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UNIVERSITY OF WEST BOHEMIAFACULTY OF MECHANICAL ENGINEERING

DEPARTMENT OF POWER SYSTEM ENGINEERING

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JET ENGINESJET ENGINES

GAS TURBINESSGAS TURBINESS

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INTRODUCTION

In turbines is converted heat and pressureenergy to kinetic energy and mechanical workwith very high efficiency

The conversion is provided in stator and rotorcanals

In stator vanes is converted heat and pressure

energy to kinetic energy In rotor blades is converted heat and pressure

energy to kinetic energy and mechanical work

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INTRODUCTION

Obtained performance on turbines is exploitedfor compressor and assembly drive. In case ofturboshaft engines, performance is also used

for propeller or rotor drive. Ground power unit use converted energy for

drive of electric generators or compressors andmany types of equipments.

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INTRODUCTION

REQUIREMENTS

High performance

High reliability

High lifetime

High efficiency

Minimal weight and dimensions Simple construction and maintenance

Low price

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GAS TURBINE TYPES

TYPES BY DIRECTION OF FLOW

Radial

Centrifugal

Centripetal

Axial

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GAS TURBINE TYPES

Fig. Centrifugal and centripetal gas turbine

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GAS TURBINE TYPES

Fig. Parts of centripetal gas turbine

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GAS TURBINE TYPES

Fig. Engine with centrifugal compressor and centripetal turbine

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GAS TURBINE TYPES

TYPES BY INLET FLOW FIELD

Turbines with homogeneous inlet flow field

Turbines with non-homogeneous inlet flow field

Fig. Turbines with homogeneous and non-homogeneousinlet flow field

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GAS TURBINE TYPES

TYPES BY NUMER OF STAGES

Single stage

Dual stage

Triple stage

Multi stage

TYPES BY NUMBER OF SPOOLS

Single spool turbines

Dual spool turbines

Triple spool turbines

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GAS TURBINE TYPES

Fig. Single stage axial gas turbine

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GAS TURBINE TYPES

Fig. Dual stage axial gas turbine

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GAS TURBINE TYPES

Fig. Triple stage axial gas turbine

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GAS TURBINE TYPES

Fig. Multi (4) stage axial gas turbine2 stages for compressor drive

2 stages for propeller drive

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GAS TURBINE TYPES

Fig. Multi (8) stage axial gas turbine

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GAS TURBINE TYPES

TYPES BY REACTION OF STAGE

Impulse stage

Impulse/Reaction (Reaction) stage

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GAS TURBINE TYPES

Fig. Impulse and reaction stage

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BASIC PARAMETERS

Flow rate

Depends on construciton 0,5-300kg.s -1

Thermal gradient

Max. 30kJ.kg-1on one stage

Temperature before turbine

Non-cooled turbines max. 1000C Cooled turbines 1200C and more

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BASIC PARAMETERS

Fig. Evolution of temperature parameters

years

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BASIC PARAMETERS

RPM (Revolutions per minute)

Depends on construction 5-90.103 min-1

Reliability

Means reliability of blades. At present days in modern enginesits approximately 10000 hours.

Efficiency

Single stage turbines 0,82-0,90

Multi stage turbines 0,88-0,94Cooling air

Depend on intensity of cooling (approximately 5% from flowrate)

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BASIC PARAMETERS

Fig. Dependence of efficiency on flow rate

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TURBINE STAGE

Fig. Elementary turbine stage

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TURBINE STAGE

Fig. Impulse turbine stage

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TURBINE STAGE

Fig. Reaction turbine stage

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TURBINE STAGE

Forces on rotor blade are created by:

Aerodynamic forces created by fluid aroundblades (impulse action of gases)

Reaction action of gases in convergent rotorblades canal where are gases accelerated

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TURBINE STAGE

Fig. Reaction turbine stage

c3

,c

3

c3150m.s

1

c4= u4 w4

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TURBINE STAGE

Work transferred to blades of elementary stagefrom 1kg of gas

From Euler equation:

We , st=u '3 . c3' uu4 . c4u[J.kg1

]

since c4u

0

We , st=u '3 . c3' uu4 . c4u[J.kg1

]

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TURBINE STAGE

Fig. Velocity triangles on elementary turbine reaction stage

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TURBINE STAGE

Fig. Ideal and real expansion on turbine stage in T-s diagram

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TURBINE STAGE

Fig. Real expansion on turbine stage in p-V and T-s diagramshows static and total parameters

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TURBINE STAGE

Work on turbine stage

Efficiency of turbine stage

We ,st=cp. T3tT4t [J.kg1

]

Wad ,st=c p. T3tT4t , ad [J.kg1]

st=We ,st

Wad , st

[1] st=T

3tT

4t

T3tT4t, ad

[1]

st=0.830.89

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TURBINE STAGE

Efficiency of multistage turbines is higher thanefficiency of every single stage (in compressorthat's NOT true)

Efficiency of multistage turbines is 0.88-094 Efficiency increasing by number of turbine

stages WHY?

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TURBINE STAGE

Efficiency of multistage turbines is higher thanefficiency of every single stage (in compressorthat's NOT true)

Efficiency of multistage turbines is 0.88-094 Efficiency increasing by number of turbine

stages WHY?

Lower velocity of gases as in single stage Losses from stage before are exploited in the next

one

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TURBINE STAGE

Reaction of elementary stage

Is ratio of adiabatic static work of rotor andadiabatic static work of elementary stage

=hR

H[1]

01

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TURBINE STAGE

Fig. Impulse and reaction turbine in T-s diagrams

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LOSSES IN GAS TURBINE

Profile losses

in stator and rotor as well

These losses are generated as soon as gas

fluid around vanes/blades. Friction losses (boundary layer)

Shock phenomenas

Wakes (high angle of atack) Profile losses are higher in rotor

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Secondary losses

Generated by pair-wakes (induced drag)

Losses in redial spaces between rotor blade

and turbine case

Other losses

Losses in bearings

Friction of disks

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Fig. Losses in rotor blade

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BLADE GEOMETRY

Characteristic shape of rotor blade is the longitudinalshape

In elementary stage is determined in the middle diameter( by flow equation )

The real flow is spatial. The peripheral speed is increasefrom rotor root to rotor tip. Absolute velocity and pressurechanged as well. All of these parameters are connected

The real flow is spatial, compressible, viscous and

non-stationary

GEOMETRY of blade must accepted these facts

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BLADE GEOMETRY

Fig. Geometric solution of rotor blade construction

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BLADE GEOMETRY

Fig. Reaction rotor blade construction

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BLADE GEOMETRY

Fig. Creating rotor back with lemniscate

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BLADE GEOMETRY

Fig. Creating a impulse rotor blade

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MULTISTAGE GAS TURBINE

Created by compiling of turbine stages in a row

Modern engines used 6 and more stageturbines because:

There are high thermal gradients Higher efficiency

Better collaboration with compressor ( biggerdiameter lower RPM )

Smooth shape of engine

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Fig. Shape of overflow canal

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Fig. Parameters through the multistage impulse turbine

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Fig. Thermal gradient distribution on multistage turbine

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TURBINE CHARACTERISTIC

Fig. Gas turbine characteristic

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TURBINE CHARACTERISTIC

Fig. Gas turbine characteristic

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STATOR VANES

Fig. Tubular stator vanes

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STATOR VANES

Fig. Stator vanes

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ROTOR BLADES

Fig. Turbine rotor blades

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ROTOR BLADES

Fig. Turbine double-rotor blades

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ROTOR BLADES

Fig. Turbine double-floor rotor blades

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Fig. Double-stage gas turbine

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Fig. Scheme of double-stage gas turbine

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Fig. Double-stage gas turbine

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Fig. 'Free' gas turbine

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Fig. Triple-stage gas turbine

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Fig. Four-stage gas turbine

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GAS TURBINE COOLING

Fig. Thermal and mechanical load blades

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GAS TURBINE COOLING

Fig. Rotor blade damaged by thermal load

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GAS TURBINE COOLING

Fig. Stator vanes damaged by thermal load

Thermal damage of pressure sideof stator blade

Cracks on cooledstator blade

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GAS TURBINE COOLING

Fig. Evolution of temperature increasingin depends on used material

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GAS TURBINE COOLING

Sources of cooling

Air from fan

Air from low pressure compressor

Air from secondary flow on CC

Air from secondary flow ( turbofan engines )

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GAS TURBINE COOLING

Fig. Turbine cooling

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GAS TURBINE COOLING

Fig. Multi-stage turbine cooling

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GAS TURBINE COOLING

Fig. Distribution of cooling air in turbine stage

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BLADES COOLING

Methods of blade cooling Convective ( Internal cooling )

Film cooling

Transpiration cooling

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BLADES COOLING

Film cooling Cooling is provided

with cooling air, which

is delivered throughthe holes on the bladesurface.

Cooling with air film is

more efficient asconvective cooling

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BLADES COOLING

Transpiration cooling Transpiration cooling is similar technique of

cooling as cooling with air film.

In this case is generated a homogeneoussurface of cooling air on surface of blade

Transpirationally cooled blades have no holes.

Air flow through the porous surface of blade.

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BLADES LOAD

Fig. Turbine rotor blades load

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REFERENCES

Otis, Vosbury: Aircraft gas turbine powerplants Jeppesen: 2002

Rolls royce The jet engine, 1996

Hanus D., Marlek J, : Studijn modul 15,Turbnov motor, CERM, s.r.o. Brno 2004

Kadrnoka J.: Tepeln turbny a

turbokompresory, CERM, s.r.o. Brno 2004

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DISCUSSION...

...QUESTIONS

08 turbines

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