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This paper describes recent progress towards Direct Injection Diesel engine combustion simulation, involving both engine data measurements and 3D computational fluid dynamics. Experimental data were obtained in two different engines and it includes LDV measurements as well as an extended engine combustion data base. CFD simulations were performed with a modified version of the Kiva2 code and experimental data were used to get initial and boundary conditions and to validate the numerical results. The initial version of the Kiva2 code was enhanced to allow computation of quite complex geometries with different physical sub-models for turbulence, injection and combustion. The present version of the code can compute the engine cycle from start of intake stroke to the end of combustion with any inflow and wall boundary conditions. Turbulence may be simulated using both a k-ε model and a second order uiuj-ε model which was recently implemented in the code.

In this study three-dimensional CFD calculations of the gas motion and spray characteristics of a small (1.9l), high-speed direct-injection Diesel engine are presented and evaluated. The calculations were performed using the SPEED code, developed within the European IDEA-EFFECT project: it uses fully implicit finite volume methodology in conjunction with an unstructured mesh to represent the full complexities of the engine geometry and solve the equations governing the gas motion, fuel spray evolution and subsequent fuel/air mixing. Submodels for particular aspects of these processes developed by various partners in the project are incorporated. The accuracy of the predictions is assessed through comparisons with detailed LDA measurements of the velocity field during the induction and compression strokes up to the time of ignition, as well as with quantitative measurements of the spray penetration and local droplet velocities. Moderately good agreement is obtained.

Computation of high pressure Diesel injection requires improvement of present spray atomization and droplet breakup models. The surface wave instability atomization (Wave) model of Reitz [2] has been coupled to a new breakup model (FIPA) which is based on the experimental correlations of Pilch et al.[3]. It has been integrated in the 3D KMB code [1] derived from the Kiva 2 code [4] of Los Alamos already including a stochastic Lagrangian description of sprays. The droplet breakup FIPA model was first fitted and validated using the monodisperse drop breakup experiments of Liu and Reitz [5]. The response of the modified spray model including the global Wave-FIPA breakup model is compared to well characterized data obtained in a high pressure and temperature vessel. This vessel is fitted with a common-rail injection system with a single hole injector tip.

A numerical study of air-fuel mixing in a direct-injection spark-ignition engine was carried out. In this paper, the numerical models are described and grid generation methods to represent a realistic port-valve-chamber geometry is discussed. To model a vaporizing hollow-cone spray resulting from an automotive pressure-swirl injector, a newly developed sheet spray atomization model was used to compute the processes of disintegration of the liquid sheet and breakup of the subsequent drops. Computations were performed of a particular 4-valve pent-roof engine configuration in which the intake process and an early fuel injection scheme were considered. After an analysis of the intake-generated flow structures in this engine configuration, the spray behavior and the spatial and temporal evolution of fuel liquid and vapor phases are characterized.

Intake flow for a four-stroke experimental gasoline engine is modeled considering moving valves and realistic port geometries. The numerical model is based on the KIVA-3 code and computed flow velocities are compared with LDV measurements. Computations start prior to intake valve opening and the pressure boundaries are specified at both the intake and exhaust pipe cross sections. Numerical results show that the in-cylinder flow pattern is well simulated in the symmetric plane passing through the cylinder axis. The computed and measured cylinder pressure and flow velocities agree reasonably well during the intake process. At top-dead-center, computations show a rotating flow pattern exists in the squish region corresponding to an area with relatively high turbulent kinetic energy. Results of intake flow modeling also show the evolution of in-cylinder averaged turbulent kinetic energy is different if the intake charging process is not modeled.

About 50-90 percent of the hydrocarbons that escape combustion during flame passage in spark-ignition engine operation are oxidized in the cylinder before leaving the system. The process involves the transport of unreacted fuel from cold walls towards the hotter burned gas regions and subsequent reaction. In order to understand controlling factors in the process, a transient one-dimensional reactive-diffusive model has been formulated for simulating the oxidation processes taking place in the reactive layer between hot burned gases and cold unreacted air/fuel mixture, with initial and boundary conditions provided by the emergence of hydrocarbons from the piston top land crevice. Energy and species conservation equations are solved for the entire process, using a detailed chemical kinetic mechanism for propane.

The spray submodel is an important component in multidimensional models for Diesel engines. The satisfactory representation of the spray is dependent on adequate representation of turbulence in the jet which, in part, determines its spread and penetration. In this work, the RNG k-ϵ model is evaluated relative to the standard k-ϵ model for computing turbulent jets. Computations are made for both gas jets and sprays. The gas jet is computed with an adequately high degree of numerical spatial resolution of the order of the orifice diameter. In the case of the spray, achieving such a high resolution would be challenging. Since the spray has similarities to the gas jet, and the gas jet may be computed with such high resolution and adequate accuracy, firm conclusions may be drawn for it and they may be applicable to sprays. It is concluded that the RNG k - ϵ model, in general, results in predictions of greater mixing in the jets relative to the standard model.

During the last few years the function of daytime running light (DRL) has been applied more frequently. According to road safety experts it is an important factor in reducing daytime collisions. The number of countries allowing or requiring the DRL continues to increase. A frequent argument against DRL is the increase in fuel consumption caused by the rise in power consumption. The development target, therefore, was a separate daytime running lamp, which would have a reduced power consumption in comparison to the low beam function frequently used. A prototype with an approved light source was to be developed to allow immediate series production. The increasing quality standards in the automotive industry are also challenging for the component life of the bulb. With the optimisation of the “bulb - lamp” system, new concepts may be introduced, which will comply with future component life requirements.

This paper presents recent developments in incandescent halogen lighting technology with emphasis on the improvements made to operating life. Prior research indicated that the current predominant forward lighting source types could be redesigned with significant gains in rated life without major impact on operating characteristics. The automotive manufacturers were among the main drivers for the redesign effort. They are offering longer vehicle warranty periods and are seeking ways to provide cost effective solutions to minimize the impact of extended warranty coverage.

The headlamp beam pattern development process contains both subjective and objective evaluations. The subjective evaluation, communication between the customer and the engineer, was developed in previous work [1][2]. This paper presents exploratory models used in the identification of objective photometric variables of a beam pattern that relate to the subjective impression of the beam pattern. Additional research will allow use of the photometric variables and their selected ranges for designing and evaluating beam patterns to achieve improved customer pleasing beam pattern driving experiences.

HELIOS is a program for calculation, simulation and analysis of lighting problems expecially designed for car lighting technologies. Base is an “experiment” in which optical elements and theire features are described. Example: The reflector is defind by CAD-data and the surface is reflective. The result of simulation will be a light distribution. The performance has to be analysed. The LDE gives us the possibility to analyse light distribution strategies before calculation of the reflector surface itself. It is a “virtual light world”. This reduces developing time and costs and gives a help to find the best technical solution for complex illumination problems.

The thermal performance of an automotive fog lamp reflector is predicted with a computational fluid dynamics program. The 2D, steady-state heat transfer model accounts for convection and radiation within the enclosure, conduction through the reflector walls, external convection and radiation losses, and transmission through the lens. A good comparison of the predicted reflector temperatures with experimental thermocouple and infrared data suggests that the specular component of the inner metal coating plays a secondary role in the overall heat transfer and that a detailed thermal model of the bulb is not required. The radiant exchange with the tungsten filament and the conductive energy losses through the bulb connections are accounted for by specifying an appropriate heat flux at the bulb surface, and the transmission of radiant energy through the lens is modeled with an appropriate heat sink.

The U.S. currently requires that reai-view mirrors installed as original equipment in the center and driver-side positions be flat. There has recently been interest in using nonplanar mirrors in those positions, including possibly mirrors with large radii (over 2 m). This has provided additional motivation to understand the effects of mirror curvature on drivers' perceptions of distance and speed. This paper addresses this issue by (1) reviewing the concepts from perceptual theory that are most relevant to predicting and understanding how drivers judge distance in nonplanar rearview mirrors, and (2) reviewing the past empirical studies that have manipulated mirror curvature and measured some aspect of distance perception. The effects of mirror curvature on cues for distance perception do not lead to simple predictions. The most obvious model is one based on visual angle, according to which convex mirrors should generally lead to overestimation of distances.

Until the late 1980s, the technology used in automotive lighting was relatively limited. Designers had little styling freedom as the main prerequisite of car makers was to reduce the size and increase the performance of lighting systems. VALEO invented SC (complex surface) technology to improve luminous efficiency. The first cars equipped with SC were the EAGLE PREMIER in the United States the CITROEN XM in Europe. SC2 followed. SC2 incorporates reflector technology that controls both the vertical and horizontal deviation of the light and increases styling freedom especially for fog lamps. The latest in the line of high performance lamps, SC3, was developed to optimize beam patterns in order to meet statutory requirements whatever bulb is used. Because SC3 uses a clear lens with an optical reflector, styling can be much more original and the angle of the lens can be increased to 60°.

Models using contrast as the measure of discernibility or detection of roadway obstacle on non-lighted roadways have not recognized the lighting effects caused by the lateral spacing of headlamps on the vehicle. When the only significant sources of roadway light are a vehicle's headlamps, shadows on the roadway behind and to the left and right of the obstacle are viewed simultaneously with the obstacle itself. It can be shown that in certain obstacle-sighting situations, where there is little or no significant background light from sources other than the headlamps themselves, sufficient contrast is provided by the shadow outlines. Shadows created by the lateral spacing of the headlamp light sources and the driver's eyepoint, framing one or both sides of the obstacle, serve to outline the illuminated obstacle on the roadway in front of a vehicle.

This paper describes the results of an experimental programme designed to investigate some effects of intake flow-generated turbulence on rates of combustion and emissions formation in a 91mm bore direct injection diesel engine. Swirl and squish were eliminated as far as possible, in order to isolate the desired effects. This was achieved by re-modelling the inlet port and by replacing the deep bowl piston cavity with a flat-topped version, with the same compression ratio. Tests were carried out with three inlet valves: a standard engine Valve (“A”) and two drilled shrouded valves, one with 15 x 6 mm dia. holes (“B”) and one with 40 x 3.5 mm dia. holes (“C”). The turbulence characteristics associated with each valve were first determined on a steady flow rig, using LDA based surveys of velocity distributions at different downstream distances. The objective was to measure absolute levels of turbulence intensity and to study the subsequent rate of decay.

The effect of ambient gas hydrocarbon content on diesel spray ignition and combustion was examined in this research project. A single-stroke rapid compression machine was used to prepare the ambient gas pressure and temperature before the diesel fuel injection process. Variations of ambient gas composition were achieved by adding different quantities of methane and propane to the intake air, the content ranged from 0.0 to 0.6 equivalence ratio. The two-color method was applied to analyze the flame temperature and KL factor was determined from the colored flame image taken by a high-speed camera. Also, compression ignition characteristics of lean methane-air and propane-air mixtures were examined.

Typical DI diesel engines operate with fuel injection taking place within a range of about 30 crank angle degrees before top dead center, at the end of the compression stroke. When injection takes place far earlier, at the beginning of the compression stroke, another form of combustion occurs, which we termed PREmixed lean Diesel Combustion, or PREDIC. With PREDIC operation, self-ignition occurs near top dead center and NOx emissions are drastically lower. When ignition occurs, the fuel-air mixture is thought to be nearly homogeneous, with only slight heterogeneity. Appropriate fuel spray formation is very important for successful PREDIC operation. Using a single-zone NOx formation model, calculations showed that the mean excess air ratio in the PREDIC combustion zone was 1.87, which resulted in very low (20 ppm) NOx emissions. Conventional combustion at the same conditions resulted in a mean combustion zone excess air ratio of 0.88.

For some years now the new HID technology has been used for headlamp systems to improve safety and comfort during night time driving. A new generation of projector type headlamps starts series production in 1997. The characteristics of the HID bulb and the specific requirements of the light distribution make it necessary to calculate special optical systems to control the high amount of light. There are different possible design strategies. On one hand, it is possible to improve the light pattern, e.g. increase the luminous flux and the range. On the other hand it is possible to build a system with extremely small dimensions. Such a system ensures an excellent light quality even in smallest headlamps and gives way to new styling possibilities. To match such different targets, some parameters of the reflector and the lens have to be optimized. Some examples of projection headlamps which are designed for different applications will be discussed.

Signal lamp for a motor vehicle with a complex reflector design is presented. The reflector is composed of set of rectangular bicubic Bezier ‘pillows’ creating desired horizontal and/or vertical light spread. Cover lens with no or weakly-spreading optics is assumed. Mathematical background is discussed in part 2 - parametric equations for individual pillow are presented, equations for control points ensuring proper optical function of the pillow are derived and parameter controlling intensity distribution of output beam is introduced. Option to prevent beam asymmetry of conventional signal lamps with big rake angles of cover lens using ‘semicomplex’ optical system (i.e. complex reflector combined with optical elements on the cover lens) is discussed, too.