192
5 Performance Measurement
5.8.5 Measurement Example
•  Rotational speed 2700 rpm (Table 5.4).
Answer: at 2700 rpm the maximum energy rise (mechanical energy rise) is 336.5 J/
kg with a zero mass flow rate; the optimum efficiency is 0.65 with a 25 kg/s mass
flow rate. The energy rise at optimum efficiency is 275.3 J/kg. With optimum efficiency, the energy rise coefficient is 0.44 and the calculated work coefficient is 0.67
(the real value presumably is about 10 % lower, so about 0.60). Specific speed and
specific diameter are 0.67 are 4.57. These values form approximately a couple on
the Cordier-diagram (Chap. 7, Fig. 7.7).
Table 5.4 Test results for the pump
Operating
point
1
2
3
4
5
6
7
8
p p (kgf/cm
2
) 0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.30
p s (kgf/cm
2
) − 0.72 − 0.60 − 0.50 − 0.38
− 0.28
− 0.12
− 0.02 0.00
T (kgfm)
4.5
4.4
4.3
4.1
3.8
3.3
2.6
2.2
Q (l/s)
42.1
38.2
33.8
29.4
25.0
17.8
8.0
0.0