Search

The ignition process initiates the combustion in spark-ignition engines. Therefore, understanding the ignition process is an important aspect in developing more efficient combustion engines. In this thesis, the vibrational temperature of an ignition spark in air under atmospheric pressure and room temperature is observed in spatial and temporal resolution. The temperature is determined by comparing simulated spectra with the measured spectra of the second positive system of N2 between 360 and 381 nm. Changing the dwell time had no significant effect on the vibrational temperature of the three spark phases. In the breakdown the vibrational temperature is about 3300 K. The vibrational temperature of the following arc discharge is in the range of 3750 K to 4350 K. The glow discharge is divided into the negative glow and the positive column. Both show similar vibration temperatures in the range of 3500 K to 3900 K.

The future of mobility presents various challenges. For the future CO2 targets, savings in the existing fleet are necessary. In this paper and the accompanying poster, the project reFuels- Rethinking Fuels is introduced and results of the developed gasoline and diesel fuels are presented. The aim of the project is to enable the use of fuels from renewable sources via BtL and PtL pathways as drop-in components to fossil fuels for use in the existing vehicle fleet. For this purpose, it is shown how the gasoline fuel blend G40 with regenerative fuel components produced from biomass has advantages in particle behavior in RDE tests compared to conventional fossil gasoline. In single-cylinder tests, a significantly reduces proportion of aromatics larger than or equal to C9 in the optimized bioliq ® fuel leads to improved particle emissions. Tests with diesel and components from regenerative sources (PtL and BtL), which mixture was within EN 590, show no adverse thermodynamic behavior but advantages from a raw emission point of view. On production engine at cold start conditions at -7 °C, paraffinic diesel shows improved particulate emissions under transient driving maneuvers, especially in idling phases, compared to fossil diesel.

In this work, the temporal and spatial rotational temperature, as an indicator of spark temperature in the gas, of an ignition spark at ambient pressure is determined. With optical emission spectroscopy, the rotational bands of the nitrogen C3Πu → B3Πg transition at a wavelength of 337 nm are for determination. In addition, the electrical values of the current and the voltage are measured with a digital storage oscilloscope. All measurements are performed with a common nickel spark plug and a commercial 90 mJ ignition coil. The dwell time of the coil is varied in four steps from 100 to 25% and the influence on the rotational temperature is measured. The results are split into the three spark phases: breakdown, arc discharge, and glow discharge. The results show a cold breakdown, which is independent from the dwell time. On average, arc discharge is the hottest discharge phase, while the glow discharge has a medium rotational temperature.

Within the so-called bioliq® process, renewable carbon resources, especially agricultural residues, are converted to gasoline. The process chain comprises pyrolysis of the feedstocks, gasification to synthesis gas, gas cleaning and conversion of synthesis gas to dimethyl ether (DME) followed by conversion of DME to hydrocarbons. Construction of all process units has been completed now and the entire plant has been successfully operated in several campaigns. Thus, hundreds of liters of a new alternative gasoline are available now, which allow for an extensive testing. The basic characteristics of the resulting bioliq®/100 fuel are described. It is rich in aromatics and a blend consisting of 90 Vol.−% of conventional RON95 E5 fuel and 10 Vol.−% of bioliq®/100, designated as bioliq®/10, has been produced which meets the DIN EN 228 standard. Initial measurements on a single cylinder research engine have been carried out focusing on efficiency and emissions. A comparison of bioliq®/10 with neat RON95 E5 revealed an improved knocking behavior of bioliq®/10 even by a small fraction of regenerative bioliq® fuel. Particle as well as hydrocarbon emissions from bioliq®/10 are significantly higher than in the case of RON95 E5. Increased particle emissions are attributed to the higher content of aromatics. Soot reactivity has been investigated and soot from bioliq®/10 exhibits higher reactivity than soot from RON95 E5.

The particle size distribution (PSD) of submicron exhaust engine-out soot, is typically determined using a method based on the electrical mobility is used. This measurement procedure is subjected to uncertainty mainly due to inaccurate dilution of the sampled aerosol, unknown flow conditions at the probe inlet and the limited measurement accuracy of the device itself. In order to determine the measurement uncertainty, two different aerosol spectrometers, a TSI EEPS 3090 and a Cambustion DMS500 were installed and operated simultaneously at a single-cylinder heavy-duty diesel engine at the Institute of Internal Combustion Engines of the Karlsruhe Institute of Technology (KIT).The engine was operated at various operating points to evaluate the ability of the spectrometers to correctly determine the PSD and the total particle number concentration (TPNC) at different boundary conditions. Variations of the position and geometry of the probe systems were performed, to evaluate the influence of the flow conditions at the probe inlet. The dilution systems of both measuring devices were verified by varying the dilution factor in three steps. Both particle sizers show good agreement in the TPNC. It could be confirmed that the probe geometry and its positioning had a negligible effect on the properties of the exhaust gas sample. A slight shift in PSD between the EEPS and the DMS was observed at the engine test bed. For a detailed evaluation, a device comparison with monodisperse polystyrene (PSL) particles with a SMPS as reference was performed at the Institute of Mechanical Process Engineering and Mechanics (KIT).