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Meniscal tears in the avascular zone have a poor self-healing potential, however partial meniscectomy predisposes the knee for early osteoarthritis. Tissue engineering with mesenchymal stem cells and a hyaluronan collagen based scaffold is a promising approach to repair meniscal tears in the avascular zone. 4 mm longitudinal meniscal tears in the avascular zone of lateral menisci of New Zealand White Rabbits were performed. The defect was left empty, sutured with a 5-0 suture or filled with a hyaluronan/collagen composite matrix without cells, with platelet rich plasma or with autologous mesenchymal stem cells. Matrices with stem cells were in part precultured in chondrogenic medium for 14 days prior to the implantation. Menisci were harvested at 6 and 12 weeks. The developed repair tissue was analyzed macroscopically, histologically and biomechanically. Untreated defects, defects treated with suture alone, with cell-free or with platelet rich plasma seeded implants showed a muted fibrous healing response. The implantation of stem cell-matrix constructs initiated fibrocartilage-like repair tissue, with better integration and biomechanical properties in the precultured stem cell-matrix group. A hyaluronan-collagen based composite scaffold seeded with mesenchymal stem cells is more effective in the repair avascular meniscal tear with stable meniscus-like tissue and to restore the native meniscus.
Non-road sectors, such as agriculture and construction machinery, require high energy densities and flexibility in use, which is why diesel engines are mainly used. The use of climate-neutral fuels, produced from renewable energies, such as Oxymethylene Ether (OME) as a diesel substitute, can significantly reduce CO2 and pollutant emissions in these sectors. In addition to CO2 neutrality, OME also offers improved combustion characteristics compared to diesel fuel, eliminating the soot–NOx trade-off and thus enabling new opportunities in engine design and calibration. In this paper, the combustion of pure OME on a close-to-production, single-cylinder non-road diesel engine with a pump–line–nozzle injection system is analyzed. A variation of the center of combustion at constant power output was performed for diesel and OME at different operating points. Two injectors were investigated with OME. A study on ignition delay and a detailed thermodynamic analysis was carried out. In addition, the exhaust emissions CO, NOx, VOC, as well as particulate-matter, -number and -size distributions were measured. With OME, a significantly shorter ignition delay as well as a shortened combustion duration could be observed, despite a longer injection duration. In addition, the maximum injection pressure increases. VOC and CO emissions are reduced. Particulate matter was reduced by more than 99% and particle number (>10 nm) was reduced by multiple orders of magnitude. The median of the particle size distribution shifts from 60 to 85 nm (diesel) into a diameter range of sub 23 nm (OME). A significant reduction of NOx emissions with OME enables new degrees of freedom in engine calibration and an efficiency advantage without hardware adaption.
Schlussbericht zum Verbundvorhaben NAMOSYN: Nachhaltige Mobilität durch synthetische Kraftstoffe
(2023)
Im Labor für Verbrennungsmotoren und Abgasnachbehandlung der OTH-Regensburg sollten im Zuge des NAMOSYN-Projektes zwei Vertreter klimaneutraler Kraftstoffe an verschiedenen Systemprüfständen (Motor-, Einspritzprüfstand, optisch zugängliche Einspritzkammer, …) und mit Hilfe von Simulationsmethoden für den Einsatz in bestehenden Verbrennungsmotoren untersucht werden. Synthetische Kraftstoffe aus der Gruppe der Oxymethylenether (OME) stellen eine CO2-neutrale Alternative zu fossilem Dieselkraftstoff dar. Für Ottomotoren wurde untersucht, ob der synthetische Kraftstoff DMC/MeFo (Dimethylcarbonat & Methylformiat) einen Ersatz für Ottokraftstoff darstellen kann, bzw. eine Drop-In-Fähigkeit gegeben ist.
Die OTH Regensburg bearbeitete 2 unabhängige Teilvorhaben zur motorischen Testung von synthetischen Kraftstoffen: „FC 1A: Motorische Testung von OME“ und „FC 2: Untersuchung von C1-Oxygenaten für Ottomotoren“. Die Projektlaufzeit betrug 3,5 Jahre, inkl. kostenneutraler Verlängerung um 6 Monate aufgrund der Corona-Pandemie.
Im FC1A "AP2-Nachrüstung Dieselmotoren" der OTH Regensburg lag der Fokus auf der Erforschung der Potentiale und der Umrüstung eines Einzylinder-Dieselmotors mit Pumpe-Leitung-Düse-(PLD)-Einspritzsystem des Projektpartners Motorenfabrik Hatz GmbH und Co. KG für OME-Betrieb.
Im AP2.1 wurden umfangreiche Daten gesammelt und Simulationsmodelle des Motors und PLD-Einspritzsystems erstellt und mit Dieselkraftstoff und OME validiert. Nachfolgend wurden Parameterstudien zur Geometrie des Einspritzsystems und der physikalischen Eigenschaften von OME durchgeführt.
In AP2.2 und AP2.3 wurden umfangreiche Untersuchungen an einem Motor- und Einspritzsystemprüfstand mit Diesel und OME durchgeführt und der Steuergerätedatensatz für den OME-Betrieb optimiert.
Die Ergebnisse zeigen, dass die Umstellung des Kraftstoffs auf OME, insbesondere bei einfachen Motoren mit rudimentärer Einspritztechnik und ohne Mittel zur NOx-Reduzierung (keine AGR oder SCR), ein enormes Potenzial zur Steigerung des Wirkungsgrads bei gleichzeitiger Reduzierung aller regulierten Schadstoffe (NOx, 𝑃N, 𝑃M, CO und 𝑉OC) eröffnet. Die Ergebnisse und generierten Simulationsmodelle unterstützen eine schnelle Serienentwicklung und Einführung von OME-Umrüstlösungen.
In FC 2 werden die vielversprechenden Kraftstoffe Methylformiat (MeFo) und Dimethylcarbonat (DMC) motorisch getestet. Untersuchungen am Kraftstoffsystem und wichtigen Komponenten dienen als Grundlage für das AP3.
Im AP3 wird die Machbarkeit der DMC/MeFo-Verbrennung am Vollmotor demonstriert und die erwarteten Emissionsvorteile gegenüber herkömmlichen Ottokraftstoffen gezeigt. Abweichend von der ursprünglichen Planung werden an der OTH Regensburg Kraftstoffblends aus Benzin und MeFo untersucht, um den Einsatzbereich des Kraftstoffs zu erweitern.
In AP5 werden potentielle Mischungsverhältnisse analysiert und die Eigenschaften der ausgewählten Kraftstoffmischungen an einem Einspritzratenprüfstand, an der Einspritzkammer und am Vollmotor untersucht. Es werden Einspritzverhalten, Gemischaufbereitung und Abgasemissionen bewertet.
Zudem wird eine Kraftstoffmischanlage entwickelt und ein optischer Zugang am Vollmotor ermöglicht. Eine Ölverdünnungsmesstechnik wird eingesetzt, um den Kraftstoffeintrag ins Motoröl zu untersuchen
A comprehensive experimental program is carried out to determine material parameters for fracture initiation and propagation in X100 pipeline steels. The quadratic Hill’48 yield function along with an isotropic hardening are used to describe plastic flow at large deformation and a phenomenological fracture criterion to predict fracture initiation. Fracture mechanics SENT specimens are used to calibrate post-initiation softening parameters necessary for ductile crack propagation in thick components. Once the material model parameters set is complete a final comparison is conducted with ring expansion test on same material.
The current analyses present results of running ductile fracture propagation in high strength X100 line pipe steels under the influence of anisotropy. Mechanical anisotropy is commonly available in pipe products as a result of the manufacturing process, especially, those subjected to hot/cold-worked deformation. The outcomes of the present analyses show that its effect on the behavior of running ductile fracture in cracked pipes undergoing depressurization is meaningful. For instance, the Crack-Tip Opening Angle (CTOA) not only exhibits a strong dependence to the pipe's diameter size, but also to the material's anisotropy nature when compared to a hypothetical isotropic material. Moreover, laboratory scale tests such as those performed on Battelle Drop Weight Tear (BDWT) samples provide useful information about initiation of ductile crack propagation when the anisotropy features are taken into account in the material description.
The increasing global competition demands continuous optimization of products and processes from companies in the process industry. Where conventional methods of Lean Management and Six Sigma reach their limits, new opportunities and challenges arise through increasing connectivity in the Industrial Internet of Things and machine learning. The majority of industrial projects do not reach the deployment or are isolated solutions, as the structures for data integration, training, deployment and maintenance of models are not established. This paper presents the conception of a reference architecture for machine learning in the process industry to support companies in implementing their own specific structures. The focus is on the development process and an exemplary implementation in the brewing industry.
Introduction: Previous studies of bone stresses in the human lumbar spine have relied on simplified models when modeling the spinal musculature, even though muscle forces are likely major contributors to the stresses in the vertebral bones. Detailed musculoskeletal spine models have recently become available and show good correlation with experimental findings. A combined inverse dynamics and finite element analysis study was conducted in the lumbar spine to investigate the effects of muscle forces on a detailed musculoskeletal finite element model of the 4th lumbar vertebral body. Materials and Methodology: The muscle forces were computed with a detailed and validated inverse dynamics musculoskeletal spine model in a lifting situation, and were then applied to an orthotropic finite element model of the 4th lumbar vertebra. The results were compared with those from a simplified load case without muscles. Results: In general the von Mises stress was larger by 30%, and even higher when looking at the von Mises stress distribution in the superio-anterior and central part of the vertebral body and in the pedicles. Conclusion: The application of spine muscles to a finite element model showed markedly larger von Mises stress responses in the central and anterior part of the vertebral body, which can be tolerated in the young and healthy spine, but it would increase the risk of compression fractures in the elderly, osteoporotic spine.