Cryogenic sloshing in aircraft fuel tanks

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Fuel sloshing in cryogenic tanks is known to have important effects on the thermodynamics in the ullage space, potentially leading to significant pressure drops and consequent inability to extract the fuel from the tank. Due to the cryogenic environment, rotating machinery such as pumps are complex to install and operate reliably, therefore the characterisation of free surface sloshing is of paramount importance for the effective design of liquid hydrogen (LH2) storage systems in next-generation civil aircraft applications.Several non-intrusive measurement techniques exist for the characterization of multiple phase (liquid/gas) flow regimes in pipes/channels. These methods are based on a variety of measurements acquired via standard sensors mounted on the outside wall of the pipe (accelerometers, strain gauges, microphones or optical sensors); advanced signal processing techniques, such as wavelet analysis; and knowledge of the flow regime based on image analysis and particle velocimetry.In this project, these techniques will be developed further to measure, and characterise, the sloshing flow (and the configuration of the liquid free surface) within cryogenic tanks on-board Airbus' ZEROe hybrid-hydrogen concept aircraft. Since the sloshing (to first approximation) is independent of liquid density and the pressure in the tank, the methods will first be calibrated via visual analysis and particle velocimetry in laboratory tests on liquid/gas systems at room temperature (where visual access to the free surface is attainable).