Summary of Presentation from the 2014 ESI SimulationX User Forum
Conference Paper by Uwe Schreiber, Andreas Abel - ITI GmbH (now ESI Group), Dresden, Germany
In this study, Schreiber and Abel address the challenges of modeling powertrains with combustion engines, particularly focusing on temperature-sensitive components. The calibration of engines, vibration dampers, couplings, and drivelines is complex due to the elasticity and damping properties of materials that change with temperature. To effectively manage torsional vibrations, components must be robust enough to handle both transient loads and steady-state operations. The authors propose a network model that accurately describes mechanical and thermal interactions, using geometry data for parameterization and material values from a database.
The paper presents a universal method applicable to all driveline components with temperature-dependent characteristics. A Diesel engine with a viscous torsional damper serves as the example system, emphasizing the importance of analyzing the steady-state temperature behavior and its impact on damper properties. This model is integrated into the Diesel engine using a commercial simulation tool, enabling both transient and steady-state simulations.
Engine with a viscous torsional vibration damper in SimulationX
Modern combustion engines, with features like downsizing, reduced cylinder counts, and variable displacement operations, face increased torsional loads and vibration excitation. Viscous torsional vibration dampers, mounted on the crankshaft, mitigate these vibrations. However, the increased load from the engine necessitates careful design and dimensioning of the dampers, considering the temperature dependence of stiffness and damping. Stiffness influences natural frequencies, while damping affects vibration power dissipation.
Classical steady-state approaches use linear transformations like Laplace or Fourier transforms to convert time-domain representations into frequency-domain representations. These methods, however, are only straightforward for linear systems. The authors employ network modeling methods, suitable for describing lumped-parameter physical systems across various domains (mechanical, fluid, thermal, electrical), where elements interact non-causally.
User-friendly parameterization with geometry data and material data from the database in SimulationX
ITI has developed a solution within the SimulationX software that allows steady-state analysis and transient simulation on the same model, enhancing modeling and simulation efficiency. The system is described as an intermeshed network of lumped parameter elements, formulated as systems of ordinary differential equations or differential algebraic equations (ODE or DAE).
For linear systems, classical frequency domain methods reduce these to algebraic equations. For nonlinear systems, the harmonic balance method allows computation of steady-state results without fully transforming the system into the frequency domain. This method computes spectral results for steady-state operations efficiently, avoiding iterative parameter tuning and multiple simulation runs.
Damping power and temperature in the viscous damper over speed
Temperature-dependent characteristics are exemplified using stiffness and damping equations for a viscous damper and a natural rubber coupling. The SimulationX model integrates thermal networks to simulate the heat flow and temperature distribution, using geometry data and material properties from a database.
Damping power and temperature over speed in case of low damping
The study demonstrates that accounting for temperature-dependent parameters is crucial for accurate driveline behavior estimation. Nonlinear system models, addressed through harmonic balance methods implemented in SimulationX, offer precise and efficient analysis without iterative approximations. This method significantly improves the accuracy and efficiency of the analysis, emphasizing the importance of considering thermal feedback in driveline dynamics.
References
[1] Abel, A., Nähring, T., Frequency-Domain Analysis Methods for Modelica Models, Proceedings of the 6th International Modelica Conference, Vol. 2, Bielefeld, pp. 383-391 (2008).
[2] Abel, A., Schreiber, U., Werner, E., Bridging the Gap between Steady-State and Transient Simulation for Torsional Vibrations under Ice Impact, Proceedings of the 12th International Conference on Computer and IT Applications in the Maritime Industries – COMPIT’ 13, Cortona, pp. 402-412 (2013).
[3] User Manual SimulationX, ITI GmbH Dresden (2014).
If interested in additional information, please contact us for the full proceedings of the 2014 SimulationX User Forum.
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