TY - CHAP A1 - Dubberke, Frithjof A1 - Priebe, Klaus-Peter A1 - Vrabec, Jadran A1 - Neef, Matthias A1 - Rödder, Maximilian T1 - Thermodynamic simulation and experimental validation of a cascaded two-stage organic Rankine cycle T2 - ASME ORC 2015, Brussels KW - simulation Y1 - 2015 CY - Brussels ER - TY - CHAP A1 - Rödder, Maximilian A1 - Neef, Matthias A1 - Laux, Christoph A1 - Priebe, Klaus-P. T1 - Systematic Fluid Selection for Organic Rankine Cycles (ORC) and Performance Analysis for a Combined High and Low Temperature Cycle T2 - Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration 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 and tolerance criteria. 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 and a low temperature cycle in which the condensation heat of the high temperature (HT) cycle provides the heat input of the low temperature (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 high temperature cycle with Toluene as the working fluid and 6,2% in low temperature cycle with iso-Butane 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. Y1 - 2015 UR - https://asmedigitalcollection.asme.org/GT/proceedings/GT2015/56673/Montreal, Quebec, Canada/236733 SN - 978-0-7918-5667-3 U6 - https://doi.org/10.1115/GT2015-42432 PB - American Society of Mechanical Engineers ER - TY - CHAP A1 - Helm, Peter A1 - Spliethoff, Hartmut A1 - Neef, Matthias T1 - Closing the Gap: Measuring Bristle Blow Down of Brush Seals T2 - 19 th International Conference on Fluid Sealing, Poitiers Y1 - 2007 CY - Poitiers ER - TY - CHAP A1 - Neef, Matthias A1 - Hepermann, Florian A1 - Sürken, Norbert A1 - Schettel, Joachim T1 - Brush Seal Porosity Modeling: Applicability and Limitations T2 - ETC7 – 7th Conference on Turbomachinery, Athens Y1 - 2007 CY - Athens ER - TY - CHAP A1 - Neef, Matthias A1 - Hummel, Dietrich T1 - Euler solutions for a finite-span flapping wing T2 - "Fixed, flapping and rotary wing vehicles at very low Reynolds numbers, Notre Dame, Indiana, USA Y1 - 2000 ER - TY - CHAP A1 - Neef, Matthias T1 - Innerstädtische Nutzung von Kleinwindkraftanlagen: Potentiale und Hürden T2 - Mülheimer Initiative für Klimaschutz, 06.05.2013 Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-21017 CY - Mülheim an der Ruhr ER - TY - CHAP A1 - Neef, Matthias A1 - Fussenecker, Claudia A1 - Niemann, Jörg A1 - Zielke, Thomas ED - Clark, Robin ED - Munkebo Hussmann, Peter ED - Järvinen, Hannu-Matti T1 - Publish your undergraduate research! A mandatory course for master students in engineering T2 - Creativity, innovation and entrepreneurship for engineering education excellence : proceedings of the 46th SEFI Annual Conference 2018, Copenhagen, Denmark N2 - Undergraduate students in engineering often have little exposure to the world of scientific publishing and the culture of sharing research work. While the beneficial exchange between research and teaching is well promoted, while the benefits of conference participation for students have already been surveyed and while courses on scientific writing are readily available, the concept of mini-conferences as part of the curriculum combines all three aspects into one. Therefore, the course "Engineering Conferences" was developed and installed as a mandatory part of a master program for engineering students. The idea is to go beyond simply teaching the standards of academic writing and skills for using scientific publications. By using a learner-centered approach, the students are engaged in typical activities around an active attendance of a real conference. Based on their bachelor thesis, they write a paper complying with common academic standards, submit the paper and review submissions of their fellow students. They also produce a poster and defend their work in a poster session held publicly on campus. This contribution is based on the experience from the first four terms teaching the course. It explains the didactic rationale behind the concept and individual teaching modules, it comprises the collection of useful resources for teaching and organizing scientific publishing and it includes the consequences drawn from course evaluation results. Y1 - 2018 SN - 978-2-87352-016-8 PB - SEFI - Société Européenne pour la Formation des Ingénieurs CY - Brussels 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 - TY - CHAP A1 - Helm, Peter A1 - Pugachev, Alexander A1 - Neef, Matthias T1 - Breaking the Swirl With Brush Seals: Numerical Modeling and Experimental Evidence T2 - Proceedings of the ASME Turbo Expo 2008 : presented at the 2008 ASME Turbo Expo, June 9 - 13, 2008, Berlin, Germany N2 - Striving for smaller losses in turbomachinery has led to many advancements in the design of seals. Modern sealing concepts such as brush seals hold a great potential to increase the efficiency of both flight engines and stationary turbines. At the same time, in order to maintain stable operating conditions of the rotor, swirl-induced forces must be kept at a minimum in the sealing channels. Therefore, the influence of the permeable and flexible bristle pack of brush seals on the flow around the rotor surface must be known. In this paper the swirl flow in the cavities of two different seal geometries is studied experimentally and numerically. A conventional three-tooth labyrinth serves as a reference. A second seal arrangement with a bristle pack upstream of two teeth is compared with the reference labyrinth. The swirl is evaluated experimentally from total and static pressure measurements in various axial and circumferential positions. Additionally, the axial swirl distribution is calculated using computational fluid dynamics (CFD). Here, the numerical model of the brush seal is based on the porous medium approach and is calibrated using the experimental values of the leakage and the bristle clearance by adjusting the thickness of the bristle pack. The calibrated CFD model is then used to study the impact of the brush seal on the swirl component of the sealing flow. The observed significant decrease of the swirl by the brush seal shows good agreement with the experimental data. The impact of changes in bristle pack clearance on the swirl is also investigated and compared with experimental evidence. The aim is to show that the brush seals have a natural tendency to interrupt seal swirl. They can therefore be used for swirl control in order to create a beneficial impact on the dynamic stability of turbomachines. Y1 - 2008 SN - 978-0-7918-4314-7 U6 - https://doi.org/10.1115/GT2008-50257 VL - 4 SP - 1387 EP - 1396 PB - ASME CY - New York ER -