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Capacitive gas-phase detection in liquid nitrogen

Title data

Kandlbinder, Christoph ; Fischerauer, Alice ; Mösch, Mario ; Helling, Tobias ; Fischerauer, Gerhard ; Siegl, Martin:
Capacitive gas-phase detection in liquid nitrogen.
In: Journal of Sensors and Sensor Systems. Vol. 6 (1 March 2017) Issue 1 . - pp. 135-143.
ISSN 2194-878X
DOI: https://doi.org/10.5194/jsss-6-135-2017

Project information

Project financing: Bayerisches Staatsministerium für Wissenschaft, Forschung und Kunst

Abstract in another language

The main and upper stages of heavy lift launchers for space applications are often fuelled by cryogenic liquids. In order to enable the re-ignition of a cryogenic upper stage for orbital changes, it is crucial to study the behaviour of these fluids in microgravity. As gaseous bubbles entering the fuel lines of the engine can cause the destruction of the engine, these bubbles are a risk for the functionality of the re-ignition mode. To measure an evolving gaseous phase and its volume, a capacitive measurement system for two-phase mixtures was realised. Its electrodes are arranged in a way that phase changes inside a vessel can be detected without parasitic heating under cryogenic conditions. Two cases have been investigated: a fill level measurement involving a large gas bubble above a homogenous liquid on the one hand and the identification of a bubble stream inside a liquid on the other hand. The system concept was tested in a cryogenic environment allowing the controlled generation of bubble streams inside liquid nitrogen and of a contiguous gaseous volume above the liquid. The characteristics of the measurable capacitances of different pairs of electrodes were experimentally determined and compared with finite-element simulations (Ansys). In addition, the electrical flux density was computed to corroborate the simulated capacitance curves with theoretical statements. The experimental findings closely agree with the simulated results if possible disturbances due to the characteristics of the capacitance measurement hardware are taken into account properly. Thus, by measuring various capacitances, it was possible to determine the level up to which a receptacle inside a liquid-nitrogen tank was filled with liquid (the space above the liquid being taken up by gaseous nitrogen), to identify the existence of a bubble stream in the liquid nitrogen and to demonstrate that the capacitance measurement results enable one to differentiate between the two cases.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties
Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Measurement and Control Technology
Faculties > Faculty of Engineering Science > Chair Measurement and Control Technology > Chair Measurement and Control Technology - Univ.-Prof. Dr.-Ing. Gerhard Fischerauer
Profile Fields
Profile Fields > Emerging Fields
Profile Fields > Emerging Fields > Energy Research and Energy Technology
Research Institutions > Research Units > ZET - Zentrum für Energietechnik
Research Institutions
Research Institutions > Research Units
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 06 Mar 2017 10:10
Last Modified: 06 Mar 2017 10:10
URI: https://eref.uni-bayreuth.de/id/eprint/36320