Post on 06-May-2015
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