Rotordynamic Analysis
Barber-Nichols, Inc. (BNI) regularly analyses high-speed turbomachinery to assure smooth operation. BNI performs damped and undamped analysis to assure that no critical frequencies are present in the operating speed range. Torsional analysis is performed on machinery trains and on highly sensitive equipment. BNI uses XLRotor® software to perform the required analyses; additionally, comprehensive empirical data is used to reconcile software predictions.
Operational Range Verification:
- Lateral Undamped
- Lateral Damped
- Torsional
- Unbalanced Response
Bearing Stiffness & Damping
A.B. Jones® high-speed bearing software and XLRotor® are used to calculate the stiffness of high speed rolling element bearings. In addition BNI can offer a variety of spring damping and bearing mounting to address rotor dynamic requirements. The stiffness and damping of fluid film bearings are calculated with XLRotor® and ARMD® software.
Undamped Critical Speeds
The first step in rotordynamic analysis is to determine the undamped rotor critical speed. To do this, the bearings are modeled as simple springs. With this information BNI can optimize the shaft configuration which includes the impeller, bearings, shaft size and turbine (if applicable).
Mode Shapes
Rotordynamic mode shapes are then calculated to assure that the bearings, impeller and turbine (if applicable) are optimally located on the shaft.
Unbalance Response
Next, the bearing load that results from rotating imbalance is calculated to verify the acceptability of the design.
Damped Eigenvalues & Stability vs. Rotor Speed
Analysis that accounts for the damping characteristics of bearings, seals, and impellers are required for machinery that incorporates fluid film bearings and for machinery that operates at extremely high speeds. Shaft instability that results from an improper design will cause vibration and threaten the integrity of the machine.