CentrifugalPump

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CentrifugalPump

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Domains: Continuous. Size: 1-D. Kind: Iconic Diagrams (Hydraulics).

Description

A centrifugal pump converts the input power of a rotating shaft into kinetic energy of a the liquid by accelerating the liquid through an impeller.

 

CentrifugalPump

 

The pump is characterized by two curves:

 

1.The head (H) as function of the volume flow at a preset speed.
2.The efficiency (n) of the pump as a function of the fluid flow at a present speed. The efficiency is defined as the flow output power divided by rotational input power.

Centrifugal1

The pump curves are approximated by two second order polynomials:

 

H = ha*q2 + hb*q + hc

n = na*q2 + nb*q + nc

 

To fit the polynomial curves, the heads and efficiencies have to be specified at three different flows. The first flow (q0) is zero. The other two flows (q1 and q2) can be chosen arbitrary.

 

Note: some pump flows extrapolate the efficiency curves to zero at zero fluid flow. This would mean that at a zero fluid flow no power can be transmitted and the pump can never start! Therefore in this model always use an efficiency that is non-zero at zero flow.

Centrifugal2

Some  pump characteristics give multiple input speeds. This model automatically takes into account for varying input speeds of the input axis by transforming the  pump curve using the affinity rules.

 

Ha = Hb*(vb/va)2

Qa = Qb*(vb/va)

 

 

Some pump characteristics give the efficiencies as regions. You have then have to estimate the efficiencies at the chosen flows q0, q1 and q2.

 

Interface

Ports

Description

p_t

p_a

p_rot

inlet port, tank (hydraulic)

outlet port (hydraulic)

axis (rotation)

Causality

 

velocity out p_rot

 

Input

 

phi

Volume flow [m3/s]

Parameters

 

q1

q2

H0

H1

H2

n0

n1

n2

v_nom

rho

flow 1 (choose an arbitrary point between zero and nominal)

flow 2 (nominal flow)

head at zero flow

head at flow 1

head at flow 2 (nominal flow)

efficiency (0 < n < 1) at zero flow

efficiency (0 < n < 1) at flow 1

efficiency (0 < n < 1) at flow 2 (nominal flow)

nominal speed of the pump

fluid density