Gas Turbine Technology

Ashish KumarMDS12M002

CONTENT:Introduction Basic structure and parts Working mechanism Types ApplicationRole in Power sector Performance variablesReference

INTRODUCTION

Type of internal combustion engine

Uses air as the working fluid

Basic Structure

Turbine

3 stages Impulse Type

Combustor

10 cansReverse Flow Type

Compressor

17 stagesAxial Type

Working Cycle • Brayton cycle is the ideal cycle for gas-turbine

T

P= Const.

1

2

3

4

QH

QL

1-2isentropic compression (in compressor) 2-3 const. pressure heat-addition (in combustion chamber) 3-4 isentropic expansion (in turbine) 4-1 const. pressure heat rejection (exhaust)

s

Combustion chamber Fan – low pressurecompressor

6 stage high pressurecompressor

8 stage intermediate pressure compressor

Inlet system

Compressor Compressor used in gas turbine is Axial –Flow typeAxial-flow compressors are dynamic rotating compressors that use arrays of fan-like airfoils to progressively compress the working fluid

Axial Compressor

• Modern Compressor Designs are Extremely Efficient gas turbine

performance rating depends greatly on the compressor efficiency

• High Performance Made Possible by Advanced Aerodynamics, Coatings, and Small Blade Tip Clearances

• Even Small Amounts of Deposits on Compressor Blades May Cause Large Performance Losses

Inlet Guide Vane

Rotor Blades(rotating)

Stator Vanes (fixed to case)

Combustor

Air Flow in Combustor

Combustion air, with the help of swirler vanes, flows in around the fuel nozzle and mixes with the fuel. This air is called primary air and represents approximately 25 percent of total air ingested by the engine. The fuel-air mixture by weight is roughly 15 parts of air to 1 part of fuel. The remaining 75 percent of the air is used to form an air blanket around the burning gases and to lower the temperature.

1

2

3 57

The Turbine

• Two Basic Types - Radial and Axial– Almost all industrial Gas Turbines use axial flow

turbines• Like the Compressor, Turbine Expansion

Takes Place in “Stages”– a row of stationary blades (nozzles)

followed by a row of moving blades= one stage.

Axial Turbine

Two Stage Axial Turbine

rotation

Rotor Blade

Nozzle

rotation

Rotor Blade

Nozzle

• First Stage Turbine Nozzle Sees the Hottest Temperatures

– Referred to as TIT (Turbine Inlet Temperature) or TRIT (Turbine Rotor Inlet Temperature)

– Modern engines run TRIT as high as 1500C (some even higher)

Turbine moduleThe axial flow turbine consists of stages, each made up primarily of a set of stationary vanes followed by a row of rotating blades,Typically modern aircraft gas turbine blades have both impulse and reaction sections.

Exhaust System Must perform four function

Reduce noise to the atmosphere

Hot gases away from personnel

Minimize backpressure to gas turbines

Mechanically well during extreme

temperature changes.

Types

Shaft power gas turbines: is a gas turbine

whose goal is mainly to deliver shaft power

Jet engine gas turbines: is a turbine whose

goal is mainly to deliver thrust

Application

Application

Plant Application

Cogeneration Power Plant

Combined Cycle Power Plant

Cogeneration Power Plant

H-25 Power Output40,500 kWOverall EfficiencyMore than80 %

Steam

Generator H-25 Gas TurbineHRSG

Air

Fuel

Water

H-25 Cogeneration – Steam Production

Typical Steam Production Quantity for H-25 Co-generation System (H-25 Uprate)

Co-generation system with HRSG provides 55-70 ton/hr steam

UNFIRED Steam Production

HRSG Inlet Temp. 562C

FIRED Steam Production

HRSG Inlet Temp. 700C

45

55

65

75

85

2 4 6

Steam Pressure (MPa.a)

8

Ste

am F

low

(t

/h)

UNFIRED Steam Production

500C

450C

400C

350C

300C250C

Saturated

70

80

90

100

110

120

2 4 6

Steam Pressure (MPa.a)

8

Ste

am F

low

(t

/h)

FIRED Steam Production

23Doc No. : GKKP-13-009 Rev.0 © Hitachi, Ltd. 2013. All rights reserved.

450C

500C

400C

350C

300C

250C

Saturated

H-25 Combined Cycle (2-2-1)

Typical Performance (2xH-25 + 2xHRSG + 1 Steam Turbine)

System Configuration

Performance

(Typical)

Fuel

Air

Steam Turbine

Generator

HRSGH-25 Gas Turbine& Generator

Condenser

Fue

l Air

24Doc No. : GKKP-13-009 Rev.0 © Hitachi, Ltd. 2013. All rights reserved.

H-25 H-25 Uprate

Total Plant Output 87, 800 kW 115,900 kW

Gas Turbine Output 29,730 kW x 2 40,500 kW x 2

Steam Turbine Output 28,340 kW 34,900 kW

Gross Efficiency 50.3 % 51.9 %

Performance variables

Environmental factor Material FactorOperation FactorFuelExhaust Temp.

Environmental Variables

Ambient Temp.Ambient pressureRelative Humidity

Ambient Temp.

Turbine Performance is changed by anything that affects the density and mass flow of the air intake to the compressor

Ref. GE3567H

Ambient Pressure

The air density Reduces as the site elevation increaseResult airflow and output decrease

Relative humidity

Material Factor

Turbine exhaust Temp is limited by material conditionAs we get higher efficiency when we increase in firing temp. result in increase in exhaust tempTill now maximum exhaust temp limit is 582 c

Efficiency at Part Load Operation

Gas Turbine Thermal Efficiency/ref versus Load P/Pmax

(Typical, for 3 arbitrarily selected industrial engines)

110

100

90

80

70

60

50

50 60 70 80 90 100

Load (%)

Re

l. T

he

rma

l E

ffic

ien

cy

(%

)

Operational factor

Fuel

Fuel heating

Heated fuel result in higher turbine efficiency due to the reduced fuel flow required to raise the total gas temp to firing temp.The source of heat for the fuel typically is IP feedwater Since use of this energy in the gas turbine fuel heating system is thermodynamically advantageous Combined efficiency is improved by approximately 0.6%

Base Load, Peak Load and Stand-By Units

• Engine Life depends on Firing Temperature (and number of starts*)

– Thus, a peak load unit can be fired at higher

temperatures without any design changes

– Higher Firing Temperature means more

power, but shorter engine life.

* According to some manufacturers

Advantages of gas turbine engines

Very high power-to-weight ratio, compared to reciprocating engines;Moves in one direction only, with far less vibration than a reciprocating engine.Fewer moving parts than reciprocating engines.Waste heat is dissipated almost entirely in the exhaust. This results in a high temperature exhaust stream that is very usable for boiling water in a combined cycle, or for cogeneration.

Low operating pressures.

High operation speeds.

Low lubricating oil cost and consumption.

Can run on a wide variety of fuels.

Disadvantages of gas turbine engines

Cost is much greater than for a similar-sized reciprocating engine since the materials must be stronger and more heat resistant. Machining operations are also more complexUsually less efficient than reciprocating engines, especially at idleLonger start up than reciprocating enginesDelayed response to changes in power settings.

Some Manufacturer

• Caterpillar PowerGeneration Systems• Electro-Motive Diesel Inc.• GE Gas Engines • Hyundai Heavy Industries Co. LtdMitsubishi Heavy Industries Ltd.• MWMRolls-RoyceHitachi Ltd.Toshiba Ltd.

Reference

Wikipedia GE Ref. Documents 6567, 3567Hitachi Gas turbine Catalog