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Laser-induced exciplex fluorescence has been applied to the mixture formation process in the combustion chamber of an optically-accessible four-cylinder in-line spark-ignition engine in order to distinguish between liquid and vapor fuel distribution during the intake and compression stroke for different injection timings. The naphthalene/N,N,N′N′-tetramethyl p-phenylene diamine (TMPD) exciplex system excited at 308nm with a broadband XeCl excimer laser is used to obtain spectrally-separated, single-shot fluorescence images of the liquid or vapor phase of the fuel. For different timings of the fuel injector this technique is applied to obtain crank-angle-resolved images of the resulting mixture in the combustion chamber. The fluorescence light is detected with an intensified slow-scan CCD-camera equipped with appropriate filters.

Quantitative 1-D spatially-resolved NO LIF measurements in the combustion chamber of a mass-production SI engine with port-fuel injection using a tunable KrF excimer laser are presented. One of the main advantages of this approach is that KrF laser radiation at 248 nm is only slightly absorbed by the in-cylinder gases during engine combustion and therefore it allows measurements at all crank angles. Multispecies detection turned out to be crucial for this approach since it is possible to calculate the in-cylinder temperature from the detected Rayleigh scattering and the simultaneously acquired pressure traces. Additionally, it allows the monitoring of interfering emissions and spectroscopic effects like fluorescence trapping which turned out to take place. Excitation with 248 nm yields LIF emissions at shorter wavelengths than the laser wavelength (at 237 and 226 nm).

The measurement of 3D coordinates using optical techniques is well known for more than 50 years. Today, modern photogrammetric systems are based on handheld digital cameras and are used to identify the location of any circular marker or feature on the object's surface. The ease of use and the accurate and automated derivation of 3D coordinates from 2D digital images helped to establish a powerful tool for position control, assembly checks and reverse engineering. A new application is the analysis of real vehicle crashes. The location of hundreds of markers on the damaged vehicle can easily be determined in vehicle body position. These coordinates are being compared to the undeformed geometry and provide herby 3D information on any displacement. Using reverse engineering techniques, surfaces are created from the 3D points and thus a 3D model of the crashed vehicle is available for an easy visualization of the deformation.

Dry dust testing of vehicles on unpaved dust roads plays a crucial role in the development process of automotive manufacturers. One of the central aspects of the test procedure is ensuring the functionality of locking systems in the case of dust ingress and keeping the dust below a certain concentration level inside the vehicle. Another aspect is the customer comfort because of dust deposited on the surface of the car body. This also poses a safety risk to customers when the dust settles on safety-critical parts such as windshields and obstructs the driver’s view. Dust deposition on sensors is also safety critical and is becoming more important because of the increasing amount of sensors for autonomous driving. Nowadays, dust tests are conducted experimentally at dust proving grounds. To gain early insights and avoid costly physical testing, numerical simulations are considered a promising approach. Simulations of vehicle contamination by dry dust have been studied in the past.

In direct-injection gasoline (GDI) engines with charge stratification, minimizing engine-out nitrogen oxide (NOx) emission is crucial since exhaust-gas aftertreatment tolerates only limited amounts of NOx. Reduced NOx production directly lowers the frequency of energy-inefficient catalyst regeneration cycles. In this paper we investigate NO formation in a realistic GDI engine. Quantitative in-cylinder measurements of NO concentrations are carried out via laser-induced fluorescence imaging with excitation of NO (A-X(0,2) band at 248 nm), and subsequent fluorescence detection at 220-240 nm. Engine modifications were kept to a minimum in order to provide results that are representative of practical operating conditions. Optical access via a sapphire ring enabled identical engine geometry as a production line engine. The engine is operated with commercial gasoline (“Super-Plus”, RON 98).

Dust testing of vehicles on unpaved roads is crucial in the development process for automotive manufacturers. These tests aim to ensure the functionality of locking systems in dusty conditions, minimize dust concentration inside the vehicle, and enhance customer comfort by preventing dust accumulation on the car body. Additionally, deposition on safety-critical parts, such as windshields and sensors, can pose threats to driver vision and autonomous driving capabilities. Currently, dust tests are primarily conducted experimentally at proving grounds. In order to gain early insights and reduce the need for costly physical tests, numerical simulations are becoming a promising alternative. Although simulations of vehicle contamination by dry dust have been studied in the past, they have often lacked detailed models for tire dust resuspension. In addition, few publications address the specifics of dust deposition on vehicles, especially in areas such as door gaps and locks.

This paper reports on a non-intrusive method for measuring the liquid fuel film thickness in the intake manifold of a series production SI engine with multi-point fuel injection. The technique is based on laser-induced fluorescence. The optical set-up uses a bifurcated optical fibre bundle for transmission of the laser light for excitation of the fluid and for detecting of the fluorescence light. Due to the special design of the optical probe head it is highly sensitive for thin film measurements and it allows the accurate determination of the fuel film thickness even between a few and 100 μm. Special emphasis is placed on the selection of an adequate tracer added to the iso-octane fuel to achieve the correct film thickness even under vaporizing conditions, and on a detailed study of the parameters influencing the evaluated film thickness.

Mixture formation analysis in the combustion chamber of a slightly modified mass-production SI engine with port-fuel injection using nonintrusive laser measurement techniques is presented. Laser Raman scattering and planar laser-induced tracer fluorescence are employed to measure air-fuel ratio and residual gas content of the charge with and without spatial resolution. Single-cycle measurements as well as cycle-averaged measurements are performed. Engine operation parameters like load, speed, injection timing, spark timing, coolant temperature, and mean air-fuel ratio are changed to study whether the effects on mixture formation and engine performance can be resolved by the applied laser spectroscopic techniques. Mixture formation is also analyzed by measurement of the charge composition as a function of crank angle. Clear correlations of the charge composition data and engine operating conditions are seen.

A recently developed Laser Raman Scattering system was applied to measure the in-cylinder air-fuel ratio and the residual gas content (via the water content) of the charge simultaneously in a firing spark-ignition engine during cold start and warm-up. It is the main objective of this work to elucidate the origin of misfires and the necessity to over-fuel at cool ambient temperatures. It turns out that the overall air-fuel ratio and residual gas content (in particular the residual water content) of the charge appear to be the most important parameters for the occurrence of misfires (without appropriate fuel enrichment), i.e., the engine behaviour from cycle to cycle becomes rather predictable on the basis of these data. An alternative explanation for the necessity to over-fuel is given.

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.

A vehicle thermal management system is required to increase the operating efficiency of components, to transfer the heat efficiently and to reduce the energy required for the vehicle. Vehicle thermal management technologies, such as engine compartment encapsulation together with grille shutter control, enable energy efficiency improvements through utilizing waste heat in the engine compartment for heating powertrain components as well as cabin heating and reducing the aerodynamic drag . In this work, a significant effort is put on recovering waste heat from the engine compartment to provide additional efficiency to the components using a motor compartment insulation technique and grille shutter. The tests are accelerated and the cost is reduced using a co-simulation tool based on high resolution, complex thermal and kinematics models. The results are validated with experimental values measured in a thermal wind tunnel, which provided satisfactory accuracy.

The need to reduce weight of large and heavy components used by the automotive and aerospace industries such as engine block, cylinder head cover and helicopter gearbox housing has led to the development of new Mg gravity casting alloys that provide adequate properties and cost effective solution. The new Mg gravity casting alloys are designed for high stressed components that operate at a temperature up to 300°C. These new alloys exhibit excellent mechanical properties and creep resistance in T-6 conditions. The present paper aims at introducing three new Mg gravity casting alloys designated MRI 201S, MRI 202S and MRI 203S, which were recently developed by the Magnesium Research Institute of DSM and VW. Apart from the excellent high temperature performance of these alloys, they provide adequate castability and dimension stability along with good weldability and corrosion resistance.

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.

The consideration of vehicle soiling in the development process becomes ever more important because of the increasing customer demands on current vehicles and the increased use of camera and sensor systems due to autonomous driving. In the process of self-soiling, a soil-water mixture is whirled up by the rotation of the car’s own wheels and deposits on the vehicle surface. The validation of the soiling characteristics in vehicle development usually takes place in an experimental manner, but is increasingly supported by numerical simulations. The droplet field at the tyre has been investigated several times in the past. However, there are no published information regarding the physical background of the droplet formation process and the absolute droplet sizes considering the position at the tyre and the behaviour at different velocities.

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.

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.

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.

In order to improve the efficiency of passenger cars, developments focus on decreasing their aerodynamic drag, part of which is caused by cooling air. Thus, car manufacturers try to seal the cooling air path to prevent leakage flows. Nevertheless, gaps between the single components of the cooling air path widen due to the deformation of components under aerodynamic load. For simulating the cooling airflow utilization ratio (CAUR), computational fluid dynamics (CFD) simulations are used, which neglect component deformation. In this paper, a computational method aiming at sufficient gap resolution and determining the CAUR of passenger cars under the consideration of component deformation is developed. Therefore, a partitioned approach of fluid structure interaction (FSI) simulations is used. The fluid field is simulated in OpenFOAM, whereas the structural simulations are conducted using Pam-Crash.

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 aerodynamic optimization of an AUDI Q5 vehicle is presented using the continuous adjoint approach within the OpenFOAM framework. All calculations are performed on an unstructured automatically generated mesh. The primal flow, which serves as input for the adjoint method, is calculated using the standard CFD process at AUDI. It is based on DES calculations using a Spalart-Allmaras turbulence model. The transient results of the primal solution are time averaged and fed to a stationary adjoint solver using a frozen turbulence assumption. From the adjoint model, drag sensitivity maps are computed and measures for drag reduction are derived. The predicted measures are compared to CFD simulations and to wind tunnel experiments at 1:4 model scale. In this context, general challenges, such as convergence and accuracy of the adjoint method are discussed and best practice guidelines are demonstrated.