Students at RSM

Die Expertise des Fachgebiets RSM soll zukünftig zur Diagnose industrieller katalytischer Verfahren eingesetzt werden. Konkret sollen Prozesse analysiert werden, welche nachhaltige Materialien einsetzen und effizientere Synthesepfade erlauben. Zur Entwicklung eines besseren phänomenologischen Verständnisses sowie zur Validierung von numerischen Modellen werden daher experimentelle Daten benötigt.

Für die Applikation der laserbasierten Messtechnik in geringem Abstand zur katalytischen Oberfläche wird ein spezieller, optisch zugänglicher Strömungskanal benötigt. Dieser muss zum einen die Anwendung verschiedener Messtechniken direkt im Prozess (operando) ermöglichen, zum anderen aber auch kontrollierte und definierte Randbedingungen bieten. In vorangegangenen Arbeiten wurden jeweils das neuartige Raman-Spektrometer (siehe Abbildung) und der katalytische Strömungskanal getrennt voneinander entwickelt. In dieser Arbeit sollen die Teilsysteme erstmals kombiniert und erste quantitative Messungen durchgeführt werden.

The institute of Reactive Flows and Diagnostics focuses on fundamental combustion research and has established world-class combustion laboratories with novel optical diagnostics methods. Advanced imaging methods combing modern lasers and cameras enable an understanding of complex gas and solid combustion processes. Reducing the carbon footprint in the energy sector has become a key challenge to mitigate climate change. Hydrogen (H2) will be widely used as a renewable clean fuel in the future energy mix. However, the combustion characteristics of H2 still require extensive investigation and understandings, especially under lean and turbulent conditions.This requires fundamental research, especially laboratory experiments. Currently, we are looking for one student assistant (HiWi) for our on-going H2 projects.

Die Expertise des Fachgebiets RSM soll zukünftig zur Diagnose industrieller katalytischer Verfahren eingesetzt werden. Konkret sollen Prozesse analysiert werden, welche nachhaltige Materialien einsetzen und effizientere Synthesepfade erlauben. Zur Entwicklung eines besseren phänomenologischen Verständnisses sowie zur Validierung von numerischen Modellen werden daher experimentelle Daten benötigt.

In aktuellen Abschluss- und Forschungsarbeiten wird ein katalytischer Strömungskanal zu diesem Zweck entwickelt. Die Besonderheit liegt in einer aufwendigen elektrischen Vorheizung des Kanals bestehend aus 24 Heizelementen und 33 Thermoelementen, welche über Interfaces/Hardware der Firma Tinkerforge und ein LabVIEW Programm geregelt werden sollen.

Neben dem Heizsystem besteht eine weitere Aufgabe in der Dosierung der teilweise flüssigen Grundstoffe, die am Katalysator reagieren sollen. Dieses muss nun in Betrieb genommen und validiert werden.

Um fossile Brennstoffe als dominierende Antriebsarten zu verdrängen, ist ein Mix an neuen Antriebsarten von Nöten. Als vielversprechend gilt dabei neben batteriebetriebenen Elektroautos die Energieversorgung mit einer Brennstoffzelle, welche insbesondere im Schwerlastverkehr ihre Vorteile hat. Die Brennstoffzelle besitzt gegenüber Batterien den Vorteil, dass das Nachtanken mit neuem Brennstoff – im mobilen Sektor i. d. R. Wasserstoff – erheblich schneller geht als der Aufladevorgang einer Batterie.

Das Fachgebiet Reaktive Strömungen und Messtechnik (RSM) nutzt Laser-diagnostische Methoden zur messtechnische Erfassung komplexer Vorgänge in der Gas- und Feststoffverbrennung. Um die Zusammensetzung von Gasen zu untersuchen, bietet abstimmbare Diodenlaser-Absorptionsspektroskopie (TDLAS) ein Messverfahren, das zeitlich hochaufgelöst in-situ verschiedenste chemische Spezies detektieren kann. Multipfadzellen bieten die Möglichkeit, durch die Anordnung optischer Elemente die Absorptionsstrecke zu erhöhen und damit die Nachweisgrenzen für die Spezieskonzentrationen zu erweitern. Eine spezielle Multipfadzelle ist die Ringzelle, in der Spiegel ringartig angeordnet werden.

Aufgabe dieser Arbeit ist es zunächst durch Simulation und Literaturrecherche ein Verständnis für Ringzellen zu erarbeiten. Anschließend wird eine Ringzelle für einen realen Prozess ausgelegt und konstruiert. Ziel der Arbeit ist es, die Zelle an einem institutseigenen Abgasprüfstand zum Einsatz zu bringen und in einer Messkampagne die Robustheit im Prozess zu untersuchen.

Chemical energy carriers are essential building blocks for a future carbon-free energy economy, mitigating wind and solar energy fluctuations due to weather and geographical limitations. One suitable candidate is ammonia (NH3) which can be synthesized with renewable energy and are employable for mobile and remote applications. However, pure NH3 is subject to high ignition temperatures, lower laminar burning velocities, narrow flammability limits, and lower extinction strain rates. One very promising technology to overcome these difficulties is to use plasma to enhance ignition and flame. Recent experiments also showed that NOx emission could be largely reduced by introducing plasma into combustion. To better understand the mechanism of plasma impact on reactions, fundamental experiments under well-defined boundary conditions are highly desired.

This project aims to set up a laminar slot burner (LSB) with the assistance of nanosecond plasma discharges. A schematic layout of a conventional LSB is shown in Fig.1 [Boushaki et al.]. The LSB consists of three main parts: a mixer, a homogenizer, and a convergent nozzle. A premixed laminar flame can be stabilized on the burner exist. This existing concept should be adapted for plasma generation with a dielectric barrier discharge (DBD). The DBD should be installed in the position of the parallel nozzle, which mainly consists of two electrodes, a nanosecond high-voltage plasma pulse generator, and corresponding control units. The designed plasma-assisted LSB should have optical access into the nozzle to characterize the plasma homogeneity. This work aims to design, construct and test this burner in the combustion laboratory of RSM.

Accurate measurement of burning particle temperature is important to understand solid fuel combustion. Currently, the commonly adopted technique for this task is imaging two-color pyrometry, which acquires radiation intensities at two wavelengths and thus the temperature can be derived using Wien’s approximation. However, two-color pyrometry is based on the grey-body assumption, which is not always valid or cannot be easily verified in experiments. Therefore, the accuracy of two-color pyrometry sometimes is uncertain. Hyper-spectrum thermometry is one promising technique that can significantly improve the measurement certainty and accuracy of solid particle temperature. It records the spectra of hot particles over a wide range of wavelength. By compare the recoded spectrum with Planck’s law, often a part the spectrum obeying grey-body emission can be selected and thus particle temperature can be determined more accurately.

Reducing the carbon footprint in the energy sector has become a key challenge of this century that requires global collaborative efforts. Chemical storage of renewable energy, such as wind and solar, followed by thermochemical conversion for energy utilization, is an important pathway to ensure a smooth transition to a carbon-neutral economy. In the future energy mix, hydrogen (H2) will be widely used as a clean fuel, and its combustion characteristics require extensive investigations, especially under lean and turbulent conditions, which is important for gas turbine applications.

In this work, the turbulent flame and flow field structures of NH3/H2 mixtures will be experimentally measured under turbulent conditions. The existing multi-regime burner (MRB), a special design for investigating the transition of premixed and non-premixed combustion, will be used to stabilize turbulent NH3/H2 flames. In the first step, constructive improvements should be performed on the MRB burner and operation conditions will be determined based on fuel mixture and laminar flame properties from simple 1D flame calculations in Cantera. To study the turbulence-flame interactions, the flame reaction zone will be measured by planar laser-induced fluorescence of OH radicals (OH-PLIF). From the OH-PLIF images, the curvature and flame surface density of the reactive flame front can be statistically determined. Simultaneously, the flow field will be determined by particle image velocimetry (PIV) or particle tracking velocimetry (PTV) measurements. By combining PIV with OH-PLIF, the local strain rates and their impact on the flame front topology could be analyzed.

In order to use novel, regenerative fuels (eFuels, e.g. hydrogen) in engines, their effects on the physical processes must be understood. Port fuel injection (PFI) can be used to produce a lean homogeneous mixture, and then the effects of adding a direct injection can be subsequently investigated.

This work is concerned with characterizing the injectors currently in use in terms of injected mass. Different atmospheric pressures and temperatures have to be considered. After designing the experimental setup, the measurements are to be carried out and evaluated.

Climate change and rising health concerns have led to increasingly strict regulatory emission standards for combustion engines over the past few years.

In order to investigate the compliance with these regulations, special measurement techniques are required. Specifically, in the context of Real Driving Emissions (RDE), compact systems that allow for in situ measurement at engine tailpipe are necessary.

Tunable diode laser absorption spectroscopy (TDLAS) is a measurement technique well suited for this task, as it allows simultaneous high speed in-situ measurement of a variety of gases. A large benefit of this technique is the application of small diode lasers which can be connected via glass-fibers and thus allowing for very small measurement devices outside the vehicles.

The extension of the regulatory requirements made the implementation of new free-space diode lasers necessary, which are not yet fiber-coupled and thus cannot be connected to existing hardware.

The goal of this work is the development and application of a fiber-coupling system for these free space mid-infrared diode lasers.

The project Clean Circles is dedicated to solving global energy problems by using iron as CO2-free, renewable and efficient chemical energy carrier. First, electricity from renewables is used to reduce iron oxide (energy storage). Then, the iron is oxidized to release thermal energy for electricity generation at a different place and time (energy release). In the collaborative research project, scientists and students from different Universities work closely on numerous experiments and simulations.

In this student work, a new metal particle ignition reactor (MPIR) with well-defined boundary conditions should be designed and tested for single iron particle experiments. MPIR will include three modules: electrostatic-based single particle generator, an optically accessible ignition channel, and an external heating system by an annular gas flame. The concept of MPIR originates from the so-called micro-flow reactor (see Fig. 1), which has been successfully applied for gaseous and liquid fuel ignition studies. The advantage of this setup is to study the ignition/reaction kinetic by converting the trainsient process to a space-dependent process. Within this work, this concept should be realized for metal fuel ignition measurements.

The topic is suitable for ADP, Bachelor and Master theses, and the work tasks are adapted accordingly.

Reducing the carbon footprint in the energy sector has become a key challenge of this century that requires global collaborative efforts. Chemical storage of renewable energy, such as wind and solar, followed by thermochemical conversion for energy utilization, is an important pathway to ensure a smooth transition to a carbon-neutral economy. In the future energy mix, hydrogen (H2) will be widely used as a renewable clean fuel. However, its combustion characteristics still require extensive investigations, especially under lean and turbulent conditions, which is crucial for gas turbine applications.

In this work, the turbulent H2 flame and flow field structures should be experimentally investigated by using laser diagnostics measurements. For this purpose, a high-velocity flame supplied by H2 or CH4/H2 mixtures from the central jet will be sustained by a pilot flat flame in a McKenna burner. The jet bulk velocity will be increased from 10 m/s (laminar) to approximately 200 m/s (highly turbulent) while the pilot remains at a constant exit velocity. Reactive mixtures with increasing H2 mole fractions will be used to investigate the preferential diffusion effect of H2 on the turbulent flame behavior. The flame reaction zone will be measured by single-shot planar laser-induced fluorescence of OH radicals (OH-PLIF). Simultaneously, the flow field will be determined by particle image velocimetry (PIV) or particle tracking velocimetry (PTV) measurements. From the OH-PLIF images, the curvature and flame surface density of the reactive flame front should be statistically determined. By combining PIV data, the local strain rate and its orientation to the flame front direction should be analyzed, providing insights into turbulence-chemistry interactions.

Climate change and rising health concerns have led to increasingly strict regulatory emission standards for combustion engines over the past few years.

In order to investigate the compliance with these regulations, special measurement techniques are required. Specifically, in the context of Real Driving Emissions (RDE), compact systems that allow for in situ measurement at engine tailpipe are necessary.

Tunable diode laser absorption spectroscopy (TDLAS) is a measurement technique well suited for this task, as it allows simultaneous high speed in-situ measurement of a variety of gases. A large benefit of this technique is the application of small diode lasers which can be connected via glass-fibers and thus allowing for very small measurement devices outside the vehicles.

The Laser Diode and Temperature control (LDC & TEC) of these lasers needs to be very precise but at the same time also compact.

The goal of this work is the software development and application of a high-speed modular FPGA (Field Programmable Gate Array) based Laser Diode and Temperature control system in LabVIEW.

Das Fachgebiet Reaktive Strömungen und Messtechnik (RSM) befasst sich mit moderner Verbrennungsforschung. Laser-diagnostische Methoden ermöglichen auf diesem Gebiet die messtechnische Erfassung komplexer Vorgänge in der Gas- und Feststoffverbrennung.

Im transdisziplinären Forschungsverbund Clean Circles wird ein innovativer Energie-Stoffkreislauf untersucht. Hierbei wird elektrische Energie aus erneuerbaren Quellen in Eisen eingespeichert, welche über thermochemische Oxidation ausgespeichert und in thermischen Kraftwerken rückverstromt werden kann. Hierfür ist es notwendig ein tiefgehendes Verständnis der Oxidationsprozesse der Eisenpartikel zu haben.

Zur Untersuchung der Oxidationseigenschaften von Eisenpartikelgruppen unter verschiedenen Umgebungsbedingungen soll ein Brenner konstruiert bei der eine Eisenstaub/Luft Bunsenflamme stabilisiert werden kann. Zur Erzeugung der zu untersuchenden Suspension ist ebenso der Aufbau eines sogenannten Seeders erforderlich, der die Partikel in die Gasströmung einbringt. Zur Bestimmung der Partikelkonzentration soll ebenso eine Laserextinktionsmessung implementiert werden. Der Prüfstand soll dabei über ein LabView Programm angesteuert werden können, sowie relevante Parameter aufgezeichnet werden.

A new Topic at the Institute for Reactive Flows and Diagnostics (RSM) is the application of laser diagnostics for the investigation of the effect of flame retardants in flames close to a wall and boundary layer flames.

Flame retardants in polymers are released during combustion and take effect through diverse mechanisms at the surface of the polymer or in the burning gas-phase. In this way flame retardants can reduce the flammability of materials and inhibit the spread of fires and save lives.

This project aims to recreate the scenario of a flame retardant being released from a polymer-surface during a fire. To understand the effect of flame retardants on a flame along a surface a new setup is to be developed, in which a gas can be injected homogeneously from an inlet in a wall. Through this a boundary layer flame can be created and the effect of flame retardants injected into this flame can be investigated.

The goal is to achieve a system that can be investigated experimentally and provide validation for numerical analysis. The design shall therefore be characterized by measuring the velocities of the gas flows using laser diagnostics. For this a PIV (Particle Image Velocimetry) approach is to be set up.

The topic is suitable for a Bachelor- or Master-Thesis and the tasks will be adapted accordingly.

The institute for Reactive Flows and Diagnostics (RSM) works on the topic of modern combustion research. Laser diagnostics enable the investigation of the complex combustion-processes for gas-, liquid- and solid-fuel-combustion. A new Topic at the Institute is the application of laser diagnostics for the investigation of the effect of flame retardants used in polymers.

Flame retardants in polymers are released during combustion together with the other products of the pyrolysis and take effect through diverse mechanisms at the surface of the polymer or in the burning gas-phase. In this way flame retardants can reduce the flammability of materials and inhibit the spread of fires and save lives.

For easier investigation, the release of the pyrolysis products is to be separated from the influenced flame to be investigated. For this purpose, a reactor is to be developed in which polymers can be pyrolyzed in order to collect the released gases and introduce them into a sample volume in a controlled manner.

The topic is suitable for an ADP, Bachelor- or Master-Thesis and the tasks will be adapted accordingly.

Das Fachgebiet Reaktive Strömungen und Messtechnik (RSM) befasst sich mit optischen Untersuchungen reaktiver Strömungen. Einer dieser Messtechniken ist die Laser Induced Breakdown Spectroscopy (LIBS) mittels derer im Rahmen des Clean-Circles-Projekts ein CO2-freier Kreislaufprozess zur Energiespeicherung untersucht werden soll. Speicher mit langen Ausspeicherzeiten und hohen Energiedichten gewinnen bei fortscheidendem Ausbau von erneuerbaren Energien immer mehr Bedeutung. In dem Kreislaufprozess des Clean-Circles-Projekts erfolgt die Einspeicherung der regenerativ erzeugten Energie mittels Reduktion von Eisenoxidpartikeln. Die entstehenden Eisenpartikel können zeitlich und räumlich getrennt durch eine Oxidation (bzw. Verbrennung des Eisens) die Energie wieder ausspeichern.

Zur Entwicklung eines besseren Verständnisses, sowie zur Validierung und Verbesserung von Modellierungen der im Detail ablaufenden Prozesse während der Reduktion und Oxidation, werden experimentelle Daten benötigt. Hierfür soll die elementare Zusammensetzung von Eisen- und Eisenoxidpartikeln mittels der Laser Induced Breakdown Spectroscopy erforscht werden.

Nachdem in vorangegangenen Masterarbeiten der Messaufbau in Betrieb genommen wurde, soll mithilfe dieser Arbeit die Detektionseinheit noch erweitert werden um den gesamten relevanten spektralen Wellenlängenbereich detektieren zu können. Im Anschluss sollen weitere Parameter untersucht werden, die einen Einfluss auf das Messsignal aufweisen (bspw. Laserpulslänge, zeitaufgelöste Analyse des Plasmas, …). Nach der Durchführung verschiedener Messreihen sollen zwei Auswertemethoden zur Bestimmung des Fe-O-Verhältnisses der einzelnen Partikel getestet und gegeneinander verglichen werden.

The project Clean Circles is dedicated to solving global energy problems by using iron as CO2-free, renewable and efficient chemical energy carrier. First, electricity from renewables is used to reduce iron oxide (energy storage). Then, the iron is oxidized to release thermal energy for electricity generation at a different place and time (energy release). In the collaborative research project, scientists and students from different Universities work closely on numerous experiments and simulations.

In this thesis, the ignition and burn time of single iron particles should be experimentally investigated. Using an existing laminar flow reactor, iron particles will be seeded in high-temperature and oxygen-rich environments, which are generated by lean methane flames. The ignition delay time and entire burn time will be measured with high-speed scientific cameras. At the same time, the particle size will be in-situ detected by measuring the shadow of particles. Different particle sizes will be investigated with increasing oxygen concentration in the gas atmospheres. By evaluating the data, the influences of particle size and oxygen concentration on the particle ignition and burn time should be focused on. This would provide a better understanding of oxidation stages at the single-particle level.

Partikelbeladene Strömungen sind in einer Vielzahl von Anwendungen in Natur und Technik allgegenwärtig. Dies umfasst beispielsweise die thermochemische Oxidation von Eisenstaub in einem Brenner oder den Transport von Sedimenten in Flüssen oder Wolken. Zur experimentellen Untersuchung der physikochemischen Phänomene in solch komplexen Strömungen liefern optische Methoden wie die Diffuse Back-Illumination (DBI) Daten, deren Messfehler unter anderem aufgrund von hohen Partikeldichten sehr groß werden können.

Eine Quantifizierung der Messfehler und deren Einflussparameter erfordert die gleichzeitige Kenntnis der wahren und gemessenen Größen. Da dies in der Realität jedoch nur unter eingeschränkten Bedingungen möglich ist, soll eine solche Messung in Software simuliert und die Messfehler des optischen Systems idealisiert quantifiziert werden. Ein solches Imaging-Tool wurde am RSM bereits erfolgreich programmiert und eingesetzt und soll innerhalb dieser Arbeit weiter verbessert werden. Hierbei soll das Tool insbesondere genutzt werden um die wichtigsten Einflussgrößen auf die Messfehler unterschiedlicher Parameter wie Partikelanzahldichte, -größe, -volumen etc. zu identifizieren und Handlungsanweisungen für Experimentatoren abzuleiten. Hierzu sind sowohl Kenntnisse der analytischen Geometrie im Kontext von Computer Vision, der Programmierung solcher Zusammenhänge in MATLAB und der Datenauswertung hilfreich.

The institute of Reactive Flows and Diagnostics focuses on fundamental combustion research and has established world-class combustion laboratories with novel optical diagnostics methods. Advanced imaging methods combing modern lasers and cameras enable understanding complex processes in gas and solid combustion.

Reducing the carbon footprint in the energy sector has become a key challenge of this century that requires global collaborative efforts. Germany has committed to achieving carbon neutrality by 2045. Chemical storage of renewable energy such as wind and solar, followed by thermochemical conversion for energy utilization, is an important pathway to ensure a smooth transition to a carbon-neutral economy. The carbon-free nature of hydrogen (H2) and ammonia (NH3) has attracted considerable attention as potential substitutes for carbonaceous fuels. Both hydrogen and ammonia have very distinct combustion characteristics compared to hydrocarbons. Strategically cofiring NH3 and H2 appears to be well suited to remedy the difficulties in utilizing either fuel. However, NH3 and NOx emission and combustion instabilities are of critical importance in NH3/H2 combustion. To enable industrial facilities to be operated with NH3/H2 blends, fundamental understandings of the combustion characteristics under various conditions are urgently needed.

For studying both emission and flame stabilization, quantitative multi-scalar data are of essential importance and provide novel insights into combustion chemistry. Simultaneous measurements of temperature and concentration of major species are only possible with combined Raman/Rayleigh scattering. However, due to incomplete spectral data libraries for high temperatures, this method requires careful calibrations in a flame with know temperature and concentrations, usually in a flat flame burner. Previous burner design used for hydrocarbon fuels are not suited for operating with NH3/H2 fuels. A new flat flame burner needs to be constructed and tested for a large variety of operation conditions (e.g., mixtures and equivalence ratio). The burner should be experimentally characterized using advanced laser diagnostics.

The topic is suitable for both Bachelor and Master theses, and the work tasks are adapted accordingly.

Das Fachgebiet Reaktive Strömungen und Messtechnik (RSM) befasst sich mit optischen Untersuchungen reaktiver Strömungen. Einer dieser Messtechniken ist die Laser Induced Breakdown Spectroscopy (LIBS) mittels derer im Rahmen des Clean-Circles-Projekts ein CO2-freier Kreislaufprozess zur Energiespeicherung untersucht werden soll. Speicher mit langen Ausspeicherzeiten und hohen Energiedichten gewinnen bei fortscheidendem Ausbau von erneuerbaren Energien immer mehr Bedeutung. In dem Kreislaufprozess des Clean-Circles-Projekts erfolgt die Einspeicherung der regenerativ erzeugten Energie mittels Reduktion von Eisenoxidpartikeln. Die entstehenden Eisenpartikel können zeitlich und räumlich getrennt durch eine Oxidation (bzw. Verbrennung des Eisens) die Energie wieder ausspeichern.

Zur Entwicklung eines besseren Verständnisses, sowie zur Validierung und Verbesserung von Modellierungen der im Detail ablaufenden Prozesse während der Reduktion und Oxidation, werden experimentelle Daten benötigt. Hierfür soll die elementare Zusammensetzung von Eisen- und Eisenoxidpartikeln mittels der Laser Induced Breakdown Spectroscopy erforscht werden.

Nachdem in einer vorrangegangenen Masterarbeit ein erster vereinfachter Messaufbau in Betreib genommen wurde soll dieser mithilfe der erarbeiteten Verbesserungen optimiert werden. Hierbei ist vor allem die Inbetriebnahme einer verbesserten Detektionseinheit zur Analyse der Plasmastrahlung entscheidend für eine genaue Bestimmung des Fe-O-Verhältnisses der einzelnen Partikel. Die Aufgabe umfasst anschießend die Durchführung von Experimenten unter Variation verschiedener Einflussparameter auf das LIBS-Signal. Mit den erzielten Daten ist anschließend ein Auswertungsschema zu Erstellen mit dem vom LIBS-Signal der Oxidzustand einzelner Partikel bestimmt werden kann.

Laser-based optical diagnostics can be used to investigate complex physical systems non-intrusively and with high resolution. Laser-induced fluorescence (LIF) is suitable for obtaining spatially and temporally resolved information about, e.g., temperature or mixing in a flow. Molecules are excited with a laser and the characteristic fluorescence emission is detected with (high speed) cameras.

In this work, the aim is to investigate mixing processes in an optically accessible engine by means of two-color or two-line LIF. The aim of this fundamental experiment is to visualize and characterize the gas exchange between cycles and the interaction between the gas flow and an injected spray.

Within the scope of the work, the exact methodology will be selected for this purpose, the experiment will be set up and carried out, and the collected data will be evaluated and analyzed.

Das Fachgebiet Reaktive Strömungen und Messtechnik (RSM) befasst sich mit moderner Verbrennungsforschung. Laser-diagnostische Methoden ermöglichen auf diesem Gebiet die messtechnische Erfassung komplexer Vorgänge in der Gas- und Feststoffverbrennung.

Im transdisziplinären Forschungsverbund Clean Circles wird ein innovativer Energie-Stoffkreislauf untersucht. Hierbei wird elektrische Energie aus erneuerbaren Quellen in Eisen eingespeichert, welche über thermochemische Oxidation ausgespeichert und in thermischen Kraftwerken rückverstromt werden kann. Hierfür ist es notwendig ein tiefgehendes Verständnis der Oxidationsprozesse der Eisenpartikel zu haben.

Um diese Oxidationsprozesse von Eisen in einer laminaren Eisenpartikel-Luft-Flamme untersuchen zu können wurde ein Seeder- und Brennerkonzept entwickelt. In der ausgeschriebenen Masterarbeit ist anhand von diversen Messtechniken dieser Aufbau mit unterschiedlichen Eisenproben zu charakterisieren und zu optimieren. Abschließend sollen Messungen zu den Oxidationseigenschaften der Eisenproben anhand des optimierten Versuchsaufbaus stattfinden und ausgewertet werden.

For the analysis of injectors in different combustion chambers, the interaction of the injected fuel quantity with the wall of the combustion chamber is of great importance. Here, fuel accumulates locally and then evaporates only slowly at the surface. In the case of the Spray G injector used, the individual wetting of the different injection plumes is also of interest.

In this work, a novel indium tin oxide (ITO) coating will be investigated for suitability for spray wetting measurements. This material is an electrical semiconductor and at the same time largely transparent in visible light, which means that the wall wetting can be measured using an infrared camera and at the same time the spray can be characterized with visible light (Mie scattering).

The institute of Reactive Flows and Diagnostics focuses on fundamental combustion research and has established world-class combustion laboratories with novel optical diagnostics methods. Advanced imaging methods combing modern lasers and cameras enable the understanding of complex processes in gas and solid combustion.

Soot emission is one of the most important issues in the utilization of hydrocarbon fuels. A deep understanding of the soot and nano-sized particle formation in gas and solid fuel flames is an essential aspect of combustion research. In laboratory-scale experiments, in-situ laser diagnostics have been widely established to gain fundamental knowledge. Laser-induced incandescence (LII) has proven to be a powerful tool for particle-concentration and particle-size measurements in combustion systems. This technique has been implemented in previous work and applied for 2D soot imaging measurements in a laminar diffusion flame fueled by ethylene, e.g., in a Gülder-burner configuration. To quantify the soot volume fraction, 1D extinction measurements have been performed simultaneously to calibrate the qualitative LII signals. These combined methods should be further applied for solid fuel combustion studies on the single-particle level. In further steps, in a well-established laminar flow reactor, semi-quantitative 2D LII imaging has been first conducted on bituminous coal and biomass particles. Here, the reaction zone and PAH formation could be visualized at the same time, e.g., by using laser-induced fluorescence (LIF) techniques, to support the interpretation of the soot formation.

The comprehensive experimental data requires intelligent data processing algorithms. Within this work, simultaneously acquired image data should be evaluated in Matlab (image processing tools) using efficient programming structures (object orientated programming). The code structures should be friendly to further extension and maintenance. The main purpose of data evaluation is to extract essential parameters related to soot formation in solid fuel combustion. They are, e.g., 1D absorption ratio, 2D soot volume fraction, soot flame topology, particle positions, particle number density, particle size and shape and etc. Conditional statistical analysis that includes all parameters should be performed in a systematic way to enable a deep understanding of soot formation processes in single particle and particle group combustion.

The topic is suitable for ARP and Master's theses, and the work tasks are adapted accordingly.

The early flame kernel development in modern spark-ignition engines is crucial in determining the efficiency and emissions involved in their operation. An extensive database of early flame images has been acquired by using high-speed planar Mie scattering (from particle image velocimetry) to record the evaporation of seeded oil droplets in an optically accessible single cylinder research engine. To analyze the flame development, the raw images must first be binarized (such that the flame is separated from the particle images).

Despite the availability of advanced digital image processing algorithms, it remains a challenge to accurately binarize experimentally-obtained flame data due to a number of factors such as inhomogeneous lighting, reflections, and noise. The figure to the right shows an example raw image and overlain contours of a flame propagating adjacent to the spark plug. Even though the flame is easily recognizable to the human eye, it is difficult to algorithmically separate the flame from the surrounding features. Therefore, the goal is to use machine learning (ML) techniques such as DeepOtsu or convolutional neural networks, to achieve a more efficient and accurate universal model for flame binarization.

For the analysis of injectors in different combustion chambers, the injection and distribution of the fuel is of great interest. Hereby the injection penetration length as well as the vaporization rate can be determined and analyzed. The usual illumination of the injection mass by means of conventional LED illumination and Mie scattering leads to multiple scattering of the fuel particles.

In this work, the Structured Light Illumination Planar Imaging (SLIPI) measurement technique will be used for spray analysis. Using the SLIPI technique, scattered light components can be effectively removed from Mie and LIF spray images, revealing spray structures of unprecedented quality.

The topic is suitable for ADPs or Master's/Bachelor's thesis and the work assignments will be adapted accordingly.