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The reduction of both harmful emissions (CO, HC, NOx, etc.) and gases responsible for greenhouse effects (especially CO2) are mandatory aspects to be considered in the development process of any kind of propulsion concept. Focusing on ICEs, the main development topics are today not only the reduction of harmful emissions, increase of thermodynamic efficiency, etc. but also the decarbonization of fuels which offers the highest potential for the reduction of CO2 emissions. Accordingly, the development of future ICEs will be closely linked to the development of CO2 neutral fuels (e.g. biofuels and e-fuels) as they will be part of a common development process. This implies an increase in development complexity, which needs the support of engine simulations. In this work, the virtual modeling of real fuel behavior is addressed to improve current simulation capabilities in studying how a specific composition can affect the engine performance.

Internal combustion engines with lean homogeneous charge and auto-ignition combustion of gasoline fuels have the capability to significantly reduce fuel consumption and realize ultra-low engine-out NOx emissions. Group research of Volkswagen AG has therefore defined the Gasoline Compression Ignition combustion (GCI®) concept. A detailed investigation of this novel combustion process has been carried out on test bench engines and test vehicles by group research of Volkswagen AG and IAV GmbH Gifhorn. Experimental results confirm the theoretically expected potential for improved efficiency and emissions behavior. Volkswagen AG and IAV GmbH will utilize a highly flexible externally supercharged variable valve train (VVT) engine for future investigations to extend the understanding of gas exchange and EGR strategy as well as the boost demands of gasoline auto-ignition combustion processes.

The new inline six cylinder Twin-Turbo gasoline engine forms the pinnacle of BMW's wide range of straight-six power units, developing maximum output of 300hp and a peak torque of 300 lb-ft with a displacement of 3.0 litre. Using two turbochargers in combination with the new BMW High Precision Fuel Injection leads to a responsive build-up of torque and to an impressive development of power over a wide engine speed range. This paper gives a detailed overview of the turbocharger-and the injection system and describes the effect of both systems on power and torque, as well as on fuel consumption and emission. The big advantage of using two small turbochargers is their low moment of inertia, even the slightest movement of the accelerator pedal by the driver's foot serving to immediately build up superior pressure and power. This puts an end to the turbo “gap” previously typical of a turbocharged power unit.

In direct-injection gasoline (GDI) engines with charge stratification, minimizing engine-out nitrogen oxide (NOx) emission is crucial since exhaust-gas aftertreatment tolerates only limited amounts of NOx. Reduced NOx production directly lowers the frequency of energy-inefficient catalyst regeneration cycles. In this paper we investigate NO formation in a realistic GDI engine. Quantitative in-cylinder measurements of NO concentrations are carried out via laser-induced fluorescence imaging with excitation of NO (A-X(0,2) band at 248 nm), and subsequent fluorescence detection at 220-240 nm. Engine modifications were kept to a minimum in order to provide results that are representative of practical operating conditions. Optical access via a sapphire ring enabled identical engine geometry as a production line engine. The engine is operated with commercial gasoline (“Super-Plus”, RON 98).

Sulfur content in gasoline is known to reduce the efficiency of the catalytic converters that are used to reduce pollutants in the exhaust gas of cars. There is some concern that nitrous oxide emissions (N2O) increase when fuel with a high sulfur content is used. The engine out and tailpipe mass emissions of two cars conforming to the California LEV-standard were analyzed. The influence of the fuel sulfur content on the emissions of the regulated and some unregulated pollutants during FTP test cycles was determined. Four fuels covering the range from less than 1 to 330 ppm sulfur content were used. Over that range of fuel sulfur concentration the engine out emissions of sulfur dioxide (SO2 ) of both cars increased. Tailpipe emissions of SO2 were only found at fuel sulfur concentrations of 150 and 330 ppm. For both vehicles a correlation between the N2O emissions and the fuel sulfur content was found.

One dimensional Spontaneous Raman Scattering measurements (RS) have been performed in a spray (standard gasoline, one-component and multi-component model fuels) which was operated in a high-temperature, high-pressure chamber, so that realistic engine conditions have been simulated. The present work investigates under what conditions 1D-RS can be employed for fuel/air-ratio measurements in realistic DI gasoline sprays. The distance from the spray axis has been determined, til that, coming from the outside, quantitative Raman measurement are possible. The equivalence ratio has been quantified for the one component fuel close to the spray. It turns out that the measurement error depends strongly on the type of fuel. These problems are caused by the PAH (polycyclic aromatic hydrocarbon) content of the fuel, which leads to interfering laser-induced fluorescence signals.

The EPEFE study (European Programme on Emissions, Fuels and Engine Technologies), /1/ and other programmes have identified an increase in tailpipe NOx emissions with reduced gasoline aromatics content for modern 3-way controlled catalyst vehicles. This effect occurs with fully warmed-up catalyst under closed-loop operation. In order to understand the reasons for this effect VW and Shell have mechanistically investigated the effects of fuel properties on EMS (engine management system) and catalyst performance. Fuels with independent variation of oxygen, aromatics and mid-range volatility were tested in different VW engines. λ was monitored using sensors located both pre and post catalyst. The results confirmed that reducing gasoline aromatics content reduced engine-out emissions but increased tailpipe NOx emissions. It could be shown that differences in H/C ratio led to differences in the hydrogen content of engine-out emissions which affected the reading of the λ sensor.

Quantitative 1-D spatially-resolved NO LIF measurements in the combustion chamber of a mass-production SI engine with port-fuel injection using a tunable KrF excimer laser are presented. One of the main advantages of this approach is that KrF laser radiation at 248 nm is only slightly absorbed by the in-cylinder gases during engine combustion and therefore it allows measurements at all crank angles. Multispecies detection turned out to be crucial for this approach since it is possible to calculate the in-cylinder temperature from the detected Rayleigh scattering and the simultaneously acquired pressure traces. Additionally, it allows the monitoring of interfering emissions and spectroscopic effects like fluorescence trapping which turned out to take place. Excitation with 248 nm yields LIF emissions at shorter wavelengths than the laser wavelength (at 237 and 226 nm).

VOLKSWAGEN has conducted a number of investigations on a Multi Fuel Vehicle (MFV), designed for variable fuel operation, to determine the influence of fuel composition and clean fuels on exhaust emissions, mainly on ozone forming potential. Results of the tests indicate a small advantage of Phase II Reformulated Gasoline and a greater one for for methanol fuel M85, compared to today's gasoline. For M85 there is an about 25 % lower ozone forming potential. The most critical components in the exhaust of methanol fueled vehicles (M85) are unburned methanol and formaldehyde, forming more than 60 % of the total ozone forming potential. Therefore improvement of cold start and warmup driving during the first two to three minutes is of great importance, because in this time about 90 % of the mentioned components are formed.

Several different possibilities will be described and discussed on the processes of reducing NOx in lean-burn gasoline and diesel engines. In-company studies were conducted on zeolitic catalysts. With lean-burn spark-ignition engines, hydrocarbons in the exhaust gas act as a reducing agent. In stationary conditions at λ = 1.2, NOx conversion rates of approx. 45 % were achieved. With diesel engines, the only promising variant is SCR technology using urea as a reducing agent. The remaining problems are still the low space velocity and the narrow temperature window of the catalyst. The production of reaction products and secondary reactions of urea with other components in the diesel exhaust gas are still unclarified.