Hochschule für Technik Allgemein

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    Publikation
    Do 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
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    Publikation
    01A - Beitrag in wissenschaftlicher Zeitschrift
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    Publikation
    Spray, 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
  • Vorschaubild
    Publikation
    A 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
  • Vorschaubild
    Publikation
    Flow 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