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Since the mechanisms leading to cyclic combustion variabilities in direct injection gasoline engines are still poorly understood, advanced computational studies are necessary to be able to predict, analyze and optimize the complete engine process from aerodynamics to mixing, ignition, combustion and heat transfer. In this work the Scale-Adaptive Simulation (SAS) turbulence model is used in combination with a parameterized lagrangian spray model for the purpose of predicting transient in-cylinder cold flow, injection and mixture formation in a gasoline engine. An existing CFD model based on FLUENT v15.0 [1] has been extended with a spray description using the FLUENT Discrete Phase Model (DPM). This article will first discuss the validation of the in-cylinder cold flow model using experimental data measured within an optically accessible engine by High Speed Particle Image Velocimetry (HS-PIV).

Two optical techniques were developed and combined with a CFD simulation to obtain spatio-temporally resolved information on air/fuel mixing in the cylinder of a methane-fueled, fired, optically accessible engine. Laser-induced fluorescence (LIF) of anisole (methoxybenzene), vaporized in trace amounts into the gaseous fuel upstream of the injector, was captured by a two-camera system, providing one instantaneous image of the air/fuel ratio per cycle. Broadband infrared (IR) absorption by the methane fuel itself was measured in a small probe volume via a spark-plug integrated sensor, yielding time-resolved quasi-point information at kHz-rates. The simulation was based on the Reynolds-averaged Navier-Stokes (RANS) approach with the two-equation k-epsilon turbulence model in a finite volume discretization scheme and included the port-fuel injection event. Commercial CFD software was used to perform engine simulations close to the experimental conditions.

In this paper, the experimental and numerical simulation of the flow field in the simplified front wheel arch of a scaled-down VW Phaeton half-model (scale 1:2,5) is presented. For wind tunnel experiments a realistic, rotating wheel model with plexiglass treads (PMMA) was designed. The construction allowed for detailed measurements of the flow field directly at the brake disk by means of the stereoscopic Particle Image Velocimetry (PIV) technique. The formation of the flow structures and the resulting three-dimensional boundary layers on the brake disk are analyzed. Furthermore, the oncoming air flow towards the brake disk and the flow field near the wheel rim openings were investigated. The experimental data is compared with results of Computational Fluid Dynamics (CFD) simulations using the Lattice-Boltzmann based solver Powerflow. The validation shows the potential and the limitations of the numerical approach and indicates areas of further improvement.

In one-dimensional engine simulation programs the simulation of engine performance is mostly done by parameter fitting in order to match simulations with experimental data. The extensive fitting procedure is especially needed for emissions formation - CO, HC, NO, soot - simulations. An alternative to this approach is, to calculate the emissions based on detailed kinetic models. This however demands that the in-cylinder combustion-flow interaction can be modeled accurately, and that the CPU time needed for the model is still acceptable. PDF based stochastic reactor models offer one possible solution. They usually introduce only one (time dependent) parameter - the mixing time - to model the influence of flow on the chemistry. They offer the prediction of the heat release, together with all emission formation, if the optimum mixing time is given.

This paper compares 4 different EGR systems by means of simulation in GT-Power. The demands of optimum massive EGR and fresh air rates were based on experimental results. The experimental data were used to calibrate the model and ROHR, in particular. The main aim was to investigate the influence of pumping work on engine and vehicle fuel consumption (thus CO2 production) in different EGR layouts using optimum VG turbine control. These EGR systems differ in the source of pressure drop between the exhaust and intake pipes. Firstly, the engine settings were optimized under steady operation - BSFC was minimized while taking into account both the required EGR rate and fresh air mass flow. Secondly, transient simulations (NEDC cycle) were carried out - a full engine model was used to obtain detailed information on important parameters. The study shows the necessity to use natural pressure differences or renewable pressure losses if reasonable fuel consumption is to be achieved.

This paper presents a complete methodology for performing finite-volume-based detached-eddy simulation for the prediction of aerodynamic forces and detailed flow structures of passenger vehicles developed using the open-source CFD toolbox OpenFOAM®. The main components of the methodology consist of an automatic mesh generator, a setup and initialisation utility, a DES flow solver and analysis and post-processing routines. Validation of the predictions is done on the basis of detailed comparisons to experimental wind-tunnel data. Results for lift and drag are found to compare favourably to the experiments, with some moderate discrepancies in predicted rear lift. Point surface-pressure measurements, oil-streak images and maps of total pressure in the flow field demonstrate the approach's capabilities to predict the fine detail of complex flow regimes found in automotive aerodynamics.

The use of a newly developed approach results in a highly accurate three dimensional analysis of the occupant movement. The central point of the new method is the calculation of precise body-trajectories by fitting standard sensor-measurements to video analysis data. With the new method the accuracy of the calculated trajectories is better than 5 to 10 millimeters. These body trajectories then form the basis for a new multi-body based numerical method, which allows the three dimensional reconstruction of the dummy kinematics. In addition, forces and moments acting on every single body are determined. In principle, the body movement is reconstructed by prescribing external forces and moments to every single body requiring that it follows the measured trajectory. The newly developed approach provides additional accurate information for the development engineers. For example the motion of dummy body parts not tracked by video analysis can be determined.

The California LEV1 II program will be introduced in the year 2003 and requires a further reduction of the exhaust emissions of passenger cars. The cold start emissions represent the main part of the total emissions of the FTP2-Cycle. Cold start emissions can be efficiently reduced by injecting secondary air (SA) in the exhaust port making compliance with the most stringent standards possible. The thermochemical conditions (mixing rate and temperature of secondary air and exhaust gas, exhaust gas composition, etc) prevailing in the exhaust system are described in this paper. This provides knowledge of the conditions for auto ignition of the mixture within the exhaust manifold. The thus established exothermal reaction (exhaust gas post-combustion) results in a shorter time to light-off temperature of the catalyst. The mechanisms of this combustion are studied at different engine idle conditions.

More stringent emissions regulations, space limitations for catalytic converters in modern automotive applications, and new engine technologies constitute design challenges for today's engineers. In that context high cell density thinwall and ultrathinwall ceramic substrates have been designed into advanced catalytic converters. Whereas the majority of these substrates have a square cell geometry, a potential for further emissions improvement has been predicted for hexagonal cell structures. In order to verify these predictions, a ceramic substrate has been developed combining the features of high cell density, ultrathin cell walls, and hexagonal cell structure. Based on modeling data, the actual cell density and wall thickness of the hexagonal cell substrate will be defined. The performance of that substrate will be assessed by comparing experimental emissions results using two modern Volkswagen engines.

Meeting strict current and future emissions legislation necessitates development of computational tools capable of predicting the behaviour of combustion and emissions with an accuracy sufficient to make correct design decisions while keeping computational cost of the simulations amenable for large-scale design space exploration. While detailed kinetics modelling is increasingly seen as a necessity for accurate simulations, the computational cost can be often prohibitive, prompting interest in simplified approaches allowing fast simulation of reduced mechanisms at coarse grid resolutions appropriate for internal combustion engine simulations in design context. In this study we present a simplified Well-stirred Reactor (WSR) implementation coupled with 3D CFD Ricardo VECTIS solver.

Due to the introduction of new safety and comfort systems in modern automobiles, stability of the vehicle electrical system is increasingly important. The increasing number of electrical components demands that additional electrical energy be provided from robust, reliable supply sources in vehicles. When designing such systems, simulation is the development tool that is used to quickly obtain information regarding electrical system stability, battery charge level, and the distribution of power to the consumer systems. This paper describes how the Saber simulation environment from Synopsys Corporation helps develop increasingly demanding and complex vehicle power systems. A Volkswagen vehicle power net serves as an illustration.

The combustion and pollutant formation processes in a 1.9 I IDI Diesel engine are simulated with the SPEED computational fluid dynamics (CFD) code. A part and a full load simulation of the production engine and a full load simulation of a modified engine design are analyzed. The mixing and combustion process is visualized for all cases by means of the isosurfaces of stoichiometric mixture. The correlation of this surface with global quantities as heat release, mean pressure and temperature and swirl ratio is emphasized. The global properties are presented resolved for the swirl, main chamber and the swirl chamber throat separately. The formation of thermal NO and soot are simulated and analyzed.

The prevention of any brake noise or brake-induced body vibrations is a key development target firmly integrated in the car development process. Emphasis is placed here on disc brake judder that is attributable to thickness variations in the disc. These deviations from the ideal plane surface can be caused either by wear and corrosion or by thermal stresses (changes within the microstructure of the disc material). They are termed “cold judder” and “thermal judder” respectively. During braking, possible vibration excitation passes through a wide frequency band due to the coupling between the judder frequency and the wheel rotational speed, and thus, resonant frequencies of many vehicle components can be excited. This includes wheel suspension components and the steering column. In this paper, it is reported on extensive investigations into the topic of “cold judder”.

Due to the increase in demand for comfort and safety features in today's automobiles, the internal vehicle communication networks necessary to accommodate these features are very complex. These networks represent a heterogeneous architecture consisting of several ECUs exchanging information via bus systems such as CAN, LIN, MOST, or FlexRay buses. Development and verification of internal vehicle networks include multiple design layers. These layers are the logical layer represented by the software application, the associated data link layer, and the physical connection layer containing bus interfaces, wires, and termination. Verification of these systems in the early stages of the design process (before a physical network is available for testing) has become a critical need. As a result, the need to simulate these designs at all their levels of complexity has become critically important.

A 3-dimensional numerical study has been conducted investigating the combustion process in a VW 1.9l TDI Diesel engine. Simulations were performed modeling the spray injection of a 5-hole Diesel injector in a pressure chamber. A graphical methodology was utilized to match the spray resulting from the widely used Discrete Droplet Spray model to pressure chamber spray images. Satisfactory agreement has been obtained regarding the simulated and experimental spray penetration and cone angles. Thereafter, the combustion process in the engine was simulated. Using engine measurements to initialize the combustion chamber conditions, the compression stroke, the spray injection and the combustion simulation was performed. The novel RTZF two-zone flamelet combustion model was used for the combustion simulation and was tested for partial load operating conditions. An objective analysis of the model is presented including the results of a numerical parameter study.

A uniform flow distribution at converter inlet is one of the fundamental requirements to meet high catalytic efficiency. Commonly used tools for optimization of the inlet flow distribution are flow measurements as well as CFD analysis. This paper puts emphasis on the experimental procedures and results. The interaction of flow measurements and CFD is outlined. The exhaust gas flow is transient, compressible and hot, making in-situ flow measurements very complex. On the other hand, to utilize the advantages of flow testing at steady-state and cold conditions the significance of these results has to be verified first. CFD analysis under different boundary conditions prove that - in a first approach - the flow situation can be regarded as a sequence of successive, steady-state situations. Using the Reynolds analogy a formula for the steady-state, cold test mass flow is derived, taking into account the cylinder displacement and the rated speed.

The investigation of vehicle soiling by improvement of vehicle parts to optimize the surrounding airflow is of great importance not only because of the visibility through windows and at mirrors but also the functionality of different types of sensors (camera, lidar, radars, etc.) for the driver assistance systems and especially for autonomous driving vehicles has to be guaranteed. These investigations and corresponding developments ideally take place in the early vehicle development process since later changes are difficult to apply in the vehicle production process for many reasons. Vehicle soiling is divided into foreign soiling and self-soiling with respect to the source of the soiling water, e.g., direct rain impact, swirled (dirty) water of other road users and own rotating wheels. The investigations of the soiling behavior of vehicles were performed experimentally in a wind tunnel and street tests.

Electromechanical steering systems (EPS) provide assisting steering force through an electric motor, often paired with a screw drive. The combination of an electric motor and a screw drive lead to high inertia and thus to a reduced feedback of tire force behavior at the steering wheel. This force behavior contains information about driving conditions and road surface. However, the electric motor can be used to actively enhance and manipulate steering feedback. This article describes the driver perception of modified steering feedback. The presented data is collected carrying out a driving simulator study with average drivers as test subjects. In this study the driver experiences a modified steering feedback at a change of road friction coefficient. Based on the test subjects ratings the perception, acceptance and controllability of the presented steering feedback modifications are assessed.

Battery electric vehicles (BEVs) are equipped with Mobile Air Conditioning systems (MACs) to ensure a comfortable cabin temperature in all climates and ambient conditions as well as the optional conditioning of the traction battery. An assessment of the global electrical energy consumption of various MACs has been derived, where the basis of the assessment procedure is the climate data GREEN-MAC-LCCP 2007 (Global Refrigerants Energy & Environmental - Mobile Air Condition - Life Cycle Climate Performance) and the improved LCCP2013 (Life Cycle Climate Performance. The percentage driving time during 6 AM and 24 PM is divided into six different temperature bins with the solar radiation and relative humidity for 211 cities distributed over Europe, North, Central, and South America, Asia, South West Pacific, and Africa. The energy consumption of the MACs is determined by a thermal vehicle simulation. In this work, four different MACs are simulated and compared.

The optimization of the mixture formation represents great potential to decrease fuel consumption and emissions of spark-ignition engines. The injector and the nozzle are of major importance in this concern. In order to adjust the nozzle geometry according to the requirements an understanding of the physical transactions in the fuel spray is essential. In particular, the primary spray break-up is still described inadequately due to the difficult accessibility with optical measuring instruments. This paper presents a methodology for the characterization of the nozzle-near spray development, which substantially influences the entire spray shape. Single hole injectors of the gasoline direct injection (GDI) with different nozzle hole geometries have been investigated in a high pressure chamber by using the MIE scattering technique. To examine the spray very close to the nozzle exit a long-distance microscope in combination with a Nd:YAG-laser was used.