Entwicklung von dynamometrischen Nordic Walking Stöcken mit einer an den Patienten angepassten Prothese

Ziel des Projekts: Entwicklung einer Kraftmessvorrichtung, welche es erlaubt die dynamischen Kräfte beim Stockeinsatz im Nordic Walking zu erfassen. Zusätzlich wurde eine Prothese entwickelt, welche an die Bedürfnisse eines Patienten angepasst wurde. Methoden / Experimente / Resultate: Am Anfang stand die Auswahl und Adaptierung eines Messverfahrens zur Bestimmung einer dynamischen Kraft. Anschliessend folgte die Konstruktion einer Vorrichtung zur Integration in einen Stock. Das System wurde mittels Dehnungsmessstreifen aufgebaut. Die Datenakquisition wurde über Labview vorgenommen. Verschiednen Testserien sollten das Verhalten von DMS und erstärkerschaltung aufzeigen. Statische Tests ergaben gute Resultate, man konnte ein Aussage über den Zusammenhang von Spannung und Kraft machen. Spätere dynamische Tests mit einer Druckmaschine zeigten, dass das System gut dynamischen Vorgängen folgen kann. In einem Thermoversuch wurde die Schaltung bei unterschiedlichen Temperaturen getestet. Diese zeigten, dass die Auswirkung der Temperatur nicht gross ist. Zusätzlich wurde das mechanische System auf sein Funktionieren überprüft. Die Rahmenpunkte der Verbesserung der Prothese wurden in einem Gespräch mit der betroffenen Person festgelegt. Die wichtigsten Punkte sind, erhöhen der Steifigkeit, sowie Verbesserung der Bedienungsfreundlichkeit. Anhand dieser Punkte wurden zwei Vorschläge ausgearbeitet. Einer von beiden beruht auf dem Grundaufbau der bestehenden Lösung, verbessert diese jedoch durch die einfacher Demontierbarkeit und Vibrationsfestigkeit der Verbindung

Development of an integrated solution to prevent spring frost damage using an aqueous-based insulating foam

In recent years, agricultural crops experience unusually early onset of vegetation due to global warming, which can cause major frost damage with devastating effects on crop yields. To mitigate the risk of frost damage, an integrated solution was developed, consisting of an aqueous-based biocompatible foam and a portable foam applicator enabling wine cultivators to treat up to 1000 m2 of vineyards with one filling containing 10 L of foam. The foam is biocompatible, stable for several days and easily removed by rain. Foam application yielded an insulation efficiency of up to 1.5°C during spring frost nights for the buds covered by the foam when combined with an electrically heated wire. Moreover, it was observed that the foam also created a 'mini greenhouse' effect at positive temperatures during the days, which might be a positive side effect helping the plants to grow at this early stage of the year

Hydro-structural stability investigation of a 100 MW Francis turbine based on experimental tests and numerical simulations

This work focuses on a 100 MW Francis turbine prototype, part of one of the four horizontal ternary groups of Grimsel 2 PSPP, in Switzerland. Due to the massive integration of new renewable energy, the number of daily starts/stops of the machines has increased. Consequently, cracks on the runner blades of the Francis turbines have been noticed, without a clear explanation regarding the phenomenon responsible for their onset. To identify the main stress-full operating condition causing these cracks, the full turbine hill chart has been covered during the in situ measurement campaign including start-up, speed no-load, deep part load, best efficiency, full load and shut-down operating conditions. Then hydro-structural stability diagnosis diagrams of the prototype have been established for the whole operating range of the turbine. In addition, CFD numerical simulations for different operating conditions, along with FEM structural and modal analysis of the runner, have been carried out. The onboard measurements evidenced the highest mechanical stresses on the runner blades at speed no-load operating condition. This conclusion is supported by CFD and FEM analysis, which put in evidence the possible excitation of one of the runner's eigen frequency by the fluctuations of the pressure field

DuoTurbo ::implementation of a counter-rotating hydroturbine for energy recovery in drinking water networks

To enhance the sustainability of water supply systems, the development of new technologies for micro scale hydropower remains an active field of research. The present paper deals with the implementation of a new micro-hydroelectric system for drinking water facilities, targeting a gross capacity between 5 kW and 25 kW. A counter-rotating microturbine forms the core element of the energy recovery system. The modular in-line technology is supposed to require low capital expenditure, targeting profitability within 10 years. One stage of the DuoTurbo microturbine is composed of two axial counter-rotating runners, each one featured with a wet permanent magnet rim generator with independent speed regulation. This compact mechanical design facilitates the integration into existing drinking water installations. A first DuoTurbo product prototype is developed by means of a Computational Fluid Dynamics based hydraulic design along with laboratory tests to assess system efficiency and characteristics. The agreements between simulated and measured hydraulic characteristics with absolute errors widely below 5% validate the design approach to a large extent. The developed product prototype provides a maximum electrical power of 6.5 kW at a maximum hydraulic head of 75 m, reaching a hydroelectric peak efficiency of 59%. In 2019, a DuoTurbo pilot was commissioned at a drinking water facility to assess its long-term behavior and thus, to validate advanced technology readiness levels. To the best of the authors knowledge, it is the first implementation of a counter-rotating microturbine with independent runner speed regulation and wet rim generators in a real-world drinking water facility. A complete year of operation is monitored without showing significant drifts of efficiency and vibration. The demonstration of the system in operational environment at pre-commercial state is validated that can be attributed to a technology readiness level of 7. The overall results of this study are promising regarding further industrialization steps and potential broad-scale applicability of the DuoTurbo microturbine in the drinking water industry

DuoTurbo ::a new counter-rotating microturbine for drinking water facilities

To enhance the sustainability of water supply systems, the development of new micro hydropower technologies remains substantial. In the framework of the DuoTurbo project, HES-SO Valais//Wallis and EPFL-LMH, in collaboration with industrial partners, have jointly developed a new micro-hydroelectric system for drinking water facilities, targeting a power range between 5 kW and 25 kW. A counter-rotating microturbine forms the core of this new energy recovery station. The modular in-line “plug & play” technology requires low capital expenditure, expecting profitable operation within 5 to 10 years. One stage of the DuoTurbo microturbine consists of two axial counter-rotating runners, each one featured with a wet permanent magnet rim generator with independent speed regulation. This compact design enables a serial installation to cover a wide range of hydraulic power. The first DuoTurbo product was investigated using CFD simulations and experimental tests to validate the design efficiency and methodology. Good agreements between simulated and measured hydraulic characteristics are observed. The developed machine provides a maximum electrical output power of about 6 kW for a head of about 75 m, reaching a hydroelectric efficiency of nearly 60 %. End of 2018, the first product was installed at a pilot test site to assess its long-term behaviour. Estimations let anticipate an annual electricity production of 26 MWh at the pilot site

Experimental and numerical investigations of high-head pumped-storage power plant at speed no-load

Due to the increasing integration of new renewable energies, the electrical grid undergoes more frequent instabilities. Hydroelectric power plants, particularly pumped storage plants, are well suited for grid control. However, this objective requires extending the operating range of the machines and increasing the number of start-up, stand-by and shut-down procedures, which reduces the lifespan of the machines due to high mechanical stresses. The current study focuses on a pumped-storage power plant equipped with ternary groups. Recently, cracks on the runner blades of the Francis turbine have been observed without finding a clear explanation for their onset. During this period, the number of starts and stops per day has strongly increased. In order to better understand the origin of the fatigue of the turbine runner, external and on-board measurements along with CFD and FEM investigations have been performed. The on-board measurements provide evidence high mechanical stresses on the runner blades during the synchronization of the machine at speed no-load (SNL) operating condition. The frequency spectrum observed on the various signals suggests that the high stresses are linked to the excitation of one of the runner modes by some flow instabilities, which is supported by the CFD and FEM analyses