How to understand that \"the unbalanced vibration remains constant in phase and is synchronized with the rotational speed.\" ”This sentence?
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On pages P65/268 of the book \"Simple Vibration Diagnosis: Techniques for On-Site Use\" written by Yi Liangji, there is a sentence that states: Unbalanced vibration remains constant in phase and is synchronized with the rotational speed. I don’t quite understand this sentence: 1. Relative to what is this phase? Or rather, where is the benchmark? What does it mean to remain constant? 2. Under what fault conditions does phase instability occur? I would be very grateful if an expert could give me some advice!
In other words, the vibration and rotational speed are the same, but there is an imbalance in the rotor. Phase refers to the constant direction of vibration; balance instruments are equipped with indicators for both phase and amplitude. If there is no rigid relationship between the imbalance amount and the rotor, the phase may not remain constant; for example, if there is a bolt inside the rotor that is not fixed in place
Understood, thank you very much! In fact, 0° represents any radial angle on the axis of rotation, and the orientation of vibration remains constant with respect to this 0°.
When measuring the absolute phase, a cursor needs to be placed on the axis as the reference point for 0°; this point serves as the relative point. When the unbalanced mass block remains in its fixed position on the impeller, the angular difference relative to the 0° reference point stays constant, so the phase remains unchanged. If the position of the unbalanced mass on the impeller changes, the phase will also change. A typical example is dust accumulation inside the hollow blades; this dust shifts its position with each rotation, thereby causing a change in phase. Of course, the above applies in the case of linear systems; when there is looseness, the entire shaft and impeller rotor system becomes unstable, and chaos ensues. The 0° reference point itself fluctuates, which further disrupts the phase alignment.
Could you take a look at these two posts? The doubt stems from a misunderstanding of the concept of phase angle, which prevents progress with the chapter on fault analysis based on phase. Borrowing someone else’s book – so anxious~~~ How to measure the phase angle using a stroboscope? http://bbs.hcbbs.com/thread-1554453-1-1.html Seeking advice on vibration analysis: regarding the vibration phase of axial looseness in the bearing housing and that of radial looseness. http://bbs.hcbbs.com/thread-1557161-1-1.html Thank you very much!