When we consider a typical rotor of a turbine or compressor it is likely to have multiple stages and in each stage several blades attached around the circumference of the disk. A single stage is schematically shown in Fig. 3.2.5. Several blades are sometimes grouped together using “lacing wires”. Also, not all the blades in a stage will be exactly identical due to various manufacturing process variations etc. The individual blades are of aero-foil cross-section and are twisted / tapered and attached at a stagger angle to the disk. Thus the dynamics of the complete bladed-disk unit is quite a challenging problem.

Fig 3.2.5

Thus you will appreciate that the field of rotor-dynamics offers many practically significant and theoretically challenging research problems. We will however restrict our discussion to just the problem of achieving “balance”.