Turbomachinery Applications

The development of turbomachinery with increasingly higher levels of efficiency makes the detailed knowledge of the mechanical, thermal and fluid dynamic processes indispensable. They serve for optimizations of the flow geometry, thermal stresses, lifetime, etc. The realistic simulation of the turbomachinery system often requires the knowledge of boundary conditions, which usually are the results of other simulation disciplines or even are strongly interrelated with each other.
In order to consider those interactions (“multiphysics”), a mapping (using MpCCI FSIMapper) or a coupled simulation (MpCCI CouplingEnvironment) is required.

© Photo Fraunhofer SCAI

Turbine streamlines colored by temperature

Blade deformation and its influence to the fluid flow

In operation, the fluid pressure field leads to deformations of the blades and thus to a change of the flow channel, which in turn influences the pressure field and the performance of the machine.
A coupled simulation (via MpCCI CouplingEnvironment) between the turbomachinery CFD analysis and the structural analysis - where the pressure and the deformation are exchanged - computes this fluid-structure-interaction.
If the influence of the blade deformation to the fluid flow is negligible, also a mapping of the pressure field to the structure is sufficient (MpCCI FISMapper).

© Photo Fraunhofer SCAI

Temperature distribution as a result of a thermal coupling

Thermal loading resulting from the fluid flow

In order to compute a realistic temperature distribution in turbomachinery, for the solution of the heat transfer equation well-chosen thermal boundary conditions are necessary. This includes, among other things, the heat input from the flow. The heat flux is influenced by the difference between fluid and wall temperature. The wall temperature is in turn dependent on the active heat flux. Only if both quantities are at equilibrium, the actual component temperatures are reached.

Project TurboKeramik

In some applications it is sufficient to map once the film temperature and the heat transfer coefficient to the thermal structural simulation. With this boundary condition a thermal stress analysis can be performed.

  • Average Over Rotation Mapping for Frozen Rotor Simulations [PDF, ]
    (Best Practice Case Flyer in preparation)
© Photo Fraunhofer SCAI

First pressure harmonic of an axial turbine row

Flow-induced vibrations

Flow-induced vibrations can lead to a high noise emission and to blade fatigue which can endanger the integrity of the whole system. The excitation is caused by pressure fluctuations in the flow field generated by interactions between rotating and stationary blade rows. Structural vibration analyses operate in frequency domain which offers fast simulation methods. This means, that the exciting transient pressure fields have to be transferred to the frequency domain in order to meet the prerequises as a vibrational boundary condition.

  • Flow-Induced Vibrations in Turbomachinery [PDF,]
    (Best Practice Case Flyer in preparation)

Features for Turbomachinery applications

  • Mapping: file-based unidirectional data transfer MpCCI FSIMapper
  • Coupling: data exchange at run-time MpCCI CouplingEnvironment
  • Support of unequal mesh densities or element types
  • Support of unequal geometry details
  • data transfer/exchange between periodic models which exhibit different section shapes and positions (also full models)
© Photo Fraunhofer SCAI

CFD mesh of a passage around one single blade

© Photo Fraunhofer SCAI

FEM mesh of a periodic section including parts of two neighboring blades

  • map the average of all periodic sections for steady state frozen rotor/MRF simulation results which do not necessarily exhibit rotational symmetry
  • perform a Fourier transformation on transient data to create and map the loading for vibration analyses
  • map harmonic CFD results having regard to the data’s inter-blade phase angle
© Photo Fraunhofer SCAI

Mapping of harmonic pressure data from a periodic source to a full target mesh in consideration of the inter-blade phase angle

Realization of new Methods and Solutions within R&D Projects

  • Coupling of harmonic simulations in frequency domain. This new feature enables a fast coupling of structural vibration and harmonic CFD analyses in order to calculate the steady state of the the fluid structure interaction.

Service Offer

  • Integration of commercial or inhouse codes into the MpCCI tools
  • Integration of MpCCI tools into customer’s CAE workflow
  • Adjusting MpCCI to customer’s specific requirements

MpCCI CouplingEnvironment

The MpCCI CouplingEnvironment offers flexible solutions for multiphysical simulations. The combinable simulation codes for this application area are shown in the following table:

Discipline

Codes

Fluid

  • FINE/Turbo, FINE/Open
  • ANSYS Fluent
  • STAR-CD
  • STAR-CCM+
  • OpenFOAM

Heat Transfer

  • Abaqus
  • ANSYS Mech.
  • MSC.Marc

Structure

  • Abaqus
  • ANSYS Mech.
  • MD Nastran
  • MSC.Marc

 

The supported quantities in this context are:

 

Quantities

Mechanical

  • pressure
  • force
  • position

Thermal

  • surface and volume temperature
  • wall heat flux
  • film temperature, heat transfer coefficient


List of all supported codes and quantities


MpCCI FSIMapper

The MpCCI FSIMapper maps simulation results from a source to a target mesh. The following two tables list the supported source and target file formats for this application area.

 

Source Formats

Quantities

CFD

  • ANSYS Fluent (.cas, .dat)
  • ANSYS CFX (.csv)
  • EnSight Gold (.case)
  • FINE/Turbo (.cgns)
  • STAR-CCM+ (.case)
  • OpenFOAM (.case)

pressure

temperature

heat flux

film temperature, heat coeff.

 

 

Target Formats

Target Analyses

FEM

  • Abaqus
  • ANSYS Mech.
  • Nastran

deformation

stress

heat transfer

NVH

fatigue


List of additionally supported source and target file formats