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 C 3 Π u → B 3 Π g 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.

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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 N 2 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.

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