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- PublikationA specifically designed injector for controlled lube oil addition in view of investigation of pre-ignition phenomena in dual–fuel/gas engines(Frontiers Research Foundation, 11.05.2021) Süess, Pascal; Schneider, Bruno; Wüthrich, Dario; Wüthrich, Silas; Herrmann, Kai [in: Frontiers in Mechanical Engineering]Internal combustion engines will continue to play a role during a transitional phase, especially in heavy-duty or marine applications. In this context, lean-burn gas/dual-fuel combustion is an attractive concept to reduce CO2, combined with considerably lower particulate and NOX pollution, and with efficiencies comparable to diesel combustion. However, ignition processes still pose considerable challenges, with pre-ignition in particular being a major issue. The underlying mechanisms are probably based on self-ignition of lube oil in hot zones. In order to investigate fundamentals of such phenomena in optically accessible test rigs, a novel injector was specifically developed to induce pre-ignitions artificially. The so-called “PieZo-Droplet-Injector” (PZDI) enables dosing of minor amounts of lubricating oil or even the injection of single droplets with diameters in the range of 100–200 µm. The working principle relies on a needle actuated with a piezo stack, which pushes a certain amount of lube oil in a bore so that (even single) droplets can be ejected through an adjustable nozzle. To confirm the PZDI functionality and to investigate droplet characteristics based on adjustable operating parameters, tests were performed under ambient conditions as well as in a constant volume combustion chamber under reasonable pressure and temperature conditions. Overall, the PZDI showed an excellent behavior in terms of capabilities to inject small amounts or even single droplets of lube oil. At last, this specially developed injector allows selective lube oil addition in an optically accessible engine test facility for upcoming examination of pre-ignition phenomena under real operating conditions.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationDer Grüngutscanner in der kommunalen Grüngutsammlung(Hochschule für Technik FHNW, 20.08.2021) Uhlmann, Philipp; Mandaliev, Petar; Biomasse SuisseDurch eine Umfrage in zehn Gemeinden in der Deutschschweiz und der Romandie, sollte die Meinung der Bevölkerung zum Grüngutscanner und den Begleitmassnahmen evaluiert werden, um daraus abzuleiten, wie der Scanner am besten eingesetzt werden soll, ohne dass die gesammelte Grüngutmenge signifikant zurückgeht. Zudem wurde der Status Quo des Scanners in der kommunalen Grüngutsammlung untersucht und mögliche Chancen und Grenzen für den Einsatz des Scanners im schweizerischen Gemeindestand diskutiert, um weitere Empfehlungen für die Zukunft des Scanners daraus abzuleiten.11 - Studentische Arbeit
- PublikationDo MCH prisms change asthenopic complaints when reading?(DOZ-Verlag, 28.06.2024) Joss, Joëlle; Jainta, Stephanie [in: Optometry & Contact Lenses]Purpose. Asthenopic symptoms mostly occur during demanding near-sighted tasks and are related to binocular symptoms (e.g. heterophoria), among others. Correction of symptomatic heterophoria with prismatic glasses is one way to treat the symptoms. This study investigates the effect of wearing a horizontal prismatic correction for 6 months. Material and Methods. A total of 87 subjects were assigned to a heterophoric prism group (N=32), a heterophoric control group (N= 31) or an orthophoric control group (N= 24) according to their MCH heterophoria. In the heterophoric prism group, the subjects were prescribed glasses with a prismatic correction for 6 months according to their distance correction; in contrast, the subjects in the heterophoric control group had to wear glasses without prismatic correction for the same period. The effect of the prisms on complaints due to asthenopic symptoms was investigated by comparing the total sum obtained in the CISS questionnaire at the beginning of the study and after 6 months (before and after wearing glasses) for the 3 groups. Results. A (long-term) prism effect was not apparent in the CISS total score. In both the heterophoric prism group and in the heterophoric control group, the CISS total score increased slightly and non-significantly after 6 months. When considering the heterophoric subjects with an increased CISS score at baseline, a nevertheless slight but non-significant decrease of symptoms was observed. All changes were observed in both the heterophoric prism group and the heterophoric control group. An additional analysis using binocular profiles showed a reduction in symptoms by numbers and specifically for subjects with reduced vergence facility. Conclusion. Wearing an individual, horizontal prismatic correction had no effect on the overall CISS-score for our test subjects. Further methods that allow a systematic recording of symptoms and optometric parameters are probably necessary to observe an effect. These could be binocular profiles that classify individuals according to their binocular parameters.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationFlow field investigation of a single engine valve using PIV, POD, and LES(MDPI, 2023) Hoffmann, Jana; Mirsch, Niklas; Vera Tudela, Walter; Wüthrich, Dario; Rosenberg, Jorim; Günther, Marco; Pischinger, Stefan; Weiss, Daniel; Herrmann, Kai [in: Energies]Due to stringent emission regulations, it is of practical significance to understand cycle-to-cycle variations in the combustion of fossil or renewable fuels to reach future emission regulations. The present study aims to conduct a parametric investigation to analyse the influence of the valve lift and different mass flows of an inlet valve of the test engine “Flex-OeCoS” on the flow structures. To gain a deeper understanding of the flow behaviour, an optical test bench for 2D Particle Image Velocimetry (PIV) and a Large Eddy Simulation (LES) are used. Turbulence phenomena are investigated using Proper Orthogonal Decomposition (POD) with a quadruple decomposition and the Reynolds stress transport equation. The results show good agreement between the PIV and LES. Moreover, the main flow structures are primarily affected by valve lift while being unaffected by mass flow variation. The turbulent kinetic energy within the flow field increases quadratically to the mass flow and to the decreasing valve lift, where large high-energetic flow structures are observed in the vicinity of the jet and small low-energetic structures are homogeneously distributed within the flow field. Furthermore, the convective flux, the turbulent diffusive flux, the rate of change, and the production of specific Reynolds stress are the dominant terms within the specific Reynolds stress transport equation.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationInteractive use-case generation tool for functional REST API testing(Hochschule für Technik FHNW, 18.08.2023) Volken, Jonas; Leu, Benjamin; Kropp, Martin; Affolter, Fabian; Tesitifi GmbHSoftware is an integral part of any business, which makes the significance of high-quality software in today’s digital age undeniable. However, despite the advancements in software testing, challenges persist in efficiently planning, generating, and executing test cases, particularly for REST API-based applications. This project addresses the issue by developing a sequence generator tool that enables testers to effortlessly create and execute sequences of requests, streamlining the creation of comprehensive test scenarios. By simplifying the process of connecting response values to subsequent request values, the software seeks to maximize test coverage, improve test quality, and enable testers to focus more on software quality enhancement than the efforts of test construction. The client for this project is Testifi GmbH, a company dedicated to enhancing software delivery processes through DevOps integrations and AI-automated quality assurance solutions. The main focus of the project was to find out if the test quality increased by using the sequence generator tool due to more edge cases and more complex scenarios being tested compared to manual API testing, as well as showing if the efficiency improvement can be measured in reduced amount of time necessary for creation sequences. To answer these questions and develop an application that offers value for Testifi GmbH, a literature review was conducted on the subjects of basic user interface design and user experience concepts for advanced users. Based on the findings, the user interface of the application was outlined and the software implemented. During development and with the finished product, multiple sets of user tests were conducted with users experienced in working with APIs, to improve the design and software during development, and to gain insights about the effectiveness of the final product. Those tests showed that the main goals of the project could be reached by demonstrating a considerable amount of time saved by using the application, while also outperforming manual testing methods in efficiency and ease of use. Key features like the linking of response values to subsequent request values and the suggestion of such links based on Testifi’s Pulse Artificial intelligence (AI) as well as previously created sequences were well received by testers and customer. The literature review also proved to be very valuable as users praised the straightforward design, while never missing any important data. When Testifi GmbH integrates the end product in their pulse workflow, its ability to create sequences easily and intuitively as well as the potential of the additional link suggestions created by the tool to be used in improving the Pulse AI will be indispensable.11 - Studentische Arbeit
- PublikationInvestigation of flow fields emanating from two parallel inlet valves using LES, PIV, and POD(MDPI, 2023) Hoffmann, Jana; Vera Tudela, Walter; Mirsch, Niklas; Wüthrich, Dario; Schneider, Bruno; Günther, Marco; Pischinger, Stefan; Weiss, Daniel; Herrmann, Kai [in: Energies]Understanding cycle-to-cycle variations (CCV) is of practical importance for the combustion of fossil and renewable fuels, as increasingly stringent emission regulations require reductions in the negative effects of such variations. The subject of this study is the flow around inlet valves, since oscillations of such inlet flows affect the flow structure in the cylinder and are thus one of the causes of CCV. To this end, a parametric analysis of the influences of the mass flow rate and valve lift of two parallel engine intake valves on the flow structures is performed. This follows on from an earlier similar study where the flow around a single intake valve was investigated. To analyse the flow behaviour and, in particular, the interactions of the flow leaving these two valves, an optical test rig for 2D particle image velocimetry (PIV) and a large eddy simulation (LES) are used. Proper orthogonal decomposition (POD), together with a quadruple decomposition and the Reynolds stress transport equations, are used to study the turbulence phenomena. The PIV and LES results are in good agreement with each other. The detailed LES analysis of the flow structures shows that, for small valve lifts, the flow separates along the whole perimeter of the intake valve, and for larger valve lifts, the flow escapes only to one side. This is, for combustion engines with the tumble concept, the stage at which the tumble movement develops. Moreover, the flow structures are strongly influenced by the valve lift, while they are unaffected by the variation in the mass flow. The turbulent kinetic energy in the flow field increases quadratically with a decreasing valve lift and increasing mass flow. The large, high-energetic flow structures are particularly dominant near the jet, and the small, low-energetic structures are homogeneously distributed within the flow field. The specific Reynolds stress transport equation shows the limitations of two-dimensionality and large timesteps in the PIV results and the limitations of the LES model.01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationSpray, combustion and soot of water-in-fuel (n-dodecane) emulsions in a constant volume combustion chamber; Part II: Effects of low temperature conditions and axygen concentrations(Elsevier, 2019) Wüthrich, Dario; von Rotz, Beat; Herrmann, Kai; Boulouchos, Konstantinos [in: Fuel]01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationSpray, combustion and soot of water-in-fuel (n-dodecane) emulsions investigated in a constant volume combustion chamber part 1: Influence of low water content(Elsevier, 2019) Wüthrich, Dario; von Rotz, Beat; Herrmann, Kai; Boulouchos, Konstantinos [in: Fuel]01A - Beitrag in wissenschaftlicher Zeitschrift
- PublikationVerändern MKH-Prismen den binokularen Vorteil beim Lesen?(DOZ-Verlag, 2022) Joss, Joëlle; Jainta, Stephanie [in: Optometry & Contact Lenses]Zweck. Beim Lesen mit beiden Augen stellt sich ein binokularer Vorteil (kürzere Lese- und Fixationszeiten im Vergleich zu monokularem Lesen), welcher durch Prozesse der motorischen und sensorischen Fusion zustande kommt, ein. Der binokulare Vorteil beim Lesen ist zum Teil von der individuellen horizontalen Heterophorie abhängig und damit stellte sich die Frage, ob sich prismatische Korrektionen (bestimmt nach der MKH-Methode, zum Ausgleich einer Heterophorie) auf den binokularen Vorteil oder auf Parameter der binokularen Koordination beim Lesen auswirken. Material und Methoden. Wir haben die binokularen Augenbewegungen von 54 Personen mit einer individuellen horizontalen Heterophorie beim Lesen vermessen (Eyelink II): für (1) monokular, (2) binokular, (3) binokular mit Disparität (entsprechend MKH-Prisma) und (4) binokular mit Disparität nach sechs Monaten präsentierte, deutschsprachige Sätze (insg. 120). In der sechsmonatigen Pause zwischen Messung (3) und (4) trugen 29 Personen Brillen mit prismatischen Korrektionen, während 25 Personen als Kontrollgruppe fungierten. Ergebnisse. Unsere Daten zeigten einen klaren, signifikantenVorteil für binokulares Lesen für alle Personen, ohne dass eine kurzfristige Präsentation einer individuellen Disparität (analog eines MKH-Prismas) daran etwas änderte. Erst nach einer Prismentragezeit von sechs Monaten zeigte sich zusätzlich ein tendenziell größerer binokularer Vorteil in der „Prismengruppe“ im Vergleich zur „Kontrollgruppe“. Parallel dazu nahm die Kopplung der Augen (Diskonjunktion) leicht zu und die objektive Fixationsdisparität nahm signifikant ab. Fazit. Das Tragen einer individuellen prismatischen, horizontalen Korrektion (MKH) hatte für unsere Studienteilnehmer*innen einen Einfluss auf die binokulare Koordination beim Lesen und erhöhte gleichzeitig den binokularen Vorteil. Dieser eher mittel- bis langfristige Effekt von prismatischen Korrektionen ist neu und sollte in weiteren Studien vertieft untersucht werden.01A - Beitrag in wissenschaftlicher Zeitschrift