TY - CHAP A1 - Jones, Kevin A1 - Castro, Breno A1 - Mahmoud, Osama A1 - Pollard, S. A1 - Platzer, Max A1 - Neef, Matthias A1 - Gonet, K. A1 - Hummel, D. T1 - A collaborative numerical and experimental investigation of flapping-wing propulsion T2 - 40th AIAA Aerospace Sciences Meeting & Exhibit N2 - An international, collaborative investigation is undertaken to evaluate the relative merits and limitations of various numerical methods and experimental measurement techniques, specifically for the analysis of flapping-wing propulsion. A finite aspect-ratio configuration is extensively investigated, both quantitatively and qualitatively, in a low-speed wind tunnel. Direct force measurements are made, as well as time-accurate and time-averaged laser Doppler velocimetry and unsteady flow visualization. The reduced frequency, mean angle of attack, aspect ratio and Reynolds number are varied in the experiments. The experiment is numerically simulated using flatplate theory, two and three-dimensional panel codes, and two and three-dimensional Euler and Navier- Stokes solvers. The ability of each of the methods to capture important aspects of the flow physics are evaluated through comparisons with each other and the experimental data. Additionally, the comparisons indicate areas where further research is needed. The collaborative effort provides a survey of available capabilities and provides a fixed set of flappingwing data for others to compare against. Y1 - 2002 UR - http://arc.aiaa.org/doi/book/10.2514/MASM02 U6 - https://doi.org/10.2514/6.2002-706 PB - American Institute of Aeronautics and Astronautics CY - Reston, Virigina ER - TY - JOUR A1 - Dubberke, Frithjof H. A1 - Linnemann, Matthias A1 - Abbas, Wameedh Khider A1 - Baumhögger, Elmar A1 - Priebe, Klaus-Peter A1 - Roedder, Maximilian A1 - Neef, Matthias A1 - Vrabec, Jadran T1 - Experimental setup of a cascaded two-stage organic Rankine cycle JF - Applied Thermal Engineering N2 - In combination with a bottoming cycle, operated with a pure fluid in transcritical mode, the usage of a zeotropic mixture as a working fluid appears to be exergetically favorable for power cycle efficiency in cascaded two-stage organic Rankine cycles (CORC). A CORC is set up and initially tested with cyclopentane and propane as working fluids in its high temperature and low temperature cycle, respectively. A thermal oil cycle serves as the heat source and is powered electrically with a maximum heat flow of 158 kW. The design of this experimental setup allows for a rapid replacement of individual components and for a wide range of conditions in terms of fluids and thermodynamic states. The components of all cycles and the measurement and control technology are described in detail. A testing procedure is presented, followed by a discussion of the measurement results, where it is shown that the intended concept of two cascaded organic Rankine cycles is operational and that the measured data are consistent. KW - organic Rankine cycle KW - cascade KW - multicomponent working fluid KW - temperature-glide KW - pinch point KW - exergetice efficiency Y1 - 2018 U6 - https://doi.org/10.1016/j.applthermaleng.2017.11.137 VL - 131 SP - 958 EP - 964 PB - Elsevier ER - TY - JOUR A1 - Feseker, Daniel A1 - Kinell, Mats A1 - Neef, Matthias T1 - Experimental Study on Pressure Losses in Circular Orifices With Inlet Cross Flow JF - Journal of Turbomachinery N2 - The ability to understand and predict the pressure losses of orifices is important in order to improve the air flow within the secondary air system. This experimental study investigates the behavior of the discharge coefficient for circular orifices with inlet cross flow which is a common flow case in gas turbines. Examples of this are at the inlet of a film cooling hole or the feeding of air to a blade through an orifice in a rotor disk. Measurements were conducted for a total number of 38 orifices, covering a wide range of length-to-diameter ratios, including short and long orifices with varying inlet geometries. Up to five different chamfer-to-diameter and radius-to-diameter ratios were tested per orifice length. Furthermore, the static pressure ratio across the orifice was varied between 1.05 and 1.6 for all examined orifices. The results of this comprehensive investigation demonstrate the beneficial influence of rounded inlet geometries and the ability to decrease pressure losses, which is especially true for higher cross flow ratios where the reduction of the pressure loss in comparison to sharp-edged holes can be as high as 54%. With some exceptions, the chamfered orifices show a similar behavior as the rounded ones but with generally lower discharge coefficients. Nevertheless, a chamfered inlet yields lower pressure losses than a sharp-edged inlet. The obtained experimental data were used to develop two correlations for the discharge coefficient as a function of geometrical as well as flow properties. KW - Compressor KW - Gas turbine engines KW - Turbine components KW - Boundary layer development KW - Fluid dynamics KW - Heat transfer KW - Measurement techniques KW - Film cooling KW - Heat transfer phenomena Y1 - 2018 U6 - https://doi.org/10.1115/1.4039842 VL - 140 IS - 7 CY - ASME ER - TY - GEN A1 - Frank, Lena A1 - Rödder, Maximilian A1 - Neef, Matthias A1 - Adam, Mario T1 - Heizung, Lüftung, Weiße Ware - Ein integriertes Systemkonzept für das Haus der Zukunft T2 - KI Kälte Luft Klimatechnik N2 - In energieeffizienten Gebäuden spielt der Bedarf an Energie für die Raumheizung gegenüber der benötigten Energie für Warmwasser und zum Antrieb elektrischer Geräte eine zusehends untergeordnete Rolle. Die thermische Energie für elektrische Haushalts­geräte, wie Waschmaschine, Kühlschrank etc., wird für gewöhnlich dezentral im Gerät erzeugt. Vor diesem Hintergrund ist das Ziel eines Forschungsprojekts der Bau und der Test eines Funktionsmusters zur funktionalen und energetischen Kopplung der Haushaltsgeräte und der Heizungs- und Lüftungstechnik des Gebäudes. Grundgedanke dabei ist die Nutzung von Synergien bei Komponenten und Wärmeströmen, wie der Wärmepumpe als Kälteaggregat für den Kühlschrank, und die effiziente Nutzung von Abwärme der Haushaltsgeräte für die Warmwasserbereitung und Raumheizung. KW - Energieeffizienz KW - energiBUS4home Y1 - 2018 SN - 1865-5432 VL - 54 IS - 11 SP - 50 EP - 56 PB - Hüthig ER - TY - JOUR A1 - Bonk, Christian Dirk A1 - Laux, Christoph A1 - Rödder, Maximilian A1 - Neef, Matthias T1 - Design of a 1 KW Organic Rankine Cycle for Teaching and Research Issues JF - Energy Procedia N2 - This paper deals with the design of a micro-scale ORC plant for teaching and research including the development of an automated control concept. The aim is to provide a safe and environmentally acceptable micro-scale heat engine, which can be developed, implemented and used in university labs for the education of students as well as for small research projects. The test rig allows the support of several learning outcomes on a multi-disciplinary level particularly for the implementation and simulation of small power systems. Special attention was given to the organic working fluid characteristics and its selection process. In addition to the above-mentioned performance goals, favourable safety properties and low global warming potential were decisive in the selection of the novel organic fluid called 3M™ Novec™ 649. The performance and the fluid behaviour of Novec 649 in a micro-scale power cycle are of major interest and the research goal for the test rig presented in this paper. Due to the expected power output of 1 kW, a scroll expander was chosen as the generator drive for the micro plant. In order to design the major parts of the ORC, the thermodynamic simulation software EBSILON®Professional was used. The supply temperature was set to 140 °C. As a result of the simulation, feasible expander inlet pressures spread from 5.5 bar to 8.5 bar. This leads to thermal efficiencies of the ORC in the order of 5 %. Adding a recuperator to the cycle system decreases the operating pressure range but in the end, the thermal efficiency can be increased by 1.5 %-points up to 6.2 %. Finally, an automated control concept is introduced, where the pump is controlled via the fill level measurement system. KW - EBSILON®Professional KW - Micro-Scale ORC Plant KW - Teaching KW - Research KW - Automated Control Concept Y1 - 2017 U6 - https://doi.org/10.1016/j.egypro.2017.09.117 VL - 129 SP - 931 EP - 938 PB - Elsevier ER - TY - JOUR A1 - Neef, Matthias A1 - Zielke, Thomas A1 - Fussenecker, Claudia T1 - „Engineering Conferences“: Wissenschaftlich Kommunizieren im Master JF - Die Neue Hochschule Y1 - 2017 VL - 58 IS - 3 ER - TY - JOUR A1 - Roedder, Maximilian A1 - Neef, Matthias A1 - Laux, Christoph A1 - Priebe, Klaus-P. T1 - Systematic Fluid Selection for Organic Rankine Cycles and Performance Analysis for a Combined High and Low Temperature Cycle JF - Journal of Engineering for Gas Turbines and Power N2 - The organic Rankine cycle (ORC) is an established thermodynamic process that converts waste heat to electric energy. Due to the wide range of organic working fluids available the fluid selection adds an additional degree-of-freedom to the early design phase of an ORC process. Despite thermodynamic aspects such as the temperature level of the heat source, other technical, economic, and safety aspects have to be considered. For the fluid selection process in this paper, 22 criteria were identified in six main categories while distinguishing between elimination (EC) and tolerance criteria (TC). For an ORC design, the suggested method follows a practical engineering approach and can be used as a structured way to limit the number of interesting working fluids before starting a detailed performance analysis of the most promising candidates. For the first time, the selection process is applied to a two-stage reference cycle, which uses the waste heat of a large reciprocating engine for cogeneration power plants. It consists of a high temperature (HT) and a low temperature (LT) cycle in which the condensation heat of the HT cycle provides the heat input of the LT cycle. After the fluid selection process, the detailed thermodynamic cycle design is carried out with a thermodynamic design tool that also includes a database for organic working fluids. The investigated ORC cycle shows a net thermal efficiency of about 17.4% in the HT cycle with toluene as the working fluid and 6.2% in LT cycle with isobutane as the working fluid. The electric efficiency of the cogeneration plant increases from 40.4% to 46.97% with the both stages of the two-stage ORC in operation. KW - Gas Turbines KW - Cycle Innovations KW - Energy KW - Power systems KW - Fluids Y1 - 2016 U6 - https://doi.org/10.1115/1.4031361 VL - 138 IS - 031701 EP - 3 PB - ASME ER - TY - JOUR A1 - Wolter, Nina A1 - Zekorn, Thomas A1 - Neef, Matthias T1 - Stationäre thermodynamische Prozesssimulationen am Beispiel eines Industriekraftwerks JF - BWK: das Energie-Fachmagazin N2 - Um bauliche Veränderungen in bestehenden Kraftwerksprozessen auf ihre Wirkungsweise untersuchen und thermodynamisch beziehungsweise wirtschaftlich bewerten zu können, werden thermische Kraftwerksprozesse mit geeigneter Simulationssoftware abgebildet und in verschiedenen Detaillierungsstufen ausgelegt oder nachgerechnet. Im Folgenden wird ein Weg aufgezeigt, wie mit Hilfe einer stationären Simulationssoftware die Gesamtjahresbilanz eines Kraftwerks vorausberechnet werden kann. Mit Hilfe von Prozessdaten aus Vorjahren wird nachgewiesen, dass das Berechnungsmodell das bestehende Kraftwerk mit einer Abweichung von weniger als drei Prozent bezüglich erzeugter elektrischer Leistung und Brennstoffeinsatz und bei bekannter Dampfproduktion abbilden kann. Das so verifizierte Modell kann zur Untersuchung von Zubaumaßnahmen oder Veränderungen im Kraftwerksprozess eingesetzt werden. KW - Energiebilanz KW - Kraftwerk Y1 - 2016 VL - 68 IS - 6 SP - 6 EP - 10 ER - TY - CHAP A1 - Laux, Christoph A1 - Gotter, Andreas A1 - Neef, Matthias T1 - Experimental investigation of a low pressure steam Rankine cycle for waste heat utilization of internal combustion engines T2 - Proceedings of the 5th International Seminar on ORC Power Systems N2 - High heat losses via exhaust gas and coolant in internal combustion engines (ICE) are the basis for numerous investigations regarding downstream processes for power generation. The most promising concepts are Organic Rankine Cycles (ORC) and Steam Rankine Cycles (SRC). In previous work of the Center of Innovative Energy Systems, Düsseldorf (Germany), the technical and economic feasibility of a low pressure SRC has been investigated and the advantages in comparison to organic Rankine cycles are highlighted. A distinctive feature of the cycle is the use of the ICE coolant heat for evaporation, which limits the cycles maximum steam pressure to values below atmospheric pressure. This work presents first results of a test rig with data reconciliation according to DIN 2048 to validate the simulation results and design calculations. As a basis for the experimental investigations, a gas fired CHP plant was selected. The design of the test rig is optimized for the operation in the laboratory, where the coolant heat is emulated by a tempering device and the exhaust heat of the CHP plant is emulated by a gas burner. With the designed test rig, it is possible to control the volume flow and the temperatures of the coolant and exhaust gas, so that different load conditions of the gas fired CHP plant can be investigated. For initial tests, the turbine in the SRC is replaced by a throttle to achieve the pressure drop of the turbine. The experimental results show, that the exhaust and coolant heat of a 36 kWel CHP plant can be emulated and the performance expectations of the cycle can be met in stable steady-state conditions. Based on the measurement results and the turbine design calculations an electric power output of the cycle of 3.8 kW will be possible, which results in a cycle efficiency of about 6.5 % and an increase of the electrical power output of the CHP plant of about 10 %. The results show that the plant concept is technically feasible and, with further optimization, also represents an alternative to ORC plants in terms of increasing the efficiency of a cogeneration plant. Y1 - 2019 SN - 978-90-9032038-0 PB - The National Technical University of Athens (NTUA) CY - Athens ER - TY - CHAP A1 - Kramer, Tim A1 - Lerner, Igor A1 - Sacher, Patrick A1 - Neef, Matthias A1 - Baier, André ED - Dederichs-Koch, Andrea ED - Mohnert, Andrea ED - Kammasch, Gudrun T1 - Blue Engineering: Was ist das und wie gelingt die Implementierung an meiner Hochschule? T2 - Diversität und Kulturelle Vielfalt - Differenzieren, Individualisieren - oder Integrieren? Wege zu technischer Bildung : Referate der 13. Ingenieurpädagogischen Regionaltagung 2018 and der Hochschule Bochum vom 7.-9. Juni 2018 KW - Blue Engineering KW - Diversität Y1 - 2018 SN - 978-3-9818728-2-8 PB - Ingenieur-Pädagogische Wissensgesellschaft (IPW) CY - Berlin ER -