Experimental investigation of droplet evaporation under extreme conditions by temporally highly resolved laser diagnostic methods
The injection of a fluid in a supercritical environment has great potential to improve energetic processes, such as the reduction of fuel in engine combustion processes or control of combustion instabilities. The specific use of supercritical injection in industrial processes is currently complicated due to the lack of knowlegde of the physical processes. This mainly regards the break-up, the "evaporation" as well as the mixing of a fluid at the transfer from subcritical to supercritical conditions (evaporation requires an interface, which doesn’t exist near supercritical conditions; hence, the term “evaporation” is used in this context to describe the transition of a fluid (, )). Only very few detailed experimental investigations, that are essential for model development and validation, have been conducted so far.
The goal of this subproject in the first period is to run extensive experimental studies of evaporation and mixing processes with isolated droplets that are injected into a supercritical or near-supercritical environment. Based on these data the mathematical multiple regime modeling of physical processes shall be improved throughout the SFB-TRR75. This leads to precise pre-defined boundaries of the experiments. As opposed to spray experiments - which are scheduled for follwing periods - reproducible boundary conditions can be defined clearly for isolated droplets. The droplets are placed in an optically accessible chamber under high pressure and high temperature. Measurement methods will be improved and will be used to make a quantitative and precise determination possible. This includes determination of droplet morphology, size, speed, mixture with the surrounding gas phase and transition from lower to supercritical conditions. In summary the goals are to describe the temporal evolution of a droplet during its transition into a supercritical state experimentally and to provide data for the validation of a mathematical multiple regime model; thus, to create the basis for future innovative fuel injection technology.
The methodical challenges of this project at first is to build a test bench which enables the controlled injection of single droplets or droplet chains into a gas environment, where pressure and temperature levels can be varied up to the supercritical conditions of the injected fluid. Furthermore, there are only a few methods that have potential to investigate the transition of an initially liquid droplet in a supercritical state and the mixing processes with the surrounding gas phase. In this project various optical methods are tested regarding their suitability of these measurement tasks. After that they are applied as a model system to investigate the evolution of acetone drops introduced in an O2/N2 environment. In the course of this the ambient conditions are set up to the supercritical range of acetone (pkrit~48±4bar, Tkrit~508±2K) with a variable O2 concentration. Based on this information sprays up to supercritical conditions will be examined in upcoming periods.
The complexity of this task requires a very extensive expertise in various sections. Therefore there are two subproject managers with different interdisciplinary skills. Only the distribution between the locations Stuttgart and Darmstadt allows such extensive experimental characterizations. In addition, the distributed project management contributes to an even closer networking. This project is also responsible for the coordination of all measurement methods applied in the Transregio.
Lamanna, G., Weckenmann F., Steinhausen, C., Weigand, B., Bork, B., Preusche, A.,Dreizler, A., Stierle R., Groß J.:
Laboratory experiments of high-pressure fluid drops.
AAIA Progress Series, High Pressure Flows for Propulsion Applications, 2017.
Bork, B., Preusche, A., Weckenmann, F., Lamanna, G., Dreizler, A.:
Measurement of species concentration and estimation of temperature in the wake of evaporating n-heptane droplets at transcritical conditions.
Proc. of the Comb. Inst., 36: 2433–2440, 2017.
Ouedraogoa, Y., Gjonaja, E., Weiland, A., Steinhausen, C., Lamanna, G., Weigand, B., Preusche, A., Dreizler, A.:
Electrohydrodynamic simulation of electrically controlled droplet generation.
Int. J. of Heat and Fluid Flow, 64: 120–128, 2017.
Steinhausen, C., Lamanna, G., Weigand, B., Stierle, R., Groß, J., Preusche, A., Dreizler, A.:
Experimental Investigation of Droplet Injections in the Vicinity of the Critical Point: A comparison of different model approaches.
28th Conference on Liquid Atomization and Spray Systems, Valencia, Spain, 2017.
G. Lamanna, H. Kamoun, B. Weigand, Dr. C. Manfletti, Dipl.-Ing. A. Rees, Dr. J. Sender, Prof. M. Oschwald, Dr. J. Steelant,
Flashing behaviour of rocket engines propellants.
Atomization and Sprays, Vol. 25, No. 10, pp. 837–856, 2015
Bork, B.: Tropfenverdampfung in transkritischer Umgebung:
Untersuchung mit laserspektroskopischen Methoden.
Dissertation, Technische Universität Darmstadt, 2015.
F. Weckenmann, G. Lamanna, B. Weigand, Dipl.-Ing. Benjamin Bork, Prof. Dr. rer. nat. Andreas Dreizler
Experimental Investigation of Droplet Injections in the Vicinity of the Critical Point
14th European Meeting on Supercritical Fluids, Marseille, 2014
Bork, Benjamin ; König, T. ; Weckermann, F. ; Lamanna, G. ; Dreizler, Andreas ; Weigand, Bernhard
Thermometry of evaporating acetone droplets in near-critical conditions by combined phosphorescence/fluorescence measurements
10th Intl. Conference series on Laser-Light and Interactions with Particles, Marseille, France, 2014
B. Bork, F. Stritzke, F. Weckenmann, G. Lamanna, B. Weigand, A. Dreizler
Acetone Photophysics Investigations for the Application of PLIFP to Droplet Evaporation Measurements under Supercritical Conditions.
ILASS–Europe, 25th European Conference on Liquid Atomization and Spray Systems, Chania, Greece, 1-4 September, 2013
Oldenhof, E.; Weckenmann, F.; Lamanna, G.; Weigand, B.; Bork, B.; Dreizler, A.
Experimental investigation of isolated acetone droplets at ambient and near-critical conditions, injected in a nitrogen atmosphere.
Progress in Propulsion Physics 4 (2013), 257-270, (eds.: L.T. DeLuca, C. Bonnal, O. Haidn and S.M. Frolov), EDP Sciences, Torus Press
G. Lamanna, Kamoun, H., Arnold, K. Schlottke, B., Weigand, B., Steelant, J.
Differential infrared thermography (DIT) in a flashing jet: a feasibility study
QIRT J. 10(1) 2013, 112-131. DOI: 10.1080/17686733.2013.786903
Brübach, J., Pflitsch, C. Dreizler, A., Atakan, B.
On surface temperature measurements with thermographic phosphors
Prog. Energy Combust. Sci. 39 (2013), 37-60
B. Bork, F. Weckenmann, G. Lamanna, B. Weigand, B. Böhm, A. Dreizler
Droplet studies at conditions near the critical point.
Spray 2012, Berlin, 21.-22. Mai 2012, 2012
Weckenmann, F.; Bork, B.; Oldenhof, E.; Lamanna, G.; Weigand, B.; Böhm, B.; Dreizler, A.
Single Acetone Droplets at Supercritical Pressure: Droplet Generation and Characterization of PLIFP.
Zeitschrift für Physikalische Chemie, 225 (11-12) pp. 1417-1431, 2011
G. Lamanna, H. Sun, M. Schüler, B. Weigand, D. Magatti, F. Ferri
Comparative study of equilibrium and non-equilibrium evaporation models for vaporizing droplet arrays at high pressure.
Advanced Combustion and Aerothermal Technologies: Environmental Protection and Pollution Reduction, Nick Syred (ed.), Springer Verlag, 2006