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A chemical sub-model for realistic CFD simulations of Diesel engines is developed and demonstrated by application to some test cases. The model uses a newly developed progress variable approach to incorporate a realistic treatment of chemical reactions into the description of the reactive flow. The progress variable model is based on defining variables that represent the onset and temporal development of chemical reactions before and during self ignition, as well as the stage of the actual combustion. Fundamental aspects of the model, especially its physical motivation and finding a proper progress variable, are discussed, as well as issues of practical implementation. Sample calculations of Diesel-typical combustion scenarios are presented which are based on the progress-variable model, showing the capability of the model to realistically describe the ignition-and combustion phase.

A progress variable approach for the 3D-CFD simulation of DI-Diesel combustion is introduced. Considering the Diesel-typical combustion phases of auto-ignition, premixed and diffusion combustion, for each phase, a limited number of characteristic progress variables is defined. By spatial-temporal balancing of these progress variables, the combustion process is described. Embarking on this concept, it is possible to simulate the reaction processes with detailed chemistry schemes. The combustion model is coupled with a mesh-independent Eulerian-spray model in combination with orifice resolving meshes. The comparison between experiment and simulation for various Diesel engines shows good agreement for pressure traces, heat releases and flame structures.

For studying the effects of injection system properties and combustion chamber conditions on the penetration lengths of both the liquid and the vapor phase of fuel injectors in Diesel engines, a holistic injection model was developed, combining hydraulic and spray modeling into one integrated simulation tool. The hydraulic system is modeled by using ISIS (Interactive Simulation of Interdisciplinary Systems), a one dimensional in–house code simulating the fuel flow through hydraulic systems. The computed outflow conditions at the nozzle exit, e.g. the dynamic flow rate and the corresponding fuel pressure, are used to link the hydraulic model to a quasi–dimensional spray model. The quasi–dimensional spray model uses semi–empirical 1D correlation functions to calculate spray angle, droplet history and droplet motion as well as penetration lengths of the liquid and the vapor phases. For incorporating droplet vaporization, a single droplet approach has been used.

Coming along with the present movement towards the ultimately variable engine, the need for clear and simple models for complex engine systems is rapidly increasing. In this context Common-Rail-Systems cause a special kind of problem due to of the high amount of parameters which cannot be taken into consideration with simple map-based models. For this reason models with a higher amount of complexity are necessary to realize a representative behavior of the simulation. The high computational time of the simulation, which is caused by the increased complexity, makes it nearly impossible to implement this type of model in software in closed loop applications or simulations for control purposes. In this paper a method for decreasing the complexity and accelerating the computing time of automotive engine models is being evaluated which uses an optimized method for each stage of the diesel engine process.

High demands in fuel consumption, efficiency, and low emissions lead to complex control functions for current and future diesel engine management systems. Great effort is necessary for their optimal calibration. At the same time, and particularly for cost reasons, many variants exist on one individual type of diesel engine management system. Not only is it used for several base engines, but these engines are also used in different environments and for different tasks. For optimal deployment, their calibration status must also be optimized individually. Furthermore, the demand for shorter development cycles and enhanced quality lead to a catalogue of new requirements for the calibration process and the affiliated tool. A new calibration system was developed, which optimally reflects the new demands.

Topology optimization in structural analysis is known for many years. In the presented procedure, “topology optimization” is used for computational fluid dynamics (CFD) for the first time. It offers the possibility of a very fast optimization process under utilization of the physical information in the flow field instead of using optimization algorithms like for example evolution strategies or gradient based methods. This enables the design engineer to generate in a first layout air guiding systems with low pressure drop in a fast and easy manner, which can than be improved further due to constraints of styling or production requirements. This procedure has been tested with many examples and shows promising results with a reduction in pressure loss up to 60% compared to a duct designed in CAD in the traditional way.

The following document offers insight into the work of the MOST Cooperation. Now that MOST is on the road, a short overview of five years of successful collaborative work of the partners involved and the results achieved will be given. Emphasis is put on the importance of a shared vision in combination with shared values as a prerequisite for targeted collaborative work. It is also about additional key success factors that led to the success of the MOST Cooperation. Your attention will be directed to the way the MOST Cooperation sets and achieves its goals. And you will learn about how the organization was set-up to support a fast progression towards the common goal. The document concludes with examples of recent work as well as an outlook on future work.

In open jet wind tunnels with high blockage ratios a sharp rise in drag is observed for models approaching the nozzle exit plane. The physical background for this rise in drag will be analyzed in the paper. Starting with a basic analysis of the dependencies of the effect on model and wind tunnel properties, the key parameters of the problem will be identified. It will be shown using a momentum balance and potential flow theory that interaction between model and nozzle exit can result in significant tunnel-induced gradients at the model position. In a second step, a CFD-based investigation is used to show the interaction between nozzle exit and a bluff body. The results cover the whole range between open jet and closed wall test section interaction. The model starts at a large distance from the nozzle, then moves towards the nozzle, enters the nozzle and is finally completely inside the nozzle.

This paper introduces the new 1.6L engine family, designed and developed by the Chrysler group of DaimlerChrysler Corporation in cooperation with BMW. An overview of the engine's design features is provided, with a detailed review of the performance development process with emphasis on airflow, combustion, thermal management and friction. This information is presented, to provide an understanding of how the engine simultaneously achieves outstanding levels of torque, power, fuel consumption, emissions and idle stability. The use of analytical tools such as Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) in the optimization of the engine is shown.

In order to fulfill the need for an efficient and reliable computational method for the aerodynamic optimization of passenger cars, a numerical simulation strategy has been developed at DaimlerChrysler in Stuttgart. The simulation strategy consists of surface preparation, three dimensional mesh generation, flow simulation using CFD, and post-processing. The method will be applied mainly in the early concept phase of the development process when 1:4 scale models with smooth underbodies are used. In this study SAE-bodies as well as modifications of real car shapes are presented. The paper also discusses which improvements are needed to establish a mainly CFD-based process in the early concept phase.

In the present study, the thermal comfort in a convertible has been evaluated using the in-house program TEKOS. The investigations have been performed for a SLK-class Mercedes with two occupants. The computational mesh consists of about 3 million hexahedra cells. TEKOS has been adapted to open driving conditions. The influence of the air-conditioning system and of different draft stops on the thermal comfort has been investigated in an autumn case. The study has shown, that in a basic case without draft stop and air conditioning the evaluation results in very poor thermal comfort values at the whole body, especially at unclothed parts of the body. If a draft stop and maximum heating is regarded, almost all parts of the body are close to the comfort range except of the head region. With TEKOS it is possible to quantify the influence of different parameters on the thermal sensation in convertibles with the advantage of an objective thermal evaluation.

This paper evaluates several durability tire models using Virtual Tire Testing (VTT) strategy. VTT conducts tire testing (simulation) using LS–DYNA based on a Virtual Tire which is built by 3–D finite element mesh. VTT is repeatable and could do special tire tests which can't be done using normal tire testing bench. A brief review is given on durability tire models and several typical tire models are selected for this study. All the necessary parameters for establishing the analytical tire models are extracted from the Virtual Tire. Quarter vehicle model is used to simulate the vehicle vertical vibration. The comments of those analytical tire models are given based on their performance vs. VTT.

This paper presents velocity and pressure measurements obtained around an isolated wheel in a rotating and stationary configuration. The flow field was investigated using LDA and a total pressure probe in the model scale wind tunnel at IVK/FKFS. Drag and lift were determined for both configurations as well as for the wheel support only. These results were used as a reference for comparing numerical results obtained from two different CFD codes used in the automotive industry, namely STAR-CD™ and PowerFLOW™. The comparison gives a good overall agreement between the experimental and the simulated data. Both CFD codes show good correlation of the integral forces. The influence of the wheel rotation on drag and lift coefficients is predicted well. All mean flow structures which can be found in the planes measured with LDA can be recognized in the numerical results of both codes. Only small local differences remain, which can be attributed to the different CFD codes.

The development of electronic intelligence and the continually increasing intensive knowledge of driving dynamics make it possible nowadays to conceive intelligent vehicle systems and to make such systems available for series production, which are capable of substantially enhancing the active safety of commercial vehicles. Through the implementation of advanced subsystems, which can be integrated as software packages into the basic electronic braking system, it will be possible to expand the possibilities of introducing assistance systems, which are capable of both, helping and relieving the driver from stress in critical situations. The driver will be relieved of all duties which could divert his attention or cause severe stress. As a consequence, the active safety of commercial vehicles will be considerably increased.

The current is an investigation of the effects of charge motion, namely tumble, on the burn characteristics of the new Chrysler Hemi SI engine. In order to reduce prototyping, several combustion system designs were evaluated; some of which were eliminated prior to design inception solely based on CFD simulations. The effects of piston top and number of spark plugs were studied throughout the conceptual stage with the AVL-FIRE CFD code. It has been concluded that large-scale, persistent and coherent tumbling flow structures are essential to charge motion augmentation at ignition only if such structures are decimated right before ignition. Piston top had a detrimental effect on tumbling charge motion as the piston approaches the TDC. When compared to single spark plug operation, dual spark plug reflected considerable improvement on burn characteristics and engine performance as a consequence. The CFD simulations demonstrated good correlation with early dynamometer data.

In the present study, the exterior air flow over convertibles together with the interior flow in the passenger compartment has been calculated using the commercial CFD program STAR-CD. The investigations have been performed for a SLK-class Mercedes with two occupants. The computational mesh consists of about 3 million hexahedra cells. The detailed informations of the calculated flow field have been used to elaborate the characteristic flow phenomena and increase the physical understanding of the flow. The influence of different geometrical modifications (variations of roof spoiler, variations of the draft stop behind the seats etc.) on the flow field and the air draft experienced by the occupants has been analyzed. To proof the accuracy of the numerical results, wind tunnel experiments in a full scale and 1:5 scale wind tunnel have been carried out for the basic car model as well as for several geometrical variations.

A two-dimensional numerical model describing the ammonia based SCR-process on vanadia-titania catalysts is presented. The model is able to simulate coated and extruded monoliths. For the determination of the intrinsic kinetics of the various NH3-NOx reactions, unsteady microreactor experiments were used. In order to account for the influence of transport effects the kinetics were coupled with a fully transient two-phase 1D+1D monolith channel model. The model has been validated extensively with laboratory data and engine test bench measurements. After validation the model has been applied to calculate catalyst NOx conversion maps, which were used to define catalyst sizes. Additional simulations were conducted studying the influence of cell density and NH3-dosage ratio.

A 1D+1D numerical model describing the ammonia based SCR process of NO and NO2 on vanadia-titania catalysts is presented. The model is able to simulate coated and extruded monoliths. Basing on a fundamental investigation of the catalytic processes a reaction mechanism for the NO/NO2 - NH3 reacting system is proposed and modeled. After the parameterization of the reaction mechanism the reaction kinetics have been coupled with models for heat and mass transport. Model validation has been performed with engine test bench experiments. Finally the model has been applied to study the influence of NO2 on SCR efficiency within ETC and ESC testcycles, Additional simulations have been conducted to identify the potential for catalyst volume reduction if NO2 is present in the inlet feed.

In the present paper, first results of an extensive and ongoing parametric study are shown. The objective of the parametric study is to clarify the influence of relevant flow and geometrical parameters on the microclimate and thermal comfort of the occupants. Flow parameters included in the study are air mass fluxes, velocity magnitude, air temperature and inflow direction at the vents. Geometrical parameters of interest are number, location, area and shape of the air vents as well as geometrical details of the passenger compartment itself. The parametric study is performed numerically on the basis of a computational model for a passenger compartment of a Mercedes E-Class sedan. The numerical method used has been published earlier and consists of a system of three programs for simulating the flow and temperature field in the cabin, the heat transfer and radiation and the thermal sensation of the occupants.

Boundary mannequin is an important concept in digital human modeling and simulation, yet complicated to deal with and utilize. In theory, the number of boundary mannequins could be as much as (n!)2n for a single gender, where n is the number of critical anthropometric dimensions. It has been recommended [1] to break a complicated task into smaller tasks to reduce the scale of problem, and limit n=2 whenever possible. Even then, the number of boundary mannequins is still high for simulations. In this paper, the authors intend to further simplify the issue. An Excel worksheet is created for the purpose. The input can be as few as two points. An ellipse representing the boundary is automatically generated through regression analysis, and the extremes on the major and minor axes of the ellipse are then obtained, and taken as the optimal boundary mannequins.