Supplementary Material, Appendix G – G.20

APPENDIX G – Pumps and Turbines

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Surge Analysis and the Wave Plan Method

Supplementary Material: Example Problems and Solutions

Appendix G – Problem 20

G.20 A pump impeller shown in the figure below is assumed to comprise 5 parts: 1. A solid circular steel plate of 200 mm diameter and 5 mm thickness, 2. A composite thick-walled cylinder of 200 mm outer diameter, 150 mm inner diameter, 70 mm length, and a total weight of 24N, 3. A composite thick-walled cylinder of 150 mm outer diameter, 100 mm inner diameter, 70 mm length, and a total weight of 20N, 4. A composite thick-walled cylinder of 100 mm outer diameter, 50 mm inner diameter, 70 mm length, and a total weight of 12N, and 5. A composite thick-walled cylinder of 50 mm outer diameter, 10 mm inner diameter, 70 mm length, and a total weight of 4N. Compute the weight moment of inertia WR² of the pump impeller with respect to its z-axis.

Solution:

I_zw = I_zw(plate) + Σ I_{zw(CompositeCylinder)}

            I_zw(plate) = W_plate * (1/2) (r²) 

I_{zw(CompositeCylinder)} = W_{CompositeCylinder} * (1/2) (r₂² + r₁²) 

I_zw = 0.06 + (0.1875 + 0.081 + 0.0187 + 0.0013) N-m²

I_zw = 0.3489 N-m²

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