Staff

The challenge of Global warming is combatted by society on different fronts. One of them is to reduce or even eliminate the emissions of Carbon dioxide (CO₂) from individual transport modes. As a part of that effort, the addition of Ethanol (C₂H₅OH) from renewable sources to gasoline has been pushed forward from political decision makers across the globe. The fuel E10 (10 % Ethanol, 90 % conventional gasoline) is the most common fuel for gasoline engines nowadays. Apart from that, the success story of Ethanol as fuel also originates from countries like Brazil, USA and Sweden, where E85 has gained a big share in the field of individual transport.

From a technical standpoint, the increasing use of alcohols in technical combustion applications raises a number of questions:

1. What are the potential emissions that challenge the health of humans and wild life when alcoholic combustion is implemented in large scales?

2. How can the alcoholic combustion be optimized to have a minimum impact on the Earths’ climate and ecosystems?

3. What can be done to optimize the alcoholic combustion with respect to performance in internal combustion engines?

These questions can partly be answered when the turbulence-chemistry-interaction during the combustion is understood. To achieve this, laser diagnostics provide a large variety of tools. One of them, the combined Raman-Rayleigh spectroscopy, has successfully enabled the quantitative derivation of major species, as well as the temperatures, of a 1D probe volume in open laminar and open turbulent Methane (CH₄) and Hydrogen (H₂) flames.

However, alcohols (C_nH_2n+1OH) are more complex molecules, with more intermediate products being produced during the reaction. To detect them, the Raman-Rayleigh spectroscopy has to be expanded to detect a higher number of species. Hereby the challenge is, that these intermediate products all resonate in a narrow spectral range. Furthermore, the spectrometer needs to be calibrated for these intermediate products as a function of the temperatures, individually. This can be challenging, as well, due to the high temperatures that are given in the flame.

Another challenge is the liquid state of the alcohols in ambient conditions. Since it is desired to investigate the combustion of the fuels premixed with air, the alcohols need to be pre-vaporized, mixed with heated air and subsequently continuously heated until the combustion.

To burn alcoholic fuels as pre-mixed flames, the burners need to be specially designed, as well. Until now, one turbulent open jet burner and one laminar counter flow burner have been designed, built and commissioned.

To characterize these burners and also to gain more knowledge about the Oxygen-hydroxyl (OH*) radical concentration near the flame front, OH-Laser-induced-fluorescence (OH-LIF) techniques are utilized in this project. This incorporates 2D qualitative imaging, as well as 1D quantitative measurements in parallel with combined Raman-Rayleigh experiments.

Typical for this kind of fundamental research, almost all systems, techniques and evaluation processes are not available as off-the-shelve solutions. Therefore, they were and are being developed in-house at TU Darmstadt’s Department of Reactive Flows and Diagnostics in close cooperation with the Thermodynamics and Alternative Propulsion Systems (TAPS) Institute at the University of Applied Sciences, Darmstadt.

We acknowledge the support of the Deutsche Forschungsgemeinschaft (DFG) through GE 2523/2-1 and DR 374/17-1.

Publications:

Turbulent Premixed Flames Fueled by Methane and Alcohols Stabilized on a Novel Temperature Controlled Piloted Jet Burner (TCPJB)

C. Becker¹, J. Trabold¹, A. Johchi², K. Dieter¹, B. Böhm², A. Dreizler², D. Geyer¹

1 Thermodynamics and Alternative Propulsion Systems (TAPS), Univ. of Appl. Sciences, Darmstadt, Germany

2 FG Reactive Flows and Diagnostics (RSM), Center of Smart Interfaces, TU Darmstadt, Germany

Paper and Poster presentation at the European Combustion Meeting 2017

Flame Structure of Turbulent Premixed Methane and Alcohol Flames Inferred from 2D OH-PLIF

J. Trabold¹, S. Walther¹, C. Becker¹, A. Johchi², B. Böhm², A. Dreizler², D. Geyer¹

1 Thermodynamics & Alternative Propulsion Systems, Univ. of Appl. Sciences, Darmstadt, Germany

2 FG Reactive Flows and Diagnostics (RSM), Center of Smart Interfaces, TU Darmstadt, Germany

Poster presentation at the International Bunsen Discussion Meeting 2017