Rotor dynamics bearing systems

Squeeze film dampers have long been used to combat rotor dynamic and stability problems that conventional bearings cannot solve on turbomachinery rotor systems. The use of squeeze film dampers in problem process machinery has tainted it as a treat-the-symptom solution, and many users shy away from using squeeze film dampers for this reason. Also, their limited use is explained by the difficulty in accurately predicting performance, particularly with o-ring supported dampers. 

Rotor-bearing system dynamic stability and calculated critical speed... 

The rotor vibrations shown correspond to a common unbalance for all cases and, as might be expected, the stiff rotor system is much less sensitive than the flexible rotor system. It is common knowledge that a plain circular profile results in the best synchronous damping properties in hydro-dynamic bearings. The relative figures in table 1 show that the partially grooved bearings approach the circular in this respect. 

AND THE IDENTIFICATION OF DYNAMIC CHARACTERISTICS OF A ROTOR-BEARING SYSTEM... 

Use of two independent electrical power supplies would likely provide sufficient electrical system robustness while minimizing electric system complexity. Two independent electrical systems could be provided by two Brayton units (without spares) or by one Brayton power unit with two separate alternators. Such an arrangement would have effects on the rotor dynamics and alternator and bearing cooling, and would therefore require more study. However, in principle, use of multiple alternators on the same shaft would also create some redundancy in shaft speed control, minimizing the likelihood of an overspeed event due to a loss of electric load. Each alternator and its associated electrical system would need to be sized for full power capability. 

The largest turbine component design uncertainties are the scale-up of the turboaltemator assembly for a single 200 kWe Brayton system and the ability of the turbine to operate for an extended lifetime in the service environment. Further rotor dynamic evaluations, bearing development and alternator cooling studies and testing would be needed. 

Rotating machines subject to imbalance caused by turbulent or unbalanced media flow include pumps, fans, and compressors. A good machine design for these units incorporates the dynamic forces of the gas or liquid in stabilizing the rotating element. The combination of these forces and the stiffness of the rotor-support system (i.e., bearing and bearing pedestals) determine the vibration level. Rotor-support stiffness is important... 

This is a system which is well-suited to fundamental research on rotor-bearing dynamics. 

---