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Slurry Characterisation with capacitive and optical probes

The use of cryogenic slush, i.e. a cryogenic liquid at its triple point, as fuel for new generation rocket engines may play a significant role for the development of future launchers due to its higher density and higher specific enthalpy compared to the pure liquid state. Being the slush a mixture of solid and liquid phases, the aerospace industries are more and more interested in the development of instruments or methodologies capable to precisely determine the slush density and concentration, to properly design the launcher propulsion systems.

This study focuses on the development of two non-intrusive measurement techniques to determine the concentration and density of a well-known slurry through a circular transparent pipe system. Instead of slush Hydrogen, typically used as space propellant, in this preliminary activity, a slurry is selected by respecting hydrodynamic similarity rules. This approach simplify the conditions for the validation of the probes at ambient temperature.

The two techniques are based on the capacitive and the optical properties of the flow. The capacitive probe is designed by means of electric field analysis (EFA). For the optical technique, background lighting is applied with a constant intensity source, and the images are recorded with a high-speed camera. The experiments are conducted on a test bench developed in the framework the ESA TRP program “PREDICT”. The validation process of the techniques is done with an additional Coriolis flow meter implemented on the slurry test bench allowing to measures the slurry density. The density and concentration results obtained from the reference meter, the capacitive probe and the optical technique are compared and discussed for three test cases. The experimental results show that three techniques are in good agreement for low mass fraction concentrations.

A research was the subject of the research master project of Ş. P. Eneren Aksoy in June 2017 and was supervised by Prof. Jeroen van Beeck, Laura Peveroni, Yushi Sakamoto

Capacitive probe section views and example of contribution of different media to the capacitance
Capacitive probe section views and example of contribution of different media to the capacitance
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