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 - TY - CHAP A1 - Neef, Matthias A1 - Sulda, Erik A1 - Sürken, Norbert A1 - Walkenhorst, Jan T1 - Design Features and Performance Details of Brush Seals for Turbine Applications T2 - Proceedings of the ASME Turbo Expo 2006 : presented at the 2006 ASME Turbo Expo, May 6 - 11, 2006, Barcelona, Spain N2 - Adaptive and contacting seals such as brush seals have been successfully applied to turbomachinery for several years. In large steam turbine applications, however, various challenges still persist. Special focus is directed at the long-term performance and longevity of brushes on conventional spring-backed seal segments in steam turbines. This issue is particularly related to wear during startup conditions. This paper discusses the results of wear tests, derived from simulated transient turbine behavior, where the resultant seal leakage under steady state conditions is monitored. It is shown that the brush seal is significantly capable of adapting to varying operating conditions, but exhibits a degree of performance degradation during the initial startups. Together with previously reported mid-term wear data and an experience based long-term phenomenological approach a general model for brush seal performance degradation is developed. This model can be used for performance prediction and exerts influence on brush seal design. Y1 - 2006 SN - 0-7918-4238-X U6 - https://doi.org/10.1115/GT2006-90404 VL - 3 SP - 1385 EP - 1392 PB - ASME CY - New York ER - TY - CHAP A1 - Hurd, Paul A1 - Truckenmueller, Frank A1 - Thamm, Norbert A1 - Pollak, Helmut A1 - Neef, Matthias A1 - Deckers, Mathias T1 - Modern Reaction HP/IP Turbine Technology Advances and Experiences T2 - Proceedings of the ASME Power Conference - 2005 : includes papers from the 2005 International Conference on Power Engineering (ICOPE) ; presented at the 2005 ASME Power Conference, April 5 - 7, 2005, Chicago, Illinois, USA Y1 - 2005 UR - https://asmedigitalcollection.asme.org/POWER/proceedings/POWER2005/41820/425/311927 SN - 0-7918-4182-0 U6 - https://doi.org/10.1115/PWR2005-50085 SP - 425 EP - 435 PB - ASME CY - New York ER - TY - CHAP A1 - Völker, Lutz A1 - Casey, Michael A1 - Neef, Matthias A1 - Stüer, Heinrich T1 - The Flow Field and Performance of a Model Low Pressure Steam Turbine T2 - 6th European Conference on Turbomachinery - Fluid Dynamics and Thermodynamics : conference proceedings; 7-11 March 2005, Lille, France N2 - A 3-stage model of a low pressure steam turbine has been equipped with extensive instrumentation to assess aerodynamic performance and for validation of numerical methods. Emphasis was placed on detailed measurements at the inlet and exit of the last stage guide vane. Two configurations were examined – the first used a guide vane with lean in the last stage and a the second used a guide vane combining both lean and sweep. The experimental results from the two configurations have been compared with data from various design methods, ranging from through-flow to 3D multistage viscous simulations with mixing planes. Despite the challenges in modelling complex rotating blades in a wet steam environment, good agreement between the numerical and experimental results was obtained, and the new stator vane combining lean and sweep achieved the desired increase in reaction at the hub section. Y1 - 2005 CY - Lille ER - TY - CHAP A1 - Windte, Jan A1 - Radespiel, Rolf A1 - Neef, Matthias ED - Kroll, Norbert ED - Fassbender, Jens K. T1 - Aerodynamic Analysis of Flapping Airfoil Propulsion at Low Reynolds Numbers T2 - MEGAFLOW - Numerical Flow Simulation for Aircraft Design KW - Lift Curve KW - Chord Length KW - Pitch Motion KW - Laminar Separation Bubble KW - Combine Motion Y1 - 2005 SN - 978-3-540-24383-0 U6 - https://doi.org/10.1007/3-540-32382-1_21 VL - NNFM, 89 SP - 299 EP - 313 PB - Springer-Verlag CY - Berlin, Heidelberg ER - TY - CHAP A1 - Neef, Matthias A1 - Hummel, D. ED - Krause, Egon ED - Jäger, Willi T1 - Euler and Navier-Stokes Solutions for Flapping Wing Propulsion T2 - High Performance Computing in Science and Engineering ’01 KW - Wing Motion KW - Computational Fluid Dynamics KW - High Performance Computing KW - Thrust Coefficient Y1 - 2002 SN - 978-3-642-62719-4 U6 - https://doi.org/10.1007/978-3-642-56034-7_37 VL - 30 SP - 386 EP - 395 PB - Springer CY - Berlin ER - TY - CHAP A1 - Neef, Matthias A1 - Hummel, Dietrich ED - Mueller, Thomas J. T1 - Euler Solutions for a Finite-Span Flapping Wing T2 - Fixed and Flapping Wing Aerodynamics for Micro Air Vehicle Applications Y1 - 2001 SN - 978-1-56347-517-7 U6 - https://doi.org/10.2514/5.9781600866654.0429.0451 VL - 16 SP - 429 EP - 451 PB - American Institute of Aeronautics and Astronautics CY - Reston, VA ER - TY - JOUR A1 - Neef, Matthias A1 - Fritzen, J. P. A1 - Schumacher, G. T1 - Evaluation of mount loads in dynamic testing of a jet engine JF - Mechanical Systems and Signal Processing N2 - In the dynamic testing of jet engines the evaluation of loads on the mount structure is vital for comparison with finite element calculations of such testing. Measuring these loads with the help of strain gauges applied to the structure becomes difficult if the mount is overdetermined and thus not every strain gauge can be assigned to a single load direction. In this study, the overdetermined mount structure of the BR715 engine was examined at one of the three mounting points between the Boeing 717 airframe and the engine, where loads in five directions were reacted. Firstly, the dependence of five measured strains upon known static load conditions at the mounting point had to be determined. For this purpose a static calibration test was carried out where defined forces and moments in known directions were applied to the structure while the output from five strain gauges was measured accordingly. The result was the desired relationship between loads and strains in terms of a matrix, which yields the corresponding load condition of the examined mounting point if multiplied with a set of strains. The same calibration procedure was carried out with a finite element model of the mount, where direct comparison to dynamic load results from the model itself was possible. With this model the validity of the above method was shown as well as possible errors which may occur while evaluating dynamic test results. The method was found to give satisfactory results even for dynamic loading, although some inertia forces disturb the signals in dynamic testing. Finally, the results from an actual dynamic engine test were processed into loads and then compared to the simulated loads from a finite element model of the engine. Good agreement was found and the indication of any remaining discrepancies was used to update the model for an even better representation of the dynamic test loads. Y1 - 2003 UR - http://www.sciencedirect.com/science/article/pii/S0888327001914050 U6 - https://doi.org/10.1006/mssp.2001.1405 VL - 17 IS - 3 SP - 665 EP - 681 PB - Elsevier ER - 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 - 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 -