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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.

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.

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.

This paper addresses the use of neat, indigenous biodiesel in advanced Mercedes-Benz passenger cars. Modern, unmodified EU3 Common-Rail diesel engines with second generation common rail technology were used to determine the effects of neat biodiesel on performance and emission characteristics. The biodiesel was made from the seeds of the Jatropha Curcas plant and sourced from the Central Salt and Marine Chemicals Research Institute in Bhavnagar, India. The production of biodiesel and the vehicle tests are part of a PPP project, funded jointly by the DaimlerChrysler AG and the German DEG. The project aims at providing additional jobs and income in rural Indian areas along with reclaiming unused wasteland. The test vehicles were operated for a cumulative 8000 kilometers with an intention to expose the vehicle and fuel to diverse climatic conditions.

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 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.

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.

In modern DI Diesel engines the raw emissions of NOx and soot are affected, apart from the fuel injection rate, by atomization of the liquid jet and mixing of the fuel with the combustion air. Thereby details of the fuel flow inside the injection nozzle play an essential role. In order to determine the general mechanisms and the effect of individual nozzle configuration parameters on the fuel atomization and the fuel spray propagation, methods for optical diagnostics and CFD have been developed at the DaimlerChrysler Research. These methods are combined with an analysis of the injection system hydraulics and linked to a detailed analysis of mixture formation and combustion inside an optically accessible engine. The first part of the paper methods for the experimental investigation with transparent 1- and 6- hole nozzles in real size geometries under high pressure conditions are described. Special emphasis is put on CFD methods for modeling the cavitating two phase nozzle flow.

In view of tight emission standards, injection strategies to reduce raw HC-emissions during the cold starting of port fuel injected engines are evaluated in this study. The relevance of spray targeting and atomization is outlined in the first part of this paper. The foundation and performance of different injector concepts with respect to spray characteristics are discussed. Laboratory experiments demonstrate that concepts relying on auxiliary energy, such as air-assistance, fuel heating and injection at elevated system pressures, are capable of producing spray droplet sizes in the SMD-range of 25μm. For future injection strategies aimed at the compliance of SULEV emission levels, this target value is considered to be essential. In the second part of this paper, emission tests of selected injector concepts are carried out using a V6-3.2I ULEV engine operated both in a vehicle and on a test bench.

In this article model-based controller design techniques are investigated for the transient operation of a common-rail diesel engine in order to optimize driveability and to reduce soot emissions. The computer-aided design has benefits in reducing controller calibration time. This paper presents a nonlinear control concept for the coordinated control of the exhaust gas recirculation (EGR) valve and the variable geometry turbocharger (VGT) in a common-rail diesel engine. The overall controller structure is set up to regulate the total cylinder air-charge with a desired fresh air-charge amount by means of controlling the intake manifold pressure and estimating the fresh air-charge inducted into the cylinders. During varying engine operating conditions the two control loops are coordinated by a compensation of the EGR valve action through the VGT controller.

For the measurement of exhaust emissions, Constant Volume Sampling (CVS) technology is recommended by legislation and has proven its practical capability in the past. However, the introduction of new low emission standards has raised questions regarding the accuracy and variability of the CVS system when measuring very low emission levels. This paper will show that CVS has the potential to achieve sufficient precision for certification of SULEV concepts. Thus, there is no need for the introduction of new test methods involving high cost. An analysis of the CVS basic equations indicates the importance of the Dilution Factor (DF) for calculating true mass emissions. A test series will demonstrate that, by adjusting the dilution and using state of the art analyzers, the consistency of exhaust results is comparable with those of LEV concepts, measured with conventional CVS systems and former standard analyzers.

The LEV II and SULEV/PZEV emission standards legislated by the US EPA and the Californian ARB will require continuous reduction in the vehicles' emission over the next several years. Similar requirements are under discussion in the European Union (EU) in the EU Stage V program. These future emission standards will require a more efficient after treatment device that exhibits high activity and excellent durabilty over an extended lifetime. The present study summarizes the findings of a joint development program targeting such demanding future emission challenges, which can only be met by a close and intensive co-operation of the individual expert teams. The use of active systems, e.g. HC-adsorber or electrically heated light-off catalysts, was not considered in this study. The following parameters were investigated in detail: The development of a high-tech three-way catalyst technology is described being tailored for applications on ultra thin wall ceramic substrates (UTWS).

The NO distribution in a directly-injected Diesel engine with realistic combustion chamber geometry was investigated with laser-induced fluorescence (LIF) imaging with KrF excimer laser excitation. The highest possible level of selectivity has been ensured using spectrally resolved LIF investigations inside the Diesel engine. To minimize interference from both, oxygen and polycyclic aromatic hydrocarbon (PAH) LIF the NO signal was detected around 237 nm, blue-shifted compared to the excitation wavelength resulting in a background contribution below 10% at the earliest detection timing possible in the engine under study (20°ca after top dead center, TDC). The in-cylinder NO LIF intensities were compared for different injection systems and operating conditions and correlated to variations in pressure traces and soot temperature measurements.

A look at the various past achievements in the field of passenger car safety raises the question whether any dramatic steps towards its improvement can still be expected. Will progress be confined to the optimization of existing systems or does the future hold new substantial safety steps? This paper elaborates on the issue that the time available before a potential accident occurs can be used to improve the safety of occupants and other involved road users. Accident analysis confirms that this is feasible for about two-thirds of all accidents. The recognition of an imminent collision bears a noteworthy potential for accident prevention, reduction of accident severity and injury severity. The former boundary between active and passive safety thus fades continually. Based upon this it is possible to describe vehicle safety by a comprehensive approach encompassing seven escalation levels.

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.

We are the first to report about a micromachined flow sensor directly integrated in the Common Rail injection nozzle body between the double guidance and the tip of the nozzle. The thermal measurement principle is chosen, because it enables a very precise and fast detection of gaseous and liquid mass flows. Additionally, the velocity field in the nozzle is only slightly influenced by the integration of the sensor in the nozzle body due to the negligible height of the sensitive layer. For a hot film anemometer, a high pressure stable ceramic substrate can be used, fabricated in a low cost batch process. The technology, to fabricate the sensor, as well as the first flow measurements, carried out at a high pressure test set up, are presented.

This paper describes the results of a joint development program focussing on the introduction of the new generation of Pt/Rh-technology for current and future emission standards as a cost effective alternative to the in serial Pd/Rh based exhaust gas concepts. In the initial phase of the program combinations of Pd- and Pt-based three-way catalyst technologies were evaluated on vehicles equipped with a 8 cylinder engine. One goal in this portion of the study was to achieve technical equivalence between a viable Pd-based technology and the new Pt/Rh technology in the underfloor position at lower precious metal loading. A combination of a close-coupled Pd/Rh technology and the new Pt/Rh in the underfloor position was able to meet the emission targets at significant lower costs of the system after a catalyst aging that resembles more than 100.000 km of vehicle German highway driving.

High demands in fuel consumption, efficiency, and low emissions lead to complex control functions for current and future diesel engine management systems. Great effort is necessary for their optimal calibration. At the same time, and particularly for cost reasons, many variants exist on one individual type of diesel engine management system. Not only is it used for several base engines, but these engines are also used in different environments and for different tasks. For optimal deployment, their calibration status must also be optimized individually. Furthermore, the demand for shorter development cycles and enhanced quality lead to a catalogue of new requirements for the calibration process and the affiliated tool. A new calibration system was developed, which optimally reflects the new demands.