Numerical analytic processes established as an inherent part of engine development in the past years. The integration of simulations into the development process, starting at the conceptual phase and ending at the SOP has turned out to be an effective possibility to reduce development time and cost.
At the Chair of Thermodynamics of Mobile Energy Conversion Systems (TME) in cooperation with the FEV GmbH methods for virtual development are developed steadily. The cooperation of construction, the disciplines of the “Computer Aided Engineering” (CAE) and engine test bench is essential for the virtual engine. CAE simulation supports construction and test bench since first calculations can be used for design reviews before a prototype has been produced. In the same way data can be calculated which can be used for additional calculations which cannot or can only hardly be captured in measurements. Experiments on the other hand are essential for the simulations and to validate and improve models.
The key points of development at the TME are:
- Gas exchange and process simulation
- CFD simulation (Computational Fluid Dynamics)
- Structural calculations
Gas exchange and process calculation
The goal of gas exchange calculation is to represent the engine process thermodynamically. Based on the reduction to one-dimensional fluid dynamics and the simplified representation of the engine parts, this calculation method is characterized by low calculation times. Gas exchange calculation is first of all used for the geometrical design of the intake and exhaust system and for dimensioning of the turbocharger. Current research projects deal with the calculation of the unsteady engine behavior for calibration support.
CFD simulation is used for a detailed and spatiotemporal flow calculation of single components. Along with the calculations for geometrical optimization of components like the intake tube, cooling jacket and catalyst inflow the simulation of the flow inside the cylinder and fuel mixture generation are central fields of research within CFD simulation.
The shapes of charge motion and turbulences have significant influence on the efficiency and on the progress of the combustion and pollutant formation in gasoline as well as diesel engines. To specify the injection process, the TME developed fuel and injection models which describe the expansion and vaporization of the fuel stream for different injector types. Using optical experiments these models got adapted and validated.
In current research projects CFD simulation in combination with optical measuring is the foundation for the analysis of new combustion processes like controlled auto ignition where CFD simulations support the understanding of the processes.
Structural calculations and AcousticsCopyright: © RWTH Aachen | TME
The main focuses of MKS are time discrete dynamical calculations. MKS is especially used for simulations of the complete engine or even powertrain. It is possible to determine strength and durability as dynamics of the selected parts. With the help of dynamic loads predictions on the durability can be calculated.
Using FEM with high-resolution models, different problems of mechanics and thermal dynamics can be solved. Central application areas are low-cycle and high cycle fatigue calculations of engine parts.
The loads determined by MKS can be adjusted to the FEM model to calculate the mechanical loads. FEM and MKS are strongly connected at the TME.
To validate the results and to improve the simulation, models of real engines are matched with the simulation results in several research projects.
Nowadays the acoustics development with using CAE methods (Computer Aided Engineering) would be impossible. Here calculation methods like FEM, MKS and the Boundary Element Method (BEM) as well as CFD methods are used.