Forschungsschwerpunkte – Main research

Competence and Research Focus No. 1 Phase Transition of Fluids in Flows

The injection of water into air (or liquids into gases in general) can be used to reduce the absorbed power of a compression process. The enthalpy raised for evaporation ideally ensures isothermal compression and reduces the power demand which in turn can be used in gas turbines to increase their performances. During the injection, the prediction of droplet sizes, their distribution and their velocities is crucial for the resulting evaporation. This knowledge serves as a basis for the design of turbomachines.

The reverse phase change of the condensation and the resulting drop formation occurs in steam turbines and expanders. Emerging drops may cause damage when they impinge the rotating components of the machine. This occurs in the low-pressure stages of steam turbines but also in radial expanders, which are designed to use decay heat. The prediction of primary and secondary drop formation can be used for the design process in order to reduce impingement damage and aerodynamic losses. Besides the damage to the components done by the impingement of the droplets, they do as well wet the surfaces of components in areas with low flow rates. This leads to different local heat transmissions and heat exchanges between fluid and component surfaces, which in turn results in temperature gradients in the components and results in increased mechanical stress on the material. These stresses limit the maximum possible load gradients of power plants. The prediction of condensation, including secondary droplet formation, droplet growth, deposition and knowledge about the heat transfer, allows to influence the load gradients and thus the flexibility of power plants.

The phase change of a fluid can be used to make turbomachines more flexible. Consequently, it provides a positive contribution to the energy transition.

Current Projects

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Competence and Research Focus No. 2 Turbomachines for Alternative Fluids and Circuits

For decades, air, water, but also chlorofluorocarbons (CFCs banned in the meantime) and then fluorocarbons (HFCs), such as R134a (tetraflurethane - CF3CH2F), have been used for cycles in energy conversion. One of the most promising alternatives is carbon dioxide, which has a greenhouse potential only in large quantities, but is otherwise an incombustible, acidic and colourless gas. It is not toxic in itself and only dangerous to humans in elevated concentrations (1-3 vol. % CO2).

Carbon dioxide reaches the critical point at 304.13 K (30.980 °C) and 7.375 MPa (73.75 bar) and the supercritical state, also known as the 4th state of aggregation, above the critical point at higher pressure and temperature. This state is characterised by the relatively high density similar to a liquid and the relatively low viscosity similar to a gas and thus combines two positive properties for energy conversion. The relatively high density contributes to a high energy density and the low viscosity to the reduction of friction losses.

When looking at the fluid properties in detail, it is noticeable that e.g. the real gas factor or the specific heat capacity etc., vary substantially near the critical point. Since the fluid properties have been thoroughly researched and all data are available, the focus of the research is on the application in circuits and their apparatus. The aim is to use the properties sketched above for energy conversion, to design circuits reliably and in particular turbomachinery for a wide range of applications.

Carbon dioxide has the potential to have a higher thermal efficiency than water at high circuit temperatures (T> 600 °C). On the other hand, there are technological challenges, which are addressed in different projects at the chair. In these EU-funded collaborative projects, the chair has developed and is currently operating a compressor-turbine unit in a small scale demonstrator in order to validate the technology in the lab. Furthermore, turbomachinery design tools are enhanced for the specific properties of sCO2 and validated with the results gained in the demonstrator. These tools are disseminated towards the scientific community and exploited by industrial partners to increase the technical readiness level further and bring the technology to the market.

The research contributes to reducing the global warming by using carbon dioxide as a substitute medium for HFCs, e.g. in cooling circuits, emergency cooling systems.  Carbon dioxide also has the potential for higher thermal efficiencies as a substitute medium for water.

Current Projects

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Kompetenz- und Forschungsschwerpunkt 3 Fluid- und Strukturdynamik von Maschinenkomponenten

  • Strömungsinduzierte Ventilschwingungen

    • Anwendung von Large-Eddy-Simulationen zur Identifizierung von Optimierungspotenzialen
    • Testen der generierten Optimierungen am Prüfstand
  • Gleitringdichtungen

    • Vermessung von Spalten zwischen einem Rotor und einem Stator im Bereich von wenigen Mikrometer
  • Akustik-Strukturkopplung in Radialverdichtern

    • Methodenentwicklung zur Vorhersage von akustische Moden
    • Verifizierung der Methode am Prüfstand
  • Strömungsphänomene in Rotor-Stator-Kavitäten

    • Vermessung der Strömung mittels Hitzdrahtanemometry bis zu Reynolds-Zahlen von Reω < 109
aktuelle Projekte

Kompetenz- und Forschungsschwerpunkt 4 Optimierung des Strömungspfads

  • Rückführbeschaufelung in Radialverdichtern

    • Vermessung der Strömung mittels Hitzdrahtanemometry und Fünflochsonden
    • Geometrievariationen mit additiver Fertigung
  • Kennfeldberechnung von Turbinen und Verdichtern für den Betrieb mit alternativen Fluiden, z.B. sCO2, H2 und die Anwendung in Gasturbinen (Turbine, Naßverdichtung)

  • Anwendung von numerischen Methoden auf Einkanalpumpen zur Verringerung der Verstopfungsgefahr

  • Entwicklung und Verifizierung von Auslegungsprogrammen für Kreiselpumpen

  • Pumpenauslegung

aktuelle Projekte

Schwerpunkte der Fakultät für Ingenieurwissenschaften

Die Fakultät für Ingenieurwissenschaften der UDE bündelt ihre Forschungsaktivitäten in vier ausgeprägt interdisziplinären Fakultätsschwerpunkten:

Die Forschungsprojekte am Lehrstuhl für Strömungsmaschinen sind den Schwerpunkten "Tailored Materials" und "Energy and Resource Engineering" zugeordnet. Bitte klicken Sie auf die Felder für weitere Informationen zu den relevanten Forschungsaktivitäten unseres Lehrstuhls innerhalb der Fakultätsschwerpunkte:



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