1D Raman/Rayleigh-scattering and CO-LIF measurements in laminar and turbulent jet flames of dimethyl ether using a hybrid data reduction strategy

In the present work, "Raman/Rayleigh scattering and CO-LIF measurements in laminar and turbulent jet flames of dimethyl ether using a hybrid data reduction strategy", the development of a hybrid data reduction strategy for spectroscopic, laser-based measurements of combustion products and reactants in laminar and turbulent flames of distinct fuels is presented.

The objective of this thesis was to merge two existing data evaluation procedures into a hybrid method to take advantage of the strengths of each method. Subsequently, the developed strategy had to be extended to provide flexibility for the investigated fuel.

The following main topics were addressed: Measurement data were taken in close cooperation with the Combustion Research Facility, Sandia National Laboratories, in Livermore, California, to provide the base for quantitative comparison of both distinct data reduction processes. For that purpose, the method "Spectral Fitting" used at the Institute Reactive Flows and Diagnostics, was adapted on the special characteristics of the experimental setup in Livermore and was used to evaluate the data. At the same time, the "Hybrid method" was developed from combining of the Spectral Fitting with the "Matrix inversion" method from Livermore. In this, the quantum mechanical models essential in the Spectral fitting for the calculation of spectroscopic characteristics of the measured molecules were adopted for the Matrix inversion method to reduce extensive calibrations and measurement uncertainties. Subsequently, during a two-month research stay in Livermore, the results of all three methods were compared and discussed. Meanwhile, new measurement data were taken to study the combustion of complexer hydrocarbons beyond methane (dimethyl ether, ethylene, ethane, propane). After the research stay, new strategies had to be developed to allow for the data evaluation of the aforementioned fuels.

The hybrid method was validated experimentally by well-known measurement objects. With the aid of numerical combustion simulation tools, new strategies for evaluating the measured Raman/Rayleigh scattering of hydrocarbons beyond methane were developed. Then, these were validated in laminar jet flames of dimethyl ether. First test measurements in turbulent dimethyl ether flames were performed, and also with the new method evaluated and presented.