Impeller, shaft and bearings form a dynamic system
We performed a vibration analysis on an ASTM A514 Grade B Steel industrial impeller to determine its natural frequencies. The proposed impeller design was intended to be used in a variety of applications and therefore subject to different operating conditions.
The fan is mounted on a drive shaft, which is supported by bearings. The impeller, shaft and bearings form a dynamic system – and any imbalance in the impeller and/or shaft produces harmonic excitations to the system.
To perform the vibration analysis, finite element models were analyzed in conjunction with rotordynamic capabilities available in the ANSYS Mechanical software. The analysis included:
1. Creating a 3-D finite element model of the impeller from a CAD model supplied by the client
2. Modal analysis to determine the natural frequencies of the impeller
3. Detailed harmonic stress analyses for the six operating speeds and two temperatures
4. Fatigue evaluation for the harmonic loads
The model was constructed using ANSYS SOLID185, CONTA174 and TARG170 elements. The analysis was performed using rotordynamic capabilities available in the ANSYS Mechanical software. Coriolis terms were included in the equations of motion by the software to account for rotational velocities and accelerations. The models were used in harmonic analysis, in which an unbalanced-mass excitation was swept at a single frequency.
A modal analysis of the combined impeller and shaft was performed. Frequencies in the range of 0 Hz to 100 Hz were sought. The analysis was performed at ambient temperature and at both operating temperatures (185 ºC and 250 ºC).
Our Team of Engineers performs thermal, stress and vibration analysis on various equipment for clients in industries including energy, manufacturing and petrochemical.
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