Module 4 Reaction Turbines: Kaplan Turbine. Module 4 Reaction Turbines: Kaplan Turbine....

Module 4

Reaction Turbines: Kaplan Turbine.

Introduction.

Radial : At entrance to runner blade, velocity has primarily radial component.

Eg: Old Francis turbines.

Mixed : At entrance to runner blade, velocity has a radial as well as axial component.

Eg: Modern Francis Turbines

Axial: At entrance to runner blade, velocity has primarily an axial component.

Eg: Kaplan and propeller turbines.

Classification of Reaction Turbines: Radial, Mixed and Axial

RadialAxial

Kaplan Turbine Schematic

Spiral casing

Guide Vane

Kaplan Runner

Draft tube

Hub

Kaplan Turbine - Photo

Kaplan Runner

Hub

Kaplan Turbine – Horizontal Installation

Kaplan Runner

Hub

Kaplan Turbine Versus Propeller turbine

Propeller turbine

Kaplan turbine: Propeller turbine with variable pitch (adjustable) propeller blades

The Kaplan turbine has runner blades that can be adjusted to run at maximum efficiency for various head (H) and flow (Q) conditions. Propeller turbines have fixed blades

Kaplan Turbine Schematic

Generator

Guide Vane

Kaplan Runner

Draft tube

Runner hub

Reaction Turbine Schematic

Francis Turbine Kaplan Turbine

Path of a water particle

1 2

Kaplan turbine - Points to remember

1. Peripheral velocites at inlet and exit, and equal.

; Since inlet and exit of a particle of water is60

at the same radius or equivalently the same diamete

u u

DNu

1 2

2 2 31

1

r D,

2.Flow velocities are assumed same at inlet and exit.

3. Flow through the turbine is Q= m /s4

where is the runner outer diameter, is the runner hub diameter

and is the flow v

o h f

o h

f

u u

D D V

D D

V

elocity at inlet.

Kaplan Turbine Runner

Path of a water particle

oDhD

Kaplan Turbine – Problem p1

2u

2fV2r

2rV

1u 1wV

1rV 1fV1V

1a 1r

3 2

3

Step 1 : Find flow rate through turbine

Shaft Power 11772 kW0.84

Water Horse Power1000

11772 kW

1000 kg/m 9.81 m/s 20 m

1000

71.428 m /s

o gQH

Q

Q

2V

A Kaplan turbine working under a head of 20 m develops 11772 kW shaft power. Outer

and hub diameters of the runner are 3.5 m and 1.75 m. Guide blade angle at extreme edge

of runner is 35 . Hydraulic an d overall efficiencies are respectively 88% and 84 % . If

velocity of whirl is 0 at outlet determine 1) Runner vane angles at inlet and exit at extreme

edge of runner 2) Speed of turbine.


2u

2fV2r

u2rV

1u 1wV

1rV 1fV1V

u

1a 1r

1

3 2 21

3

12 22 2

Step 2 : Find flow velocity at inlet

71.428 m /s4

71.428 m /s

3.5 m 1.75 m4 4

9.9 m/s

f

o h f

f

o h

V

Q D D V

QV

D D

Guide blade angle Angle made by fluid

absolute velocity to runner peripheral

velocity







2u

2fV2r

u2rV

1u 1wV

1rV 1fV1V

u

1a 1r



velocity






1

11

1

11

Step 3 : Find whirl velocity at inlet

from inlet velocity triangle.

tan tan 35

9.9 m/s14.14 m/s

tan 35 tan 35

w

fa

w

fw

V

V

V

VV


2u

2fV2r

u2rV

1u 1wV

1rV 1fV1V

u

1a 1r



velocity






1

11 12

1

Step 4 : Find peripheral vel at inlet

14.14 m/s0.88

9.81 m/s 20 m

12.21 m/s

wh

u

uV u

gH

u

1 1 2Runner PowerHydraulic Efficiency =

Water power

w wm V u V

0

2

1 1 2w w

u

QH

Q V u V

0

21 1w

u V u

gQH gH


2u

2fV2r

u2rV

1u 1wV

1rV 1fV1V

u

1a 1r

1

11

1 1

1

Step 5 : Runner vane angle at inlet

9.9 m/stan

14.14 m/s 12.21 m/s

78.97

r

fr

w

r

V

V u







2u

2fV2r

u2rV

1u 1wV

1rV 1fV1V

u

1a 1r

2

1 2 1 2

2 12

2 1

1

Step 6 : Find vane angle at outlet

For Kaplan turbine and

9.9 m/stan

12.21 m/s

39.035

r

f f

f fr

r

u u V V

V V

u u







2u

2fV2r

u2rV

1u 1wV

1rV 1fV1V

u

1a 1r

1

Step 7 : Find Speed Of Turbine N

3.5 m12.21 m/s =

60 6066.63 rpm

NDNu

N






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Module 4 Reaction Turbines: Kaplan Turbine. Module 4 Reaction Turbines: Kaplan Turbine....

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