Gas Turbine Technology : Flying Machine to Ground Utilities

P M V SubbaraoProfessor

Mechanical Engineering Department

A White Collar Power Generation Method…

Progress in Rankine Cycle

Year 1907 1919 1938 1950 1958 1959 1966 1973 1975

MW 5 20 30 60 120 200 500 660 1300

p,MPa 1.3 1.4 4.1 6.2 10.3 16.2 15.9 15.9 24.1

Th oC 260 316 454 482 538 566 566 565 538

Tr oC -- -- -- -- 538 538 566 565 538

FHW -- 2 3 4 6 6 7 8 8

Pc,kPa 13.5 5.1 4.5 3.4 3.7 3.7 4.4 5.4 5.1

,% -- ~17 27.6 30.5 35.6 37.5 39.8 39.5 40

The most Unwanted Characteristic of Rankine Group of Power Generation Systems

• The amount of cooling required by any steam-cycle power plant is determined by its thermal efficiency. 

• It has nothing essentially to do with whether it is fuelled by coal, gas or uranium. 

• Where availability of cooling water is limited, cooling does not need to be a constraint on new generating capacity. 

• Alternative cooling options are available at slightly higher cost.

• Nuclear power plants have greater flexibility in location than coal-fired plants due to fuel logistics, giving them more potential for their siting to be determined by cooling considerations.

Cooling Problems !!!!

• The bigger the temperature difference between the internal heat source and the external environment where the surplus heat is dumped, the more efficient is the process in achieving mechanical work. 

• The desirability of having a high temperature internally and a low temperature environmentally. 

• In a coal-fired or conventionally gas-fired plant it is possible to run the internal boilers at higher temperatures than those with finely-engineered nuclear fuel assemblies which must avoid damage. 

• The external consideration gives rise to desirably siting power plants alongside very cold water.

Steam Cycle Heat Transfer

• For the heat transfer function the water is circulated continuously in a closed loop steam cycle and hardly any is lost. 

• The water needs to be clean and fairly pure.

• This function is much the same whether the power plant is nuclear, coal-fired, or conventionally gas-fired. 

• Cooling to condense the steam and surplus heat discharge.

• The second function for water in such a power plant is to cool the system so as to condense the low-pressure steam and recycle it. 

• This is a major consideration in siting power plants, and in the UK siting study in 2009 all recommendations were for sites within 2 km of abundant water - sea or estuary.

Water, Water & Water ….!!!!!

• A nuclear or coal plant running at 33% thermal efficiency will need to dump about 14% more heat than one at 36% efficiency. 

• Nuclear plants currently being built have about 34-36% thermal efficiency, depending on site (especially water temperature). 

• Older ones are often only 32-33% efficient.  

• The relatively new Stanwell coal-fired plant in Queensland runs at 36%, but some new coal-fired plants approach 40% and one of the new nuclear reactors claims 39%.

History & Repetition• 1791: A patent was given to John Barber, an Englishman,

for the first true gas turbine. • His invention had most of the elements present in the

modern day gas turbines. • The turbine was designed to power a horseless carriage. • 1872: The first true gas turbine engine was designed by Dr

Franz Stikze, but the engine never ran under its own power.

• 1903: A Norwegian, Ægidius Elling, was able to build the first gas turbine that was able to produce more power than needed to run its own components, which was considered an achievement in a time when knowledge about aerodynamics was limited.

• Using rotary compressors and turbines it produced 11 hp (massive for those days).

• He further developed the concept, and by 1912 he had developed a gas turbine system with separate turbine unit and compressor in series, a combination that is now common.

• 1914: Application for a gas turbine engine filed by Charles Curtis.

• 1918: One of the leading gas turbine manufacturers of today, General Electric, started their gas turbine division.

• 1920: The practical theory of gas flow through passages was developed into the more formal (and applicable to turbines) theory of gas flow past airfoils by Dr A. A. Griffith.

• 1930: Sir Frank Whittle patented the design for a gas turbine for jet propulsion.

THE WORLD‘S FIRST INDUSTRIAL GAS TURBINE SET – GT NEUCHÂTEL

4 MW GT for Power Generation

First turbojet-powered aircraft – Ohain’s engine on He 178

The world’s first aircraft to fly purely on turbojet power, the Heinkel He 178.

Its first true flight was on 27 August, 1939.

Steam Turbine Vs Gas Turbine : Power Generation• Experience gained from a large number of exhaust-gas turbines for

diesel engines, a temp. of 538°C was considered absolutely safe for uncooled heat resisting steel turbine blades.

• This would result in obtainable outputs of 2000-8000 KW with compressor turbine efficiencies of 73-75%, and an overall cycle efficiency of 17-18%.

• First Gas turbine electro locomotive 2500 HP ordered from BBC by Swiss Federal Railways

• The advent of high pressure and temperature steam turbine with regenerative heating of the condensate and air pre-heating, resulted in coupling efficiencies of approx. 25%.

• The gas turbine having been considered competitive with steam turbine plant of 18% which was considered not quite satisfactory.

• The Gas turbine was unable to compete with “modern” base load steam turbines of 25% efficiency.

• There was a continuous development in steam power plant which led to increase of Power Generation Efficiencies of 35%+

• This hard reality required consideration of a different application for the gas turbine.

Anatomy of A Jet Engine

1 2 34 5 6

Variation of Jet Technologies

Thermal Energy Distribution

Ideal Jet Cycles

T0

2

3

4

5

Direction

1

6j

TurboJet

6f 7f

6p 7p

Turbofan

Turboprop

~1970sAero Rejected Engines & Aero Derivative Engines

Brayton Cycle

1-2 Isentropic compression (in a compressor)

2-3 Constant pressure heat addition

3-4 Isentropic expansion (in a turbine)

4-1 Constant pressure heat rejection

pv & Ts diagrams

SSSF Analysis of Control Volumes Making a Brayton Cycle:

CV

outin

CV WgzV

hmgzV

hmQ

22

22

CV

outin

wgzV

hgzV

hqCV

22

22

Specific Energy equation of SSSF :

No Change in potential energy across any CV

CVoutin whhqCV

,0,0

Calorically perfect and Ideal Gas as working fluid.

CVoutpinp wTCTCqCV

,0,0

)( 010212 TTchhw pcomp 1 –2 : Specific work input :

2 – 3 : Specific heat input :

3 – 4 : Specific work output :

4 – 1 : Specific heat rejection :

)( 020323 TTchhq pin

)( 040343 TTchhw ptur

)( 010414 TTchhq pout

Isentropic Processes:

1

01

02

01

02

T

T

p

p 1

04

03

04

03

T

T

p

p

01040203 & pppp Constant Stagnation Pressure Processes:

1

04

031

01

02

04

03

01

020

T

T

T

T

p

p

p

pr p

01

1

00102

TrTT p

0

031

0

0304

T

r

TT

p

)()( 01020403

01020403

TTTTc

hhhhwww

p

compturnet

)1(1

)()(

0010

003

010103

03

TTc

TTT

Tcw

p

pnet

)( 0103

0103

T

TTTcw pnet

)( 010030203 TTchhq pin

)(

0103

010

0301003

TTc

TT

TTc

q

w

p

p

in

netth

11

11

10

0

pin

netth

rq

w

11

10

0

p

th

r

010030

001

0

030

0010

003

1)1(

)1(1

TTcTT

c

TTcw

pp

pnet

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 10 20 30

th

pr0

Pressure Ratio Vs Efficiency

netw

pr0

Pressure Ratio Vs Specific Workoutput

0

0.2

0.4

0.6

0.8

0 10 20 30Pressure ratio

th

wnet

0

0.2

0.4

0.6

0.8

0 10 20 30Pressure ratio

1872, Dr Franz Stikze’s Paradox