Friedrich-Alexander-Universität Erlangen-Nürnberg

Fundamental combustion research and applied combustion technology

Fundamental combustion research and applied combustion technology

The working field of the group “combustion technology” is the development and application of laser diagnostics for investigation of mixture formation and complex reactive flows. Besides fundamental research in those fields also applied combustion investigations is a topic for the development of technical combustion systems, internal combustion engines and gas turbine processes regarding fuel efficiency and pollutant emission reduction.

In modern gas turbines mainly lean premixed combustion is applied to reduce the thermally generated nitrogen oxides (NOx). However, this can lead to stability problems, and therefore, to an increase in carbon monoxide emissions due to a more incomplete combustion. For flame stabilization and active control of thermo-acoustic flame oscillation in the combustion chamber an electric field is applied. Non-invasive laser based measurement techniques enable nowadays a better understanding of the ongoing processes of flames in electric fields in detail. In the literature, two possible explanations exist for the electric field effects: The “ionic wind” as the prevailing mechanism and as an alternative mechanism, changes in flame chemistry due to the production of reactive radicals below the actual flame front. In order to answer these open questions, experiments with electric fields have been carried out in a laminar premixed Bunsen flame at different operating conditions. Two imaging measurement techniques have been applied, planar laser-induced fluorescence (PLIF) for measuring species concentrations and particle image velocimetry (PIV) to determine the flow fields. By this, for the first time two-dimensional information was achieved with high temporal and local resolution to study the influence of electric fields on premixed flames. It is shown with the help of species profiles of formaldehyde and OH-radicals and flow velocity profiles that the so called “ionic wind” alone may be responsible for the effect since no clear influence of the electric field on flame chemistry and radical production was indicated. Exemplary results are shown in the figure below.

Visualisation of a laminar premixed flame exposed to an electric field; comparison of OH radical fluorescence (left) and formaldehyde fluorescence (right) for 0.0 kV (no electric field) and 8.0 kV (maximum electric field)

References:

Altendorfner, F.; Kuhl, J.; Zigan, L.; Leipertz, A.: Study of the influence of electric fields on flames using planar LIF and PIV techniques. Proceedings of the Combustion Institute 33, p. 3195–3201, 2011

Kuhl, J., Jovicic, G., Zigan, L., Leipertz, A.: Fundamental investigation of the influence mechanism of an electric field on flames by simultaneous PIV and PLIF measurements. Proceedings of the European Combustion Meeting, Cardiff, Wales, 2011

Altendorfner, F., Beyrau, F., Leipertz, A., Hammer, T., Most, D., Lins, G., Branston, D.W.,Technical Feasibility of Electric Field Control for Turbulent Premixed Flames, Chemical Engineering & Technology 33 (4) (2010) 647–6

Pfadler, S., Dinkelacker, F., Beyrau, F., Leipertz, A., High resolution dual-plane stereo-PIV for validation of subgrid scale models in large-eddy simulations of turbulent premixed flames, Combustion and Flame 156 (2009) 1552-1564 

Mission

SAOT provides an interdisciplinary research and education program of excellence within a broad international network of distinguished experts to promote innovation and leadership in the areas

Optical Metrology
Optical Material Processing
Optics in Medicine
Optics in Communication and Information Technology
Optical Materials and Systems
and Computational Optics.