Question 2 Pump manufacturers typically present the performance characteristics of their pumps in dimensional form as shown in figure below, where the flow rate is in m/s and the head added by the pump is in meters. The efficiencies in % at various operational states are represented by dashed lines on the performance curve. The performance curves shown below are for homologous pumps with a motor speed of 3500 rpm and impeller sizes of 178 mm, 165 mm, 152 mm, 140 mm, and 127 mm. (a) Plot on a single graph the dimensionless performance curve for each of the pumps. (b) Compare the dimensionless performance curves and assess whether these pumps are really from a homologous series. (c) Identify the maximum efficiency and specific speed for each impeller size. The points in the table to the right are read from the graphical dimensional performance curves: 880 70 80 60 60 Head, hp (m) 30 32 20 60 50 . 40 10 10 -25%- 35%- --40%- -45%- ' -55% .57% Q Head, h, for impeller D 59.5% (m/h) 0 59% 5 ----57% 178 165 152 140 127 mm mm mm mm mm 68.2 55.4 46.4 37.0 29.0 69.0 55.6 46.2 37.5 28.8 178 mm 10 55% 15 53% 68.0 54.6 45.0 36.4 27.8 66.6 52.4 42.8 33.8 25.5 165 mm 20 50% A 63.7 49.5 39.5 29.1 19.5 25 152 mm 59.4 44.7 34.0 - 45% 30 54.1 39.9 - -140 mm 127 mm 5 10 15 20 25 25 30 35 40 40 Flow rate, Q (m/h)