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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

  • Load ChangesLoad Changes