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The future worldwide emission regulations will request a drastic decrease of Diesel engine tailpipe emissions. Depending on the planned application and the real official regulations, a further strong decrease of engine out emissions is necessary, even though the utilized exhaust after-treatment systems are very powerful. To reduce NOx emissions internally, the external exhaust gas recirculation (EGR) is known as the most effective way. Due to the continuously increasing requirements regarding specific power, dynamic behavior and low emissions, future air path systems have to fulfill higher requirements and, consequently, become more and more complex, e.g. arrangements with a 2-stage turbo charging or 2-stage EGR system with different stages of cooling performance.

In Common-Rail DI Diesel Engines, a low combustion temperature process is considered as one of the most important possibilities to achieve very small emissions and optimum performance. To reduce NOx and Soot strongly, it is necessary to achieve a homogenization of the mixture in order to avoid the higher local temperatures which are responsible for the NOx formation [1]. Through the homogenization it is also possible to obtain a stoichiometric air-fuel ratio in order to significantly reduce the Soot emissions. One way to achieve this homogeneous condition is to start injection very early together with the use of higher EGR rates. The direct effect of these conditions cause a longer ignition delay (this is the time between start of the injection and auto-ignition during physical and chemical sub processes such as fuel atomization, evaporation, fuel air mixing and chemical pre-reactions take place) so that the mixture formation has more time to achieve a homogeneous state.

So far, the effect of injection rate shaping on the diesel combustion in small-bore DI diesel engines has not been extensively investigated, especially at high part load conditions with high EGR rates. The benefit of injection rate shaping is already verified for heavy duty engines at high load conditions with and without EGR. For this investigation, single cylinder engine investigations were conducted at the VKA / RWTH Aachen University. In order to meet the future NOx legislation limits like US-Tier2Bin5 it is crucial to reduce NOx especially at the high load points of the certification cycles, as FTP75 or US06. For the single cylinder investigations two part load points were chosen, which have relevance for the mentioned certification cycles. The experimental work focuses on different rate shapes as rectangular (Common-Rail type), ramp and boot shape at high EGR rates.

One of the basic topics in the design of new injection systems for DI Diesel engines is to decrease the soot emissions. A promising approach to minimize soot production are nozzles with clustered holes. A basic idea of the Cluster Configuration (CC) nozzles is to prevent a fuel rich area in the center of the flame where most of the soot is produced, and to minimize the overall soot formation in this way. For this purpose each hole of a standard nozzle is replaced by two smaller holes. The diameter of the smaller holes is chosen so that the flow rate of all nozzles should be equal. The basic strategy of the cluster nozzles is to provide a better primary break up and therefore a better mixture formation caused by the smaller nozzle holes, but a comparable penetration length of the vapor phase due to merging of the sprays. Three possible arrangements of the clustered holes are investigated in this study. Both the cluster angle and the orientation to the injector axis are varied.

Two single-cylinder diesel engines were optimised for advanced combustion performance by means of practical and cumulative hardware enhancements that are likely to be used to meet Euro 5 and 6 emissions limits and beyond. These enhancements included high fuel injection pressures, high EGR levels and charge cooling, increased swirl, and a fixed combustion phasing, providing low engine-out emissions of NOx and PM with engine efficiencies equivalent to today's diesel engines. These combustion conditions approach those of Homogeneous Charge Compression Ignition (HCCI), especially at the lower part-load operating points. Four fuels exhibiting a range of ignition quality, volatility, and aromatics contents were used to evaluate the performance of these hardware enhancements on engine-out emissions, performance, and noise levels.

This paper describes an alternative catalyst aging process using a hot gas test stand for thermal aging. The solution presented is characterized by a burner technology that is combined with a combustion enhancement, which allows stoichiometric and rich operating conditions to simulate engine exhaust gases. The resulting efficiency was increased and the operation limits were broadened, compared to combustion engines that are typically used for catalyst aging. The primary modification that enabled this achievement was the recirculation of exhaust gas downstream from catalyst back to the burner. The burner allows the running simplified dynamic durability cycles, which are the standard bench cycle that is defined by the legislation as alternative aging procedure and the fuel shut-off simulation cycle ZDAKW. The hot gas test stand approach has been compared to the conventional engine test bench method.

Fuels derived from biomass will most likely contain oxygen due to the high amount of hydrogen needed to remove oxygen in the production process. Today, alcohol fuels (e. g. ethanol) are well understood for spark ignition engines. The Institute for Combustion Engines at RWTH Aachen University carried out a fuel investigation program to explore the potential of alcohol fuels as candidates for future compression ignition engines to reduce engine-out emissions while maintaining engine efficiency and an acceptable noise level. The soot formation and oxidation process when using alcohol fuels in diesel engines is not yet sufficiently understood. Depending on the chain length, alcohol fuels vary in cetane number and boiling temperature. Decanol possesses a diesel-like cetane number and a boiling point in the range of the diesel boiling curve. Thus, decanol was selected as an alcohol representative to investigate the influence of the oxygen content of an alcohol on the combustion performance.

Six diesel, kerosene, gasoline-like, and naphtha fuels have been tested in a single cylinder diesel engine and a demonstrator vehicle, both equipped with similar engine technology and optimized for advanced combustion performance. This study was completed in order to investigate the potential to reduce engine-out emissions while maintaining engine efficiency and noise levels through changes in both engine hardware and fuel properties. The fuels investigated in this study were selected in order to better understand the effects of ignition quality, volatility, and molecular composition on engine-out emissions and performance. The optimized bench engine used in this study included engine hardware enhancements that are likely to be used to meet Euro 6 emissions limits and beyond, in part by operating under advanced combustion conditions, at least under some speed and load conditions.

Increasing concern for the environment and the impending scarcity of fossil fuels requires continued development in hydrocarbon combustion science. For compression-ignition engines, adding oxygenated compounds to the fuel can reduce noise, soot formation, and unburned hydrocarbons while simultaneously increasing thermal efficiency. In order to reliably model and design compression-ignition engines to use new fuel blends, accurate spray characteristic data is required. In this study, the spray characteristics of various blends of the oxygenated compound di-n-butyl ether (DNBE) with standard EN590 Diesel fuel are presented, including spray cone angle and spray penetration length for both liquid and gas phases. The experiments were conducted in a spray chamber at ambient conditions of 50 bar and 800 K, simulating TDC conditions in a Diesel engine. Injection pressures were varied from 700-1600 bar.

Within the Cluster of Excellence “Tailor-Made Fuels from Biomass” at RWTH Aachen University, the Institute for Combustion Engines carried out an investigation program to explore the potential of future biofuel components in Diesel blends. In this paper, thermodynamic single cylinder engine results of today's and future biofuel components are presented with respect to their engine-out emissions and engine efficiency. The investigations were divided into two phases: In the first phase, investigations were performed with rapeseed oil methyl ester (B100) and an Ethanol-Gasoline blend (E85). In order to analyze the impact of different fuel blends, mixtures with 10 vol-% of B100 or E85 and 90 vol-% of standardized EN590 Diesel were investigated. Due to the low cetane number of E85, it cannot be used purely in a Diesel engine.

Since the CO2 emissions of passenger car traffic and their greenhouse potential are in the public interest, natural gas (CNG) is discussed as an attractive alternative fuel. The engine concepts that have been applied to date are mainly based upon common gasoline engine technology. In addition, in mono-fuel applications, it is made use of an increased compression ratio -thanks to the RON (Research Octane Number) potential of CNG-, which allows for thermodynamic benefits. This paper presents advanced engine concepts that make further use of the potentials linked to CNG. Above all, the improved knock tolerance, which can be particularly utilized in turbocharged engine concepts. For bi-fuel (CNG/gasoline) power trains, the realization of variable compression ratio is of special interest. Moreover, lean burn technology is a perfect match for CNG engines. Fuel economy and emission level are evaluated basing on test bench and vehicle investigations.

The aggressive reduction of future diesel engine NOx emission limits forces the heavy- and light-duty diesel engine manufacturers to develop means to comply with stringent legislation. As a result, different exhaust emission control technologies applicable to NOx have been the subject of many investigations. One of these systems is the NOx adsorber catalyst, which has shown high NOx conversion rates during previous investigations with acceptable fuel consumption penalties. In addition, the NOx adsorber catalyst does not require a secondary on-board reductant. However, the NOx adsorber catalyst also represents the most sulfur sensitive emissions control device currently under investigation for advanced NOx control. To remove the sulfur introduced into the system through the diesel fuel and stored on the catalyst sites during operation, specific regeneration strategies and boundary conditions were investigated and developed.

The DEXA Cluster consisted of three closely interlinked projects. In 2003 the DEXA Cluster concluded by demonstrating the successful development of critical technologies for Diesel exhaust particulate after-treatment, without adverse effects on NOx emissions and maintaining the fuel economy advantages of the Diesel engine well beyond the EURO IV (2000) emission standards horizon. In the present paper the most important results of the DEXA Cluster projects in the demonstration of advanced particulate control technologies, the development of a simulation toolkit for the design of diesel exhaust after-treatment systems and the development of novel particulate characterization methodologies, are presented. The motivation for the DEXA Cluster research was to increase the market competitiveness of diesel engine powertrains for passenger cars worldwide, and to accelerate the adoption of particulate control technology.

The European research co-operation Lotus is presented. The main objectives of the project were i) to show the potential for a urea-based SCR system to comply with the EU standard of years 2005 and 2008 for heavy-duty Diesel engines for different driving conditions with optimal fuel consumption, ii) to reach 95 % conversion of NOx at steady state at full load on a Euro III engine, iii) to reach 75 % NOx reduction for exhaust temperatures between 200-300°C, and 85 % average NOx reduction between 200-500°C. The energy content of the consumed urea should not exceed 1.0 %, calculated as specific fuel consumption. These targets were met in May 2003 and the Lotus SCR system fulfilled the Euro V NOx legislative objectives for year 2008.

SI engines with gasoline direct injection are currently the focus of development for almost all car manufacturers. After the introduction of DISI engines, first to the Japanese market and after a short time delay also in Europe, a broad variety of technical solutions for efficient stratified concepts can be stated. The targets of the development activities in this field are defined by legislation and customer's demands. The potential reduction of fuel consumption with stratified operation has to be combined with a further improvement of the full load potential of the DISI engine. A substantial part of the development activities are the fulfillment of current and future emission standards. Therefore, in order to realize a highly efficient lean operation, new technologies and strategies in the field of exhaust gas aftertreatment and vehicle application are required.

Like all technical fluids, lubricants are able to solve gases. While solved gas is a neutral part of the lubricant, dissolved gas has an influence especially on the compressibility behavior. The effects of oil aeration on engine drive causes malfunctions of several components. A successful optimization of the oil circulation concerning the oil aeration presupposes a safe and reproducible measuring procedure. The FEV has developed a measurement apparatus according to the principle of the volume measurement which allows a simple but efficient oil aeration measurement.

Today, SULEV legislation represents the most stringent emission standard for vehicles with combustion engines, and it will be introduced starting by Model Year 2003. In order to meet such standards, even higher effort is required for the development of the exhaust gas emission concept of SI engines. Beyond a facelift of the combustion system, exhaust gas aftertreatment, and the engine management system, new approaches are striven for. The principle keys are well known: low HC feed gas, high thermal load for quick light-off, exhaust system with low heat capacity and highly effective exhaust gas aftertreatment.

Environmental concern demands that emissions and fuel consumption of vehicles have to improve considerably in the next 10 years. New technologies for gasoline engines, downsizing with high boosting, direct injection and fully variable valve train systems, are being developed. For Diesel engines, improved components including piezobased injectors and particle filters are expected. In the drive train new starter-generator systems as well as automated manual transmissions are being developed. In parallel alternative fuels are investigated and the use of hybrid drives and fuel cells are developed. This paper reports the progress made in the recent years and gives a comparative assessment on the different technologies with a prediction of the introduction dates and volumes into the market.

With regard to increasingly stringent emission legislation natural gas is gaining interest as an alternate fuel. Concerning mobile application natural gas is often considered to produce potentially lower exhaust emissions compared to diesel and gasoline fuel. Nevertheless, also the exhaust gas of diesel and gasoline fuelled vehicles will be improved by applying advanced technical solutions. The paper reveals the state-of-the-art in exhaust emission behaviour of diesel, gasoline, liquified petroleum gas and natural gas fuelled vehicles. Passenger cars and light-duty trucks will be considered as well as HD-trucks. Emissions include NOx, THC, NMHC, CO, Aldehydes and PAH. In addition CH4 and CO2 emissions are discussed with respect to increasing concern about the greenhouse effect. From the viewpoint of the HD-engines the alternate fuels Dimethylether (DME) and Diesel/water-Emulsion are also considered.

The introduction of the new emission standards in 2002/04 for heavy-duty diesel engines requires a substantial reduction of the NOx emissions while the particulate emissions remain on a constant level. The application of cooled EGR appears to be the most common approach in order to achieve the required target, although other means such as advanced combustion systems and the application of emission control devices to reduce NOx emissions have to be taken into account as well. The purpose of this study is to investigate the potential of such alternative solutions in comparison with cooled EGR to meet the upcoming emission standards.