APPENDIX G – Pumps and Turbines
Surge Analysis and the Wave Plan Method
Supplementary Material: Example Problems and Solutions
Appendix G – Problem 18
G.18 The lightweight cylinder described in the previous problem is replaced by a series of rectangular alternate blocks of steel and lightweight material (density = 100 kg/m3) arranged to form a cylindrical shape equivalent to that described in the previous example. The outer diameter of the composite cylindrical shape is 1000 mm, the inner diameter is 900 mm, and the length is 300 mm. The number of steel blocks used for this assembly is same as the number of blocks of lightweight material. The volume of each steel block is exactly the same as the volume of the lightweight material block. The diameter of the solid steel plate is 1200 mm with a thickness of 30 mm. Compute the weight moment of inertia WR2 of the object with respect to z-axis.
Solution:
Weight moment of inertia WR2 of flywheel is the sum of polar weight moment of inertias of the cylinder and the plate.
Izw = Izw(CompositeCylinder) + Izw(plate)
Izw = WCompositeClinder * (1/2) (r22 + r12) + Wplate * (1/2) (r2)
Density of the composite cylinder = 0.5*(7800+100) = 3950 kg/m3
WCompositeClinder = 1734.726 N, Wplate = 2596.195 N, r1 = 0.5m, r2 = 0.45m, r = 0.6m
Izw = 859.797 N-m2
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