Centrifugal Pump

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  • 8 Centrifugal Pump

    *******************

    (Performance) 1. 132.1 (5.2 ) 38.1 (1.5 ) 38.1 (1.5 ) 2. 3. 4. 5. (Weir) 6. 7. (Tachometer) Volute Guide Vane

    2

    2

    221

    2

    11

    22Z

    g

    V

    g

    pHZ

    g

    V

    g

    pP

    1

    2

    112

    2

    22

    22Z

    g

    V

    g

    pZ

    g

    V

    g

    pH P

    PH (Water Horse Power) PHQgP 3

  • kmutt | MEE362 Mechanical Engineering Laboratory II 2/2556 2

    2

    2

    22

    2Z

    g

    V

    g

    pH P

    , g

    P2

    AVQ A

    1Z (Brake Horse Power) TP2 (Torque) FRT

    R

    F

    60

    2 N

    N N 60

    T

    HQg PP

    : 1. 2. 3. 4. 5. 6. 7. ( 3000 ) 8. 9.

  • kmutt | MEE362 Mechanical Engineering Laboratory II 2/2556 3

    10. 11. 12. 3 1500 , 2000 , 2500 () 1. 2. (Brake Horse Power) 3. 4. 1, 2 3 Iso efficiency Curve 5.

    Head Coefficient, 2ND

    gHP

    Flow Coefficient, 3ND

    Q

    PUMP IN SERIES AND PARALLEL

    1.

    1.1

    1.2

    1.3 Orifice Meter

    1.4 6

    (1.3)

    1.5

  • kmutt | MEE362 Mechanical Engineering Laboratory II 2/2556 4

    2.

    2.1

    2.2 2

    2.3 2

    Orifice Meter

    2.4 6

    (2.3)

    3. 3.1

    3.2 2 3.3 2 Orifice Meter 3.4 6 (3.3)

    1. -

    2.

    -

    50 . Orifice 25.4 . Pressure Gauge

  • Laboratory Notes for:Centrifugal Pump

    Wanchai Asvapoositkul

    IntroductionThe configuration of turbomachinery can be used to interpret its

    characteristic. The axial pump is configurated to provide a high volume, low headcharacteristic whereas the radial pump is configurated to provide a comparativelylow volume and a higher head characteristic. In this study, a centrifugal pump isbxamined.

    Pump CharacteristicsA typical performance curve for variation of head with capacity at a

    constant speed is shown in Fig 1. The variation of head, capacity, and brakehorsepower with speed follows definite rules knows as affinity laws.

    Qr-nrQz n2

    z : 2H, f n ' lt - l

    H2 [n , /bhp,

    _ ( .n , ) 'bt'p, - [t]

    Head (m) Efficienry (%)

    head bhp., - - ' * - - - - - - - r :

    1 -_ \__ -+

    ' a. 4 n' ' z v

    0 2 4 6 ^ 8 1 0 1 2flow rate (mr/min)

    Fig I Centrifugal pump characteristics

    Dimensionless Group for Pump PerformanceThe conditions for kinematic similarity and dynamic similarity of the

    centrifugal machines can be represented in terms of dimensionless group.

    oCapacity coefficient: llo = -t;x NDr

    ?n

    25

    1 5

    1 0

    0

    1 0 0

    80

    OU

    40

    ZU

    n

  • Head coefficient:

    Power coefficient:

    gHl l H =

    . , tN-D-bhp

    rrD - -------:----;'

    PN,D,

    Reynolds number: IIR. = PND' or Re =tr

    Form parameters

    _

    ilq xilH _

    pegh"P- f l p

    -bpL

    m - b h P'rmotor

    E.P.l'loverall = 1'lp X l]motor

    Specific speed:N, = NJO(eu);For further information consult:

    White, F.M. (1994): "Fluid Mechanics", 3rd edition, McGraw-Hill, Inc.

    Questions:* What types of data are to be collected?* How can we correct of that data? Describe what precautions must be taken if

    correct readings are to be obtained.* How many data are to be collected?* How can we present the data?

    Confidence limit:From the Statistical point of view we can estimate confidence limit by using

    't' distribution.

    pIlD

    The parameters in which the machine dimension D is eliminated, tell ussomething of the characteristics of the type of machine, irrespective of its size arecalled form parameters. The another is called size parameters.

    If lz- =

    3

    lI:..n

    where N is the number of datai is the averagevalue of the data.

    Therefore, the confidence limit can be defined as

    6p=

    where 't' is the value from the table 1.This can tell us the probability of the value in the

    Illustrative example:

    S .D .x t-{N

    ranse x+6^ .v

  • The speed of a pump is recorded in the followings.1490, 1495, 1485, 1493, 1497, 1478 and 1499 rpm.

    x : 1491 rpm.S .D . : 7 .37

    wi th P : 0 .95 and N-1 = 6, t :2 .447Therefore 6^ : 6.82 or the chance that the speed of the pump will be in the range

    IJ1491 + 6.82 rpmis 95o/o.

    Table 1:'t ' distribution

    c : \turbo_m\lab-cep. doc 21 October, 2001

    N-1 P= 0.50 0.90 0.95 0.99I2J

    456

    8910

    1 .000 .8160.7650.14r0.7270 .7180.7110.7060.7030.700

    6.3142.9202.3532.1322.0r51.9431 .8951 .860L8331.8r2

    12.7064.3033.1822.7762.57r2.4472.3652.3062.2622.228

    63.6579.9255.8414.6044.0323.7073.4993 .3 553.2503.169

    T2T4I61820

    0.6950.6920.6900.6880.687

    1.7821 .7611.7461.734t .725

    2.1792.1452.r202.IOT2.086

    3 .0552.9772.9212.8782.845

    30O

    0.6830.674

    r .6971.645

    2.0421.960

    2.7502.576