The development and validation of detailed simulation models of incylinder combustion, emission formation mechanisms and reaction kinetics in the exhaust system are of crucial importance for the design of future low-emission powertrain concepts. To investigate emission formation mechanisms on one side and to create a solid basis for the validation of simulation methodologies (e.g. 3D-CFD, multidimensional in-cylinder models, etc.) on the other side, specific detailed measurements in the exhaust system are required. In particular, the hydrocarbon (HC) emissions are difficult to be investigated in simulation and experimentally, due to their complex composition and their post-oxidation in the exhaust system.In this work, different emission measurement devices were used to track the emission level and composition at different distances from the cylinder along the exhaust manifold, from the exhaust valve onwards. A fast-FID (FFID) was used to measure the cycle-resolved total-HC (THC) emissions and an ion molecule reaction massspectrometer (IMR-MS) to determine the average concentration of some selected HC components. Conventional exhaust analyzers were used additionally to measure the average levels of the important exhaust gas components (THC, NOx, CO, CO2, O2).The measurements were conducted on a 0.4 l single-cylinder sparkignited (SI) research engine. The effects and cross-effects on emissions of several relevant operating parameters were evaluated. Different result patterns are observed in the different measuring positions. In this work, selected results on the effect of air-to-fuel ratio and spark timing are presented. For the air-fuel-ratio variation, the FFID results show that the THC quenching increases with lean operating condition and the IMR-MS that this increase corresponds to an increase in fuel-HC and a reduction in non-fuel-HC. In the spark timing variation, the trends of THC in the exhaust port and in the exhaust runner suggest the presence of HC oxidation in the exhaust port, due to higher exhaust temperature with retarded combustion. Additionally, the IMR-MS confirm the presence of late and incomplete oxidation with the increase of non-fuel species.

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Alternative fuels have become of great importance in order to secure a sustainable mobility within the next decades. Within the Cluster of Excellence, ''Tailor-Made Fuels from Biomass'' at RWTH Aachen University, several possible fuel candidates could be derived from (hemi-)cellulose by selective catalytic conversion. The proposed fuel candidates include furans, ethers, alcohols, and ketones. Experiments with the isomers di-n-butyl ether and 1-octanol have proven their suitability for diesel-type combustion. With di-n-butyl ether being prone to auto-ignition, overall hydrocarbon, carbon monoxide, and soot emissions are reduced compared to diesel. In contrast, the prolonged ignition delay with 1-octanol causes an increase in HC and CO emissions particularly at low engine loads. However, soot emissions are even below those of di-n-butyl ether. With regard to particulate matter, an Exhaust Emissions Particulate Sizer Spectrometer (EEPS ä ) has been utilized to investigate the particle size or number distribution. Compared to diesel, a reduction of the total particle number up to 80% was seen with the oxygenates next to a shift toward reduced particle mobility diameter. The HC emissions of both di-n-butyl ether and 1-octanol have been studied in detail by means of gas chromatographymass spectrometry. As a main result, not only the general emission reduction potential of the biofuel alternatives 1-octanol and di-n-butyl ether can be shown with this work. Gas chromatography-mass spectrometry revealed that the composition of hydrocarbons emitted with the C 8 -oxygenates is almost equal to those with diesel, except for the unburned fuel that is present in the exhaust gas. Quantification showed that the carcinogenic component 1,3-butadiene increased with the alternative fuel candidates, whereas particularly benzene and ethyl benzene reduced. Since both di-n-butyl ether and 1-octanol are found in high proportions in the exhaust gas, the effects on the aftertreatment system have to be investigated in a subsequent campaign.

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The washcoat composition and the catalytic properties of two commercially available lean NOx traps (LNTs) were investigated. Both catalysts contained nominally the same NOx storage and catalytic materials but differed strongly in their amount and activity as well as in the composition of their layered washcoat architecture. In lean‐rich cycle experiments under realistic engine‐out gas compositions using a laboratory gas test bench, the LNTs showed comparable NOx storage behavior. At temperatures below 250 °C, the lean phase durations last up to 300 s until 50 % of the NOx storage capacity is reached. The simultaneously calculated NOx storage efficiencies drop rapidly below 35 %, resulting in a high NOx slip. Strong variations were observed in N2O and NH3 selectivity and in CO slip during regeneration of both LNTs caused by the different oxygen storage capacity (OSC), water gas shift (WGS) activity and rhodium distribution in the catalytic layers. Based on the obtained results, proposals were made to optimize the storage and regeneration performance, leading to highly efficient LNT catalysts for coupling with a downstream SCR catalyst.