Rotordynamics Module Updates
For users of the Rotordynamics Module, COMSOL Multiphysics® version 5.6 includes active magnetic bearing modeling, attachments for a rotor–stator connection, and the ability to model turbulence effects in hydrodynamic journal bearings. Learn about these and other rotordynamics features below.
Active Magnetic Bearing
An active magnetic bearing (AMB) is an electromagnetic bearing supported by a feedback control mechanism. You can now model such a bearing with a PID controller in both the Solid Rotor and Beam Rotor interfaces. Like any other bearing, they provide support to a rotating component on a stationary component. Active magnetic bearings can also be used to control large-amplitude vibrations when needed. These bearings are commonly used in an environment where the use of lubricants is prohibited. Due to contactless support, this type of bearing has minimal losses. You can see this feature used in the new Vibration Control in a Motor Drive Using an Active Magnetic Bearing tutorial model.
The vibration response of the motor drive without AMB.
The vibration response of the motor drive with AMB.
Attachments for Rotor–Stator Connection
Attachments can now be used as the foundation of a bearing to connect rotor and stator components. To support this, attachments are now available with a Rotordynamics Module license; they are added in structural mechanics interfaces such as Solid Mechanics, Shell, Beam, etc. With this functionality, it is a lot easier to set up a connection between stationary and rotating parts through bearings. You can view this new functionality in the Modeling of Vibration and Noise in a Gearbox: Bearing Version and Vibration Control in a Motor Drive Using an Active Magnetic Bearing tutorial models.
Turbulence Effects in Hydrodynamic Journal Bearings
Turbulence effects in hydrodynamic journal bearings can now be modeled in an averaged sense using a set of flow factors and shear stress factors. This effect can be modeled in the following two cases:
- Turbulence induced due to high speed of the rotor with sufficiently smooth surfaces of the journal and bearings
- Turbulence induced due to roughness of the journal and bushing surfaces
In the second case, two lubrication regimes can be modeled: full-film lubrication and mixed lubrication. For full-film lubrication, the contact load is supported by the pressure in the lubricant film only. For mixed lubrication, the contact load is supported by both the lubricant film pressure and the asperity contact pressure. Mixed lubrication modeling is important in heavily loaded contact surfaces.
Preload in Roller Bearings
Preload in roller bearings is used to make the contact between rollers and races more uniform. This helps in reducing bearing vibration, noise, and wear. You can apply an axial or radial preload in a roller bearing depending on its type. For preloaded bearings, a prestressed analysis can also be performed to determine the eigenfrequency and frequency response of a rotor-bearing system.
Improvement in Dynamic Coefficients for a Gas Bearing
Previously, dynamic coefficients in bearings were calculated by ignoring the compressibility effects of the lubricants. For liquid lubricants, this is a good approximation, but for gas bearings, the effects of compressibility of the gas and journal acceleration during whirl are very important for accurately computing the dynamic coefficients. Both of these effects are now accounted for in the dynamic coefficient computation of gas bearings.
Evaluation Group for Dynamic Coefficients
An evaluation group is automatically added by default in Results if you choose to compute the dynamic coefficients of a bearing. After the computation is completed, you can evaluate the Dynamic Coefficients in a table, using this group. If you have performed a parametric study, the coefficients for each parameter value are available in a table. You can quickly create a table plot to study the variation of each coefficient with respect to the studied parameter. You can see this new functionality used in these updated models: Evaluation of Dynamic Coefficients of a Plain Journal Bearing and Damping Coefficients of a Squeeze Film Damper.
New Tutorial Models
COMSOL Multiphysics® version 5.6 brings several new tutorial models to the Rotordynamics Module.
Vibration Control in a Motor Drive Using an Active Magnetic Bearing
Application Library Title:
vibration_control_with_amb
Thermal Stress in a Rotor Due to Bearing Heat Loss
Application Library Title:
rotor_thermal_stress
Modeling of Vibration and Noise in a Gearbox: Bearing Version
Application Library Title:
gearbox_vibration_noise_bearing