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As regulations regarding exhaust gas emissions of the internal combustion engine become more stringent, new concepts are necessary. The implementation of lean operation, direct injection to increase turbulence and facilitate stratified mixtures as well as methane as fuel in combination with high compression ratios can reduce exhaust gas emissions. Conventional electrical spark ignition systems reach their limits as higher pressures lead to faster erosion of the electrodes. Laser ignition profits from rising pressures at the time of ignition and has additional advantages such as the lack of electrodes leading to less heat dissipation and the possibility of arbitrarily positioning the ignition location. In this work results of experiments carried out in a rapid compression machine using directly injected methane to facilitate a partially stratified charge are presented.

The usage of alternative fuels inside internal combustion engines (ICE), is one promising approach to meet the higher requirements concerning the efficiency and emission of modern combustion systems. The injection and mixture formation of such fuels has a major impact on the subsequent combustion as well as the formation of pollutants. To rate the influence and to gain a better understanding of those new alternatives a basic understanding of these dominant processes is mandatory. The principle of laser-induced fluorescence (LIF) is a well-known method to display and evaluate fuel distributions inside combustion chambers. A suiting online calibration routine allows the visualization of air-fuel equivalence ratio (λ) two-dimensionally during different operation modes. As cyclic variations can become a more critical issue while using alternative fuels, cycle- resolved test series become more and more important.

Gaining detailed knowledge about the injection and mixture formation inside engines and combustion chambers during different operation modes is of major importance for improving conventional systems as well as developing new, innovative concepts. To reduce pollutants while maintaining high performance and efficiency an advanced understanding of these mechanisms is necessary. Additional challenges arise when it comes to analyzing transient engine operation and cyclic fluctuations as well as rating their contribution to the formation of emissions. This study contains the evaluations of the injection and mixture formation inside a rapid compression machine (RCM) with directly injected methane. A newly developed highly repetitive optical measurement system based on laser-induced fluorescence (LIF) is used for the quantitative visualizations of the air-fuel equivalence ratio (λ).

Diesel particulate filters are effective devices to remove particulate matter from the diesel exhaust and to fulfill emission standards. However, the operating behavior is crucially influenced by the characteristics of the deposited and accumulated soot and ash, which is affected by different diesel engine operating parameters. This is especially relevant for the thermal control of the regeneration process that poses a challenge resulting from the lack of knowledge concerning the operation behavior of the filter. Within this study, the regeneration behavior of diesel particulate filters with several age-related states is compared. For that purpose, filters were aged with an accelerated method. These filters were loaded with different steady state conditions at the engine test bench. The subsequent regeneration was applied via post-injection. Therefore, it was possible to investigate the influence of different ash levels on the regeneration behavior of the filter.

The removal of particulate matter (PM) from diesel exhaust is necessary to protect the environment and human health. To meet the strict emission standards for diesel engines an additional exhaust aftertreatment system is essential. Diesel particulate filters (DPF) are established devices to remove emitted PM from diesel exhaust. But the deposition and the accumulation of soot in the DPF influence the filter back pressure and therefore the engine performance and the fuel consumption. Thus a periodical regeneration through PM oxidation is necessary. The oxidation behavior should result in an effective regeneration mode that minimizes the fuel penalty and limits the temperature rise while maintaining a high regeneration efficiency. Excessive and fast regenerations have to be avoided as well as uncontrolled oxidations, which may lead to damages of the filter and fuel penalty.

This work capitalizes on the investigation of the effect of split injection on the combustion and in-cylinder soot formation performance of low Compression Ratio GTL-fueled DI diesel engine. An optically-accessed Rapid Compression Machine was deployed allowing the application of optical diagnostics. A shadowgraph imaging was used to analyze spray development and detect ignition zones while imaging of soot incandescence was used to determine the temporal and spatial development of soot. In addition the rate of heat release was calculated for the analysis of the combustion characteristics. It has been found that split injection shortens sprays length while increases their penetration velocity. It alters the combustion from fully premixed to two-mode, premixed and non-premixed. Soot with split injection was, therefore, significantly larger while combustion noise was reduced by factor of 4.