On the transverse critical speed and torsional critical speed of centrifuges
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Why do centrifuges have a lateral critical speed and a torsional critical speed? What do these two values mean?
Due to factors such as uneven material distribution and machining errors, the centroid of the shaft deviates from the axis, resulting in centrifugal force. As the shaft rotates, this centrifugal force (direction) changes periodically → leading to periodic disturbing forces → lateral bending vibrations. When the vibration frequency matches the natural bending frequency of the shaft itself, bending resonance occurs. Furthermore, when the power transmitted by the shaft varies periodically → torsional vibration → torsional resonance. As I understand it, one type of vibration is caused by the centrifugal force generated by the rotational speed of the machine’s shaft itself ； Additionally, torque vibration is caused by changes in shaft power and is related to the system load.
Then which critical speed is meant by the term used in everyday conversation? Also, at startup, both the lateral critical speed and the torsional critical speed should be avoided, right?
The critical speed refers to the transverse critical speed; the machine should quickly pass through this speed or avoid it during operation
Both need to be avoided, but twisting is more dangerous; it usually occurs when the load changes