Search Results

Further improvements of internal combustion engines to reduce fuel consumption and to face future legislation constraints are strictly related to the study of mixture formation. The reason for that is the desire to supply the engine with homogeneous charge, towards the direction of a global stoichiometric blend in the combustion chamber. Fuel evaporation and thus mixture quality mostly depend on injector atomization features and charge motion within the cylinder. 3D-CFD simulations offer great potential to study not only injector atomization quality but also the evaporation behavior. Nevertheless coupling optical measurements and simulations for injector analysis is an open discussion because of the large number of influencing parameters and interactions affecting the fuel injection’s reproducibility. For this purpose, detailed numerical investigations are used to describe the injection phenomena.

The industry is working intensively on the precision of thermal management. By using complex thermal management strategies, it is possible to make engine heat distribution more accurate and dynamic, thereby increasing efficiency. Significant efforts are made to improve the cooling efficiency of the engine water jacket by using 3D CFD. As well, 1D simulation plays a significant role in the design and analysis of the cooling system, especially for considering transient behaviour of the engine. In this work, a practice-oriented universal method for creating a 1D water jacket model is presented. The focus is on the discretization strategy of 3D geometry and the calculation of heat transfer using Nusselt correlations. The basis and reference are 3D CFD simulations of the water jacket. Guidelines for the water jacket discretization are proposed. The heat transfer calculation in the 1D-templates is based on Nusselt-correlations (Nu = Nu(Re, Pr)), which are derived from 3D CFD simulations.

As part of a system model, a PEM fuel cell stack model is presented for functional tests and pre-calibration of control units on hardware-in-the-loop (HiL) test benches. From the basic idea to couple a 1-D membrane model with a spatially distributed abstraction of the gas channel, a real-time capable 1-D+1-D PEM FC stack model is constructed. Fundament for the HiL usage is an explicit formulation of the commonly implicit model equations. With that, not only calculation time can be reduced, but also model accuracy is preserved. A validation using test bench data emphasizes the accuracy of the model. Finally, a runtime and eigenvalue analysis of the stack model proves the real-time capability.

A simulation approach to predict the amount of snow which is penetrating into the air filter of the vehicle’s engine is important for the automotive industry. The objective of our work was to predict the snow ingress based on an Eulerian/Lagrangian approach within a commercial CFD-software and to compare the simulation results to measurements in order to confirm our simulation approach. An additional objective was to use the simulation approach to improve the air intake system of an automobile. The measurements were performed on two test sites. On the one hand we made measurements on a natural test area in Sweden to reproduce real driving scenarios and thereby confirm our simulation approach. On the other hand the simulation results of the improved air intake system were compared to measurements, which were carried out in a climatic wind tunnel in Stuttgart.

As a consequence of reduced fuel consumption, direct injection gasoline engines have already prevailed against port fuel injection. However, in-cylinder fuel homogenization strongly depends on charge motion and injection strategies and can be challenging due to the reduced available time for mixture formation. An insufficient homogenization has generally a negative impact on the combustion and therefore also on efficiency and emissions. In order to reach the targets of the intensified CO2 emission reduction, further increase in efficiency of SI engines is essential. In this connection, 0D/1D simulation is a fundamental tool due to its application area in an early stage of development and its relatively low computational costs. Certainly, inhomogeneities are still not considered in quasi dimensional combustion models because the prediction of mixture formation is not included in the state of the art 0D/1D simulation.

A new generation of instrument panels will be characterized by a single material design. In the design process, more and more attention is directed to the life cycle steps after the usage phase of parts, products or systems. For this reason, the aim of every designer should be the development of a recyclable part, product or system. The request for the development should not only be recyclability, but also economic efficiency as well as low environmental impact during production and usage phase. Life Cycle Assessment (LCA) is a tool for the development and design process to obtain an optimized economic and ecological (low environmental impact during the whole life cycle) product. A methodology, how Life Cycle Assessment could be integrated into the development and design process for parts, products and systems, will be presented.

The Institute for Polymer Testing and Polymer Science of the University of Stuttgart has been investigating automotive parts, structures and cars during their life cycle in plenty cooperation with the European automobile producers and their suppliers for the last 9 years. Therefore a holistic approach has been developed to combine tasks from technique, economic and environment in a methodology called Life Cycle Engineering (LCE). The goal is to find a way to support designer and engineers as well as police makers and public with this three-dimensional interrelated information to have the possibility to manufacture future products in a more sustainable way without loosing contact two the traditional parameters technique and costs.

In this paper, a simulation approach is introduced which takes into account all relevant heat sources and sinks in the combustion engine and in the engine compartment. With this approach, it is possible to calculate the appearing power flow and enthalpy flow as well as the component temperatures. Therefore, the complex thermodynamic and friction processes in the engine are described as simple as possible; the complete system can still be described reliably within certain limits, and the effects of different thermal optimization measures can be shown. It is an essential point for the modeling that only two integral quantities are necessary (the high pressure efficiency and the high pressure wall heat loss) for the complete combustion model.

For integrating Life Cycle Assessment into the design process it is more and more necessary to generate models of single life cycle steps respectively manufacturing processes. For that reason it is indispensable to develop parametric processes. With such disposed processes the aim could only be to provide a tool where parametric environmental process models are available for a designer. With such a tool and the included models a designer will have the possibility to make an estimation of the probable energy consumption and needed additive materials for the applied manufacturing technology. Likewise if he has from the technical point of view the opportunity, he can shift the applied joining technology in the design phase by changing for instance the design.

One of the most important means used for suppressing squeal noise in disc brakes is the application of shims on the pad backplates. In many cases this proves a very efficient tool depending on the type of shim applied in the specific cases. Building up knowledge on the effects of shims have been ongoing for several years, and measuring the important parameters characterizing the shims is crucial for understanding how to develop and implement the shims in an optimal way. Several methods are described in literature for measuring the constrained layer damping effect and one method is described for direct measurement of the shear stiffness and shear damping properties. However, up to now no method has been available that can measure and characterize the normal stiffness and damping properties of shims. This is one of the most important properties of shims as it controls the de-coupling effect in the direction of the normal forces.

Today, a number of simulation codes are available for pre-designing gas exchange systems of IC engines with good accuracy (e.g. PROMO, WAVE, GT-Power). However, optimizing such systems still requires numerous time consuming and inefficient trial and error runs. Also, accounting for constraints as size, volume, peak combustion pressure etc. multiplies the necessary efforts additionally. Hence there is a strong need for efficient procedures for finding optimum designs automatically and reliably. To automatically find the global optimum design parameters under a given set of real constraints of a practical case, a multi-membered evolution-strategy based optimization code was developed. The code which efficiently finds the true optimum dimensions of gas exchange systems (duct lengths, duct diameters, volumes) of an IC engine. The code can be readily generalized, and adapted to arbitrary optimization problems.

Automotive electric and electronic devices are commonly tested with standard pulses at the battery lines according to ISO 7637-Part 1 and 2. As these pulses do not cover all disturbances that occur in modern passenger cars, each OEM defines its own additional test-pulses which makes it difficult for component suppliers to satisfy all existing requirements. The paper shows a comparison between measurement and simulation such as slow “ignition on” pulses of a modern passenger car. Additionally, the ability of the computing model to calculate the propagation of fast transients and characteristic pulses of currently used electric and electronic devices is demonstrated. This data can be used for the definition of new test-pulses.

Today, mechanical systems such as the piston groups of internal combustion engines are simulated using Multiple Body-System (MBS) - approaches. However, the use of these models is restricted to a few problems as their adaptability is limited. The simulation of mechanical systems only by means of finite elements shows great promise for the future. In order to consider lubrication effects between two touching bodies of a mechanical system, a hydrodynamic contact algorithm (HCA) for finite element (FE) applications was developed. This paper discusses the technical background and first results for the simulation of a piston group using this new approach.

Improvement of heat-transfer calculation for SI-engines in the three-dimensional simulation has been achieved and widely been tested by using a phenomenological heat-transfer model. The model is based on the local application of an improved Re-Nu-correlation (dimensional analysis) proposed by Bargende [1]. This approach takes advantage of long experience in engine heat transfer modeling in the real working process analysis. The results of numerous simulations of different engine meshes show that the proposed heat-transfer model enables to calculate the overall as well as the local heat transfer in good agreement with both real working process analyses and experimental investigations. The influence of the mesh structure has also been remarkably reduced and compared to the standard wall function approach, no additional CPU-time is required.

The strong demand for advanced lightweight structures in the automotive industry has increased activities in the development of new structural materials with low densities and tailored properties. Weight savings in the wheel suspension by the use of lightweight materials provide the additional benefit of an improvement in comfort behavior and driveability. The replacement of iron based materials with ceramics offers the possibility for a significant mass reduction. In the case of high tribological, environmental and thermal loads, ceramics provide the additional advantages of excellent wear, corrosion and temperature resistance with tailored properties for application as brake disk material. Silicon carbide (SiC) ceramics are promising structural materials in various high temperature and tribological applications.

The costs for development and production of draw dies for car outer panels are extremely high and should be reduced. Furthermore it is necessary to reduce the time for developing, designing and producing the dies for the production of parts. This paper discusses new press techniques, die designs and an adjustment program for press operators. The trend goes to single action presses with CNC-controlled multipoint cushion systems in the press table and to special designed dies. These systems lead to a more robust and reproducible forming process with improved product quality. This paper deals with: Cushion Systems, New Binder Designs for Draw Dies for Sheet Metal Automotive Parts, New Computer Program to Adjust the Blankholder Forces of Modern Hydraulic Cushion Systems of Single Action Presses and Pressure Measurement for Detecting the Pressure between the Blank and the Binders of Draw Dies for Sheet Metal Automotive Parts.

The EU SPARC Project (Secure Propelled Vehicle with Advanced Redundant Control) has developed a new system architecture that enables effective application of driver assisted systems in an X-by-wire powertrain. A major challenge in the conception of such a system is development of a reliable electrical energy supply. A simulation is the most important tool for enabling the fundamental aspects to work, as for example, a dimensioning of the powernet. This article explains our approach in this SPARC simulation. We provide suggestions through examples of how to find simulation solutions for powernet dimensioning, as well as for the conception and validation of energy management strategies.

A numerical simulation program for the design of the cooling air duct and the cooling system of vehicles for stationary operating conditions is introduced. This program allows the simulation of interactions with the system environment resp. an air conditioning. Hot recirculations of air in the front part of the car and the inhomogenious flow through the heat exchangers radiator and condensor in their affects on the heat transfer capacity are simulated. The power demand of the fan, the water pump and the compressor is taken into account for calculating the heat flow from the engine into the cooling water.

A real-time 3-dimensional, nonlinear simulator for the dynamical behaviour of trucks has been developed. The simulator serves as industrial test stand for examinations on different electronic control systems. This paper describes the challenging task of developing a powerful real-time simulator with hardware coupling based on parallel transputer systems. The integration of an anti-lock braking system (ABS) as hardware-in-the-loop by means of an interface electronic device is described. The interface electronics provide the coupling of the electronic control unit (ECU). The special demands on the signals and the resulting concept for the developed electronic interface are specified. Some results from dynamic braking simulations show the quality of the simulator.

During sheet metal forming processes, the friction conditions have a decisive influence on forming limits, the robustness of the production process and the quality of the parts produced, with significant forces required to overcome friction between the sheet and the tools. If lot-to-lot reproducibility is to be guaranteed, an appropriate method of characterizing the sheet surface topography is needed to monitor the sheet metal fabrication process. Newly developed optical measurement techniques and computer workstation technology are presented which enable the topography of sheet surfaces to be described in three dimensions.