Optische Untersuchung der dieselmotorischen Verbrennung mit Biokraftstoffen

  • Optical investigation of the compression ignition combustion process with biofuels

Ottenwälder, Tamara Sophia; Pischinger, Stefan (Thesis advisor); Grünefeld, Gerd (Thesis advisor)

Aachen (2019)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019


In this doctoral thesis, the basic understanding of low-temperature combustion processes and alternative tailor-made fuels is improved with optical measurement methods. Therefore, different optical measurement techniques have been applied using different fuels in a high-pressure injection chamber. In the high-speed measurements different techniques are working simultaneously to detect characteristic values of mixture formation and combustion like liquid and gaseous penetration length as well as flame lift-off length: Mie scattering, shadowgraphy and OH*-radiation. With the help of fundamental spectroscopic laser measurement techniques based on laser induced fluorescence, nitrogen oxide can be quantitatively detected in the jet central region for the first time. Several steps are required for the quantification: correction of the absorption through the flame, correction of the different temperatures in the flame, correction of fluctuations in laser energy and determination of an absolute calibration factor. Quantitative nitrogen oxide concentrations were measured at different times and at two different distances from the injector nozzle hole. The measurement of the quantitative nitrogen oxide concentrations is also possible early in the flame and can be conducted directly next to the lift-off length. It was also used with two alternative fuels. The quantitative nitric oxide measurement shows non-negligible nitrogen oxide concentrations in the middle of the burning jet, in contrast to the prevailing classical diesel combustion model where nitrogen oxides are only formed at the edge of the diffusion zone of the flame. Furthermore, it is shown that due to the different flow states in the combustion nitrogen oxides are affected. To support the measurement, the application of a 0-d constant pressure simulation with a detailed flame chemistry and a prompt-NOx mechanism was performed. As a result, the detection of prompt-NO formation in the flame is possible. To compare with the experiments a 3-d-CFD-LES-simulation was conducted.