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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.

The main objective of engine 3D CFD simulation is nowadays the support for combustion design development. New combustion concepts (e.g. Low Temperature Combustion, HCCI, multiple injection strategies …) could be analyzed and predicted through detailed thermodynamical computation. To achieve this aim many simulation tools are needed: each of them has to be capable to reproduce the sensitivities of combustion design parameters through physically based models. The adopted approach consists of the coupling of different models for 3D-nozzle flow, orifice-resolved spray formation in Eulerian coordinates and combustion. The advantages of the method will be proofed on an operative DI-diesel truck engine case, run with different nozzle geometries.

Over the next decades to come, fossil fuel powered Internal Combustion Engines (ICE) will still constitute the major powertrains for land transport. Therefore, their impact on the global and local pollution and on the use of natural resources should be minimized. To this end, an extensive fundamental and practical study was performed to evaluate the potential benefits of simultaneously co-optimizing the system fuel-and-engine using diesel as an example. It will be clearly shown that the still unused co-optimizing of the system fuel-and-engine (including advanced exhaust after-treatment) as a single entity is a must for enabling cleaner future road transport by cleaner fuels since there are large, still unexploited potentials for improvements in road fuels which will provide major reductions in pollutant emissions both in vehicles already in the field and even more so in future dedicated vehicles.

A Mercedes E320 CDI vehicle has been modified for more optimal operation on Gas-To-Liquids (GTL) diesel fuel, in order to demonstrate the extent of exhaust emission reductions which are enabled by the properties of this fuel. The engine hardware changes employed comprised the fitment of re-specified fuel injectors and the reduction of the compression ratio from 18:1 to 15:1, as well as a re-optimisation of the software calibration. The demonstration vehicle has achieved a NOx emission of less that 0.08 g/km in the NEDC test cycle, while all other regulated emissions still meet the Euro 4 limits, as well as those currently proposed for Euro 5. CO2 emissions and fuel consumption, were not degraded with the optimised engine. This was achieved whilst employing only cost-neutral engine modifications, and with the standard vehicle exhaust system (oxidation catalyst and diesel particulate filter) fitted.

Investigations of the aerodynamic influence of rotating wheels on a simplified vehicle model as well as on a series production car are presented. For this research CFD simulations are used together with wind tunnel measurements like LDV and aerodynamic forces. Several wheel rim geometries are examined in stationary and in rotating condition. A good agreement could be achieved between CFD simulations and wind tunnel measurements. Based on the CFD analysis the major aerodynamic mechanisms at rotating wheels are characterized. The flow topology around the wheels in a wheel arch is revealed. It is shown, that the reduction of drag and lift caused by the wheel rotation on the isolated wheel and the wheel in the wheel arch are based on different effects of the airflow. Though the forces decrease at the front wheel due to the wheel rotation locally, the major change in drag and lift happens directly on the automotive body itself.

External Exhaust Gas Recirculation, EGR, is a central issue in controlling emissions in up-to-date diesel engines. An empirical model has been developed that calculates the EGR ratio as a function of the engine speed, the engine load and special characteristics of the heat release rate. It was found that three combustion characteristics correlate well with the EGR ratio. These characteristics are the ignition delay, the premixed combustion ratio and the mixing-controlled combustion ratio. The calculation of these characteristics is based on parameter subsets, which were determined using an optimization routine. The model presented was developed based on these optimized characteristics.

A new six-speed transaxle has been introduced by the Chrysler Group of DaimlerChrysler AG. Along with the six forward ratios in the normal upshift sequence, this transaxle features a seventh forward ratio used primarily in a specific downshift sequence. A significant technical challenge in this design was the control of so-called double-swap shifts, the exchange of two shift elements for two other shift elements. In the case at hand, one of the elements is a freewheel. A unique solution is discussed for successful control of double-swap shifts. The new design replaces a four-speed transaxle but makes use of a large percentage of parts and processes from the four-speed design. This approach enabled the new transaxle to reach production in three years from concept. The new transaxle, referred to as the 62TE, has substantially improved performance and passing maneuvers coupled with a new 4.0L high output engine for which the 62TE was developed.

To fulfill future emission standards for diesel engines, combined after-treatment systems consisting of different catalyst technologies and diesel particulate filters (DPF) are necessary. For designing and optimizing the resulting systems of considerable complexity, effective simulation models of different catalyst and DPF technologies have been developed and integrated into a common simulation environment called ExACT (Exhaust After-treatment Components Toolbox). This publication focuses on a model for the NOx storage and reduction catalyst as a part of that simulation environment. A heterogeneous, spatially one-dimensional (1D), physically and chemically based mathematical model of the catalytic monolith has been developed. A global reaction kinetic approach has been chosen to describe reaction conversions on the washcoat. Reaction kinetic parameters have been evaluated from a series of laboratory experiments.

A numerical model describing the ammonia based SCR process of NOX on zeolite catalysts is presented. The model is able to simulate coated and extruded monoliths. The development of the reaction kinetics is based on a study which compares the activity of zeolite and vanadium based catalysts. This study was conducted in a microreactor loaded with washcoat powder and with crushed coated monoliths. A model for the SCR reaction kinetics on zeolite catalysts is presented. After the parameterization of the reaction mechanism the reaction kinetics were coupled with models for heat and mass transport. The model is validated with laboratory data and engine test bench measurement data over washcoated monolith catalysts. A numerical simulation study is presented, aiming to reveal the differences between zeolite and vanadium based SCR catalysts.

The integration of CAD/CAM/CAE in product development is the key to realize concurrent engineering. Generally, different systems are employed in product development department. These different systems create a lot of troubles such as difficult communication, misunderstanding and so on. A new approach to integrate CAD/CAM/CAE in one system based on CATIA for the end-to-end process in cylinder head development is presented. Multi-Model Technology (MMT) is used to create consistent and associated CAD models for the end-to-end process in cylinder head development. The concept and method to create and organize multi- models are discussed. A typically four-layer structure of MMT for mechanical products is defined. The multi-level structure of the cylinder head models based on MMT is provided. The CAD models of cylinder head created based on MMT can be used as the consistent model.

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.

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.

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.

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.

After-treatment systems (ATS) consisting of new catalyst technologies and particulate filters will be necessary to meet increasingly stringent global regulations limiting particulate matter (PM) and NOx emissions from heavy duty and light duty diesel vehicles. Fuels and lubes contain elements such as sulfur, phosphorus and ash-forming metals that can adversely impact the efficiency and durability of these systems. Investigations of the impact of lubricant formulation on the transfer of ash-forming elements to diesel particulate filters (DPF) and transfer of sulfur to NOx storage catalysts were conducted using passenger car diesel engine technology. It was observed that for ATS configurations with catalyst(s) upstream of the DPF, transfer of ash-forming elements to the DPF was significantly lower than expected on the basis of oil consumption and lube composition. Sulfur transfer strongly correlated with oil consumption and lubricant sulfur content.

Accident statistics show that rollover accidents contribute to a large proportion of fatal traffic accidents in the U.S.. In the past it has been documented that some light passenger cars showed tendencies to roll over in evasive lane change maneuvers. In 1997, a newly developed mini van rolled over in a severe double lane change test called “moose-test”. Recently (2001), a new SUV showed similar tendencies in the Consumers Union Short Course test. It is not immediately clear why these evasive test maneuvers are so strongly related to untripped rollover of light passenger vehicles. Therefore, the goal of current research is to understand the circumstances and effects causing modern passenger vehicles to roll over in evasive maneuvers on the road. This paper discusses research activities concerning the following questions: How do critical steering strategies lead to untripped rollover? Are resonant frequencies excited during maneuvers leading to rollover?

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.

To meet future emission levels the industry is trying to reduce tailpipe emissions by both, engine measures and the development of novel aftertreatment concepts. The present study focuses on a joint development of aftertreatment concepts for gasoline engines that are optimized in terms of the exhaust system design, the catalyst technology and the system costs. The best performing system contains a close-coupled catalyst double brick arrangement using a new high thermal stable catalyst technology with low precious metal loading. This system also shows an increased tolerance against catalyst poisoning by engine oil.

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.

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.