How Gas Turbine Engine Works

HOW GAS TURBINE ENGINE WORKS

Indra Yudhipratama XI-KI

Introduction

Most commercial jets are powered by turbofan engines, and turbofans are one example of gas turbine engines.You may have never heard of gas turbine engines, but they are used in all kinds of un expected places.

Types of Turbine

There are many different kinds of turbines:

Steam turbine. The steam runs through a huge and very carefully designed multi-stage turbine to spin an output shaft that drives the plant's generator.

Hydroelectric dams use water turbines in the same way to generate power. This turbines look completely different from a steam turbine because water is so much denser (and slower moving) than steam, but it is the same principle.

Wind turbines, also known as wind mills, use the wind as their motive force. A wind turbine looks nothing like a steam turbine or a water turbine because wind is slow moving and very light, but again, the principle is the same.

A gas turbine is using the same concept. In all modern gas turbine engines, the engine produces its own pressurized gas, and it does this by burning something like propane, natural gas, kerosene or jet fuel. The heat that comes from burning the fuel expands air, and the high-speed rush of this hot air spins the turbine.

Part of Gas Turbine Engine

Gas turbine engines are, theoretically, extremely simple. They have three parts: Compressor - Compresses the incoming air to high pressure Combustion area - Burns the fuel and produces high-pressure, high-velocity

gas Turbine - Extracts the energy from the high-pressure, high-velocity gas flowing

from the combustion chamber

Compressor

The compressor is basically a cone-shaped cylinder with small fan blades attached in rows. Assuming the light blue represents air at normal air pressure, then as the air is forced through the compression stage its pressure rises significantly. The high-pressure air produced by the compressor is shown in dark blue.

RR

AA

DD

II

AA

L L

FF

LL

OO

WW

AXIAL

FLOW

Axial vs. Radial Axial

Advantages:simple and

inexpensivelight weight

Disadvantages:less efficientlarge frontal arealimited

compression ratio (4:1 ratio)

• RadialRadial– Advantages:Advantages:

•efficientefficient•high high

compression compression ratios (20:1)ratios (20:1)

– Disadvantages:Disadvantages:•complexcomplex•expensiveexpensive

GTE AIRCompressed Air Distribution:

– Primary Air - 30% of the compressed air is supplied directly to the combustion chamber

– Secondary Air - 65% of the air provides cooling for the combustion chamber

– Film Cooling Air - 5% of the air provides cooling directly to the turbine blades

Combustion Area

The high-pressure air then enters the combustion area, where a ring of fuel injectors injects a steady stream of fuel. The special piece that located in combustion area called a "flame holder," or sometimes a "can." The can is a hollow, perforated piece of heavy metal. The injectors are at the right. Compressed air enters through the perforations. Exhaust gases exit at the left.

Turbine

At the far left is a final turbine stage, shown here with a single set of vanes. It drives the output shaft. This final turbine stage and the output shaft are a completely stand-alone, freewheeling unit. They spin freely without any connection to the rest of the engine. And that is the amazing part about a gas turbine engine.

Gas Turbine Cycle

The cycle usually describes the relationship between the space occupied by the air in the system. The Brayton cycle (1876), shown in graphic form as a pressure-volume diagram, is a representation of the properties of a fixed amount of air as it passes through a gas turbine in operation.

Advantages of Gas Turbine Engines

There are two big advantages of the turbine over the diesel:

Gas turbine engines have a great power-to-weight ratio compared to reciprocating engines. That is, the amount of power you get out of the engine compared to the weight of the engine itself is very good.

Gas turbine engines are smaller than their reciprocating counterparts of the same power.

Disadvantages of Gas Turbine Engines

The main disadvantage of gas turbines is that, compared to a reciprocating engine of the same size,

They are expensive Tend to use more fuel when they are

idling They prefer a constant rather than a

fluctuating load.

Airplane

What is the Goal of Gas Turbine Engine in Aircraft The goal of a turbofan engine is to

produce thrust. Generated under Newton's Third

Law. Generally measured in pounds in

the United States.

How Thrust can be Produce?

http://www.grc.nasa.gov/WWW/K-12/airplane/ngnsim.html

Engine PerformancePress. (psi)

0

50

100

150

1 2 3 4 5 6 7 8

Press (psi)

Engine PerformanceTemp. (R)

0

500

1000

1500

2000

2500

3000

1 2 3 4 5 6 7 8

Temp (R)

GENX

The GEnx is expected to produce thrust from 53,000 to 75,000 lbf (240 to 330 kN). Boeing predicts reduced fuel consumption of up to 20%.

Type Turbofan

Manufacturer GE Aviation

First run 2000s

Major applications

Boeing 747-8Boeing 787

Developed from

General Electric GE90

CCGT Power Plant

The Combined Cycle power plant is a combination of a fuel-fired turbine with a Heat Recovery Steam Generator (HRSG) and a steam powered turbine. These plants are very large, typically rated in the hundreds of mega-watts.Depending on the power requirements at the time, the combined cycle plant may operate only the fired turbine and divert the exhaust.

M-1 Tank

EngineHoneywell AGT1500C

multi-fuel turbine engine1,500 hp (1,119 kW)

Power/weight 24.5 hp/metric ton

Transmission Allison DDA X-1100-3B

Fuel capacity 500 gal (1,892 liters)

Operationalrange

289 mi (465.29 km)

With NBC system: 279 mi (449.19 km)

SpeedRoad: 42 mph (67.7 km/h)

Off-road: 30 mph (48.3 km/h)

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