of 15

• date post

12-Jun-2018
• Category

## Documents

• view

222

6

Embed Size (px)

### Transcript of impulse turbines - Pelton wheels - Website Staff turbines - Pelton wheels. Construction and...

• Dr. Ir. Harinaldi, M.EngMechanical Engineering Department

Faculty of Engineering University of Indonesia

impulse turbines -Pelton wheels

• Construction and ComponentConstruction and Component

• ConstructionConstruction

Multi Jet

Single Jet

• InstallationInstallation

• Velocity TriangleVelocity TriangleEuler Equation:

Assume no loss of relative velocity, W1 = W2

For maximum E dE/dU = 0

• Velocity TriangleVelocity TriangleIn practice :Surface friction of the bucket W2 W1

• Losses and EfficiencyLosses and EfficiencyPipeline transmission efficiency pipeline losses, hf

11

1

reservoirat availableenergy pipeline of endat energy

HH

HhH f

trans

Nozzle efficiency nozzle losses, hin

HH

HhH

hHhhH in

f

infN

'inlet nozzleat energy outlet nozzleat energy

1

1

Energy available in jet at nozzle outlet : gCH 2' 21Nozzle velocity coefficient

gHCCv 2inlet nozzleat ty jet veloci ltheoretica

outlet nozzleat ty jet veloci actual 1 2vN C

Hydraulic efficiency

gCE

HE

H 2'outlet nozzleat jet in availableenergy nsferredenergy tra

21

• Losses and EfficiencyLosses and EfficiencyOverall Efficiency

gQHP

o

inlet nozzleat availablePower turbineby the developedPower

Turbine discharge, Q

121 4

outlet nozzleat ty jet veloci actual nozzleareaCdAC

Q

d = nozzle diameter

• ExampleExampleA Pelton turbine develops 2000 kW under a head of 100 m and with an overall efficiency of 85%. The coefficient of velocity for the nozzle is 0.98. Determine: (a) The theoretical velocity of the jet ?(b) The actual velocity of the jet ?(c) The flow rate ?(d) The diameter of the nozzle

Solution:Given: P = 2000 kW; H = 100 m; o = 0.85 ; Cv= 0.98Let : d = diameter of the nozzle ; Q = discharge flow rate of the turbine

(a) The theoretical velocity of the jet

m/s 3.44)100)(81.9(22 gHCtheo

(b) The actual velocity of the jet

smCCgHCCgH

CC

theovv

v

/ 4.433.4498.02

2

1

1

• ExampleExample(c) The flow rate

smgHPQ

gQHP

o

o

/ 4.285.010081.910

10.2000 33

3

(d) The diameter of the nozzle

mC

Qd

CdACQ

265.04.43

4.244

4

1

12

1

• Design of Pelton WheelsDesign of Pelton Wheels

Pelton wheel is designed to find out the following data:1. Diameter of the wheel (D)2. Diameter of the jet (d)3. Size (i.e. width and depth) of the buckets4. Number of buckets (z)

Pelton wheel is designed with the following input:1. Head of water2. Power to be developed3. Speed of the runner

Pelton wheel is usually designed with the following assumption:1. Overall efficiency, o between 80% and 87% 2. Coefficient of velocity, Cv as 0.98 to 0.993. Ratio of peripheral velocity to the jet velocity, U/C1 as 0.43 to 0.48

• Design of Pelton WheelsDesign of Pelton WheelsSize of the buckets

16 to11

2.1 to8.0

4 to3

3 to2

dDdTdBdL

Number of the buckets (z)Theoretical :

oz 360

26.05.0cos

DRdRdR

where:

Empirical :

dDz2

15

• Characteristics CurvesCharacteristics Curves

Efficiency and jet speed ratio Efficiency vs speed at various nozzle setting

Power vs speed at various nozzle setting Variation of efficiency with load

• Load ChangesLoad ChangesIn practice :U must remain constant when the load changes to maintain maximum efficiency U/C1 must stay the same change the input of water power change in Q change in nozzle area A

Load Control : spear valve and deflector plate