introduction to gt &ccpp

8/3/2019 Introduction to GT &CCPP

http://slidepdf.com/reader/full/introduction-to-gt-ccpp 1/84

IntroductionTo

GT & CCPP



Simple Gas Turbine Plant



Thermodynamic Process

Compression

Constant pressure heat addition

Expansion

Constant pressure Heat Rejection



BRAYTON CYCLE

P

RE

S

S

U

R

E

VOLUME

SUCK

BURN

SQUEEZE BLOW



COMPRESSOR

VOLUME

BRAYTON CYCLE

P

R

E

S

S

UR

E

COMBUSTOR

TURBINE



Brayton Cycle



Brayton Cycle

Eff t f T bi Effi i &



Effect of Turbine Efficiency & pressure

ratio on Thermal efficiency



Effect of pressure ratio & Temperature

ratio on Efficiency



Effect of Pressure ratio on Efficiency



Energy Losses In Gas Turbine



They are more compact

They can be started and take more

load quickly

They are simpler in design and

easy maintenance

Merits



They consume less metal other materials for the same capacity

They cost less.

They require almost no water for cooling.

Man power is 25% of theconventional coal based plants.

Merits



Land requirement is less than30%

Availability is as high as 90%

Low gestation period.

The pollution is less

Merits



They have a low specific power

They have the lower efficiency at the

modern state of progress

They have a shorter service life

They are more sensitive to fuel

quality

Demerits



High cost of spare parts

High fuel cost-very volatile in case of liquid fuel

High generation cost

Demerits



Energy Losses CC Concept



Gas turbine plus Unfired steam

generator

Gas turbine plus supplementary

fired steam generator

Gas turbine plus furnace fired

steam generator



Supercharged furnace fired steam

generator plus gas turbine

Integrated coal Gasification and

combined cycle Power plant

Diesel engine based combined

cycle



Generally steam pressures are limited

to 60 ata. And SH temperatures limited

to 420/480

Gas turbine output will be 60-75%

Steam turbine output 30-35%

Net plant heat rate is in the order of

2500-2800 Kcal/kwh



The flue gas temperature isincreased to 940

Steam generation can be doubledthat of an Unfired waste heat

recovery boiler Steam turbine and gas turbine

will be sharing the output equally

Net plant heat rate is 2250-2500Kcal/kwh



Majority of the fuel is fired in the

steam generator

70-85 % of the plant load can bemet by the steam turbines

Increase in thermal efficiency 4-5%

Heat rate in the order of 2300Kcal/Kwh



• Plant heat rate is in the order of 2250-2500Kcal/kwh

• Heat transfer co efficients are

significantly improved



•Single shaft system

•Multi shaft system



Modifications -Basic Cycle

Increase in power output

Increase in combustion

turbine efficiency



By increasing the mass flow

through the turbine

Recovering heat from the

waste gas Reducing compressor work

Increasing the averagetemperature of the heat source



• Evaporative cooling cycle

• Recuperative cycle

• Intercooled cycle

• Humid air turbine cycle

• Steam Injected cycle



• Reheat cycle

• Intercooled steam injectedcycle

•Intercooled reheat steaminjected cycle

•

Intercooled reheat chemicallyrecuperated cycle



Radial Flow



t if l



centrifualcompressor

Have an appreciably shorter length, Since the

pressure ratio attainable in a single stage is

B=4.5.(High pressure ratio per stage) They are simpler in design and easy to

manufacture thus leads to lower cost.

Under all operating conditions, more reliable

in operation. Centrifugal compressor is rugged in

construction and is less susceptible to the effects

of deposits left on the flow passages by the air.

centrif alcompressor



centrifualcompressor

They are less sensitive to the fouling of

the flow path Maintains good efficiency over a wide

range of operations. (Their efficiency drops

down less strongly in off rated-regimes.With a low volume discharge of air, acentrifugal compressor often turns out to bemore efficient, since the efficiency of an

axial compressor reduces substantially insuch cases owing to increasing lossesassociated with the low height of blading.)



Axial Flow



Axial Flow Compressor



A high delivery, upto 430-450 kg/s or

even more.

The highest efficiency possible incompressor is 83-90%. A high compressor pressure ratio due

to many stages with low losses as required for gas-

turbine plants. Small transverse dimensions (Low

cross sectional area) even with a high delivery.



Axial compressors are having alarge number of stages and hence asophisticated design and appreciable lengthsince pressure ratio of single stage does notexceed 1.25. Has narrower operating range for good

efficiency. Higher weight and higher cost. • Starting power can be high.



Film Cooling



1. Directionally solidified

2. Single crystal

3. Normal Casting

1

2 3

introduction to gt &ccpp

Documents