Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)
Pipeline, Waterflood and CO 2 Pumps 141 Figure 10-2. Specific speed describes impeller shape. These losses can be generally classified as hydrodynamic, mechanical, ring leakage, and disc friction. Analysis of these losses for one specific performance at various speeds is shown in Figure 10-1. Pump efficiency is a result of the sum of these losses and is influenced by specific speed, which is basically a non-dimensional number. As discussed in Chapter 2, the physical meaning of specific speed has no practical value; however, it is an excellent means of modeling similar pumps and describes the shape of the impeller under discussion (Figure 10-2). Pump efficiency is also influenced by hydrodynamic size (Figure 10-3). For any given speed, pump efficiency increases with size of pump or with hydrodynamic size (Figure 10-4). Through careful selection of pump speed and stage number, optimum specific speed and hydrodynamic size can be determined fo j r maximum efficiency. Condition Changes Many pipeline conditions require low-capacity, low-pressure start-up with ultimate change over to high-capacity, high-pressure. By considering this requirement at the design stage, pumps can be built to accommodate the initial and ultimate conditions through field modifications. One method is to adjust the ratio of liquid velocity leaving the impeller to liq-
Figure Pump size with
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Pipeline, Waterflood <strong>and</strong> CO 2 <strong>Pumps</strong> 141<br />
Figure 10-2. Specific spe<strong>ed</strong> describes impeller shape.<br />
These losses can be generally classifi<strong>ed</strong> as hydrodynamic, mechanical,<br />
ring leakage, <strong>and</strong> disc friction. Analysis of these losses for one specific<br />
performance at various spe<strong>ed</strong>s is shown in Figure 10-1. Pump efficiency<br />
is a result of the sum of these losses <strong>and</strong> is influenc<strong>ed</strong> by specific spe<strong>ed</strong>,<br />
which is basically a non-dimensional number. As discuss<strong>ed</strong> in Chapter 2,<br />
the physical meaning of specific spe<strong>ed</strong> has no practical value; however, it<br />
is an excellent means of modeling similar pumps <strong>and</strong> describes the shape<br />
of the impeller under discussion (Figure 10-2).<br />
Pump efficiency is also influenc<strong>ed</strong> by hydrodynamic size (Figure<br />
10-3). For any given spe<strong>ed</strong>, pump efficiency increases with size of pump<br />
or with hydrodynamic size (Figure 10-4). Through careful selection of<br />
pump spe<strong>ed</strong> <strong>and</strong> stage number, optimum specific spe<strong>ed</strong> <strong>and</strong> hydrodynamic<br />
size can be determin<strong>ed</strong> fo j r maximum efficiency.<br />
Condition Changes<br />
Many pipeline conditions require low-capacity, low-pressure start-up<br />
with ultimate change over to high-capacity, high-pressure. By considering<br />
this requirement at the design stage, pumps can be built to accommodate<br />
the initial <strong>and</strong> ultimate conditions through field modifications. One<br />
method is to adjust the ratio of liquid velocity leaving the impeller to liq-