Pump
    • 16 Aug 2022
    • 6 Minutes to read
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    Pump

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    Article summary

    Data

    Field in Data Entry Form

    Description

    Name in Datafile

    Upstream Node

    Suction side node label

    Label1

    Downstream Node

    Delivery side node label

    Label2

    Controller Label

    Control Unit label (used for `CONTROLLER' operating mode only)

    Label3

    Maximum Speed

    Full operating speed of pump (rpm)

    rpmful

    Optimal Head

    Pumping head at optimum point of operation (m)

    hopt

    Optimal Flow

    Pump discharge at optimum point of operation (m3/s)

    qopt

    Optimal Efficiency

    Pump efficiency at optimum point of operation (between 0.0 and 1.0)

    effopt

    n/a

    Number of head, flow, efficiency data sets in teh following pump curve data

    ndat

    Pumping Head

    Pumping head (m)

    head

    Flow

    Pump discharge (m3/s)

    flow

    Efficiency

    Pump efficiency (defaults to effopt, as given above)

    eff

    Control Method

    Switch type keyword for pump unit - either `TIME' for pump controlled according to model time; `CONTROL' for pump under automatic control from control module unit(s); or `LOGICAL' for pump controlled by included logical RULES subunit

    swtype

    n/a

    Number of time, control mode, pump mode switch data sets

    nswch

    Units of Time

    Optional keyword or value for units of time in the following data set. Can be any numerical multiplier or one of the following: seconds (the default), minutes, hours, days, weeks, fortnight, lunar (month, i.e. 28 days), month (of 30 days), quarter, year or decade

    tm

    Data Extending Method

    Policy for extending data if the run finishes after the end of the data.

    Options are :

    • REPEAT - if the data are to be repeated from the beginning
    • EXTEND - if the data are to be fixed at the last given values
    • NOEXTEND - for no extension

    If NOEXTEND is used (or the field is left blank) then the program will stop with an error message if there are insufficient data for the length of the run.

    repeat

    Time

    Model time (in units defined by tm - see above)

    time

    Mode

    Control mode (Keyword `AUTO' for automatic control or `MANUAL' for manual control); for `CONTROLLER' or `LOGICAL' switch types only

    cmode

    Pump Mode

    Pump operation mode (Keyword `OFF', `ON' or `STOPPED')

    pmode

    Theory and Guidance

    This unit models the behaviour of a generalised open channel pump. Time dependent switching is available, along with options to control the pump using automatic controllers and the logical RULES subunit.

    The user can specify the head flow relationship to be used by the pump unit. Suter's method is then used to extend this relationship to give a full four-quadrant pump curve. This method uses the optimum values of head, flow and efficiency to extrapolate the pump characteristics, based on experimental observations of a variety of pumps.

    Flexible switching facilities allow the pump to be turned on and off at certain model times (keyword `TIME'). Alternatively pump switching can be achieved by use of the RULES subunit (keyword `LOGICAL').

    The head-flow relationship produced by this unit can be checked prior to a full computational run using Flood Modeller's boundary mode. This will also be written in tabular form to the .zzu file during an unsteady run.

    There are three possible modes of operation - OFF, STOPPED and ON. When the pump is OFF (mode 0) the unit simply equates the heads and flows at the two nodes connected to the pump. When the pump is in STOPPED mode (mode 1) the flow is set to zero - this simulates the effect of a pump with a connected check valve being turned off. When the pump is ON (mode 2) the pump is assumed to be operating at the given maximum speed and the output heads and flows are calculated using the Q-h relationship derived from the user supplied head-flow curve spliced onto that generated by Suter's method.

    For time switching operation when the model time (in seconds) exceeds the time associated with the given pump mode, the pump will switch to that mode.

    When in `LOGICAL' switching mode the pump will use logical rules that are contained within a specific `RULES' data block to control the current operating mode of the pump unit; this data block must appear immediately after the main part of the pump datafile entry (see example datafile entry later). For full details of how to use this option, please refer to the Rules topic.

    When operating in either controller or logical mode there are two sub-modes of operation; automatic (`AUTO') and manual (`MANUAL') control. Pumps can switch freely between these two modes of operation depending on the instructions the user has put into the datafile entry.

    When in automatic mode the pump will be driven by currently valid rules within the RULES data block (in `LOGICAL' switching mode). These instructions will be updated when the polling time interval has elapsed. Instructions are interpreted as a command to move to a new operating mode, and this will be effected immediately.

    When operating in manual control mode, the new operating modes are obtained from the appropriate line of the time switch data in the datafile entry for the pump unit. When the model time reaches or exceeds the time value in the switch data, the pump unit will switch to the new operating mode.

    Equations

    There are eight possible modes of operation, five of which are Pump Open modes where the pump acts like an orifice:

    Mode 0 - Pump Off

    Equations

    Equation

    Q1 = Q2

    H1 = H2

    where:

    Q1 is the flow at the inlet (suction) node [m3/s],

    Q2 is the flow at the outlet (delivery) node [m3/s],

    H1 is the water level at the inlet (suction) node [mAD], and

    H2 is the water level at the outlet (delivery) node [mAD].

    Mode 1 - Pump Stopped

    Equations

    Equation

    Q1 = Q2 = 0

    where:

    Q1 is the flow at the inlet (suction) node [m3/s], and

    Q2 is the flow at the outlet (delivery) node [m3/s].

    Mode 2 - Pump On

    Equations

    Equation

    Q1 = Q2 = Qp

    where:

    Q1 is the flow at the inlet (suction) node [m3/s],

    Q2 is the flow at the outlet (delivery) node [m3/s], and

    Qp is the discharge of the pump [m3/s].

    The other equation is derived from the Q-h relationship defined for the pump.

    (For full explanation of the method used to calculate heads and flows, please refer to Wylie and Streeter (1978) , pp 102 et seq.)

    Mode 10 - Pump Open, dry sill

    Equations as for Orifice Mode 0

    Mode 11 - Pump Open, unprimed

    Equations as for Orifice Mode 1

    Mode 12 - Pump Open, free weir-type flow through pump

    Equations as for Orifice Mode 2

    Mode 13 - Pump Open, drowned weir-type flow through pump

    Equations as for Orifice Mode 3

    Mode 14 - Pump Open, orifice-type flow through pump

    Equations as for Orifice Mode 4

    General

    Where a time switch is used, time values must be given in increasing order.

    When using controller' or logical' modes, if the datafile is set up so that for a particular run a pump starts up in `AUTO' mode, the corresponding datafile entry in the switch data set must have a pump operating mode present; the pump will initially be switched to this operating mode. Other `AUTO' entries in the switch data set need not have a corresponding pump operating mode as the pump will receive its new switching instruction from the control system or from the logical rules sub-block. If pump modes are given in the datafile in this instance, they will be ignored during the run.

    Full 4-quadrant pump characteristics are generated for each given operating speed from the corresponding optimal point values of head, flow and efficiency specified in the datafile. These characteristic head-flow relationships will be used outside the region defined by the head, flow, efficiency data set.

    Following an unsteady or boundary mode run, the pump head-flow curve (along with some other data) is written to the .zzu file. It is often a good idea to check that the transitions between the computer generated head-flow curve, and that defined in the head, flow, efficiency data set is reasonably smooth. This is obviously particularly important if the pump is expected to cross one or more of these transition points during the model run. You may wish to alter the head, flow efficiency data sets (or the optimal point data) to smooth the transition points.

    Typically, the difference between manufacturers data and generated performance curves will not be large, and so data for the optimal point only may allow a sufficiently accurate representation of a pump's performance.

    For more information on Suter's method for the generation of pump characteristics, please refer to Wylie and Streeter (1978).

    The unit state for this unit is the pump operating speed (in rpm).

    Datafile Format

    Line 1 - Keyword `OCPUMP' [comment]

    Line 2 - Label1, Label2 [, Label3]

    Line 3 - rpmful, hopt, qopt, effopt

    Line 4 - swtype

    Line 5 - Keyword `TRIGGER MODE'

    Line 6 - nswch [, tm, repeat]

    Line 7 to Line 6+nswch - time, [ cmode,] pmode

    Line 7+nswch - Keyword `HEAD FLOW EFFICIENCY'

    Line 8+nswch - ndat

    Line 9+nswch to Line 8+nswch+ndat - head, flow [, eff]

    RiverNodesimagesPumpData.gif



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