Vortexing in the compressor unit

Is there a problem with the connection of the instrument sensors?

If there is a counter-precession phenomenon, should there be slight static and dynamic friction? Does the amplitude change?

I really didn’t understand the issue when I saw it; I looked it up online and found that a professional instrument is needed for diagnosis. Here is what was copied from the Internet: It’s like children playing with a jump rope; the first type of rotation of the axis is similar to the rotation of the jump rope itself (although in reality the jump rope doesn’t rotate). The second type of rotation is like a bow-shaped jump rope moving around in space, and that’s why it’s called bow-shaped rotation; here it’s referred to as vortex motion. For a normal rotating shaft, the vortex angular velocity Ω is equal to the rotational angular velocity w; therefore, it is referred to as synchronous vortexing. In any case of synchronous vortexing, if a certain direction on the rotating shaft is under tension or compression, it will remain under tension or compression while in a rotating state. However, when the rotor experiences self-excited vibration, asynchronous eddy currents occur because the speed of the eddy currents does not match the rotor speed. When the direction of the vorticity is the same as the rotation direction of the rotor, this type of vorticity is called forward vorticity, or positive precession ； When the direction of the vortexing is opposite to the rotation direction of the rotor, it is called reverse vortexing, or negative precession. Whether it is forward vortexing or reverse vortexing, one side of the rotating shaft will alternately be under tension or compression; in other words, while the rotor is rotating, the high points on the rotor move periodically in the same direction or in the opposite direction of rotation. Obviously, when the swirl velocity is lower than the rotor speed, the higher positions on the rotor will move in the opposite direction, and vice versa; the movement speed is w-Ω or Ω-w. Due to the cross-stiffness present in hydrodynamic film bearings, the vibration of the unit under normal conditions always contains both positive and negative precession components; however, in most cases the positive precession dominates (for example, due to rotor imbalance). When rubbing occurs, the counter-precession momentum exceeds the positive precession momentum, and the vibration shows a dominance of counter-precession ； When there is misalignment, the magnitudes of the first and second-order positive and negative precession moments are similar. When the rotor rotates for some reason (such as eccentric installation) and comes into contact with the housing (also known as sliding friction), dry-friction precession may occur. This precession has occurred in the turbine rotors of aeroengine turbines, and it can also occur in turbine pump rotors. When the rotor comes into radial contact with the housing, the tangential dry friction force exerted by the housing on the rotor at the point of contact acts in the opposite direction to the rotation speed. If this friction force is simplified to an equivalent force acting at the geometric center of the rotor, then this simplified couple requires an increased driving torque. The tangential force acting through the axis causes the rotor to precess in the opposite direction along the inner wall of the housing (as if it were crawling along the inner wall without rolling perfectly), and this precession further increases the centrifugal force on the rotor, leading to greater radial contact. This, in turn, increases the friction force that causes precession, potentially resulting in the rotor becoming unstable due to such precession. It is worth noting that the back-precession instability caused by dry friction is relatively complex, and it may induce asynchronous precession of the natural frequencies of various orders of back-precession; therefore, it is not necessarily subsynchronous precession. A general diagnostic system monitors the condition of a machine based on its vibration signals during operation, and diagnoses machine faults by analyzing changes in these vibration signals. To monitor counterprecession, monitoring and diagnostic methods based on the testing and analysis of the rotor’s axis motion trajectory are primarily used; that is, the axis motion trajectory is measured online and subjected to vector analysis to extract fault characteristic quantities (first, second, and third-order positive and negative precession moments), thereby enabling fault diagnosis. In the system, the spectrum analysis function is also retained; the measured harmonic components of various orders can be used in conjunction with the positive and negative precession moments for monitoring and diagnosis. Research shows that the first, second, and third-order positive and negative precession moments are information that more accurately reflects the main vibration faults of the rotor. By using them as monitoring characteristics, it is possible to more precisely distinguish between different types of rotor faults, thereby improving the reliability of fault diagnosis. Furthermore, this monitoring feature not only reflects changes in the rotor vibration amplitude but also includes phase change information that is highly sensitive to the occurrence of faults, which **improves the sensitivity of fault detection**.

There is a change; the passband width varies by approximately 2 micrometers. In the waveform spectrum, it can be seen that the amplitude of the 1X component is higher