Analyze Clamped Rotor with Zero Clearance

In this example, the vibration of a rotor with a housing without a clearance in between is shown. The only difference from the free rotor example is the stiffer system, leading to a higher resonance frequency.

It is recommended to run the model in slow motion (set Time Scale = 0.1 in the animation window) and look at the position of the mass unbalance and the red arrow. At low speeds, their positions are the same. A view of the system in the axial direction at zero speed is shown in Figure 1.

Figure 1: Clamped rotor with zero clearance housing.

Note that the geometry of the ring does not change during the animation, but since the contact is flexible, it looks like there is a small penetration of the disk in the ring when there is a resonance, as shown in Figure 2.

Figure 2: Clamped rotor at the moment the penetration occurs.

Figure 3 shows the two response curves. Blue is without contact and orange is with contact all the time; i.e. the blue curve is from the example RunningUpFreeRotor and the orange is the response from the system in this example.

Figure 3: Disk deflections under increasing rotor speed.

Full contact between the rotor and housing makes the system stiffer, as the housing provides additional support. This increased stiffness pushes the critical rotor frequency further. Adding full contact can reduce machinery vibrations at certain speeds, but if the running speed is not estimated correctly, it can create even more significant hazards for the machinery.