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Bio-fuels of the 2nd generation constitute a key approach to tackle both Greenhouse Gas (GHG) and air quality challenges associated with combustion emissions of the transport sector. Since these fuels are obtained of residual materials of the agricultural industry, well-totank CO2 emissions can be significantly lowered by a closed-cycle of formation and absorption of CO2. Furthermore, studies of bio-fuels have shown reduced formation of particulate matter on account of the fuels’ high oxygen content therefore addressing air quality issues. However, due to the high oxygen content and other physical parameters these fuels are expected to exhibit different ignition behaviour. Moreover, the question is whether there is a positive superimposition of the fuels ignition behaviour with the benefits of an alternative ignition system, such as a corona ignition. To shed light on these questions two oxygenic compounds, oxymethylene ether-1 (OME1) and dimethyl carbonate (DMC) have been studied with respect to OH* emission throughout ignition and onset of flame-front propagation in a combustion chamber with a large optical access via a quartz window. OH* measurements have been recorded via a highspeed optical camera (5 kHz) coupled with 308 nm optical filter and image intensifier. Sealing material swelling tests have yielded a perfluoroelastomer (FFKM 72) as an ideal, cost-efficient material regardless of the applied fuel. Comparative measurements with both ignition systems for combustion of gasoline as well as moderate blend admixtures of OME1 and DMC have demonstrated the superior ignition stability with likewise implications on flame-kernel development for the corona ignition. Furthermore a strong influence of the mode of discharge on OH* formation rates was observed especially for the oxygenic blends. Finally, for admixture variations of both oxygenates, an increased OH* level was shown during discharge thereby proving the hypothesis of a positive superimposition of oxygenic fuel and corona ignition system.

Particulates and nitrogen oxides comprise the main emission components of the Diesel combustion and therefore are subject to exhaust emission legislation. Yet, with more stringent emission standards and test-procedures, such as in passenger vehicle applications, resulting exhaust gas after-treatment systems are complex and costly. Hence, new technologies for emission control have to be explored. The application of non-thermal plasma (NTP) as a means to perform exhaust gas after-treatment is one such promising technology. One way to generate a NTP is by a corona high-frequency discharge. Apart from few other publications dealing with NTP exhaust gas aftertreatment where a NTP was generated via dielectric barrier discharges (DBD), the experiments in this publication were conducted on an operated series-production Diesel engine with an industrial pilot-type corona ignition system. Originally developed as an alternative for a spark-plug system in SI engines its attributed properties, such as large penetrated volume and high radical concentration, may also be utilized in the exhaust gas stream as it has been done in this publication. To investigate the effects of a corona discharge on Diesel engine emissions, four igniters were integrated in the exhaust duct of a CRDI 2.0 liter engine equipped with DPF. The impact on particle number, size distribution as well as on nitrogen oxides has been studied for various operational parameters of the corona system. The particle number was measured downstream of the DPF to observe the level of improvement for remaining unfiltered nanoparticles. In this first series of tests, a reduction in particle number of up to 10 % was achieved depending on engine load. Particle size distribution was measured upstream of the DPF. In this case, the highest reduction of 10 % was observed in the mid-range particle size of about 60 nm. No increase in other particulate size ranges has been observed.