Alan Champneys - “Balancing rotating machines”

Problem statement:

• Problems with rotor imbalance arise in many areas of industry e.g. in washing machines, wheel design, CD players and jet engines.

• Open question: Can rotors be made to balance themselves?

• Patented technology exists - add ball races containing 2 or more ball bearings. Unbalanced load on rotor is corrected by balls moving naturally to equilibirum positions. Solution works very well in certain operating conditions (in particular, provided that rotor speed is high
enough).

• However, in certain regions of parameter space (e.g. near resonances) ball race solution can, in fact, make the problem much worse. Also have problems with rotor run-up and transient effects. Would like a solution which works across the whole range of parameter space likely
to be encountered in practice.

• Possible solutions: Add more balls (but this doesn’t seem to help)? More damping in ball race? Other topologies e.g. noncircular ball races or pendula instead of ball races? Partitioning the ball race?

Suggestions/comments:

• SDH: Recall study group problem - washine machine manufacturer experimenting with water in a tube partitioned by baffles.

• EJH: Electronic control system? Would have to have a very quick response time.

People interested in follow-up: