In addition to various possibilities in the field of testing, FEV also has advanced expertise in the numeric examinations of turbochargers. The process that begins with the transfer of CAD data is automated to the greatest extent possible, whereby the complicated and time-consuming new connection can be avoided even for changes in the geometry by switching the waste gate position on the turbocharger, for example. In addition to stationary examinations with the frozen rotor approach, fully transient CFD examinations are located in the FEV portfolio. The simulation under various conditions and the post-processing of the results are also part of the automated process.
In addition to adiabatic characteristic simulations, FEV has a lot of experience in the simulation of entire turbocharger models, including heat transfers between fluid and solid body structure (Conjugate Heat Transfer). Evaluation levels can be placed at any point within the 3D CFD models in order to fully evaluate the aerodynamic performance independently of complex measuring equipment at the test bench. Numeric examinations are also offered in the area of the catalyst inflow and the exhaust manifold as connecting engine components to the turbocharger. The simulation results are incorporated as a framework condition or as a comparison in the optimization of individual components or serve as an assessment of operational behavior in the preliminary selection of turbochargers.
Bearings and multi-body simulation
The radial bearings of the rotor of an exhaust turbocharger (ETC) are usually listed as hydrodynamic fully floating bushing bearings, individually as roller bearings. Axial guidance is usually handled by a double-sided, hydrodynamic axial segment bearing. The complete rotor dynamics of the ETC and the bearing behavior are analyzed using elastic multibody simulation (MBS) and the coupled thermo-elasto-hydrodynamic (TEHD) calculations with the help of the commercial MBS software FEV Virtual Engine ©.
In addition to synchronous and subsynchronous vibrations, the hydrodynamic lubricant film pressures and bearing friction can also be determined in this way in the early ETC development phase and optimized early on in the ETC.
Typical computational results here are
- Bearing reaction forces and torques
- Contact and lubricant film pressures, minimum lubricant film thicknesses, and friction losses
- Shift paths and bearing eccentricities
- Rotor movements and excitations (Campbell diagrams and waterfall plots for stability and NVH analysis)
In addition to the rotor dynamic and the bearing, focus can also be placed on the dynamic of other ETC components that can vibrate, such as the turbine-side bypass / waste gate level system. To this end, previously determined excitation forces are applied to the entire ETC system and analyzed.
With the help of the standardized co-simulation interface FMI (Functional Mock-up Interface), FEV Virtual Engine © also offers the option of carrying out coupled simulations with additional simulation tools – for example, using GT-POWERTM. As an example, the entire engine oil circuit is coupled with the ETC dynamic in order to represent even more detailed bearing effects through the oil supply.
More Information on Virtual Engine.