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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.

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.

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.

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.

In view of limited crude oil resources, alternative fuels for internal combustion engines are currently being intensively researched. Synthetic fuels from natural gas offer a promising interim option before the development of CO2-neutral fuels. Up to a certain degree, these fuels can be tailored to the demands of modern engines, thus allowing a concurrent optimization of both the engine and the fuel. This paper summarizes investigations of a Gas-To-Liquid (GTL) diesel fuel in a modern, post-EURO 4 compliant diesel engine. The focus of the investigations was on power output, emissions performance and fuel economy, as well as acoustic performance, in comparison to a commercial EU diesel fuel. The engine investigations were accompanied by injection laboratory studies in order to assist in the performance analyses.

In the automotive industry, the model-based approach is increasingly establishing itself as a standard paradigm for developing control unit software. Just as code reviews are widespread in classical software development as a quality assurance measure, models also have to undergo a stringent review procedure – particularly if they serve as a starting point for automatic implementation by code generators. In addition to these model reviews, the generated production code is reviewed later in the development process by performing auto code reviews. This article will present procedures for and give an account of experiences with model and code reviews which have been adapted to the model-based development process.

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.

Automotive catalysts close coupled to gasoline engines operated under high load are frequently subjected to bed temperatures well above 950 °C. Upon deceleration engine fuel cut is usually applied for the sake of fuel economy, robustness and driveability. Even though catalyst inlet gas temperatures drop down immediately after fuel cut - catalyst bed temperatures may rise significantly. Sources for catalyst temperature rise upon deceleration with fuel cut are discussed in this contribution.

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.

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.

This paper investigates the potential of using FEA poro-elastic Biot elements for the modeling carpet-like trim systems in a simplified setup. A comparison between FEA computations and experiments is presented for two layer (mass-spring) trim systems placed on a test-rig consisting in a 510×354×1.6 mm flat steel plate clamped in a stiff frame excited at its base. Results are presented for a given heavy layer with two different poro-elastic materials: one foam and one fibrous material. The investigations included accelerometer measurements on the steel plate, laser-doppler vibrometer scans of the heavy layer surface, sound pressure measurements in free field at a distance of 1 meter above the plate, as well as sound pressure in a closed rectangular concrete-walled cavity (0.5×0.6×0.7 m) put on top of the test-rig. Computations were carried out using a commercial FEA software implementing the Biot theory for poro-elastic media.

This paper describes a method to simulate underhood temperature distributions in passenger cars. A simplified engine compartment simulation test rig is used to perform measurements with well known boundary conditions to validate the simulation strategy. The measurement setup corresponds to idle without working fan. The aim of this setup is to validate cases with strong natural convection, e.g. thermal soaking. A coupled steady-state CFD run and thermal analysis is undertaken to simulate the temperature distribution in the test rig. Convective heat transfer coefficients and air temperatures are calculated in StarCD™. The radiative and conductive heat transfer is considered in a RadTherm™ analysis. The strong coupling of flow field and wall temperature in buoyancy driven flows requires an iterative process. Calculated temperatures are compared to measured results in order to validate the simulation method as far as possible. Some of the results are reported in this paper.

This paper describes work supporting the development of a new Diesel particulate trap system for heavy duty vehicles based on porous sintered metal materials that exhibit interesting characteristics with respect to ash tolerance. Experimental data characterizing the material (permeability, soot and ash deposit properties) are obtained in a dedicated experimental setup in the side-stream of a modern Diesel engine as well as in an accelerated ash loading rig. System level simulations coupling the new media characteristics to 3-D CFD software for the optimization of complete filter systems are then performed and comparative assessment results of example designs are given.

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.

The oil ash accumulation on modern three way catalyst (TWC) as well as its influence on catalyst deactivation is evaluated as a parameter of oil consumption, kind of oil additive compound and additive concentration. The oil ash accumulation is characterized by XRF and SEM/EDX in axial direction and into the washcoat depth of the catalyst. The deposition patterns of Ca, Mg, P and Zn are discussed. The catalytic activity of the vehicle and engine bench aged catalysts is measured by performing model gas tests and vehicle tests, respectively. The influence of oil ash accumulation on the lifetime emission behavior of the vehicle is discussed.

Development times in the automotive industry are becoming increasingly shorter. For this reason, design decisions based on simulation results must be made at an early development stage. The dynamic simulation of an automotive refrigeration cycle with Dymola/Modelica as part of the design process will be described in the following paper. The component supplier's expertise as well as the automotive manufacturer's knowledge of vehicle parameters in one simulation platform will also be discussed.