ROTOR DYNAMICS OF TURBOMACHINERY

• OUTLINE OF DYNAMICS 4
  • General Properties
  • Functional Capacity
  • General Problems of Linear Dynamics
  • General Problems of Non-linear Dynamics
  • User interface
• MAIN MODELING ELEMENTS
  • Elements to Determine Subsystem Parameters
  • Linear Elements for Modeling Subsystems
  • Linear Links for Connection of Subsystems
  • Loads
  • Nonlinear Links for Connection of Subsystems
  • Other Elements and Functions

DESCRIPTION OF SOME LINEAR AND NON-LINEAR MODELING ELEMENTS

Linear Elements

Alford's force element

The element allows computing of aerodynamic cross-coupling forces operating in axial flow compressors and leading to instability of rotor system. It is based on the correlation discovered by J.S. Alford.

Wachel's force element

The element allows computing aerodynamic cross-coupling forces acting in centrifugal compressors and leading to instability of rotors. It is based on J.C. Wachel's empirically derived correlation

Block of code and elements for computation of shaft systems with gearings

This allows computing shaft systems with cylindrical, bevel, helical and hypoid gearings.

Function of import of super elements from FEM systems

The element gives an opportunity to combine solutions obtained in FEM program and in DYNAMICS R4 by means of modal synthesis method. It allows to take into account the complex configuration of separate assembly units, for example, cases and housings.

Non-linear Elements

"Clearance" element ("Elastic Damping Lateral Restraint" element)

This element allows to model different cases of full or partial rubbings of rotating and non-rotating structures. This allows you to model most cases of instability in rotating systems with clearances. It takes into account any kinds of contact with external and internal damping, with friction in contact point, weight and circumferential irregularity of clearance. The element is indispensable to engineers' education of fundamental non-linear dynamics.

Journal bearing element

This element allows computing the rotating system with two notable cases of plain bearing: "short" bearing and the "long" bearing. Different kinds of cavitation of fluid film are considered: uncavitated (2-π film) damper and cavitated (π-film) damper. It allows to compute dynamical systems in steady-state and non-steady state conditions.

Squeeze-film damper element

This element models two well-known cases of hydrodynamic damper: the "short" damper and the "long" damper. Combinations of these cases are also possible. Different kinds of fluid film cavitations are considered: uncavitated (2-π film) damper and cavitated (π-film) damper. Fluid inertia effects are also included in squeeze film damper models. It allows to compute dynamical systems in steady-state and non-steady state conditions. Any number of squeeze-film dampers in rotating system. Fast computation.

User-programmable non-linear element

It allows to use the user's own algorithms of nonlinear effects in rotating machinery to program new elements and also to integrate them into DYNAMICS R4 program system. The new element can be of any complexity and it can be used in a rotor model in combination with other non-linear elements of DYNAMICS R4. The language of programming is the script language Python (www.python.org) built-in in DYNAMICS R program system and can be easily mastered by the user. This element is indispensable to engineers and post-graduate students carrying out investigations in the rotor dynamics field. By the user's request the new element which was made in a script language can be adapted and included in program system by DYNAMICS R4 developers (Alfa-Tranzit Co., Ltd). It will make it possible to speed up computation dozen in times.

Rolling bearing element

This element allows to model the main types of rolling bearings - angular-contact (ball) bearing , roller bearing, etc. The Hertz theory is used for computing speed dependent stiffness and bearing forces. Clearances in bearings can also be taken into account. The user has an opportunity to specify bearing linear and nonlinear damping.

Active magnetic bearing support element

This element allows modeling active magnetic bearing (AMB). Three main types of AMB are modeled: radial, cone and axial. Two different input types are possible - standard(common parameters set) and expert. Expert input parameters used for simulation of special cases and requires knowledge of the algorithm of magnetic bearings. The model takes into account: radial clearance, maximal current and current density, electromagnetic poles number, control pole number, coil remove option. Pole control is the axis coinciding with direction of the resultant force from the closest to it electromagnet. Two control options are possible - PD – controller and PID – controller.

Seismic excitation

The link allows modeling of kinematic excitation of the setting foundation and appearing transient processes. One of the particular cases is the work of the setting under earthquake conditions. The element allows adjusting stiffness of the foundation with the setting in three directions and giving ground response spectra of seismic excitation from the part of the foundation. Influence is set as a polyharmonical signal acting simultaneously in three directions. Time interval of influence is divided into several ranges. They are the ranges of divergent, constant and damped amplitudes.

Individual options are offered to customers who have purchased the Dynamic R4 program system. Development of the non-linear elements can be made according to their needs.

• PURCHASING OPTIONS