CryoSense: Final Report

Kurzfassung

The Final Report provides an overview of the activity “Advanced Measurement Techniques for the Validation of CFD for Cryogenic Flows in Reduced Gravity”, reviewing the conducted sensor study of novel technologies for measuring surface topologies, bubbles, temperature fields and other quantities of interest in cryogenic liquids. For new insights into cryogenic experiments and for CFD validation, the need for sensor tests in relevant environments is motivated. The results of such tests, performed in liquid nitrogen (LN2) and liquid hydrogen (LH2) at 77K and 20K respectively, are presented. Tomographic techniques (such as Ultrasound Tomography and Electrical Capacitance Tomography) are emphasised, as are fibre-optic sensors (fibre-optic bundles and fibre-optic temperature sensors). Some technologies were brought to the cryogenic domain for the first time. For ultrasound tomography and electrical capacitance tomography, measurements were performed with custom-made sensor rings and bubble traps (mimicking bubble sizes in microgravity conditions) in LN2. For fibre-optic temperature sensors, temperature fields and temperature profiles were recorded in LN2 and LH2 with high spatial resolution after optimising fibre coatings and obtaining calibration curves. Cryogenic compatibility and performance of the technologies could therefore be assessed in a detailed manner. Recommendations were given for further studies, such as extending tests to dynamic cases (e.g. sloshing) and to LH2.