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Due to experimental challenges, combustion of diesel-like jets has rarely been characterized by laser-based quantitative multiscalar measurements. In this work, recently developed laser diagnostics for combustion temperature and the concentrations of CO, O2, and NO are applied to a diesel-like jet, using a highly oxygenated fuel. The diagnostic is based on spontaneous Raman scattering (SRS) and laser-induced fluorescence (LIF) methods. Line imaging yields multiscalar profiles across the jet cross section. Measurements turn out to be particularly accurate, because near-stoichiometric combustion occurs in the central region of the jet. Thereby, experimental cross-influences by light attenuation and interfering emissions are greatly reduced compared to the combustion of conventional, sooting diesel fuel jets. This is achieved by fuel oxygenation and enhanced premixing.

The HSDI Diesel engine contributes substantially to the decrease of fleet fuel consumption thus to the reduction of CO2 emissions. This results in the rising market acceptance which is supported by desirable driving performance as well as greatly improved NVH behavior. In addition to the above mentioned requirements on driving performance, fuel economy and NVH behavior, continuously increasing demands on emissions performance have to be met. From today's view the Diesel particulate trap presents a safe technology to achieve the required reduction of the particle emission of more than 95%. However, according to today's knowledge a further, substantial NOx engine-out emission reduction for the Diesel engine is counteracts with the other goal of reduced fuel consumption. To comply with current and future emission standards, Diesel engines will require DeNOx technologies.

In order to reduce engine out CO2 emissions, it is a main subject to find new alternative fuels from renewable sources. For identifying the specification of an optimized fuel for engine combustion, it is essential to understand the details of combustion and pollutant formation. For obtaining a better understanding of the flame behavior, dynamic structure large eddy simulations are a method of choice. In the investigation presented in this paper, an n-heptane spray flame is simulated under engine relevant conditions starting at a pressure of 50 bar and a temperature of 800 K. Measurements are conducted at a high-pressure vessel with the same conditions. Liquid penetration length is measured with Mie-Scatterlight, gaseous penetration length with Shadowgraphy and lift-off length as well as ignition delay with OH*-Radiation. In addition to these global high-speed measurement techniques, detailed spectroscopic laser measurements are conducted at the n-heptane flame.

The increasingly stringent limits on pollutant emissions from internal combustion engine-powered vehicles require the optimization of advanced combustion systems by means of virtual development and simulation tools. Among the gaseous emissions from spark-ignition engines, the unburned hydrocarbon (HC) emissions are the most challenging species to simulate because of the complexity of the multiple physical and chemical mechanisms that contribute to their emission. These mechanisms are mainly three-dimensional (3D) resulting from multi-phase physics - e.g., fuel injection, oil-film layer, etc. - and are difficult to predict even in complex 3D computational fluid-dynamic (CFD) simulations. Phenomenological models describing the relationships between the physical-chemical phenomena are of great interest for the modeling and simplification of such complex mechanisms.

Within this study a dual-fuel concept was experimentally investigated. The utilized fuels were conventional EN228 RON95E10 and EN590 Diesel B7 pump fuels. The engine was a single cylinder Diesel research engine for passenger car application. Except for the installation of the port fuel injection valve, the engine was not modified. The investigated engine load range covered low part load operation of IMEP = 4.3 bar up to IMEP = 14.8 bar at different engine speeds. Investigations with Diesel pilot injection showed that the dual-fuel approach can significantly reduce the soot/NOx-trade-off, but typically increases the HC- and CO-emissions. At high engine load and gasoline mass fraction, the premixed gasoline/air self-ignited before Diesel fuel was injected. Reactivity Controlled Compression Ignition (RCCI) was subsequently investigated in a medium load point at IMEP = 6.8 bar.

Cyclic fluctuations of the in-cylinder processes in a Direct Injection Spark Ignition (DISI) engine may strongly affect the engine operation causing misfires or variations in the indicated mean effective pressure (imep). Particularly misfires prevent compliance with current or future exhaust emission legislations. Nevertheless, the origin of cyclic fluctuations is not well understood since fluctuations of in-cylinder air flow, fuel injection and wall interaction have to be considered. This paper focusses on a detailed experimental analysis of the origin of cyclic fluctuations in a DISI engine with an air guided combustion process by means of advanced Laser Induced Exciplex Fluorescence (LIEF) measurements. It reveals that cycle-to-cycle variations primarily originate from the air/fuel ratio at the spark plug.

Gasoline Controlled Auto-Ignition (GCAI) combustion, which can be categorized under Homogeneous Charge Compression Ignition (HCCI), is a low-temperature combustion process with promising benefits such as ultra-low cylinder-out NOx emissions and reduced brake-specific fuel consumption, which are the critical parameters in any modern engine. Since this technology is based on uncontrolled auto-ignition of a premixed charge, it is very sensitive to any change in boundary conditions during engine operation. Adopting real time valve timing and fuel-injection strategies can enable improved control over GCAI combustion. This work discusses the outcome of collaborative experimental research by the partnering institutes in this direction. Experiments were performed in a single cylinder GCAI engine with variable valve timing and Gasoline Direct Injection (GDI) at constant indicated mean effective pressure (IMEP). In the first phase intake and exhaust valve timing sweeps were investigated.

With Post Euro 6 emission standards in discussion, stricter particulate number (PN) targets as well as a decreased PN cut-off size from 23 to 10 nm are expected. Sub-23 nm particulates are considered particularly harmful to human health, but are not yet taken into account in the current vehicle certification process. Not considering sub-23 nm particulates during the development process could lead to significant additional efforts for Original Equipment Manufacturers (OEM) to comply with future Post Euro 6 PN emission limits. It is therefore essential to increase knowledge about the formation and filtration of particulates below 23 nm. In the present study, a holistic Gasoline Particulate Filter (GPF) characterization has been carried out on an engine test bench under varying boundary conditions and on a burner bench with a novel ash loading methodology.

The requirement of reducing worldwide CO₂ emissions and engine pollutants are demanding an increased use of bio-fuels. Ethanol with its established production technology can contribute to this goal. However, due to its resistive auto-ignition behavior the use of ethanol-based fuels is limited to the spark-ignited gasoline combustion process. For application to the compression-ignited diesel combustion process advanced ignition systems are required. In general, ethanol offers a significant potential to improve the soot emission behavior of the diesel engine due to its oxygen content and its enhanced evaporation behavior. In this contribution the ignition behavior of ethanol and mixtures with high ethanol content is investigated in combination with advanced ignition systems with ceramic glow-plugs under diesel engine relevant thermodynamic conditions in a high pressure and temperature vessel.

The optimization study presented herein is aimed to minimize the fuel consumption and engine-out emissions using commercially available EN15940 compatible HVO (Hydrogenated Vegetable Oil) fuel. The investigations were carried out on FEV’s 3rd generation HECS (High Efficiency Combustion System) multi-cylinder engine (1.6L, 4 Cylinder, Euro 6). Using a global DOE approach, the effects of calibration parameters on efficiency and emissions were obtained and analyzed. This was followed by a global optimization procedure to obtain a dedicated calibration for HVO. The study was aiming for efficiency improvement and it was found that at lower loads, higher fractions of low pressure EGR in combination with lower fuel injection pressures were favorable. At higher loads, a combustion center advancement, increase of injection pressure and reduced pilot injection quantities were possible without exceeding the noise and NOx levels of the baseline Diesel.

With the implementation of the “Worldwide harmonized Light duty Test Procedure” (WLTP) and the highly dynamic “Real Driving Emissions” (RDE) tests in Europe, different engineering methodologies from virtual calibration approaches to Engine-in-the-loop (EiL) methods have to be considered to define and calibrate efficient exhaust gas aftertreatment technologies without the availability of prototype vehicles in early project phases. Since different types of testing facilities can be used, the effects of test benches as well as real and virtual vehicle operators have to be determined. Moreover, in order to effectively reduce harmful emissions, the reproducibility of test cycles is essential for an accurate and efficient application of exhaust gas aftertreatment systems and the calibration of internal combustion engines.

The demand for lower CO2 emissions requires not just the optimization of every single component but the complete system. For a transmission system, it is important to optimize the transmission hardware as we well as the interaction of powertrain components. For automatic transmission with wide ratio spreads, the main losses are caused by the actuation system, which can be reduced with use of ondemand actuation systems. In this paper, a new on-demand electromechanical actuation system with validation results on a clutch test bench is presented. The electro-mechanical actuator shows an increase in the efficiency of 4.1 % compared to the conventional hydraulic actuation in a simulated NEDC (New European Driving Cycle) cycle. This increase is based on the powerless end positions of the actuator (engaged and disengaged clutch). The thermal tension and wear are compensated with a disk spring. This allows a stable control over service life.

Partly competing objectives, as low fuel consumption, low friction, long oil maintenance rate, and at the same time lowest exhaust emissions have to be fulfilled. Diminishing resources, continuously reduced development periods, and shortened product cycles yield detailed knowledge about oil consumption mechanisms in combustion engines to be essential. There are different ways for the lubricating oil to enter the combustion chamber: for example as blow-by gas, leakage past valve stem seals, piston rings (reverse blow-by) and evaporation from the cylinder liner wall and the combustion chamber. For a further reduction of oil consumption the investigation of these mechanisms has become more and more important. In this paper the influence of the mixture formation and the resulting fuel content in the cylinder liner wall film on the lubricant oil emission was examined.

With increasing interest in new biofuel candidates, 1-octanol and di-n-butylether (DNBE) were presented in recent studies. Although these molecular species are isomers, their properties are substantially different. In contrast to DNBE, 1-octanol is almost a gasoline-type fuel in terms of its auto-ignition quality. Thus, there are problems associated with engine start-up for neat 1-octanol. In order to find a suitable glow-plug position, mixture formation is studied in the cylinder under almost idle operating conditions in the present work. This is conducted by planar laser-induced fluorescence in a high-speed direct-injection optical diesel engine. The investigated C8-oxygenates are also significantly different in terms of their evaporation characteristics. Thus, in-cylinder mixture formation of these two species is compared in this work, allowing conclusions on combustion behavior and exhaust emissions.

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.

Numerical analyses of the liquid fuel injection and subsequent fuel-air mixing for a high-tumble direct injection engine with an active pre-chamber ignition system at operation conditions of 2000 RPM are presented. The Navier-Stokes equations for compressible in-cylinder flow are solved numerically using a hierarchical Cartesian mesh based finite-volume method. To determine the fuel vapor before ignition large-eddy flow simulations are two-way coupled with the spray droplets in a Lagrangian Particle Tracking (LPT) formulation. The combined hierarchical Cartesian mesh ensures efficient usage of high performance computing systems through solution adaptive refinement and dynamic load balancing. Computational meshes with approximately 170 million cells and 1.0 million spray parcels are used for the simulations.

Lignocellulosic biomass consists of (hemi-) cellulose and lignin. Accordingly, an integrated biorefinery will seek to valorize both streams into higher value fuels and chemicals. To this end, this study evaluated the overall combustion performance of both cellulose- and lignin derivatives, namely the high cetane number (CN) di-n-butyl ether (DnBE) and low CN anisole, respectively. Said compounds were blended both separately and together with EN590 diesel. Experiments were conducted in a single cylinder compression ignition engine, which has been optimized for improved combustion characteristics with respect to low emission levels and at the same time high fuel efficiency. The selected operating conditions have been adopted from previous “Tailor-Made Fuels from Biomass (TMFB)” work.

The high-speed Dl-diesel engine has made a significant advance since the beginning of the 90's in the Western European passenger car market. Apart from the traditional advantage in fuel economy, further factors contributing to this success have been significantly improved performance and power density, as well as the permanent progress made in acoustics and comfort. In addition to the efforts to improve efficiency of automotive powertrains, the requirement for cleaner air increases through the continuous worldwide restriction of emissions by legislative regulations for diesel engines. Against the backdrop of global climate change, significant reduction of CO2 is observed. Hence, for the future, engine and vehicle concepts are needed, that, while maintaining the well-established attractive market attributes, compare more favorably with regard to fuel consumption.

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.

The use of pistons made of fine grain carbon was investigated in a spark-ignition engine within a European Community funded research project (TPRO-CT92-0008). Pistons were designed and manufactured and then tested in a single cylinder engine. Due to the carbon material's lower coefficient of thermal expansion the top land clearance between piston and cylinder can be reduced by a factor of three in comparison to standard aluminium designs. Under steady-state part-load operating conditions the emission of unburned hydrocarbons can be reduced by more than 15% compared to aluminium pistons, without significant penalties in NOx-emissions. Simultaneously, a small improvement in fuel economy of about 2% is observed. At full-load blow-by leakage flow is reduced by more than 50%. The piston crown temperature is about 30°C higher with the carbon piston than with the standard aluminium piston, due to the lower thermal conductivity of the carbon material.