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The small-displacement direct-injection (DI) diesel engine is a prime candidate for future transportation needs because of its high thermal efficiency combined with near term production feasibility. Ford Motor Company and FEV Engine Technology, Inc. are working together with the US Department of Energy to develop a small displacement DI diesel engine that meets the key challenges of emissions, NVH, and power density. The targets for the engine are to meet ULEV emission standards while maintaining a best fuel consumption of 200g/kW-hr. The NVH performance goal is transparency with state-of-the-art, four-cylinder gasoline vehicles. Advanced features are required to meet the ambitious targets for this engine. Small-bore combustion systems enable the downsizing of the engine required for high fuel economy with the NVH advantages a four- cylinder has over a three-cylinder engine.

The future challenges for spark ignition (SI) engines to drastically reduce the exhaust emissions and fuel consumption while still maintaining high specific power output will be addressed. In order to further improve stoichiometric engine concepts with three-way-catalyst, reduced cold start and warm-up fuel enrichment as well as a higher EGR tolerance gain fundamental importance. Both objectives will be met if the combustion system of the engine features a high lean burn capability. Due to less freedom of multi-valve engines in combustion chamber shapes, resulting in minor squish effects, the intake generated charge motion plays the dominant role to assure an efficient combustion of even highly diluted mixtures. Basing on results of experimental combustion and flow test bench studies, the performance of swirl and tumble intake systems for multi-valve SI engines will be compared and evaluated.

Knowledge of the relevant cause-effect relationships for the combustion process, such as the interaction between the in-cylinder flow and the combustion behavior, are becoming essential for future combustion engines. Apart from the general interdependencies between the combustion rate and the turbulence intensity, specific combustion concepts, known from lean-burn engines, also strongly depend on the global flow structure which for example controls the mixing processes. Particle tracking velocimetry (PTV) was used to analyse the bulk in-cylinder flow of multi-valve production engines. The PTV results gave rise to well-aimed modifications of the intake ports and thus of the in-cylinder flow in order to achieve an optimized mixing of the charge or to affect the turbulence production during the compression stroke.

This paper describes research and development activities dealing with a technique which allows the measurement of gaseous and particulate concentrations inside the combustion chamber. This so-called fast-timed gas sampling technique was used for both the observation of the development of gaseous pollutants and soot during combustion and expansion and for getting information about the particle size history. The system has been applied to a modern passenger car DI diesel engine (Volkswagen). The investigation covers the early combustion phase beginning with the start of combustion and throughout the expansion phase until exhaust valve opening. Particles with a size of about 10 nm up to 1 μm were found. Slight variations in the smaller size classes could be observed during the combustion and expansion process.

This paper presents investigations on the combustion process in a single cylinder SI engine with direct injection. Different nozzle types are examined i.e. hollow cone nozzles and hole type nozzles both with different geometry of the injected spray. These nozzle types have been compared in view of their suitability of creating a homogeneous as well as a stratified mixture in the combustion chamber. To create a homogenous mixture, the fuel was injected during the intake stroke. In order to examine the homogeneity of the mixture in the case of direct injection, the engine was driven with mixture formation generated through intake port injection. The comparison of the direct injection method with the intake port injection for homogenous mixture formation has shown only small differences in engine behavior. To create a stratified mixture in the combustion chamber, the fuel was injected at the end of the compression stroke.

The charge motion controlled combustion concept for SI engines with direct fuel injection exhibits an excellent fuel economy and emission potential in comparison with other DI combustion concepts. It realizes a stable combustion behavior all over the engine map. Because injection and ignition timing has little bearing on emission and ignition safety, the new concept can be easily applied under DI specific operational conditions. The combination of fired engine tests and optical investigations with CFD calculations enables an efficient process optimization under the boundary conditions as imposed by the respective design. The high EGR tolerance enables a large reduction of NOx emission, which is the expected basic requirement to meet future emission standards. In addition to favorable part load behavior, the new combustion concept also displays all of the characteristics for a good full load behavior.

During the lifetime of an internal combustion engine, deposits are formed at various locations. In diesel engines, deposits in the combustion chamber and at the injection nozzles lead to an increase in the emissions, especially the particulate emissions, and the exhaust gas odor. Additionally, durability problems can also arise. Deposits in the combustion chamber of SI engines can increase the octane requirement, deposits at intake valves can reduce engine efficiency and driveability and increase emissions. A detailed theory on the mechanism of deposit formation, considering the physical effects, is presented. This theory contains a deposit transport mechanism, a mechanism of deposit attachment including an induction phase, a deposit growth phase and a deposit removal mechanism. This complex theory is based on fundamental investigations at different locations in and around internal combustion engines.