@misc{GernKaufVaccaetal., author = {Gern, Maike Sophie and Kauf, Georg Malte and Vacca, Antonino and Franken, Tim and Kulzer, Andr{\´e} Casal}, title = {Ganzheitliche Methode zur Bewertung der Wassereinspritzung}, series = {MTZ - Motortechnische Zeitschrift}, volume = {80}, journal = {MTZ - Motortechnische Zeitschrift}, number = {7-8}, issn = {2192-8843}, doi = {10.1007/s35146-019-0070-x}, pages = {124 -- 129}, abstract = {Die k{\"u}nftige Effizienzsteigerung bei Ottomotoren mit Direkteinspritzung sowie die Reduktion von gas- und partikelf{\"o}rmigen Emissionen erfordern innovative Ans{\"a}tze. Durch die neue RDEGesetzgebung f{\"u}r leichte Kraftfahrzeuge verschiebt sich der Fokus hin zu dynamischen Testzyklen mit 12 \% mehr Hochlastbetriebspunkten im Vergleich zum WLTC (Worldwide harmonized Light Duty Test Cycle). Die Steigerung des Mitteldrucks bei Ottomotoren f{\"u}hrt zu einem effizienten Betrieb, der jedoch durch das Risiko irregul{\"a}rer Verbrennung und hohen Abgastemperaturen limitiert ist. Durch den Einsatz von Wassereinspritzung k{\"o}nnen sowohl die Klopfneigung als auch die Abgastemperatur reduziert werden, was den Schutz der Abgasnachbehandlungskomponenten bei gleichzeitiger Wirkungsgradsteigerung erm{\"o}glicht. Im Rahmen des FVV-Projekts „Wassereinspritzung bei Ottomotoren" wird der Einfluss der NiederdruckWassereinspritzung (NDWE) und Hochdruck-Wassereinspritzung (HDWE) untersucht. Insbesondere die Auswirkungen auf Gemischbildung, Verbrennung und Abgasnachbehandlung werden durch die Vernetzung von Experiment und Simulation analysiert.}, language = {de} } @misc{FrankenSeidelMatriscianoetal., author = {Franken, Tim and Seidel, Lars and Matrisciano, Andrea and Mauß, Fabian and Kulzer, Andre Casal and Schuerg, Frank}, title = {Analysis of the Water Addition Efficiency on Knock Suppression for Different Octane Ratings}, series = {SAE World Congress}, journal = {SAE World Congress}, issn = {2688-3627}, doi = {10.4271/2020-01-0551}, pages = {5}, abstract = {Water injection can be applied to spark ignited gasoline engines to increase the Knock Limit Spark Advance and improve the thermal efficiency. The Knock Limit Spark Advance potential of 6 °CA to 11 °CA is shown by many research groups for EN228 gasoline fuel using experimental and simulation methods. The influence of water is multi-layered since it reduces the in-cylinder temperature by vaporization and higher heat capacity of the fresh gas, it changes the chemical equilibrium in the end gas and increases the ignition delay and decreases the laminar flame speed. The aim of this work is to extend the analysis of water addition to different octane ratings. The simulation method used for the analysis consists of a detailed reaction scheme for gasoline fuels, the Quasi-Dimensional Stochastic Reactor Model and the Detonation Diagram. The detailed reaction scheme is used to create the dual fuel laminar flame speed and combustion chemistry look-up tables. The Detonation Diagram is used as a novel approach in the Quasi-Dimensional Stochastic Reactor Model to evaluate the auto-ignition characteristic in the end gas and determine if it is a harmless deflagration or developing detonation. First, the Quasi-Dimensional Stochastic Reactor Model is trained for three engine operating points and a RON95 E10 fuel. Its performance is evaluated based on experimental results of a single cylinder research engine. Subsequently, different spark timings and water-fuel ratios are investigated for different Primary Reference Fuels. The results outline that water addition can effectively reduce the strength of auto-ignition in the end gas for different Primary Reference Fuels. Thereby, it can be stated that the reduction of the auto-ignition strength through water addition by 50 - 80 \% water-fuel ratio for high octane number fuels corresponds to the spark timing delay of 6 °CA or an increase of research octane number by 10 points.}, language = {en} } @misc{FrankenSeidelShresthaetal., author = {Franken, Tim and Seidel, Lars and Shrestha, Krishna Prasad and Gonzalez Mestre, Laura Catalina and Mauß, Fabian}, title = {Multi-objective Optimization of Gasoline, Ethanol, and Methanol in Spark Ignition Engines}, abstract = {In this study, an engine and fuel co-optimization is performed to improve the efficiency and emissions of a spark ignition engine utilizing detailed reaction mechanisms and stochastic combustion modelling. The reaction mechanism for gasoline surrogates (Seidel 2017), ethanol, and methanol (Shrestha et al. 2019) is validated for experiments at different thermodynamic conditions. Liquid thermophysical properties of the RON95E10 surrogate (iso-octane, n-heptane, toluene, and ethanol mixture), ethanol, and methanol are determined using the NIST standard reference database (NIST 2018) and Yaws database (Yaws 2014). The combustion chemistry, laminar flame speed, and thermophysical data are pre-compiled in look-up tables to speed up the simulations (tabulated chemistry). The auto-ignition in the stochastic reactor model is predicted by the detailed chemistry and subsequently evaluated using the Bradley Detonation Diagram (Bradley et al. 2002, Gu et al. 2003, Neter 2019), which assigns two dimensionless parameters (resonance parameter and reactivity parameter). According to the defined developing detonation limits, the auto-ignition is either in deflagration, sub-sonic auto-ignition, or developing detonation mode. Ethanol and methanol show a knock-reducing characteristic, which is mainly due to the high heat of vaporization. The multi-objective optimization process includes mathematical algorithms for design space exploration with Uniform Latin Hypercube, pareto front convergence with Non-dominated Sorting Genetic Algorithm II (NSGA-II), and multi-criteria decision making (Deb et al. 2002). The optimization input parameter ranges are selected according to the previous sensitivity analysis, and the objectives are to minimize specific CO2 and specific CO and maximize indicated efficiency. The performance study of different optimization algorithms shows that the incorporation of metamodels is beneficial to improve the design space exploration, while keeping the optimization duration low. The comparison of different reaction mechanisms, which are applied in the optimization process, shows a strong impact on the pareto front solutions. This is due to differences in the emission formation and auto-ignition between the different reaction schemes. Overall, the engine efficiency is increased by 3.5 \% points, and specific CO2 emissions are reduced by 99 g/kWh for ethanol and 142 g/kWh for methanol combustion compared to the base case. This is achieved by advanced spark timing, lean combustion, and reduced C:H ratio of ethanol and methanol in relation to RON95E10.}, language = {en} } @misc{FrankenShresthaSeideletal., author = {Franken, Tim and Shrestha, Krishna Prasad and Seidel, Lars and Mauß, Fabian}, title = {Effect of Gasoline-Ethanol-Water Mixtures on Auto-Ignition in a Spark Ignition Engine}, series = {International Conference on Knocking in Gasoline Engines}, journal = {International Conference on Knocking in Gasoline Engines}, editor = {Sens, Marc}, publisher = {expert}, address = {T{\"u}bingen}, isbn = {978-3-8169-3544-5}, doi = {10.24053/9783816985440}, pages = {175 -- 222}, abstract = {The climate protection plan of the European Union requires a significant reduction of CO2 emissions from the transportation sector by 2030. Today ethanol is already blended by 10vol-\% in gasoline and further increase of the ethanol content to 20vol-\% is discussed. During the ethanol production process, distillation and molecular sieving is required to remove the water concentration to achieve high-purity ethanol. However, hydrous ethanol can be beneficial to suppress knock of spark ignition engines. The hygroscopic nature of ethanol can allow to increase the water content in gasoline - water emulsions even more, without adding additional surfactants, and improve the thermal efficiency by optimized combustion phasing, while keeping the system complexity low. Hence, the effect of gasoline - ethanol - water mixtures on the auto-ignition in a single-cylinder spark ignition engine is investigated by using multi-dimensional simulation and detailed chemistry. The gasoline - ethanol mixtures are defined to keep the Research Octane Number constant, while the Motored Octane Number is decreasing. In total five surrogates are defined and investigated: E10 (10vol-\% ethanol-in-gasoline), E20, E30, E70 and E100. The water content is determined according to experimentally defined ternary diagrams that evaluated stable gasoline - ethanol - water emulsion at different gasoline - ethanol blending ratios. The auto-ignition modes of the surrogates are analyzed using the diagram, which determines if hotspots are within harmless deflagration or harmful developing detonation regime. The strongest auto-ignition is observed for the E10 surrogate, while increasing ethanol content reduces the surrogate reactivity and increases the resonance parameter. No auto-ignition of the unburnt mixture is observed for the E70 and E100 surrogates. The addition of hydrous ethanol decreased the excitation time of the surrogates, especially at low ethanol content, wherefor the reactivity parameter is significantly increased. The hotspots for E10, E20 and E30 surrogates with hydrous ethanol are found within the developing detonation regime, while hotspots of the E70 surrogate with hydrous ethanol are found in the transition regime. For the hydrous E100 surrogate no auto-ignition is predicted because of reduced temperature of the unburnt mixture due to water vaporization, which outweighs the increased reactivity due to water vapor addition.}, language = {en} }