axial compressor (2006, p.27). He

also mentions that axial-flow compressors consist of two process. The first, the fluid is

accelerated and then it is diffused by compressor. So that pressure reaches the high level. The

row of rotating airfoils or blades (the rotors) makes the fluid speed up. Then the fluid is

diffused by row of stationary blades (the stator) purpose of diffusion in the stator is that the

increased velocity that is transformed to high pressure by using rotors. A compressor

generally occur multiple stage. One rotor and one stator are one of these stages. Also one row

of fixed blades (inlet guide vanes) generally is used at the compressors inlet as additionally. In

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order to ensure that the air enters the first-stage rotors at the desired angle. Another

additionally application applies to the stator. An extra diffuser is put the end of the

compressor to arrange the velocity of fluid (2006, p.27). In the light of this explanation it can

be said that air pressure getting rise, while air go from one stage to other stage. He also

implies that the fluid is sent through the impeller. Because of that the impeller blades rotate

very quickly in the typical centrifugal compressor. The velocity of fluid is transformed to

pressure. Some of these processes apply in the impeller and rests of them apply the diffuser.

However more of the velocity is transformed to pressure in the diffuser. The diffuser has

specific vanes which are digressive to the impeller. Velocity is converted to pressure energy

by these vanes passage diverge (2006, p.30).This makes it clearly that although there are some

difference between axial and centrifugal compressors, their construction is almost same. The

second part is combustion area. Boyce report that the combustion occur at the primary zone.

In the combustion area, the chemical reaction is happened by natural gas which are carbon

hydrogen oxygen. Heat occur instead of reaction. End of the reaction carbon dioxide and

water are generated by reaction. This reaction is stoichiometric. The air get into combustor

two different type. One of them is straight through flow and another one is reverse flow.

While most aero-engines use the straight through flow type combustors. Most of the large

frame type units use reverse-flow. The role of circulation zone is that vaporizes, partly burn

the air coming and arrange the fuel that is used by the rest of burning zone for quickly

combustion. Theoretically all the fuel has to be burned at the end of the burning zone.

Because only task of the dilution zone is that to combine hot gas and the air which mixing at

dilution zone. When the mixture leave, The temperature and the velocity distribution of

mixture should have specific value that is accepted by guide vanes and turbine (2006, p.33).

Obviously, although the gas turbine combustors are designed various type. Whole gas turbine

combustion chamber has three main zone; recirculation zone, burning zone and dilution zone.

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Recirculation zone and burning zone can be called primary zone. The last part is turbine.

Giampaolo states that there is not differences between rotor inlet and rotor exit as pressure in

the impulse type turbine. Thus, its relative inlet velocity will not change by comparison with

the blades relative discharge velocity. The nozzle guide vanes rise the pressure and drop the

velocity which are done to form passage (2009, p.74). He also mentions that direction of flow

is changed by the nozzle guide in the reaction turbine. The convergent form of the passage

between the rotor blades overcomes the decrease in pressure and increase in velocity of gas

(2009, p.74). Taking this intro consideration one can say that mechanism of turbine is

combined by impulse turbine and reaction turbine. Consequently compressor, combustion

area and turbine generate gas turbine working principles.