What is rotor stiffness?

The stiffness of the rotor supports is very important, as is the stiffness of the rotor itself. Hydrodynamic oil bearings common in large turbines and aerodynamic bearings used as sealing elements in dry gas seals have no static stiffness, as dynamic bearings require motion to generate the lubricating film.

What is cross coupling stiffness?

Cross-coupled stiffness (CCS) can be generated from fluid pressure forces in internal machine components such as gas/liquid seals, hydrodynamic bearings, axial flow turbomachinery stages, and centrifugal impellers. These CCS forces are purely distortive to the orbit and are not de-stabilizing.

What is meant by torsional vibration?

Torsional vibration is angular vibration of an object—commonly a shaft along its axis of rotation. Torsional vibration is often a concern in power transmission systems using rotating shafts or couplings where it can cause failures if not controlled.

What is whirl speed?

Whirl Speed Map is a linear plot of damped natural frequencies vs. shaft rotational speeds. The damped natural frequency is usually referred to as whirl speed. The following whirl speed map is generated for a typical rotor system with isotropic and constant bearing stiffness.

What is critical rotor speed?

1 Critical speed: Schematic amplitude profile of the rotational frequency induced vibration of a rotor as a function of rotational speed. The critical speed nk (n in min-1, w und f in s-1) occurs in the operating range where the rotational frequency coincides with one of the natural frequencies fi (f1, f2, f3).

What is a rotor bearing?

The rotor-bearing system consists of a planar and rigid disk of mass M mounted on a flexible shaft of negligible mass and stiffness k at the mid-span between two symmetric bearing supports (see Fig. 6 when a=b).

What is cross coupling effect?

Cross-coupling is the effect that one axis has on another axis. More specifically, when one axis of a gimbal purposedly slews at a fast angular speed, the other axis reacts and rotates as well. The same phenomenon occurs when one axis reacts to vibration and the other axis reacts to it in turn.

What is cross coupling force?

These terms are called cross-coupled stiffness, cross-coupled damping, and cross-coupled mass. When there is a positive cross-coupled stiffness, a deflection will cause a reaction force opposite the direction of deflection to react the load, and also a reaction force in the direction of positive whirl.

What are the two types of rotordynamic analysis?

Rotordynamic Analyses There are two types of rotordynamic analysis commonly performed on compressor drive trains: lateral and torsional. Torsional analysis evaluates the twisting interaction between rotors and couplings. A lateral analysis evaluates the rotor vibration in a compressor or train of equipment.

How is DTI used in Surface damping systems?

It utilizes Vibrating Beam Technique to measure and characterize the properties of viscoelastic materials and uses that information to aid in the design of surface damping systems. DTI’s mission is to remedy our customers’ noise and vibration problems.

How are destabilizing forces represented in a rotor system?

Assessing rotordynamic stability is an accounting exercise, quantifying the rotordynamic forces of each component on the stability of the overall rotor system. Destabilizing forces can be represented by cross-coupled stiffnesses, which will be described in more detail in a later chapter.

What is the supporting structure called in rotor dynamics?

At its most basic level, rotor dynamics is concerned with one or more mechanical structures ( rotors) supported by bearings and influenced by internal phenomena that rotate around a single axis. The supporting structure is called a stator.